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2019 - 201912020 - 20211
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Author: Harpreet Kaur × Start date: 2017 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Genome-wide association mapping for Fe, Zn and yield traits in pigeonpea
    (Punjab Agricultural University, Ludhiana, 2021) Harpreet Kaur; Inderjit Singh
    In the present study, an effort was made to understand the complex nature of yield and quality traits and genome-wide association studies (GWAS) was undertaken to identify QTLs associated with traits. The analysis of variance (ANOVA) revealed significant variation among all genotypes in both the years and pooled data. Measurement of skewness and kurtosis indicated presence of duplicate and complementary gene interaction for different traits. The seed yield exhibited highly positive and significant correlation with number of primary branches per plant, number of secondary branches per plant and number of pods per plant for both the years and pooled data across two years. Path analysis identified pods per plant, number of primary and secondary branches as the major contributing traits to grain yield in both the years and pooled data. Yield per plot and pods per plant exhibited high heritability along with high genetic advance showing additive gene effect and could be considered during selection. In genotypic analysis, a total of 7366 filtered SNPs were used for genome-wide association studies through ddRAD-Seq. A total of 30 highly significant associated SNPs in 2018-19, 23 significant associated SNPs in 2019-20 and 25 significant associated SNPs in pooled data were identified through combination of two or more than two models for different traits. Most of the SNP loci were found to be environment and trait specific but few stable and consistent SNPs were identified. Some of the SNPs associated with days to maturity, yield per plot and grain iron content were observed to be consistent in 2018-19 and pooled conditions. The candidate regions were defined by the average LD decay distance or the LD block. Biological function of the identified candidate genes revealed their role in plant growth and development, organogenesis, pollen development and source-sink relationship. These genes were found to be present on chromosome 02, 03 and 09. Three polymorphic KASP markers for traits viz., grain iron content, number of primary branches and yield per plot were validated and showed that parents have homozygous alleles for the traits and alleles were found to be segregating in the F2:3 population. Promising genotypes for grain iron, grain zinc content and yield attributing traits were identified which can be used as donor parents in pigeonpea breeding programme and developed markers can be used in marker assisted selection (MAS) for identifying desirable genotypes having allele of interest.
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    ThesisItemOpen Access
    Contribution of different chemical pools of potassium towards wheat nutrition
    (Punjab Agricultural University, Ludhiana, 2019) Harpreet Kaur; Gill, Roopinder Singh
    The field and pot experiments were conducted to study the effect of potassium (K) application on availability of K to wheat and contribution of exchangeable and non exchangeable K towards wheat nutrition. In pot experiment, twenty bulk soil samples having a range in available K were used and K was applied @ 0, 15, 20, 25 and 30 kg K ha-1soil. Wheat (cv PBW 725) was grown as a test crop. The different potassium fractions i.e. water soluble, exchangeable, available and non exchangeable K were determined. The amount of corresponding forms ranged between 8.86 to 23.7, 66.1 to 379.8, 75.1 to 403.1 and 898.4 to 1861.3 mg kg-1 soil in these soils. The mean grain yield varied from 8.43 to 20.58 g pot-1. All the forms of K showed positive and significant correlation with grain & straw yield, K content and K uptake. The highest positive and significant correlation of wheat grain yield was found to be with water soluble K (r = 0.905*) followed by available K (r = 0.836*), exchangeable K (r = 0.831*) and non exchangeable K (0.815*). In K deficient oils, grain yield of wheat increased significantly with graded levels of applied K. However, in K sufficient soils, grain yield increased significantly up to application of 25 kg K ha-1. In both K deficient and sufficient soils, K concentration and uptake by grain and straw of wheat increased significantly with incremental levels of applied K. About 83.6 per cent variation in grain yield of wheat was due to the combined influence of water soluble and exchangeable potassium while available and non exchangeable form of potassium explained only 2.3 per cent variation in grain yield of wheat. However, in K deficient soils, contribution of non exchangeable K towards grain yield was higher as compared to K sufficient soils. The critical limit of available and non exchangeable potassium for wheat as determined by graphical method was 168 and 1338 kg K ha-1, respectively. The field experiment was conducted at two sites, at the Research Farm of Department of Soil Science, Punjab Agricultural University (PAU), Ludhiana (medium in available potassium i.e. 228.9 kg ha-1) and at Regional Research Station, Gurdaspur (low in available potassium i.e. 125.6 kg ha-1). The K was applied @ 0, 10, 15, 20, 25, 30, 35 and 40 kg K ha-1 soil and wheat (cv PBW 725) was grown as test crop. The mean grain yield in PAU, Ludhiana and RRS, Gurdaspur soil was found 47.5 and 42.5 q ha-1, respectively. In PAU, Ludhiana soil, the significant response of wheat to applied potassium was recorded up to 25 kg K ha-1 soil, however, in RRS, Gurdaspur soil response was recorded up to 40 kg K ha-1. The water soluble, exchangeable, available and non exchangeable K were found to be 13.8, 75.9, 84.5 and 1053.6 mg kg-1 soil, respectively in PAU, Ludhiana soil and 10.1, 61.1, 70.5 and 969.7 mg kg-1 soil, respectively, in RRS, Gurdaspur soil. The kinetics of non-exchangeable K release from ten bulk soil samples having a range in available K was investigated using 0.01 M oxalic acid. The cumulative amount of K released in 200 h ranged between 86 and 253 cmol kg-1 x 10-2. The highest amount of non exchangeable K release (253 cmol kg-1 x 10-2) was found in Mansa soil (sufficient in K) and lowest amount (86 cmol kg-1 x 10-2) was recorded in Gurdaspur soil (deficient in K). Kinetics of non exchangeable K release from soils were adequately described by Elovich, first order, power function and parabolic diffusion models while zero order model was not suitable to describe K release.