Browsing by Author "Shikha, Kumari"

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    Genetic gains in tropical maize hybrids across moisture regimes with multi-trait-based index selection
    (Frontiers Media S.A., 2023) Singamsetti, Ashok; Zaidi, Pervez H.; Seetharam, Kaliyamoorthy; Vinayan, Madhumal Thayil; Olivoto, Tiago; Mahato, Anima; Madankar, Kartik; Kumar, Munnesh; Shikha, Kumari
    Unpredictable weather vagaries in the Asian tropics often increase the risk of a series of abiotic stresses in maize-growing areas, hindering the efforts to reach the projected demands. Breeding climate-resilient maize hybrids with a cross-tolerance to drought and waterlogging is necessary yet challenging because of the presence of genotype-by-environment interaction (GEI) and the lack of an efficient multi-trait-based selection technique. The present study aimed at estimating the variance components, genetic parameters, inter-trait relations, and expected selection gains (SGs) across the soil moisture regimes through genotype selection obtained based on the novel multi-trait genotype�ideotype distance index (MGIDI) for a set of 75 tropical pre-released maize hybrids. Twelve traits including grain yield and other secondary characteristics for experimental maize hybrids were studied at two locations. Positive and negative SGs were estimated across moisture regimes, including drought, waterlogging, and optimal moisture conditions. Hybrid, moisture condition, and hybrid-by-moisture condition interaction effects were significant (p ? 0.001) for most of the traits studied. Eleven genotypes were selected in each moisture condition through MGIDI by assuming 15% selection intensity where two hybrids, viz., ZH161289 and ZH161303, were found to be common across all the moisture regimes, indicating their moisture stress resilience, a unique potential for broader adaptation in rainfed stress-vulnerable ecologies. The selected hybrids showed desired genetic gains such as positive gains for grain yield (almost 11% in optimal and drought; 22% in waterlogging) and negative gains in flowering traits. The view on strengths and weaknesses as depicted by the MGIDI assists the breeders to develop maize hybrids with desired traits, such as grain yield and other yield contributors under specific stress conditions. The MGIDI would be a robust and easy-to-handle multi-trait selection process under various test environments with minimal multicollinearity issues. It was found to be a powerful tool in developing better selection strategies and optimizing the breeding scheme, thus contributing to the development of climate-resilient maize hybrids. Copyright � 2023 Singamsetti, Zaidi, Seetharam, Vinayan, Olivoto, Mahato, Madankar, Kumar and Shikha.
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    Genome-wide association mapping in maize: status and prospects
    (Springer Science and Business Media Deutschland GmbH, 2021) Shikha, Kumari; Shahi, J.P.; Vinayan, M.T.; Zaidi, P.H.; Singh, A.K.; Sinha, B.
    Genome-wide association study (GWAS) provides a robust and potent tool to retrieve complex phenotypic traits back to their underlying genetics. Maize is an excellent crop for performing GWAS due to diverse genetic variability, rapid decay of linkage disequilibrium, availability of distinct sub-populations and abundant SNP information. The application of GWAS in maize has resulted in successful identification of thousands of genomic regions associated with many abiotic and biotic stresses. Many agronomic and quality traits of maize are severely affected by such stresses and, significantly affecting its growth and productivity. To improve productivity of maize crop in countries like India which contribute only 2% to the world�s total production in 2019�2020, it is essential to understand genetic complexity of underlying traits. Various DNA markers and trait associations have been revealed using conventional linkage mapping methods. However, it has achieved limited success in improving polygenic complex traits due to lower resolution of trait mapping. The present review explores the prospects of GWAS in improving yield, quality and stress tolerance in maize besides, strengths and challenges of using GWAS for molecular breeding and genomic selection. The information gathered will facilitate elucidation of genetic mechanisms of complex traits and improve efficiency of marker-assisted selection in maize breeding. � 2021, King Abdulaziz City for Science and Technology.
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    Genomic-regions associated with cold stress tolerance in Asia-adapted tropical maize germplasm
    (Nature Research, 2023) Shikha, Kumari; Madhumal Thayil, Vinayan; Shahi, J.P.; Zaidi, P.H.; Seetharam, Kaliyamoorthy; Nair, Sudha K; Singh, Raju; Tosh, Garg; Singamsetti, Ashok; Singh, Saurabh; Sinha, B.
    Maize is gaining impetus in non-traditional and non-conventional seasons such as off-season, primarily due to higher demand and economic returns. Maize varieties directed for growing in the winter season of South Asia must have cold resilience as an important trait due to the low prevailing temperatures and frequent cold snaps observed during this season in most parts of the lowland tropics of Asia. The current study involved screening of a panel of advanced tropically adapted maize lines to cold stress during vegetative and flowering stage under field conditions. A suite of significant genomic loci (28) associated with grain yield along and agronomic traits such as flowering (15) and plant height (6) under cold stress environments. The haplotype regression revealed 6 significant haplotype blocks for grain yield under cold stress across the test environments. Haplotype blocks particularly on chromosomes 5 (bin5.07), 6 (bin6.02), and 9 (9.03) co-located to regions/bins that have been identified to contain candidate genes involved in membrane transport system that would provide essential tolerance to the plant. The regions on chromosome 1 (bin1.04), 2 (bin 2.07), 3 (bin 3.05�3.06), 5 (bin5.03), 8 (bin8.05�8.06) also harboured significant SNPs for the other agronomic traits. In addition, the study also looked at the plausibility of identifying tropically adapted maize lines from the working germplasm with cold resilience across growth stages and identified four lines that could be used as breeding starts in the tropical maize breeding pipelines. � 2023, The Author(s).
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    Genotype � environment interaction and selection of maize (Zea mays L.) hybrids across moisture regimes
    (Elsevier B.V., 2021) Singamsetti, Ashok; Shahi, J.P.; Zaidi, P.H.; Seetharam, K.; Vinayan, M.T.; Kumar, Munnesh; Singla, Saurav; Shikha, Kumari; Madankar, Kartik
    Genotype � environment (GE) interaction effect is one of the major challenges in identifying cultivars with stable performance across environments and years. Objective of the present study was to identify maize hybrids with high and stable yields under different soil moisture regimes such as drought, waterlogged and well-watered conditions. The trials were carried out in subsequent winter (Rabi) and summer-rainy (Kharif) seasons of 2017 and 2018 totaling seven test environments at the two different locations of India viz, Banaras Hindu University, Varanasi and CIMMYT, Hyderabad. After observing substantial and statistically significant GE interaction for studied traits, the phenotypic stability of maize hybrids was analyzed by AMMI, GGE biplot and multi-trait stability index (MTSI) methods. The study emphasized on the significance of AMMI and GGE biplots in deciphering the GE interactions based on grain yield data. Estimation of stability indices, WAASB (Weighted Average of Absolute Scores from the singular value decomposition of the matrix of BLUPs) for the GE interaction effects and WAASBY (a combination of WAASB and yield) scores for identification of the best suitable genotypes with high stability and maximum yield potential was highlighted. The investigation delineated the applicability of MTSI that computed based on the genotype-ideotype distance considering the multiple variables. The methods studied were concordant in the identification of the promising maize hybrids with high mean performance and greater phenotypic stability across the different soil moisture conditions. � 2021 Elsevier B.V.
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    Hybrids and abiotic stress tolerance in horticultural crops
    (Elsevier, 2021) Singh, Anil Kumar; Shikha, Kumari; Shahi, Jai Prakash
    Horticultural crops need more attention in cultivation due to their organoleptic and nutritional properties. Abiotic stresses such as drought, flood, heat, cold, salinity, nutrient deficiency, and heavy metal stress strongly impair the growth and productivity of horticultural crops. Further, climate change has also increased the risk of abiotic stresses and affects the growth and quality of the crops. It is imperative to understand the mechanism underlying abiotic stress tolerance in different crop species as tolerant plants may switch on or off different physiological or biochemical pathways to acclimatize or to overcome the unfavorable effect of abiotic stresses. Potential for tolerance and susceptibility to a specific abiotic stress vary in different crop species. Even some wild relatives and exotic germplasms are carriers of abiotic stress-tolerant genes or QTLs that can be employed to develop resistant hybrids by incorporating such genes into susceptible cultivars. The development of smart climate-resilient hybrids is one of the best alternatives to lessen the losses due to abiotic stresses. Classical breeding alone does not suffice to meet the needs of abiotic stress-tolerant hybrids. There is a need to utilize the untapped potential of modern plant breeding strategies, say double haploid technology, transgenic methods, somaclonal variation, somatic hybridization, marker-assisted backcrossing breeding, genome-wide association studies, and genomic selection to develop hybrids with improved performance and resistance against abiotic stress. In this chapter, we have tried to emphasize the importance of hybrids to tolerate abiotic stresses and the mechanism of abiotic stress tolerance in horticultural crops. � 2021 Elsevier Inc.
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    Rust (Uromyces viciae-fabae Pers. de-Bary) of Pea (Pisum sativum L.): Present Status and Future Resistance Breeding Opportunities
    (MDPI, 2023) Singh, Anil Kumar; Kushwaha, Chanda; Shikha, Kumari; Chand, Ramesh; Mishra, Gyan P.; Dikshit, Harsh Kumar; Devi, Jyoti; Aski, Muraleedhar S.; Kumar, Shiv; Gupta, Sanjeev; Nair, Ramakrishnan M.
    Uromyces viciae-fabae Pers. de-Bary is an important fungal pathogen causing rust in peas (Pisum sativum L.). It is reported in mild to severe forms from different parts of the world where the pea is grown. Host specificity has been indicated in this pathogen in the field but has not yet been established under controlled conditions. The uredinial states of U. viciae-fabae are infective under temperate and tropical conditions. Aeciospores are infective in the Indian subcontinent. The genetics of rust resistance was reported qualitatively. However, non-hypersensitive resistance responses and more recent studies emphasized the quantitative nature of pea rust resistance. Partial resistance/slow rusting had been described as a durable resistance in peas. Such resistance is of the pre-haustorial type and expressed as longer incubation and latent period, poor infection efficiency, a smaller number of aecial cups/pustules, and lower units of AUDPC (Area Under Disease Progress Curve). Screening techniques dealing with slow rusting should consider growth stages and environment, as both have a significant influence on the disease scores. Our knowledge about the genetics of rust resistance is increasing, and now molecular markers linked with gene/QTLs (Quantitative Trait Loci) of rust resistance have been identified in peas. The mapping efforts conducted in peas came out with some potent markers associated with rust resistance, but they must be validated under multi-location trails before use in the marker-assisted selection of rust resistance in pea breeding programs. � 2023 by the authors.