Browsing by Author "Kumar, Naveen"

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    Leveraging genomic mapping and QTL analysis to enhance drought tolerance of cultivated peanut (Arachis hypogaea L.)
    Kumar, Naveen (Virginia Tech, 2022-09-19)
    Peanut (Arachis hypogaea L.) is second major legume crop grown after soybean in the United States, and its productivity is often limited by drought stress. Drought negatively impacts the yield and quality of peanut. Drought stress in peanut causes an annual loss of approximately $520 million in the United States. Improving peanut yield under water deficit conditions is crucial for peanut growers to maintain their profitability in the market. To achieve this, it is essential to either breed or adopt already available drought tolerant cultivars that can produce higher yield under water deficit conditions. Therefore, the objectives of this research were to (1) evaluate five commercially available virginia and runner type peanut cultivars for pod yield stability using multilocation trials by studying G x E interaction across 13 environments including year, location, and irrigation regime. Linn and Binns, AMMI, Shukla, Wricke's, Finlay and Wilkinson stability models were used to determine pod yield stability. Bailey and Sullivan showed higher stability and adaptability across all stability indices whereas Wynne and TUFRunner presented high mean productivity with lesser stability across environments reflecting specific adaptation to just a few environments. Bailey and Sullivan are recommended for sustainable production across the growing region of Virginia and Carolinas. The second objective (2) was identification of drought tolerance related quantitative trait loci (QTL) and genetic markers to facilitate the development of drought tolerant cultivars. Three diverse recombinant inbred line (RIL) populations, derived from crossing lines N05006 x N04074FCT (Pop-1), line N05006 x Phillips, an old virginia-type cultivar (Pop-2), and lines N08086olJCT x PI 585005 (Pop-3) were phenotyped for the Normalized Difference Vegetation Index (NDVI), Canopy Temperature Depression (CTD), SPAD-meter relative chlorophyll content of the leaves (SPAD) and wilting for QTL mapping. Mapping identified 27 minor QTL on eight chromosomes for all physiological characteristics, i.e NDVI, CTD, SPAD and wilting, with logarithmic of odds values ranging from 2.5 to 38.5 and the phenotypic variance explained by these traits from 1.04 to 11.46 %. There were 4 loci on chromosome 2 associated with NDVI in Pop-1 and Pop-3, explaining 1.8 to 10.38% of the phenotypic variation. These genomic regions may be important resources in peanut breeding programs to improve drought tolerance. Further research is needed to increase the marker density in order to fine map the identified QTL and validate markers linked with these regions.
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    Multilocation Evaluation of Virginia and Runner-Type Peanut Cultivars for Yield and Grade in Virginia-Carolina Region
    Kumar, Naveen; Haak, David C.; Dunne, Jeffrey C.; Balota, Maria (MDPI, 2022-12-16)
    The peanut is mostly grown in semi-arid tropical regions of the world, characterized by unpredictable rainfall amounts and distribution. Average annual precipitation in the Virginia–Carolina (VC) region is around 1300 mm; however, unpredictable distribution can result in significant periods of water deficit and subsequent reduction in yield and gross income. The development of new peanut cultivars with high yield and acceptable levels of yield stability across various water-availability scenarios is an important component of the peanut breeding program in Virginia and the Carolinas, where the large-seeded Virginia-type peanut is the predominantly grown market type. In addition, the simultaneous use of runner cultivars developed in the dryer southeastern region has been proposed as a practical solution to limited irrigation availability in the VC region. Still, the identification and adequate utilization of available commercial cultivars with the best combination of yield, drought tolerance, and gross income is more immediately beneficial to the peanut industry, yet this assessment has not been carried out to date. The aim of this study was to identify cultivars that maintain high yield and grade, therefore gross income, across a wide range of environmental conditions. We evaluated five commercially available Virginia and runner-type peanut cultivars for pod yield stability using multilocation trials over four years across 13 environments. Additive main effects and multiplicative interaction (AMMI) and different stability approaches were used to study genotype (G), environment (E), and their interaction (G × E) on pod yield. Pod yield stability was specifically assessed by using the Lin and Binn approach, Wricke’s ecovalence, Shukla’s stability, and the Finlay–Wilkinson approach. The combined analysis of variance showed highly significant effects (p ≤ 0.001) for genotypes, environments, and G × E for pod yield. The environments varied in yield (2840–8020 kg/ha). Bailey, Sullivan, and Wynne are Virginia-type cultivars. The grade factors SMK, SS, and TK changed with water regime within both market types. Among the runner cultivars, TUFRunner 297 presented high mean productivity; however, it showed specific adaptation to limited environmental conditions. Based on different stability approaches, this study concludes that Sullivan and Bailey are the most stable and adaptable cultivars across the testing environments, whereas Wynne exhibited specific adaptability to some environments. These findings have important implications for peanut cultivar recommendations in terms of meeting peanut industry standards for yield, grading quality, and breeding progress.
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    Phenotypic Dissection of Drought Tolerance in Virginia and Carolinas within a Recombinant Inbred Line Population Involving a Spanish and a Virginia-Type Peanut Lines
    Kumar, Naveen; Haak, David C.; Dunne, Jeffrey C.; Balota, Maria (MDPI, 2024-06-08)
    Peanut (Arachis hypogaea L.) is a rainfed crop grown in both tropical and subtropical agro-climatic regions of the world where drought causes around 20% yield losses per year. In the United States, annual losses caused by drought are around $50 million. The objective of this research was to (1) identify genetic variation for the normalized difference vegetation index (NDVI), canopy temperature depression (CTD), relative chlorophyll content by SPAD reading (SCMR), CO2 assimilation rate, and wilting among recombinant inbred lines (RILs) derived from two diverse parents N08086olJCT and ICGV 86015, to (2) determine if the physiological traits can be used for expediting selection for drought tolerance, and (3) experimental validation to identify lines with improved yield under water-limited conditions. Initially, 337 lines were phenotyped under rainfed production and a selected subset of 52 RILs were tested under rainout shelters, where drought was imposed for eight weeks during the midseason (July and August). We found that under induced drought, pod yield was negatively correlated with wilting and CTD, i.e., cooler canopy and high yield correlated positively with the NDVI and SPAD. These traits could be used to select genotypes with high yields under drought stress. RILs #73, #56, #60, and #31 performed better in terms of yield under both irrigated and drought conditions compared to check varieties Bailey, a popular high-yielding commercial cultivar, and GP-NC WS 17, a drought-tolerant germplasm.