Insights into the genetic diversity of an underutilized Indian legume, Vigna stipulacea (Lam.) Kuntz., using morphological traits and microsatellite markers.

Vigna stipulacea (Lam.) Kuntz., commonly known as Minni payaru is an underutilized legume species and has a great potential to be utilized as food crop. To evaluate and select the best germplasm to be harnessed in the breeding programme, we assessed the genetic diversity of V. stipulacea (94 accessions) conserved in the Indian National Genebank, based on morphological traits and microsatellite markers. Significant variation was recorded for the morphological traits studied. Euclidean distance using UPGMA method grouped all accessions into two major clusters. Accessions were identified for key agronomic traits such as, early flowering (IC331436, IC251436, IC331437); long peduncle length (IC553518, IC550531, IC553557, IC553540, IC550532, IC553564); and more number of seeds per pod (IC553529, IC622865, IC622867, IC553528). To analyse the genetic diversity among the germplasm 33 SSR primers were used anda total of 116 alleles were detected. The number of alleles varied from two to seven, with an average of 3.52 per loci. The polymorphic information content values varied from 0.20 to 0.74, with a mean of 0.40. The high number of alleles per locus and the allelic diversity in the studied germplasm indicated a relatively wider genetic base of V. stipulacea. Phylogenetic analysis clustered accessions into seven clades. Population structure analysis grouped them into five genetic groups, which were partly supported by PCoA and phylogenetic tree. Besides, PCoA and AMOVA also decoded high genetic diversity among the V. stipulacea accessions. Thus, morphological and microsatellite markers distinguished V. stipulacea accessions and assessed their genetic diversity efficiently. The identified promising accessions can be utilized in Vigna improvement programme through introgression breeding and/or can be used for domestication and enhanced utilization of V. stipulacea.

Genetic diversity and population genetic structure analysis of an extensive collection of wild and cultivated Vigna accessions.

Vigna is a large, pan-tropic and highly variable group of the legumes family which is known for its > 10 cultivated species having significant commercial value for their nutritious grains and multifarious uses. The wild vignas are considered a reservoir of numerous useful traits which can be deployed for introgression of resistance to biotic and abiotic stresses, seed quality and enhanced survival capability in extreme environments. Nonetheless, for their effective utilization through introgression breeding information on their genetic diversity, population structure and crossability is imperative. Keeping this in view, the present experiment was undertaken with 119 accessions including 99 wild Vigna accessions belonging to 19 species and 18 cultivated genotypes of Vigna and 2 of Phaseolus. Total 102 polymorphic SSRs were deployed to characterize the material at molecular level which produced 1758 alleles. The genotypes were grouped into four major clusters which were further sub-divided in nine sub-clusters. Interestingly, all cultivated species shared a single cluster while no such similarities were observed for the wild accessions as these were distributed in different groups of sub-clusters. The co-dominant allelic data of 114 accessions were then utilized for obtaining status of the accessions and their hybrid forms. The model-based population structure analysis categorized 114 accessions of Vigna into 6 genetically distinct sub-populations (K = 6) following admixture-model based simulation with varying levels of admixture. 91 (79.82%) accessions resembled their hierarchy and 23 (20.18%) accessions were observed as the admixture forms. Maximum number of accessions (25) were grouped in sub-population (SP) 6 and the least accessions were grouped in SP3 and SP5 (11 each). The population genetic structure, therefore, supported genetic diversity analysis and provided an insight into the genetic lineage of these species which will help in effective use of germplasm for development of cultivars following selective prebreeding activities.

Cooking fat types alter the inherent glycaemic response of niche rice varieties through resistant starch (RS) formation.

Studies over the decades highlighted the role of lipids in modulating inherent glycaemic response of rice, still much needed to elucidate how the chain length and saturation of fatty acid (FA) influence this. Hence in this study, we investigated the in vitro glycaemic response, starch-lipid complexing ability and resistant starch (RS) formation in three rice types [white rice (WR), black rice (BR) and red rice (RR)] cooked with four fats [ghee, coconut oil (CO), virgin coconut oil (VCO) and rice bran oil (RBO)], with three cooking conditions ('before', 'during' and 'after'). Inherent glycaemic response was found least in RR (81.9%) and among the fats used, RBO rich in long chain unsaturated FA (72.6%) further reduced the least glycaemic response with maximum complexing ability and enriched RS content. Cooking conditions also resulted significant variation in the parameters studied, the most significant effect with complexing ability (28.67%) and RS (2.26%) observed when RBO added 'during' with RR. FTIR fingerprint within 950 to 1200 cm-1 region validated the complex interactions of amylose among FA, alcohols and acids present in the RBO. This is the first report proposing a 'lipid induced resistance towards glycaemic response' model highlighting the importance of FA type towards modulating the molecular configuration, complexing ability and RS-V formation.

Heterochromatin distribution and comparative karyo-morphological studies in Vignaumbellata Thunberg, 1969 and V.aconitifolia Jacquin, 1969 (Fabaceae) accessions.

Chromosome studies along with heterochromatin distribution pattern analysis have been carried out in two domesticated species of Vigna Savi, 1824 which grow in contrasting geo-climatic conditions of India: Vignaumbellata Thunberg, 1969, a legume well acclimatized to subtropical hilly regions of North-east India and Vignaaconitifolia Jacquin, 1969, a species of arid and semi-arid regions in desert plains of Western India. Karyo-morphological studies in both species reveal 2n = 22 chromosomes without any evidence of numerical variation and the overall karyotype symmetry in chromosome morphology suggest that the diversification at intraspecific level in genus Vigna has occurred through structural alteration of chromosomes, rather than numerical changes. Heterochromatin distribution as revealed by fluorochrome binding pattern using CMA3 and DAPI, confirms the occurrence of relatively more GC content in Vignaaconitifolia as compared to Vignaumbellata. However, AT content was found to be comparatively higher in Vignaumbellata which perhaps play a role in species interrelationships.

Heterochromatin characterization through differential fluorophore binding pattern in some species of Vigna Savi.

Heterochromatin regions are the most intensively studied and best known chromosome markers in plants. In Vigna species, blocks of constitutive heterochromatin were found either in the terminal or interstitial region of the chromosomes. The number and distribution of CMA(+) and DAPI(+) binding sites exhibit high chromosomal variability with characteristic unique banding patterns in all the eight taxa. A predominant feature was observed, i.e., most of the CMA(+) binding sites were in the terminal region of the short arm of some chromosomes while DAPI(+) binding sites were found mostly in the intercalary region of the chromosomes. The higher divergence in the heterochromatin blocks, as revealed by chromomycin A3 (CMA) binding pattern, in a few taxa, viz. Vigna glabrescens, Vigna khandalensis, and Vigna mungo, suggests that the processes of divergent evolution of repetitive sequences in genomic DNA involve a guanine-cytosine (GC)-rich region. On the contrary, Vigna dalzelliana had shown a prominent adenine-thymine (AT)-rich repetitive DNA sequence in terminal regions in the short arm of chromosomes while Vigna umbellata had shown in interstitial regions. The presence of prominent heterochromatic-rich regions, either GC- or AT-rich regions, does facilitate the rate of chromosomal rearrangements leading to restructuring of the karyotypes and thereby helping the species to attempt structural alterations as means of speciation.