Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces: I. Field Pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

An experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study the extent and pattern of genetic diversity in Ethiopian field pea (Pisum sativum L.) landraces. One hundred forty-eight germplasm accessions were grown in an alpha lattice design with 2 replications. Data on 12 traits were collected and analyzed. Differences among the accessions were significant for most of the traits (except number of seeds/ pod) at each location even though differences pooled over location were mostly non-significant. The accessions were grouped into five clusters of different sizes. Accessions from the southern part of the country (Arsi) distributed overall clusters while those from the northern half (North and South Wello, North Gonder and North Shewa) fell into clusters C₁ to C₃. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. There was no definite relationship between geographic diversity and genetic diversity as overlapping was encountered in clustering pattern among accessions from different parts of the country. Accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances among most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable genetic recombination. Selection should also consider the special advantages of each cluster and each accession within a cluster. Future germplasm collection, conservation and breeding efforts should focus not only on inter-regional diversity but also on intra-regional diversity.     

Extent and Pattern of Genetic Diversity for Morpho-agronomic Traits in Ethiopian Highland Pulse Landraces II. Faba Bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.)

A field experiment was conducted in 2001 at Holetta and Kulumsa, Ethiopia, to study genetic diversity in Ethiopian faba bean (Vicia faba L.) landraces. One hundred sixty random germplasm accessions were grown in an alpha lattice design with two replications. Data on 12 traits were collected and analyzed. Significant differences were observed among the accessions for most of the traits (except number of pods/podding nodes) at each location even though differences pooled over location were mostly non-significant. Cluster analysis distinguished seven diversity classes of different sizes. Accessions from the northern half of the country (North and South Wello, North Gonder and North Shewa) were closely related while those from the southern part of the country (Arsi) were highly diverse. Cumulative effects of a number of characters dictated differentiation of the accessions into clusters. Some overlapping were encountered between accessions from the northern and those from the southern parts of the country. The study revealed that accessions from different regions might have similar genetic background and those from the same origin might also have different genetic background. Therefore, geographic diversity should not necessarily be used as an index of genetic diversity and parental selection should be based on a systematic study of genetic diversity in a specific population. Genetic distances between most of the clusters were significant that crosses between parents selected out of them are expected to generate desirable progenies. Future germplasm collection, conservation and utilization strategies should put more focus not only on inter-regional diversity in the country as a whole but also on intra-regional diversity in Arsi.     

Demand-driven breeding of food legumes for plant-nutrient relations in the tropics and the sub-tropics: serving the farmers; not the crops!

A number of improved cultivars of food legume crops have been developed and released in the tropics and the sub-tropics. Most of these cultivars have been developed through conventional breeding approaches based on the development of crop varieties under optimum soil fertility levels. Nevertheless, it is hardly possible to say that the varietal provisions made by the past approach have been readily accepted, and properly utilized to boost productivity of food legumes grown by resource-poor farmers. The approach itself did not fully appreciate the actual circumstances of the resource-poor farmers where marginal production systems prevail and the poorest farmers could not afford to use cultivars developed under optimum soil fertility level. Therefore, the limitations and strategic implications of past experiences made to develop crop cultivars need to be analyzed in order to formulate better strategies and approaches in the future. The main purpose of this article is to review the efforts made, the technical difficulties associated with the genetic improvement in food legumes as related to plant-nutrient relations, causes of limited breeding success and thereby draw lessons useful to designing future breeding strategies. The scope of nutrient deficiency stress and the approaches to breeding for plant-nutrient relations are discussed and the need for refining the approach and better targeting of the breeding methodologies suggested.     

Genetic diversity analysis of common bean (Phaseolus vulgaris L.) genotypes for resistance to Mexican bean weevil (Zabrotes subfasciatus), using single nucleotide polymorphism and phenotypic markers

ABSTRACT

The objective of this study was to examine the genetic diversity present among 297 common bean genotypes using 2554 SNPs and 12 insects and seed-related traits. The phenotyping was done under laboratory condition while the genotyping was conducted by using the Illumina SNP BeadChip. High phenotypic diversity among traits were recorded, ranging from 0.87 to 0.96, with a mean of 0.92. Principal component and discriminant analyses identi?ed four PCs and three discriminant functions, which explained 82% and 100% of the total phenotypic variations among genotypes, respectively. Polymorphic Information Content ranged from 0.21 to 0.38, with a mean of 0.34. The mean gene diversity among genotypes ranged from 0.24 to 0.50, with a mean of 0.44. Genetic distance ranged from 0.19 to 0.82, with a mean of 0.62, while the phenotypic distance ranged from 0.00 to 1.00, with a mean of 0.64 were observed aamong genotypes. The analysis of molecular variance revealed highly signi?cant differences (p<0.001) among and within individuals and among populations. Both the SNP and the phenotypic markers grouped the 297 genotypes into two major distinct clusters and three sub-clusters. This information is useful for identi?cation and development of common bean germplasm with economically valuable traits and the conservation and utilization of genotypes.     

Efficiency of drained selection environments for improving grain yield in faba bean under undrained target environments on vertisol

Waterlogging is a major constraint of faba bean (Vicia faba L.) production in the highland vertisols of Ethiopia. Genotypes are currently evaluated under both the drained conditions of Broad Bed and Furrow(BBF) and the undrained flatbeds. The objective of this research was to determine if selection of genotypes under BBF is efficient for identification of genotypes for the flatbed conditions. Yields under the flatbed conditions were lower by 20–50% (38% on average) than yields under the BBF. Genetic variation, heritability and predicted genetic gains for grain yield due to direct selection were also lower under the flatbeds than they are under the BBF. There were good levels of genetic correlation (r = 0.20–0.75 or0.45 on average) between yield performances under BBF and flatbeds, indicating that selection under BBF may identify good genotypes for flatbeds and vice versa. There was also high association (r =0.91) between relative yield reduction under flatbeds and the ratio of the predicted genetic gains from indirect selection under BBF to the predicted genetic gains from direct selection under flat beds. This indicates that indirect selection under BBF may be useful to identify better genotypes for flatbed conditions, but the relative efficiency of indirect selection was lower than direct selection under flatbeds themselves. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic diversity in spring faba bean (Vicia faba L.) genotypes as revealed by high-throughput KASP SNP markers

Genetic Resources and Crop Evolution - Faba bean is one of the oldest legume crop grown around the world for its cheap source of protein and for being used in crop rotation with cereals to improve...