Identification of maker-trait associations for yield and drought tolerance in greengram (Vigna radiata) using SSR markers

Abstract

The study entitled “Identification of marker-trait associations for yield and drought tolerance in greengram (Vigna radiata) using SSR Markers” was conducted at the Department of Genetics and Plant Breeding, College of Agriculture, Vellayani during 2022-2024 with an objective of assessing genetic diversity among greengram accessions for yield and drought tolerance using SSR markers to identify superior climate resilient genotypes. The research programme encompassed of three experiments. In the first experiment, drought tolerance of 50 greengram genotypes was evaluated under laboratory and pot conditions using polyethylene glycol (PEG) 6000 treatments and controlled water stress. Morpho-physiological and biochemical traits were assessed, revealing significant differences in drought tolerance indicators among the genotypes. High heritability and genetic advance were observed for all the characters studied except seedling shoot length, root-shoot ratio and total chlorophyll. Correlation and path analysis revealed strong positive relationship between root traits and proline content, emphasizing its importance in drought tolerance. The genotypes were categorized based on germination drought tolerance index and root length drought tolerant index values as highly susceptible, susceptible, moderately susceptible, moderately tolerant and tolerant. Andhra local, ML 1415, Co 8, C4 PDM 139 and VBN 5 emerged as promising candidates for drought tolerance based on both the drought tolerance indices. In Experiment II, a field trial was conducted from June to September 2024 to evaluate yield-related traits in 40 selected genotypes, using Randomized Block Design (RBD) in three replications. The genotypes were evaluated for various biometric and biochemical traits and significant differences were observed for all the traits. The study found high heritability coupled with high genetic advance for traits such as the number of primary branches, plant height, number of pods per plant, individual pod weight, hundred seed weight and seed yield per plant, highlighting the strong potential of these genotypes for yield improvement. A significant positive correlation was shown by number of pods 178 per plant, number of seeds per pod, pod length, individual pod weight and hundred seed weight with seed yield per plant. Path coefficient analysis also revealed that the number of pods per plant had the highest direct effect on seed yield per plant followed by pod length, individual pod weight and hundred seed weight. The genetic divergence analysis grouped the 40 genotypes into six clusters based on biometric and biochemical traits indicating high diversity between the clusters. Cluster I, with 17 genotypes was the highest and included the identified drought-tolerant genotypes, while Clusters II, with 15 genotypes and cluster V, with 3 genotypes were characterized by high-yielding genotypes. Discriminant function analysis further validated the selection, and based on the selection index value the genotypes IPM 2057, Kozhikode local, Kayamkulam local, Co GG 912 and EC 398884 were identified as high yielding superior genotypes. In Experiment III, SSR markers were used to genotype 50 greengram accessions, with seven of ten markers revealing polymorphism. Out of the 10 markers, CEDG 014 produced highest percentage of polymorphism information content (PIC) value, while CEDG 008 produced the lowest. The Jaccard's similarity coefficient was computed utilizing the DNA banding patterns derived from the selected greengram genotypes and polymorphic SSR markers. The greengram genotypes were categorized into two distinct clusters based on their genotypic data: cluster one comprised of single genotype, cluster two included majority genotypes. The cluster 2 was again divided into 2 sub-clusters, in which the sub-cluster 2 comprises the identified drought tolerant and superior high yielding greengram genotypes. The study revealed, the genotypes, Andhra local, Co 8, ML 1415, C4 PDM 139 and VBN 5 as drought tolerant superior genotypes while, IPM 2057, Kozhikode local, Kayamkulam local, Co GG 912 and EC 398884 as high yielding superior genotypes. The genotypes Kozhikode local and Kayamkulam local were found to be moderately tolerant to drought and high yielding. The clustering of the genotypes using SSR markers also grouped them into a single cluster. The superior genotypes identified can be 179 recommended for future hybridization programmes as parents to develop a variety with high yield and drought tolerance in greengram.The research programme encompassed of three experiments. In the first experiment, drought tolerance of 50 greengram genotypes was evaluated under laboratory and pot conditions using polyethylene glycol (PEG) 6000 treatments and controlled water stress. Morpho-physiological and biochemical traits were assessed, revealing significant differences in drought tolerance indicators among the genotypes. High heritability and genetic advance were observed for all the characters studied except seedling shoot length, root-shoot ratio and total chlorophyll. Correlation and path analysis revealed strong positive relationship between root traits and proline content, emphasizing its importance in drought tolerance. The genotypes were categorized based on germination drought tolerance index and root length drought tolerant index values as highly susceptible, susceptible, moderately susceptible, moderately tolerant and tolerant. Andhra local, ML 1415, Co 8, C4 PDM 139 and VBN 5 emerged as promising candidates for drought tolerance based on both the drought tolerance indices. In Experiment II, a field trial was conducted from June to September 2024 to evaluate yield-related traits in 40 selected genotypes, using Randomized Block Design (RBD) in three replications. The genotypes were evaluated for various biometric and biochemical traits and significant differences were observed for all the traits. The study found high heritability coupled with high genetic advance for traits such as the number of primary branches, plant height, number of pods per plant, individual pod weight, hundred seed weight and seed yield per plant, highlighting the strong potential of these genotypes for yield improvement. A significant positive correlation was shown by number of pods 178 per plant, number of seeds per pod, pod length, individual pod weight and hundred seed weight with seed yield per plant. Path coefficient analysis also revealed that the number of pods per plant had the highest direct effect on seed yield per plant followed by pod length, individual pod weight and hundred seed weight. The genetic divergence analysis grouped the 40 genotypes into six clusters based on biometric and biochemical traits indicating high diversity between the clusters. Cluster I, with 17 genotypes was the highest and included the identified drought-tolerant genotypes, while Clusters II, with 15 genotypes and cluster V, with 3 genotypes were characterized by high-yielding genotypes. Discriminant function analysis further validated the selection, and based on the selection index value the genotypes IPM 2057, Kozhikode local, Kayamkulam local, Co GG 912 and EC 398884 were identified as high yielding superior genotypes. In Experiment III, SSR markers were used to genotype 50 greengram accessions, with seven of ten markers revealing polymorphism. Out of the 10 markers, CEDG 014 produced highest percentage of polymorphism information content (PIC) value, while CEDG 008 produced the lowest. The Jaccard's similarity coefficient was computed utilizing the DNA banding patterns derived from the selected greengram genotypes and polymorphic SSR markers. The greengram genotypes were categorized into two distinct clusters based on their genotypic data: cluster one comprised of single genotype, cluster two included majority genotypes. The cluster 2 was again divided into 2 sub-clusters, in which the sub-cluster 2 comprises the identified drought tolerant and superior high yielding greengram genotypes. The study revealed, the genotypes, Andhra local, Co 8, ML 1415, C4 PDM 139 and VBN 5 as drought tolerant superior genotypes while, IPM 2057, Kozhikode local, Kayamkulam local, Co GG 912 and EC 398884 as high yielding superior genotypes. The genotypes Kozhikode local and Kayamkulam local were found to be moderately tolerant to drought and high yielding. The clustering of the genotypes using SSR markers also grouped them into a single cluster. The superior genotypes identified can be 179 recommended for future hybridization programmes as parents to develop a variety with high yield and drought tolerance in greengram.