M. Byre Gowda

Genetic diversity within Lablab purpureus and the application of gene-specific markers from a range of legume species

Molecular markers have been used to study genetic diversity within a set of Lablab purpureus accessions collected from the southern states of India. Amplified fragment length polymorphism (AFLP) molecular marker studies using a total of 78 L. purpureus accessions with nine primer combinations showed there was very little genetic diversity within the L. purpureus accessions from the southern Indian germplasm collection as compared to a set of 15 accessions from other international germplasm collections that included African accessions. The set of 15 were selected from a random amplified length polymorphism (RAPD) marker study and chosen on the basis of widest genetic distance. Further molecular analysis with polymerase chain reaction (PCR) markers from 97 expressed sequence tag (EST) and genespecific primer pairs, designed from a range of legume sequences, concurred with the AFLP analyses. Both of these approaches provide a wealth of markers for diversity and mapping studies. The 97 sequence-specific primer pairs tested in L. purpureus resulted in 70% amplification success, with 44% of primer pairs amplifying single bands and 10% double bands. Markers generated from these EST and genomic sequences provide useful cross-reference to comparative legume genomics that will potentially have long-term benefit to legume plant breeding.

Development of Core Sets of Dolichos Bean (Lablab purpureus L. Sweet) Germplasm

Development of a reduced representative set of a large base collection enables greater use of genetic resources in crop improvement programs. Efficiency of standard stratified clustering (SSC) and heuristic approaches were compared for developing core sets of Dolichos bean from a base collection of 648 accessions on the basis of data on 21 qualitative and 20 quantitative traits. The SSC approach with a combination of two core sizes (10% and 15%), two sampling strategies (proportional and logarithmic), and two allocation strategies (random and preferred) were used to develop eight core sets. Two additional core sets of 10% and 15% sizes were developed following a heuristic approach. Similarity of classes on the basis of qualitative traits of 10 core sets with the base collection was examined using Chi-square test, Shannon-Weaver diversity index, and ‘class coverage’ statistics. Univariate statistics, based on quantitative traits, such as mean and variance and multivariate statistics, standardized mean difference (SMD %), coincidence ratio (CR %), variance difference (VD %), and variable difference (VR %) were also used to assess the representativeness of core sets. Heuristic approach-based core sets retained higher CR%, VD%, and VR% based on quantitative traits. The study suggested that core sets developed based on heuristic method are better than those developed based on SSC approach relative to their representativeness of the base collection.

Development and Validation of a Core Set of Dolichos Bean Germplasm

Increased use of genetic resources is necessary to sustain crop improvement. Large numbers of germplasm entries and possible existence of duplicate/redundant accessions are impediments to effective management, evaluation, and utilization. A core collection is a limited set of accessions chosen to represent the maximum genetic spectrum with minimum redundancy of the existing germplasm collection. Six hundred forty-four indigenous and exotic germplasm accessions of Dolichos bean [Lablab purpureus (L.) Sweet] and four check entries were characterized for 21 qualitative traits and evaluated for 20 quantitative traits at the University of Agricultural Sciences, Bangalore, India, during the 2012 rainy season. A core set of size 10% (n = 64 accessions) was developed using software that applies advanced M-strategy with a heuristic search. The core set was examined for its representativeness of the base collection for both qualitative and quantitative traits using univariate and multivariate statistics. The core set retained more than 90% of quantitative traits variability and polymorphism of qualitative traits. The core set is suggested for evaluation across target production environments and years to identify widely/specifically adapted and stable accessions to foster enhanced access and use of Dolichos bean germplasm.

Identification of AFLP markers linked to Fusarium wilt disease in pigeonpea [Cajanus cajan (L.) Millsp.]

An experiment was conducted to identify markers linked to Fusarium wilt disease resistance, Parents namely TTB 7 and ICP 8863 were screened using 151 SSRs markers and 16 AFLP primer combinations. Parental screening revealed five SSR primers and 12 AFLP primer combinations polymorphic between parents. Bulk segregant analysis identified five AFLP primer combinations generating seven markers polymorphic between resistant and susceptible bulks while, none of the SSR markers were polymorphic. This indicates that, these markers are putatively linked to wilt disease. Screening of F2 segregating population of cross TTB 7 x ICP 8863 with these putatively linked markers revealed four markers (E-AAT/M-CTG850, ETCG/M-CTT650, E-TCG/M-CTA730 and E-TCG/M-CTT230) which segregated in 3:1 mendelian pattern. Simple linear regression performed on these four markers had identified two markers namely E-TCG/M-CTT650 and E-TCG/M-CTA730 linked to disease.

Wide Crossing Technology for Pigeonpea Improvement

Pigeonpea (Cajanus cajan Millsp,) has ample genetic and genomic information now. It is endowed with rich germplasm in different gene pools. One of the easiest material to use in those are in the primary gene pool, which are closely related to cultivated pigeonpea. It is observed that species placed beyond the primary gene pool are a rich source of genetic variation. They contribute beneficial traits to pigeonpea such as pest or disease resistance, resistance to abiotic stresses, cytoplasmic male sterile systems (CMS) leading to yield improvement, and some novel traits such as homozygous pigeonpea lines. To effectively utilize the immense variation present in the secondary, tertiary, and quaternary gene pool of pigeonpea, a thorough knowledge of crossability and concerted effort is essential.

Identification of Trait-Specific Accessions from a Core Set of Dolichos Bean Germplasm

ABSTRACT A core set of crop genetic resources are considered “first-look-sources” of trait-specific accessions for use in crop-breeding programs. Sixty-four core germplasm accessions of dolichos bean (Lablab purpureus L. Sweet Var. Lignosus) and two check entries were characterized/evaluated for five qualitative traits and seven quantitative traits at the University of Agricultural Sciences (UAS), Bengaluru, India, during the rainy seasons of 2012 and 2014. Substantial variability among the accessions for quantitative traits and polymorphism for qualitative traits were documented. The germplasm accessions could be grouped into six clusters following model-based K-means clustering approach. The quantitative trait means and variances of accessions distributed among the clusters differed significantly. The accessions superior for six productivity traits were identified. The accessions, such as GL 142, GL 527, GL 110, GL 447, GL 576, KA, FPB-35, GL 441, GL 12, and GL 66, were promising for multiple quantitative traits and also for farmer- and consumer-preferred qualitative traits. Results are discussed in relation to suitable strategies to be adopted for breeding dolichos bean for improved productivity. One of the strategies could be to use identified trait-specific accessions in generating variability by recombining them with elite breeding genotypes followed by selection for economically important traits.