Genomic Assisted Mapping Of Nematode (Meloidogyne Graminicola) Resistance From Oryza Longistaminata
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Date
2023
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Punjab Agricultural University
Abstract
India's rice production averages 195.43 million tonnes over 46.379 million hectares but is threatened by the destructive nematode Meloidogyne graminicola. This parasite can cause yield losses of up to 70% in lowland, upland, and deep-water rice, posing a significant risk to rice cultivation. Managing M. graminicola in rice fields typically involves flooding, nematicides, and crop rotation, but these methods have limitations. Exploring resistance in rice genotypes offers a promising alternative to reduce crop losses. This present study aims to identify the gene/QTLs responsible for resistance against the root-knot nematode (Meloidogyne graminicola) sourced from Oryza longistaminata acc. IRGC89153, by utilizing the F2 generation resulting from a cross between Oryza sativa cv. PR121 and Oryza longistaminata acc. IRGC89153. The F2 and F3 generations were screened in triplicates during the Kharif 2022 and Kharif 2023 respectively, within nematode-infested sick plot, where the initial nematode population density was 3 J2/gram of soil. After screening, the soil revealed a final nematode density of 10 J2/gram, signifying a threefold rise in the M. graminicola population from the initial density. These nematodes induce the development of root galls, impeding root growth, disrupting physiological processes, and obstructing the transport of water and nutrients through the root's vascular system. This leads to observable above-ground symptoms, including stunting, reduced vigour, chlorosis ultimately resulting in significant yield losses. Morphological trait analysis, encompassing parameters like plant height and root length, disclosed significant differences between infested and controlled (non-infested) conditions. Based on screening, resistant and susceptible bulks were made from the F2 population and along with parents were sent for whole genome re-sequencing. The analysis identified QTLs for nematode resistance on chromosomes 4 (qNR4.1) as a major QTL and a minor QTL on chromosome 10 (qNR10.1) with differing SNP counts and densities. The development of SNP-based molecular markers from these QTL regions will aid in identifying markers closely associated with rice root-knot nematode resistance. These markers will facilitate the accelerated improvement of genotypes for nematode resistance through marker-assisted breeding.
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Jessica Kaur (2023). Genomic Assisted Mapping Of Nematode (Meloidogyne Graminicola) Resistance From Oryza Longistaminata (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.