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Thesis

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2018 - 20202
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Subject: Agricultural Biotechnology × Author: Amandeep Kaur × Type: Thesis ×
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    QTL Mapping For Terminal Heat Stress Tolerance In Synthetic Hexaploid Wheat Derived Population
    (Punjab Agricultural University, Ludhiana-, 2020) Amandeep Kaur; Satinder Kau
    Common bread wheat (2n=AABBDD) ranks among the primary cereal crop throughout the world and is an allohexaploid evolved from two spontaneous hybridization events followed by spontaneous chromosome doubling. The D-genome of this polyploidy is the least diverse among the three constituting wheat genomes and is unarguably less diverse than that of diploid progenitor Aegilops tauschii (2n=DD). Due to this considerable similarity, Ae. tauschii is extensively used in wheat improvement programs introducing new genetic diversity for various biotic and abiotic traits. A large number for Ae. tauschii accessions are available at Punjab Agricultural University, Ludhiana. Seven of these accessions were used to generate wheat synthetics targeting heat stress tolerance. All of these SHWs performed better than elite cultivars under terminal heat tolerance. Two of these synthetics, Syn14128 and Syn14170 selected on the basis of their better and stable performance under heat stress. These two synthetic wheat were crossed with stripe rust resistant version of two elite wheat varieties PBW343 and HD2967 to generate four nested population of chromosomal segmental substitution lines (CSSLs). CSSLs thus generated, were evaluated for terminal heat tolerance and yield associated traits under timely and late sown conditions. A majority of CSSLs out-performed the checks for different traits like number of effective tillers, ear length, TGW and harvest index, as compared to checks and recurrent parents used in the study. The genotypic performance evaluated using Heat Susceptibility Index (HSI) further suggested that almost 50 percent CSSLs from each set were either highly heat tolerant or moderately heat tolerant. Further, to assess the extent of alien introgressions these lines, genotype-by-sequencing was outsourced and unique SNP from SHW and derived populations were identified. A total of 724 synthetic wheat specific SNPs found in syn14170xHD2967 derived CSSLs while 1546 synthetic specific SNPs were identified in syn14128xPBW343 derived CSSLs. The graphical genotype of SNPs derived from syn14170xHD2967, identified four potential introgressions on chr 2A, 3D, 6D and 7A. Based on yield per plot, harvest index and TGW, 18 out-performing lines had one or more of these introgressions. In CSSLs derived from syn14170xPBW343, two potential introgressions on chr 1B and 5B were found. Based on yield per plot, harvest index and TGW, 15 outperforming lines had introgressions either on chr 1B or 5B. Further to explore the seedling stage heat tolerance in the selected SHW lines, a 35°C heat shock for 12- and 20-hr was given to 4 day old seedlings. A significant variation was observed in the content of MDA, DPPH, total phenols and total flavanols, total sugars and amylase activity along with antioxidant scavenging activities and synthetics better activities of most of these parameters compared to elite and durum wheats. One of the synthetic, Syn14128 had higher amylase activity and better recovery even after a heat shock of 20hrs which was confirmed by the gene expression analysis of α-amylase gene. A better performance of synthetics under both seedling stage and terminal stage heat stress makes them the potential source for the improvement of heat tolerance in the present day wheat cultivars. However, a deep exploration the exotic introgressions in the synthetic derived lines will also help to refine useful exotic chromosome segments for improving various traits and increasing D-genome diversity among cultivated varieties.
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    ThesisItemOpen Access
    INTROGRESSION OF crtRB1 AND LcyE GENES FOR HIGH β-carotene INTO QUALITY PROTEIN MAIZE (QPM)
    (Punjab Agricultural University, Ludhiana, 2018) Amandeep Kaur; Malhotra, Pawan Kumar
    Maize (Zea mays L.) being the queen of cereals deficient in Vitamin A which causes the malnutrition and major health problems. Quality protein maize has enhanced level of the amino acids, lysine, and tryptophan over normal maize varieties. However, QPM varieties are low in provitamin A, a precursor of vitamin A which can lead to vitamin A deficiency in human. In the present investigation, the grain quality of QPM inbred is further enriched for β-carotene by introgressing of crtRB1 and LcyE gene through marker assisted backcross breeding. Rare natural genetic variation of crtRB1 and LcyE gene enhances β-carotene in the kernel by blocking its conversion to further components. Traditional yellow maize though contain high kernel carotenoids, but the concentration of provitamin A is quite low (<1.5µg/g) as compared to the recommended level (15µg/g). Development of biofortified maize enriched in provitamin A, lysine and tryptophan thus holds significant potential in the alleviation of micronutrients. Marker assisted stacking of crtRB1, LcyE and o2 were undertaken in the genetic background of QLM13, inbred of PMH1 hybrid. Foreground selection was carried out using gene-specific primers on BC2F1 population of QLM 13 and background selection was carried out using SSR markers to check the recovery of recurrent parent genome. The plants of favorable alleles (crtRB1 and LcyE) and 88.5-90.1% recurrent parent genome recovery were selected and selfed to generate BC2F2 population. Foreground selection was carried out on BC2F2 population using crtRB1 and LcyE gene-specific markers and plant carrying favorable homozygous allele were selfed to generate BC2F3 progenies. Quality analysis for determination of β-carotene and tryptophan analysis was carried out on BC2F3 progenies. The introgressed BC2F3 progenies possessed a high concentration of provitamin A (1.29–11.75 µg/g) as compared to recurrent parent QLM13 (4.69 µg/g). The selected lines of high beta-carotene and tryptophan content were crossed to reconstitute PMH1 hybrid. Introgressed inbred having contrast for pigmentation in glume base and silk with respective to recurrent parents possess great utility for registration and unambiguous identification in the field.