Browsing by Author "Sharma, Megha et al"

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    Genotypic characterization on the basis of chilling requirement in apple (Malus × domestica Borkh.) using simple sequence repeat (SSR) markers
    (Springer, 2026-06-03) Tiwari, Madhuri; Sharma, Rajnish; Sharma, Megha et al
    Molecular characterization was performed using simple sequence repeat (SSR) markers among apple (Malus × domestica Borkh.) cultivars categorized based on the chilling requirement in this study. In total, 191 alleles, with an average of 3.47 per locus, were revealed utilizing 55 informative polymorphic SSR primers among the 84 total SSRs initially screened. The mean per cent polymorphism was obtained to be 96.21 in the characterized cultivars, with an average number of monomorphic (0.13) and polymorphic (3.35) bands. The mean polymorphic information content, effective multiplex ratio, Shannon index, expected heterozygosity value, observed heterozygosity, observed allele number, effective allele number, marker index, and resolving power were 0.65, 3.26, 0.93, 0.61, 0.84, 2.93, 2.45, 2.19, and 4.23, respectively. The similarity coefficient range was 0.26–0.96. The population structure showed an admixture of two genetic pools in the examined cultivars. Cluster analysis divided the subjected apple cultivars into two major clusters: the first cluster of high-chilling cultivars, while the second cluster of mid-chilling and low-chilling cultivars. The present study inferred clear and distinct characterization of low, mid, and high chilling cultivars using SSR markers that confirms the standard classification in accordance with the available literature. Hence, the results so obtained will serve as a base for further research towards developing trait-specific markers and to unfold the genetic base behind varied chilling requirements in apples.
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    High-resolution QTL mapping of horticultural traits in muskmelon (Cucumis melo L.) using genotyping-by-sequencing
    (Springer, 2026-04-16) Kaur, Anroop; Sharma, Megha et al
    Muskmelon (Cucumis melo L.) is an economically and nutritionally important vegetable crop with significant genetic variability. Fruit traits significantly influence consumer preference and market value, with most quality parameters governed by multiple genes and influenced by environmental factors. High-resolution quantitative trait loci (QTL) mapping can elucidate the genetic basis of these traits, facilitating marker-assisted breeding. In this study, QTL mapping was performed for melon quality traits using an F2:4 population of 110 individuals derived from a cross between muskmelon variety Punjab Sunehri and Snap melon accession SM2012-1. The F4 population was phenotyped during the spring and rainy seasons of 2023. A genetic linkage map was constructed using the Genotyping-by-Sequencing (GBS) approach, comprising 13 linkage groups and 1962 single nucleotide polymorphism (SNP) markers. Nine horticultural traits were evaluated: days to first male flower appearance, fruit maturity, fruit weight, fruit length, fruit width, flesh thickness, fruit cavity length, cavity width and total soluble solids. QTLs were identified across both seasons on chromosomes 1, 2, 3, 5, 9, 10, and 12, explaining 7–71% of the phenotypic variance (PVE), with logarithm of odds (LOD) scores ranging from 2.6 to 8.7. Notably, overlapping QTLs for fruit weight, fruit length, and fruit maturity were consistently detected at the same positions on chromosomes 3 and 9 in both seasons. These results provide valuable insights for fine-mapping of QTLs and support the integration of marker-assisted selection (MAS) in melon breeding programs.