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Genetic relatedness studies using 12 quantitative traits on 252 genotypes in horsegram revealed wide spectrum of variability for yield components. The genotypes were grouped into 25 clusters based on estimates of D2 statistic. Cluster I had the largest number with 83 genotypes followed by cluster II (77 genotypes), cluster IV (33 genotypes) and cluster III (30 genotypes). On the contrary, 20 solitary clusters from cluster V to XXV were formed except cluster XIV (9 genotypes) which could be given priority for specific trait improvement. Cluster XXI recorded the highest mean value for single plant yield (65.51 g). The intra and inter cluster distance was varying in magnitude indicating the presence of larger genetic diversity among accessions. The highest intra cluster distance was noticed in cluster XIV (23.63) followed by cluster IV (22.37). Maximum inter cluster distance was observed between solitary clusters viz., cluster XXI and XVII followed by cluster XXI and XV and cluster XXI and VII. These clusters would offer superior segregants when employed in hybridization programme.

Increase in global warming poses a severe threat on agricultural production thereby affecting food security. A drastic reduction in yield at elevated temperature is a resultant of several agro-morphological, physiological and biochemical modifications in plants. Heat tolerance is a complex mechanism under polygenic inheritance. Development of tolerant genotypes suited to heat extremes will be more advantageous to tropical and sub tropical regimes. A clear understanding on heat tolerance mechanism is needed for bringing trait based improvement in a crop species. Heat tolerance is often correlated with undesirable traits which limits the economic yield. In addition, high environmental interactions coupled with poor phenotyping techniques limit the progress of breeding programme. Recent advances in molecular technique led to precise introgression of thermo-tolerant genes into elite genetic background which has been reviewed briefly in this chapter.

Horse gram is one of the lesser-known beans widely grown in India. One hundred and twenty-three homozygous horse gram mutants were screened for powdery mildew (PM) disease resistance using the grade 0 to 4. The mutants were grouped based on the disease level of 0 to 2 (resistant) and susceptible (3 to 4). The PM altered the chlorophyll fluorescence (a/b ratio), maturity duration, and yield attributing traits. The yield loss ranged from 4.55% to 72.66%. After affirming the resistance level, the resistant mutant (RM) with minimum yield loss (scale:0) and the susceptible mutant (SM) with maximum loss (scale:4) were used for metabolomic analysis through GC-MS. PM infection induced expression of 66 metabolites representing 32 functional classes. The number of unique classes in RM and SM was 13 and 11, respectively, while eight were common. A fold change in the common metabolites indicated an enhanced accumulation of amine, alcohol, and ester in RM. Along with pathogen-induced defensive metabolites, RM produced silane and fluorene, whose biological significance in disease resistance is unknown. Though SM expressed defence-related bio-molecules, it failed to yield better.

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Horse gram [Macrotyloma uniflorum Lam. (Verdc.)] is an under-utilized legume grown in India. It is a good source of protein, carbohydrates, dietary fiber, minerals, and vitamins. We screened 252 horse gram germplasm accessions for horse gram yellow mosaic virus resistance using the percent disease index and scaling techniques. The percentage values of highly resistant, moderately resistant, moderately susceptible, susceptible, and highly susceptible were 0.34, 13.89, 38.89, 46.43, and 0.34, respectively. Repetitive trials confirmed the host-plant resistance levels, and yield loss was assessed. The present disease index ranged from 1.2 to 72.0 and 1.2 to 73.0 during the kharif and rabi seasons of 2018, respectively. The maximum percent yield loss was noticed in the HS (75.0 –89.4), while HR possessed the minimum (1.2–2.0). The methanolic leaf extracts of highly resistant and highly susceptible genotypes with essential controls were subjected to gas chromatography–mass spectrometry analysis. Differential accumulation of metabolites was noticed, and a total of 81 metabolites representing 26 functional groups were identified. Both highly resistant and susceptible genotypes harbored eight unique classes, while ten biomolecules were common. The hierarchical cluster analysis indicated a distinct metabolite profile. Fold change in the common metabolites revealed an enhanced accumulation of sugars, alkanes, and carboxylic acids in the highly resistant genotype. The principal component analysis plots explained 93.7% of the variation. The metabolite profile showed a significant accumulation of three anti-viral (octadecanoic acid, diphenyl sulfone, and 2-Aminooxazole), one insecticidal (9,10-Secocholesta-5,7,10(19)-triene-3,24,25-triol), one antifeedant (cucurbitacin B), and six metabolites with unknown biological function in the highly resistant genotype.

Aim: The study was conducted to explore the magnitude of variability induced by gamma rays, electron beam and its combinations for quantitative traits in horsegram (Macrotyloma uniflorum (Lam) Verdc.). Methodology: The horsegram cultivar PAIYUR 2 was irradiated with twelve combinations involving G, EB and G+EB. Desirable mutagenic doses were identified in M1 based on plant injuries and forwarded to M2. Data on 11 yield component traits were recorded on normal looking M2 plants for identification of micro-mutants. Promising mutants were forwarded to M3 and the induced variability was ascertained using multivariate statistics. Results: Significant transgressive variants were observed in M2. The G+EB combination induced superior variants for yield. A positive shift in mean for yield and its attributing traits was observed in M3. Most of the polygenic traits were governed by additive gene effects. Interpretation: The increased mean for most of the polygenic traits in M3 population proved that selection made on early generation was highly effective. The isolated high yielding mutant progenies of selected families will contribute towards yield improvement in horsegram.