Farmers’ perception for classification and genetic erosion of yams landraces in Ethiopia: Implications for Breeding and Conservation

 

Tewodros Mulualem^1,2*, Firew Mekbib², Shimelis Hussein³, Endale Gebre⁴

¹Jimma Agricultural Research Center, P.O. Box 192, Jimma, Ethiopia.

²Haramaya University, School of Plant Sciences, P.O. Box 138, Dire Dawa, Ethiopia.

³African Centre for Crop Improvement, School of Agriculture, Earth and Environmental Sciences,

University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa.

⁴Ethiopian Institute of Agricultural Research, P.O. Box 2003, Addis Ababa, Ethiopia.

 

ABSTRACT:

Background and Objective: Understanding on-farm classification and rates of loses of crop genetic resources are crucial for breeding and conservation. The objective of this study was to assess farmers’ insight for classification, quantify the rate of landraces loss and identify major factor that causes of genetic erosion on yam in Southwest Ethiopia for conservation. Materials and Methods: A participatory rural appraisal study was conducted in 22 kebeles from seven districts of southwest Ethiopia. Data were collected from 240 yam growers using a semi-structured questionnaire, focus group and key informant discussions and field observations. Results: farmers’ classification system on yam varied and depends on the domestication status, sex type, used value and maturity. The rate of genetic erosion at district and kebele levels varied from 28.80% in Yeki to 57.93% in Kersa districts and 0% in Gubea muleta to 25% in Mehal sheko kebeles with an average rate of 44.48% and 14.1%, respectively. Number of farmers growing landraces decreased drastically in all surveyed districts in the past decades. Low attention given to the crop (95%), drought (93%), porcupine attack (90%), shortage of farm land (74%) and dilution of the crops by improved technologies (72%) were the prominent factors for ending landrace cultivation. Moreover, farmers’ preference for yield potential and cash crops subsequently reduced the chance of maintaining landraces. To conserve the landraces at district/kebele level, 30.2%, 52.6% and 15.2% of respondents mentioned provide training on the value, use, production of yams; genetic enrichment between district/kebele and collect landraces from different markets, respectively. The remaining 2.0% of the farmers had no suggestion for conservation of yams. Conclusion: Yam variety development programs should discourse the farmers classification system and identified factors for erosion for breeding and conservation in Southwest Ethiopia.

 

 

 

INTRODUCTION:

Yams (Dioscorea spp.) constitute a diverse group of plant species widely distributed throughout the tropical and sub-tropical areas of the world (Alexander and Coursey, 1969; FAO, 2012). Most Dioscorea species exhibit considerable morphological variability both in the aerial and underground tuber (Scarcelli et al., 2011). Combined analyses of morphological traits and farmers’ knowledge have been widely used, to determine the relationships, classification and spatial distribution of the species and landraces (Loko et al., 2013; Dansi et al., 2013a). Landraces are the result of selection from centuries by farmers and are a major source of genetic diversity in agriculture providing much of the genetic resources for plant breeding (Vavilov, 1951; Mashilo et al., 2015). However, study on landraces and their use by farmers are problematic in that the vernacular names used for landraces vary greatly and are not consistent (Demuyakor et al., 2013). Popular landraces can have several names even within the same district and different landraces may have the same name (Mekbib, 2007). Thus, assessing the classification and spatial distribution of landraces in relation to vernacular names are imperative. Besides, determination of vernacular names of landraces with the phenotypic and genetic characterization with farmers’ indigenous management system is paramount importance (Mignouna et al., 2002; Siqueira et al., 2014).

 

In Ethiopia, there is large pool of yams that are broadly dispersed in major growing areas in complex cropping system with wide genetic base (Edward, 1991; Miege and Demessew, 1997; Hildebrand, 2003). Farmers have their own descriptor for classification and management of their landraces. Like other indigenous technical knowledge, folk taxonomy might have lake of consistency (Tamiru et al., 2011). Hence, uniformity of the naming system is the key issue for validation (Mekbib, 2007). The existed local classification system is consistent to some extent with conventional botanical classification. As traditional farmers’ numbering in the millions have turned away from their traditional landraces, the knowledge of how to maintain the selected landraces that performed well in particular habitats and conditions has fallen victim to even greater erosion than the landrace itself. While plant collectors have managed to save some of the abandoned genetic diversity, the knowledge that produced and maintained the diversity over many generations remains on site and has only rarely been recorded in connection with the collection of landraces for ex situ conservation (Friis Hanse and Guarino, 1995; Loko et al., 2015). The erosion of indigenous knowledge which accompanies genetic erosion may be as damaging to the local community as the loss of the genetic material itself.

 

Presently, the indigenous yam genetic resources in Ethiopia are becoming seriously endangered owing to the high rate of genetic erosion resulted from natural calamities, displacement of yams by high value crops, changes in production systems and markets preferences (Hildebrand et al., 2002; Megersa, 2014). Further, the climate change and the availability of very limited funds for conservation have largely increased the genetic vulnerability of yam in the country. Moreover, limited attention has been given to assess the diversity and conservation of indigenous yam genetic resources and research is a rudimentary stage for identification, classification, description and evaluation of the available yam genetic resources for different use. Besides, the causes and effects of the genetic erosion of plant genetic resources are poorly understood in Ethiopia (Megersa, 2014). As a result, some of yam genetic resources in Ethiopia are in danger of extinction, and unless urgent efforts are taken to characterization, evaluation and conservation, they may be lost even before they described and documented. In addition, the majority of yam genetic resource diversity found in the country, where documentation is scarce and risk of extinction is the highest and increasing. Further, genetic erosion of agricultural crops on farmers' fields receives less media attention even though, it is of far greater importance to the livelihood of millions of farmers, however, within the international community concerned with conservation and use of plant genetic resources, the causes and effects of the genetic erosion of agricultural crops and possible ways of limited such erosion have been heatedly discussed during the UNCED conference in 1992 (in the preamble to the Convention of Biological Diversity (UNCED, 1992) and in particular loss and threat to crop species has received much attention in recent years and there are often widely differing views on the issues involved.

 

To address these constraints, genetic control through use of tolerant landrace are necessary (Yifru and Karl, 2006). Such landraces are expected to be found within the existing yam diversity in Ethiopia, which are yet to be studied. Moreover, the diversity of yam landraces maintained per districts and households throughout agro-ecology and administrative zones has never been assessed and the rate of landrace loss at national and regional levels is still unknown. The name of the existing landraces hardly recognized; the ethno botanical, farmers’ classification system and the spatial distribution of landraces per growing district by scientific research hardly assessed and it limits producers and researchers to access yam genetic resources in Ethiopia. Consequently, estimation of diversity and spatial distribution of yam, ethno botany and management of the existing diversity is crucial for conservation and sustainable utilization of yams in Ethiopia. Accordingly, the objectives of this study were: to assess farmers’ classification system, estimate the rate of landrace loss (genetic erosion), analyze its spatial distribution and variation of yams across study districts and kebeles and identify major factors that causes of genetic erosion in Southwest Ethiopia.

 

MATERIALS AND METHODS:

Description of study areas:

The study was conducted in 22 kebeles (kebele is the least administrative hierarchy in Ethiopia) from seven districts of major yam growing areas of Jimma (Manna, Shebe sombo, Dedo, Seka chekorsa and Kersa), Sheka (Yeki) and Bench-maji (Sheko) zones, which are the main yam production areas in Ethiopia (Figure 1). These areas were selected for study based on strong tradition in cultivating and domesticating various yam landraces with wide genetic base (Hildebrand, 2003; Demissew et al., 2003; Abebe et al., 2013), high production potential and long history on production and management system of yam with farmers’ traditional knowledge (Miege and Demissew, 1997).

 

Figure 1: Map of study districts in Southwest Ethiopia

 

Sampling households and data collection:

A semi-structured questionnaire, transect walks, and field visits, key informants and focus group discussions were used to collect information from selected farmers. Data assembled from transect walks, field visits; group and key informants were used to support and validate the information obtained from the semi-structured questionnaire. From each district, on average 34 farmers, 15 to 20 yam growers with five DAs and 10 key informants were sampled from different social groups for individual interviews, group and key informants’ discussions. In total, 240 farmers were interviewed using the semi-structured questionnaire and key informants’ discussions. Through the semi-structured questionnaire, the local name of existed landraces, domestication status, agronomic traits, use value, farm size covered by yam, the number of existed, before and newly introduced landraces in each district and the time of maturity were gathered. Each landrace was properly evaluated based on, extent of the production, distribution, degree of consumption, perceived nutritional value, cultural and medicinal importance, sex type, market preferences and contribution to household income. Other PRA tools used to gather information included the distribution, variability within the landraces; trends of landrace losses and change in cropping systems, reasons for loss and changes were collected.

 

Data analysis:

The collected data were coded and analyzed using IBM Statistical Package for Social Science (SPSS) software, version 20 (IBM, 2012). Cross-tabulation tables were constructed and descriptive statistics were generated to summarize data from the questionnaires. To make statistical inferences, descriptive statistics, frequencies and percentages were conducted to analyze relationships between variables. The rates of landraces loss (RLL) were calculated by using the formula described by Kombo et al. (2012) with some modification to assess the loss per district and kebele level.

 

 

Where n= number of landrace cultivated by few households on small areas within a district/kebele, k= number of newly introduced landraces in kebele/district and N= total number of landraces recorded in the district/kebele level.

 

To analyze common, unique, rare/endangered and distribution of landraces at districts and kebele level, four cell analysis and the principal component analysis was adopted by using Minitab statistical software (Minitab, 2010 version 16). Similarly, the degree of similarity and association between explored landraces and farmers identified causes of genetic erosion, the principal component analysis was also adopted based on likert scale method (Likert, 1932) (ranked 1-3, where, 1= low contribution, 2= medium contribution and 3= higher contribution to erosion) and clustering of landraces computed based on Un-weighted pair group methods with arithmetic average (UPGMA) using Statistical Analysis System (SAS) package (version 9.0 of SAS Institute Inc, 2000) for conservation measure.

 

RESULTS AND DISCUSSION:

Socio economic characteristics of surveyed households:

The summary of the sociodemographic characteristics of the respondents was presented in Table 1. Out of 240 farmers interviewed, 238(98%) were married with mean family size of 6.74, which indicated married people are more responsible to control and manage farming activities in the areas. The mean age distribution of the farmers between districts revealed that the highest (55.0) and the lowest (45.62) ages was recorded in Dedo and Sheko districts, respectively. Of all farmers, 182 (75.83%) were males and 58 (24.17%) females, which suggested that there was gender disparity in the study.

 

 

Table 1: Sociodemographic characteristics of the farmers in the study areas

Districts	No. of farmers	No. of Kebele	No. of landraces	Sex		Mean age of farmers	Mean family size	Mean farm size (ha)	Mean elevation
				Male	Female
Dedo	38.0	3	15	28	10.0	55.08	8.00	1.63	1873
Kersa	42.0	3	10	30.0	12.0	47.83	6.19	0.86	1750
Manna	35.0	4	17	28.0	7.0	47.46	6.08	1.47	1889
Seka-chekorsa	30.0	3	10	27.0	3.0	51.67	6.80	1.44	1785
Shebe-sombo	31.0	3	14	23.0	8.0	52.35	6.90	1.40	1622
Sheko	32.0	3	13	22.0	10.0	45.62	6.43	1.13	1725
Yeki	32.0	3	11	24.0	8.0	50.11	6.80	1.51	1306
Total	240.0	22	90.0	182.0	58.0	350.12	47.20	9.44
Mean	34.3	3.14	12.86	26.0	8.28	50.01	6.74	1.35	1707.1

 

The extensive gap between number of males and females participating in the study was higher in Seka-chekorsa (90% males and 10% females) and in Shebe-sombo (74.20% males and 25.80% females). The high percentage of male farmers suggested to their access to farmland and their position as head of family. In this regard, similar study was conducted by Olweny et al,. (2013) who concluded that farming is a male dominated profession. The lower percentage of female farmers could be due to the former land ownership system which discriminated against women.

 

In each district, almost all farmers had similar knowledge in regards to the name of landraces that was cultivated in their village. This provides for a good setting to access the number of landraces grew, evaluation and selection of yam in traditional agriculture using named landraces with a minimum influence of language polymorphism within the farmers. More than half of the respondents (73.2%) had 8-25 years of experience in yam production and 26.8% had between 26 and 43 years of experience. The experienced respondents (26.8%) can be useful agents in gathering information on farmers’ landrace identification, classification system, trends and identification of major factors that causes of landrace loss in the areas. the average farm sizes pointed out that 82.5% of the farmers had more than one hectare. Very few (17.5%) of the farmers in Kersa had 0.86 ha. Based on household family size, in all surveyed areas had almost similar average household family size (Table 1).

 

Identification and naming of landraces:

Farmers used their own local descriptors for identification of the landraces. Those descriptors are related to: morphological characteristics (vine color and length, twinge direction, tuber color, shape and string on flesh tuber) and agronomic characteristics (tolerant to drought, disease and pests, maturity time). The local farmers sometimes used the combinations of two or more descriptors for identification landraces (Tamiru et al., 2011; Tewodros, 2016). The descriptors that are related to the use value, culinary quality and agronomic characteristics came only after morphological characteristics (Brush et al., 1981; Dansi et al., 2013a). Results from this study indicated that 64%, 52% and 42% of the respondents had own descriptors for identification of their landraces based on tuber color, maturity and twing direction, respectively. Some descriptors such as, tuber flesh and surface color were used by farmers for the identification of a limited number of landraces. For example, sharp and angular vine with white tuber flesh, as descriptor used specifically for landrace badaye to distinguish from the other landraces. In all study districts, famers’ give separate vernacular name for each landrace they grew (Table 2). The names are often descriptive and reflect the variations of landraces in places of geographical origin, morphology, agronomic and culinary characteristics. Further, some farmers’ tie up the names of places in neighboring districts to the names of the landrace; for example, in this study, the name of landrace pada was originally collected from Dauro zone of Southern region by Dedo farmers and had white flesh color, therefore, pada sometimes called Dauro white in tested district. Furthermore, the naming may also include the indication of physical entities. In other instances, farmers exactly used words to describe the specific morphological, agronomic and cooking quality attributes of the particular landraces (Magule et al., 2014). From all surveyed districts, a total of 38 farmers’ named yam landraces were identified and the attributes of each landraces are presented in Table 2.

 

Table 2: Yam landraces grown in tested districts of southwest Ethiopia and their associated traits.

Landraces	Major attributes	Landraces	Major attributes
Afra	·    White and red mixture flesh ·    Thorny tuber and vine ·    Used as food and medicine ·    Tolerance to drought	Gurshume	·    Deep purple flesh color ·    Used as a medicine ·    Late maturing type ·    Tolerance to drought
Anchiro	·    White tuber flesh color ·    More palatable and broad leaves ·    Early maturing and female	Hati boye	·    White tuber flesh color ·    More palatable and used as a food ·    Early maturing and female type
Badaye	·    Early maturing type ·    White, purple and white purple flesh ·    Thick and a square vine ·    Tasty, fill seasonal food shortage	Karakachi	·    Vigorous growth and large tuber ·    Thorns on vine and tuber ·    White yellowish tuber flesh ·    Wild type and tolerant to drought
Badenseye	·    White and black mixture flesh type ·    Testy, early maturing	Kerta boye	·    Tolerance to drought ·    Big tuber size
Baki boye	·    Thick vine, late maturing type ·    Used as food and medicine ·    Resistant to disease and pests	Liyan	·    White aerial bulbils flesh ·    Big tuber and testy ·    Used as food and medicine
Bambuche	·    Big and longer tuber ·    Resistant to disease and pests	Mecha boye	·    White tuber flesh color, nd used as a food ·    Early maturing and female type
Banda	·    Mixed black and white flesh ·    Used as a food and medicine	Offea	·    Purple aerial bulbils flesh color ·    Small tuber and testy
Bola boye	·    Highly branched tuber ·    Big tuber size	Pada	·    Early maturing and female type ·    White tuber flesh color and testy
Bori boye	·    Large dark green leaves ·    Early maturing	Sesa	·    Wild type and used as medicine ·    Thorny on vine and tuber
Chebesha	·    Used as a food & more palatable ·    Early maturing and female ·    Low water holding content after boil	Torebea	·    White tuber flesh color ·    Late maturing type ·    Used as food and medicine
Dakuy	·    Deep red tuber flesh color ·    Big tuber size and used as medicine	Tsedeboye	·    Black tuber flesh color ·    Big tuber size
Dapo	·    White yellowish tuber flesh ·    Used as a food	Wadela boye	·    Deep purple tuber flesh color ·    Used as a medicine
Dartho	·    Purple and white purple flesh color ·    Tolerance to drought ·    Used as food and medicine	Woko	·    White bulbils flesh color ·    Big tuber, testy and early mature ·    Used as food and medicine
Doni	·    Variegated tuber flesh color Early type and use to fill food shortage ·    Used as a food and market	Washinea	·    Large and black flesh yam ·    Thorns on tuber surface ·    Tolerance to drought
Erkabea	·    White flesh ·    Resistant to disease and pests	Wayera	·    Vigorous growth and spiny vine ·    White flesh color and market
Feda	·    White yellowish flesh color ·    Big tuber size and market	Welmeka	·    Variegated bulbils flesh color ·    Big tuber and testy
Geano boye	·    Large and deep red tuber flesh ·    Used as a medicine and male yam ·    Late maturing type	Zankur	·    Deep purple flesh color ·    Used as a medicine ·    Tolerance to drought and disease
Gesa boye	·    Variegated tuber flesh color ·    Used as food and medicine	Zatemera	·    Small dark green leaves ·    Tolerance to drought
Goshitea	·    Late maturing ·    Used for medicine and market ·    Tolerance to drought	Zawera	·    deep purple and inner white flesh ·    Big tuber and testy ·    Resistant to disease

 

Farmers based yam classification system:

Farmers’ used folk classification systems to assembly their landraces into different categories. In this study, farmers used domestication status (wild and cultivated), sex type (male and female), use value (food, and medicine) and maturity type (early, medium and late) as a method to classify their landrace (Table 3). From the total identified landraces 2 (5.26%) and 36 (94.74%) of the landraces grouped as wild and cultivated type, respectively. During the key informant’s discussion and agricultural expert meetings, participants identified wild yams found in natural forest areas of Sheko (karakachi) and Manna districts (sesa) of Southwest Ethiopia (Figure 2).

 

Figure 2: Wild yam landraces karakachi and sesa from Sheko and Manna districts

 

Further, due to the dioecious in nature, yam landraces grouped as ‘female and male’ is a remarkable aspect of the local classification system. The two categories reflected mere differences in agro-morphological traits, consumption qualities and ecological adaptation (Tsegaye, 2002; Magule et al., 2014). Of the total 38 landraces identified, 9(23.68%) were classified as 'male', 16(42.11%) as 'female' and the remaining 13(34.21%) landrace had unclear sex designation, some farmers claiming them 'male' and others claiming them 'female'. Based on use value, farmers classified the landraces in two comprehensive use groups: food use and medicinal value. Although most landraces can be used as both for food and medicine, there are preferences for specific landrace among the societies for scrupulous purposes. In all districts, farmers planted the landraces primarily for food and others for medicinal uses. Farmers grouped their landraces as early, medium and late types. Based on farmers’ recognition, early type landraces mature within a short period (four to five months after plant) of time. All farmers used these landraces to fill their seasonal food and economic gaps. Medium and late mature landraces are matured between 6-8 months and 8-11 months after plant, respectively (Figure 3). In this study, 18(47.37%), 11(28.95%) and 9(23.68%) landraces identified as early, medium and late maturing yam landraces, respectively (Table 3). Both early and medium types harvested twice while, late maturing landraces harvested only once in all areas. Similarly, Onwueme and Charles, (1994) reported maturity types varied within yam species. For example, D. Cayenensis matures within 280-350 days (9-11) after plant and D. rotundata matures within a range of 200-330 days (6-11) after plant.

 

Table 3: Folk classification of yam landraces in tested districts

Folk classification bases	Categories	Characteristics of landrace in each category	Landraces in each Category (%) (N=38)
Domestication status	Wild	Sexually reproduced; occurring naturally in forest areas;	2 (5.26%)
	Cultivated	Vegetative propagated: it occurs in home garden under farmers' management condition	36 (94.74%)
Sex type	Female	Early maturing, more tender, with edible storage tuber	16 (42.11%)
	Male	Late maturing, vigorous, drought tolerant, with medicinal tubers	9 (23.68%)
	Un clear	Some of them are medium maturing yams used to fill seasonal food and economic gaps	13 (34.21%)
Use-value of landrace	Food use	Mainly used for yam-based foods	NA
	Medicine	Mainly used as medicine	NA
	Both	Mainly used as a food and medicine	NA
Maturity	Early	Mature within 4-5months	18 (47.37%)
	Medium	Mature within 6-8months	11 (28.95%)
	Late	Mature more than 8months	9 (23.68%)

NA-Not available

 

Figure 3: Early, medium and late maturing yam landraces grown in southwest Ethiopia

 

Genetic erosion of yams:

Genetic erosion is a complex process and several factors that involved either directly or indirectly on existed landraces (Mulualem, 2016). Some factors are related to socio-economic factors in general, while others are related to biotic and a biotic factor (Brush and Meng, 1998). In the present study, the causes of abandoning landraces identified throughout the kebeles and districts were diverse and varied from one district and kebele to another. At district level, the rate of genetic erosion varied from 28.80% in Yeki to 57.93% in Kersa with a mean rate of 44.48% (Table 4).

 

The common, unique and rare/endangered landraces or species of yam at kebele and district level was identified through four cell analyses. The results also revealed that, only a few landraces (2.5) on average per kebele were cultivated by many households and on large areas. According to the producers, these landraces were found to have good agronomic (high productivity, high multiplication rate, etc.), utilization and culinary characteristics and therefore their production are economically profitable (Table 4). Landraces cultivated by many households but on small areas (3.9) on average per kebele had exceptional culinary characteristics (good taste, quality for medicine) but presenting a lot of weaknesses. They had low productivity, high staking demand, poor postharvest storage and post maturity conservation in the mounds, high susceptibility to poor soils fertility, low multiplication rate, etc. making their production economically unprofitable. Some landraces (1.4) on average per kebele were cultivated by few households on large areas. According to the farmers, these landraces had good agronomic and culinary qualities but had some particularity: difficulty to harvest, soil selectivity and long dormancy. Lastly, some landraces (2.3) on average per kebele were cultivated by a few households and on small areas indicated that, landraces had high growth performance and were threatened or being disappeared (Table 4). Similarly, Loko et al. (2013) reported that yam cultivars produced by few households and distributed on small areas considered as threatened last generally only five years and most often, effectively disappear after this period from the villages where they identified. If this trend continues, the indigenous yam diversity and farmers knowledge could be lost in the near future (Hammer and Laghetti, 2005).

 

Likewise, Diehi (1982), Manyong and Nokea (2003) and Ashiedu and Alieu (2010) predicted the future decline yam production based on socio economic and agronomic consideration. For example, according to Hildebrand et al. (2002), who described five farmers’ landraces namely, erkabea, don-babu, don-bai, chebesha and kuchi-kundi to be threatened in Sheko district. In the present survey, except erkabea and chebesha, three landraces were lost and not described by farmers in the same district.

 

Table 4. Distribution, extent of analysis and the rate of landrace loss in the study districts and kebeles

District	Kebele	TNL	SH	DH	DET				NIL	RLL%
					ML	MS	FL	FS
Dedo	Afolea dawea	14.0	2	12	3	4	2	4	1	21.42
	Billo adicho	13.0	3	10	4	5	2	2	0	15.38
	Keta kedida	11.0	2	9	4	3	1	2	1	9.09
	Total	38.0	7	31	11	12	5	8	2	45.89
Kersa	Ankaso	21.0	9	12	5	7	3	5	1	19.04
	Beda buna	12.0	2	10	4	4	2	2	0	16.67
	Marewa	9.0	2	7	2	4	1	2	0	22.22
	Total	42	13	29	11	15	6	9	1	57.93
Manna	Bilida	9.0	2	7	2	4	1	2	0	2.22
	Gubea muleta	6.0	1	5	1	3	0	1	1	0.00
	Meati	10.0	1	9	3	4	1	2	0	20.00
	Somodo	10.0	3	7	2	4	1	2	1	10.00
	Total	35	7	28	8	15	3	7	2	32.22
Seka chekorsa	Boye kecema	17.0	5	12	3	6	4	4	0	23.52
	Gibe boso	6.0	2	4	1	3	1	1	0	16.67
	Sheni qoche	7.0	3	4	3	2	1	1	0	14.28
	Total	30	10	20	7	11	6	6	0	54.47
Shebe sombo	Kishea	9.0	2	7	2	3	1	2	1	11.11
	Sebeka dabeye	14.0	4	10	3	5	2	3	1	14.28
	Sebeka wala	8.0	2	6	1	4	1	1	0	12.50
	Total	31	8	23	6	12	4	6	2	37.89
Sheko	Gaziqa	9.0	2	7	1	3	2	2	1	11.11
	Mehal sheko	12.0	2	10	3	5	1	3	0	25.00
	Shami	11.0	2	9	2	3	1	3	1	18.08
	Total	32	6	26	6	11	4	8	2	54.19
Yeki	Addis alem	13.0	1	12	3	5	1	2	1	7.69
	Addis berhan	9.0	2	7	2	3	1	2	1	11.11
	Selam ber	10.0	2	8	2	3	2	2	1	10.00
	Total	32	5	27	7	11	4	6	3	28.80
Mean		10.9	2.5	8.4	2.5	3.9	1.4	2.3	0.5	14.1

TNL= Total number of landraces; SH= Single harvest landraces; DH= Double harvest landraces; DET= Distribution and extent; RLL=Rate of landraces loss; NIL= Newly introduced landraces; ML=Many households and large area; MS = Many households and small area; FL= Few households and large area; FS = Few households and small area.

 

Furthermore, changes in production systems, market preferences, environmental hazards and the availability of very limited funds for conservation reduced the diversity of yams genetic resources in many countries (Dansi et al., 2010; Sesay et al., 2013). From the 22 kebeles assessed, the rate of genetic erosion (loss of landraces diversity) varied from 0% in Gubea-muleta to 25% in Mehal-sheko with an average rate of 14.1% (Table 4). The zero rate of diversity loss recorded in Gubea-muleta is not an indication of a better preserver, but rather a maximum threshold of landraces abandonment reached. Similar results reported by Dansi et al., (2010) on yam collection from Togo and Kombo et al., (2012) cassava from the republic of Congo. Furthermore, results from this study indicated that farmers verbally reported some vernacular names of landraces that were no longer found in their districts/kebeles and thought to be lost and some other landraces had undergone notable reductions during recent years. Comparable results reported by Megersa, (2014) and Tsegaye and Berg, (2007) conveyed the decline the production of farmers named barley and wheat genotypes in north and east Shewa zone of Oromiya region. Further, Farmers’ named landraces had decreased cultivation areas or which entirely disappeared and were no longer cultivated by farmers in many areas (Brush, 2004; Mark, van de et al., 2009).

 

Causes of genetic erosion:

The loss of diversity on yam in study districts could be attributed to several reasons. Low attention given to the crop (95%), drought (93%), porcupine attack (90%), poor management (82%), land shortage (74%), dilution of the crop by high technology (72%), stake and labor shortage (49% and 23%, low market preference (4%), and soil fertility (3%), respectively (Table 5). Further, some socio-economic parameters, such as the age of the households and years of experience in yam production, the size of the family and farm size of the household and labor supply give the impression to affect the farmers’ decision making in the number of landraces to maintain. Drought was the greatest constraint for landrace loss in all kebeles, the year to year variation in rainfall with frequent drought spells was the justification of ranking drought as the main constraint of landrace loss. Moreover, 98.7% of the respondents recognized decreasing the trend of yam diversity in the areas due to the frequent drought. In this regard, recollection of one elder farmer in Sheko district gives a more specific picture of decline in household yam production. During his childhood and adolescence (40 years ago), each household had a field of yams containing 15-25 rows of stakes. Such a field would have 260-350 individual plants with multiple harvests per season, would have yielded approximately 100 family evening meals with leftovers for breakfast. Today, in the same district most farmers plant 1-6 rows of stake yams across a narrower area (Hildebrand et al., 2002). Similar results reported by Megersa, (2014) who stated the tendency of barley genetic resources in north Shewa zone of Oromia region of Ethiopia deteriorated through decades without any measure.

 

Table 5: Causes of genetic erosion of yam in in seven tested districts in southwest Ethiopia

Causes of genetic erosion		Districts						Total
	Dedo	Kersa	Manna	Seka chekorsa	Shebe sombo	Sheko	Yeki
Low attention given to the crop	11.0	20.0	18.0	17.0	16.0	8.0	5.0	95.0
Drought	31.0	3.0	7.0	2.0	9.0	18.0	23.0	93.0
Porcupine attack	17.0	7.0	5.0	25.0	13.0	15.0	8.0	90.0
Poor management	4.0	20.0	14.0	10.0	6.0	8.0	20.0	82.0
Land shortage	8.0	17.0	13.0	4.0	2.0	8.0	22.0	74.0
Replaced by high value crops	16.0	4.0	7.0	2.0	2.0	17.0	24.0	72.0
Attacked by mole rat	0.0	14.0	3.0	10.0	18.0	7.0	8.0	60.0
Stake shortage	11.0	0.0	13.0	10.0	12.0	1.0	2.0	49.0
Labor shortage	5.0	0.0	0.0	3.0	2.0	13.0	0.0	23.0
Low market value	0.0	2.0	2.0	0.0	0.0	0.0	0.0	4.0
Low soil fertility	0.0	2.0	0.0	1.0	0.0	0.0	0.0	3.0
Lack of extension services	0.0	0.0	1.0	0.0	0.0	0.0	0.0	1.0

Figures in parenthesis refer to number of farmers surveyed in each district. Source: own survey result, sum greater than 100 is due to double counting.

 

The ranks of farmers named landraces and identified the causes of genetic erosion was used for cluster analysis (Table 6). The results cluster analysis revealed that landraces clustered into six distinct groups with different sizes based on the rank of 38 landraces given by farmers for genetic erosion (Figure 4). The number of landraces in each cluster varied from one in cluster VI to eighteen in cluster II. Cluster I had seven (18.42%) of the total landraces. All of them had 73.49% similarity and had highly prejudiced by most of the causes of genetic erosion identified by farmers. Cluster II, consisted the maximum number and accounted 18(47.36%) % of the total landraces. Landraces grouped in this cluster had 80.07% of similarity and exposed to most of the factors that cause of genetic loss. Conversely, landraces in this cluster had low influenced by drought and wild animal attacks. Cluster III and V had three entries (7.89%) from each, all of them had moderately affected by most of the factors that causes of erosion. Similarly, cluster IV and VI had seven landraces (18.42%) and noted 70.32% and 40.20% of similarity, respectively and high contribution to drought, shortage of farm land, management and mole rat attack.

 

Table 6: Rank of landraces given by farmers to genetic erosion in study districts

Landraces	A	B	C	D	E	F	G	H	I	J	K	L
Afra	3.0	2.0	2.0	1.0	1.0	2.0	2.0	2.0	2.0	2.0	1.0	1.0
Anchiro	2.0	2.0	1.0	1.0	2.0	2.0	1.0	3.0	2.0	1.0	1.0	1.0
Badaye	2.0	2.0	2.0	1.0	1.0	2.0	1.0	2.0	1.0	2.0	1.0	1.0
Badenseye	2.0	2.0	3.0	2.0	1.0	2.0	1.0	2.0	1.0	2.0	1.0	2.0
Baki boye	3.0	2.0	2.0	2.0	1.0	2.0	2.0	2.0	2.0	1.0	1.0	1.0
Bambuche	3.0	3.0	2.0	2.0	2.0	2.0	1.0	3.0	2.0	2.0	1.0	2.0
Banda	3.0	2.0	2.0	1.0	2.0	1.0	1.0	2.0	2.0	1.0	1.0	2.0
Bola boye	2.0	3.0	1.0	1.0	2.0	3.0	1.0	1.0	1.0	1.0	1.0	1.0
Bori boye	2.0	2.0	3.0	1.0	1.0	1.0	2.0	1.0	1.0	1.0	1.0	2.0
Chebesha	2.0	3.0	1.0	1.0	1.0	1.0	1.0	2.0	1.0	1.0	2.0	1.0
Dakuy	3.0	2.0	2.0	1.0	2.0	2.0	1.0	2.0	2.0	1.0	2.0	1.0
Dapo	2.0	3.0	2.0	1.0	2.0	2.0	1.0	2.0	2.0	2.0	2.0	1.0
Dartho	2.0	1.0	2.0	2.0	3.0	2.0	2.0	2.0	2.0	2.0	2.0	1.0
Doni	2.0	3.0	2.0	2.0	3.0	2.0	1.0	2.0	1.0	1.0	2.0	1.0
Erkabea	3.0	2.0	2.0	3.0	3.0	2.0	2.0	3.0	1.0	2.0	3.0	2.0
Feda	2.0	2.0	3.0	2.0	3.0	2.0	1.0	1.0	1.0	2.0	2.0	2.0
Geano boye	2.0	1.0	1.0	2.0	2.0	1.0	2.0	2.0	2.0	1.0	2.0	1.0
Gesa boye	3.0	2.0	2.0	2.0	2.0	3.0	2.0	1.0	2.0	2.0	1.0	1.0
Goshitea	1.0	2.0	1.0	1.0	2.0	2.0	2.0	3.0	2.0	1.0	1.0	1.0
Gurshume	2.0	2.0	3.0	2.0	2.0	3.0	1.0	2.0	2.0	3.0	1.0	1.0
Hati boye	2.0	1.0	2.0	3.0	2.0	2.0	2.0	3.0	2.0	2.0	2.0	1.0
Karakachi	2.0	2.0	1.0	2.0	2.0	1.0	3.0	2.0	1.0	1.0	1.0	1.0
Kerta boye	2.0	1.0	2.0	2.0	3.0	2.0	2.0	2.0	1.0	2.0	1.0	2.0
Liyan	3.0	2.0	3.0	2.0	2.0	1.0	2.0	2.0	2.0	3.0	1.0	2.0
Mecha boye	2.0	2.0	2.0	1.0	2.0	3.0	2.0	2.0	2.0	2.0	2.0	2.0
Offea	2.0	2.0	2.0	1.0	1.0	1.0	1.0	2.0	2.0	2.0	1.0	1.0
Pada	2.0	3.0	2.0	2.0	2.0	1.0	1.0	1.0	1.0	2.0	1.0	1.0
Sesa	2.0	2.0	3.0	2.0	2.0	1.0	2.0	2.0	1.0	3.0	2.0	2.0
Torebea	2.0	3.0	2.0	2.0	1.0	2.0	2.0	3.0	2.0	3.0	2.0	2.0
Tsedeboye	2.0	3.0	1.0	1.0	1.0	1.0	1.0	2.0	2.0	2.0	1.0	2.0
Wadela boye	3.0	2.0	2.0	1.0	2.0	2.0	1.0	2.0	2.0	2.0	1.0	2.0
Woko	2.0	3.0	2.0	1.0	2.0	2.0	1.0	2.0	3.0	2.0	2.0	2.0
Washinea	2.0	1.0	2.0	2.0	3.0	2.0	2.0	2.0	3.0	2.0	1.0	1.0
Wayera	2.0	3.0	2.0	2.0	3.0	2.0	1.0	2.0	1.0	2.0	2.0	1.0
Welmeka	3.0	2.0	2.0	3.0	3.0	2.0	2.0	2.0	3.0	2.0	2.0	2.0
Zankur	2.0	2.0	3.0	2.0	3.0	2.0	1.0	3.0	2.0	2.0	3.0	1.0
Zatemera	2.0	1.0	1.0	2.0	2.0	1.0	2.0	2.0	2.0	3.0	2.0	3.0
Zawera	2.0	2.0	2.0	1.0	1.0	2.0	1.0	2.0	1.0	1.0	2.0	2.0

1=low cause, 2=Medium cause and 3= Higher cause for landrace erosion

A= Low attention to the crop, B= Drought at early stage, C= Porcupine attack, D= Need more management, E= Shortage of farm land, F= Replaced by high value crop, G= Attacked by mole rat, H=Shortage of stake, I= Labor shortage, J= Low market value, K= Low soil fertility and L= Lack of extension service.

 

 

Figure 4: UPGMA based clustering of 38 yam landraces based on 12 farmers’ identified causes of genetic erosion

 

The results obtained from bi-plot principal component analysis evidently showed, genetic erosion is an important constraint in yam production in Ethiopia (Figure 5). The first two principal components contributed 25.40% (PCA-I) and 13.60% (PCA-II) of the total variation and showed a clear association between farmers named landraces and identified causes of genetic erosion in all districts. The positive direction of the first component attributes such as low attention given to the crop, porcupine attack, drought, dilution of the crop by high value crops (chat and coffee) and availability of low extension services are the most important sources of genetic erosion and 72.0 % of the identified yam landraces were eroded by these factors in Southwest Ethiopia. Thus, by improve the extension service and awareness creation to farmers, 72% of yam landraces protected from loss. While, stake shortage and poor soil fertility had the higher score in the negative direction of the first component (Figure 5).

 

Figure 5: The association between38 yam landraces and 12 causes of genetic erosion in the study areas

 

Furthermore, the bi-plot principal component also clearly indicated the relationships among yam landraces and degree of tolerance to the factors that cause genetic erosion. Landraces torebea, baki boye, badaye and tsede-boye were quite similar in terms of tolerance to drought and porcupine attack. Further, gesa- boye, goshitea, gurshume, hati boye, karakachi, kerta boye, liyan, mecha boye, offea, pada and sesa were found to be stable tolerance to most of the factors, as the points where close to the origin of the bi-plot. On the other hand, landraces zatemera, washinea and geano boye are sensitive for poor management, low soil fertility and market preference. Thus, the knowledge of genetic erosion and interaction with the landraces are significantly important to apply conservation measure.

 

Conservation of yam landraces:

To conserve the landraces at district/kebele level, 30.2% of farmers mentioned provide training on the value, use, production and postharvest utilization of yams; 52.6% of replied exchange of landraces (genetic enrichment) between farmers and kebeles and 15.2% of farmers reacted collect different yam landraces from different market sources. The remaining 2.0% of the farmers had no suggestion for conservation of yams. Further, 82.6% of farmers suggested the combination of one or more strategies for conservation. Although yam is vegetative propagated, it cannot only rely on farmers to maintain all landraces that might be available particularly when the landrace is unknown.

 

CONCLUSION:

Farmers in the study area have extensive traditional awareness on yams. Due to the past research neglect, farmers are commonly the bases of information on yams in southwest Ethiopia. Subsequently, the analysis of indigenous knowledge, farmers’ perception in designing conservation and improvement programs are critical to solve the identified problems in the study areas. Farmers’ classification systems are mainly based on very specific needs, preferences and socio-cultural aspects; thus, research in cooperation with farmers becomes necessary for breeding and conservation. In this study, the major causes of genetic erosion and its distribution on yam was identified, thus, training to farmers, diversity fair, diversity block, genetic enrichment/diversity kits across districts and kebeles are crucial for sustainable utilization of yam genetic resources in Ethiopia.

 

ACKNOWLEDGMENTS:

We are grateful to EIAR and JARC for the financial support of this study. We also thank yam growers in Southwest Ethiopia who participated and shared their invaluable knowledge with us, members of the zonal and district agricultural officers and particularly the development agents who gave us all help we needed during site selection and survey work.

 

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Received on 05.08.2020         Modified on 24.08.2020

Accepted on 06.09.2020  ©AandV Publications All right reserved