1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Marker assisted backcross breeding in rice variety jyothi for drought tolerance(Centre for Plant Biotechnology and Molecular Biology, College of Agriculture, Vellanikkara, 2024-01-03) Shankar, C.; Abida, P SDrought is one of the important abiotic stressors that can substantially reduce rice production by 35 - 40 per cent. Water stress will significantly impact the growth and development of rice crops, but drought at the reproductive stage will directly affect the grain yield. In 2018, the State Disaster Management Authority, Kerala declared major rice growing districts including Palakkad and Alappuzha as drought affected. Jyothi is a high-yielding popular rice variety, widely cultivated variety across Kerala. Despite its widespread popularity, it exhibits poor spikelet fertility per cent under water deficit conditions, indicating that it is susceptible to drought. Considering the negative impact of drought stress on rice production and the losses incurred by farmers, efforts were initiated at the College of Agriculture, Vellanikara to pyramid QTLs (qDTY4.1, qDTY6.1, and qDTY9.1) for yield under drought into the rice variety Jyothi (recurrent parent) from the drought tolerant variety Chuvannamodan (donor parent). The present work was conducted during 2021-2023 with the objective of introgressing the target QTLs of interest into variety Jyothi through marker assisted backcross breeding. Genomic DNA was isolated from both parents and subjected to PCR amplification for parental polymorphism using a set of 208 microsatellites. Out of which, 85 markers were found to be polymorphic between the parents. Parental varieties were hybridized and resultant F1 hybrids were confirmed using foreground markers (RM518, RM587 and RM566). A total of 27 F1 hybrids showed heterozygous banding pattern for all foreground markers. The F1 hybrids were backcrossed with recurrent parent for the production of the BC1F1 population. Also, F1 hybrids were allowed to selfing for the production of F2 and subsequently F3 generation. Gene annotation and enrichment analysis were done using Simple Sequence Repeat (SSR) markers associated with the target QTLs of interest. It was found that 23 genes were associated with drought tolerance, spikelet fertility and root related traits at three different QTL regions. Foreground selection in 200 BC1F1 progenies along with the parents was done to identify the plants with the target QTLs. SSR markers RM518, RM587 and RM566 closely linked with qDTY4.1, qDTY6.1 and qDTY9.1, respectively were used as foreground markers. Screening of BC1F1 population revealed that 60 progenies possessed heterozygous alleles for at least one QTL. A total of 27 BC1F1 progenies including 10 with qDTY4.1 + qDTY6.1, 9 with qDTY6.1 + qDTY9.1 and 8 with qDTY9.1 + qDTY4.1 were identified to possess two QTLs pyramided. Background selection of 27 BC1F1 foreground selected progenies using 76 SSR markers, polymorphic between the parents, revealed the presence of wide variability among these progenies with respect to recurrent parent genome recovery (RPGR). The results of graphical genotyping revealed a maximum RPGR of 57.7 per cent in the BC1F1 progeny 24.165, followed by 56 per cent in progeny 1.2. Drought tolerance of 15 BC1F1 with two QTL combination along with the parental varieties was characterized under reproductive stage drought stress using thirteen traits as per standard evaluation system (IRRI, 2002), including water mining traits. All the backcrossed progenies exhibited better performance under water deficit condition than the susceptible parent, Jyothi. It was found that progeny 20.118 (qDTY4.1 + qDTY6.1) had a higher number of filled grains (FG) per panicle (41) and spikelet sterility (SS) per cent (49.38 %) compared to Jyothi with 1 FG and 99.29 % SS under drought. The progeny 1.10 (qDTY9.1 + qDTY4.1) possessed higher root length (97 cm), root volume (100 cc), root to shoot ratio (1.70), root dry weight (25.9 g) than Jyothi (82.2 cm, 76 cc, 1.4, 14.64 g). Also, progenies 23.153 (qDTY4.1 + qDTY6.1) and 3.30 (qDTY6.1 + qDTY9.1) exhibited delay of 8 days to show the leaf rolling symptoms than Jyothi with 4.2 days. The BC1F1 progenies positive in foreground selection was backcrossed with the recurrent parent and 87 BC2F1 seeds were harvested. The resultant BC2F1, BC1F2 and F3 lines with potential drought tolerant QTLs can serve as the base population for enhancing the drought tolerance in Jyothi. Further, genotypic and phenotypic evaluation of the QTL pyramided progeny in subsequent generations will lead to the development of drought tolerant cultivar in the background of popular rice variety Jyothi.Item Development of cytoplasmic male sterile line in an identified rice variety of Kerala through marker assisted back crossing(Department of Plant Breeding & Genetics, College of Agriculture, Vellayani, 2019) Tejashree Shivaputra Lachyan; Jayalekshmy, V GItem Genome wide marker assay for the recovery of recurrent parent genome in rice (oryza sativa)(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2018) Bhagyalekshmi, R; Jayalekshmy, VGBacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major constraint in major rice growing areas of the world particularly in Asia. The disease is prelevant in the kharif season and it results in a greater yield loss. Since there is no valid chemical control measure, exploiting host plant resistance is an efficient way to tackle this problem. Approximately 40 genes conferring resistance to BB were identified. Pyramiding of these genes into the background of susceptible parent with good agronomical traits is the best strategy that can be adopted to develop plant varieties durable resistance to BB. So the present study entitled “Genome wide marker assay for the recovery of recurrent parent genome in rice (Oryza sativa)” was undertaken in College of Agriculture, Vellayani, Thiruvananthapuram to estimate the reconstitution of genome of Aiswarya (RP) rice variety in the BC2F1 plants pyramided with genes for resistance to Bacterial leaf blight through molecular markers covering the entire genome of Aiswarya. DNA markers closely linked to the BB resistance genes,viz.,xa13 pro (xa13gene), pTA248 (Xa21gene), RMWR7.1 (Xa33gene) were used for validation of the marker polymorphism in the donors for the genes. Improved Samba Mahsuri with xa13 and Xa21, Samba Mahsuri with Xa33, were taken as donors and Aiswarya was chosen as the recipient parent. The validation of gene specific markers confirmed the absence of the genes in the recurrent parent used in the study. And these markers were further used for foreground selection in BC2F1 plants. Also, the donor and recurrent parents used in the study were screened with 320 SSR primers in order to find the markers specific to the recurrent parent. In this screening out of 320 markers used, 44 were found to be polymorphic and these polymorphic markers were used in the background selection. Foreground selection was performed initially in all the 149 BC2F1 plants to identify the presence of these genes. In the foreground selection, a total of 149 plants were screened and 79 plants were found to have xa13 gene and 38 plants confirmed the presence of Xa21 gene while none of the screened plants showed the presence of Xa33 gene. 23 plants were found to possess two gene combinations of xa13+Xa21 and these plants were subjected to background selection to estimate the percentage introgression of the recurrent parent genome. Background screening of the plants identified with two gene combination using the 44 markers specific to recurrent parent revealed the number of markers showing homozygosity and heterozygosity with the recurrent parent. With this information percentage recovery of RPG was calculated and found that among 23 plants, the maximum recovery found was 84.09% and a total of 5 lines were showing more than 80% recovery of recurrent parent genome. The present study could identify BC2F1 plants identified with xa13 and Xa21 with genome recovery of more than 80% and further screening can be done in the BC2F2 generation to develop Essentially Derived Variety.