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Title:	Molecular dissection of rice blast disease resistance genes in diverse germplasm and segregating mapping populations
Authors:	Ankitta Mishra (P67822)
Supervisor:	Wickneswari Ratnam, Prof. Dr.
Keywords:	Rice blast disease Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	30-Sep-2019
Description:	Blast disease caused by pathogenic fungus Magnaporthe oryzae is a main disease of rice in Malaysia that decreases yield and rice quality. This study used molecular marker approaches to decipher the blast disease resistance genes in rice crop. Six new isolates of M. oryzae from infected leaf samples collected from Kedah and Kelantan were successfully isolated using single spore cultures technique. The virulence level of these isolates was identified under greenhouse condition using two differential genotypes, Pongsu Seribu 2 (PS2) (resistant) and Mahsuri (susceptible). Result shows that four out of six isolates were found to be virulent while isolate 3 was also found to be the highest sporulating and virulent blast isolate. These isolates were induced to sporulate and later used for greenhouse and rice field blast screening. A set of 23 rice genotypes was screened using 51 molecular markers comprising 38 simple sequence repeat (SSR), 10 Indels and three gene specific SSR markers underlying 22 blast genes/QTLs across nine chromosomes in the rice genome. All these rice genotypes materials were later genotyped with 51 single nucleotide polymorphic (SNP) markers closely linked to six major blast disease resistance genes studied extensively (Pi9, Pi5, Pib, Piz, Pita and Pi54) distributed over five rice chromosomes (chromosome 2, 6, 9, 11 and 12). SNP analysis confirmed the presence of 11 sequence variants conferring blast resistance for the 23 rice genotypes tested. Two resistance genes Pita and Pi54 were found to carry co-segregating markers in two phases. Although all of the high yielding genotypes were carry some of the blast resistance genes but various level of resistance was shown in the greenhouse screening. Rice genotype IR65482-4- 136-2-2 (Pi40 near isogenic line for blast disease resistance), PS2 (highly resistant), and Oryza rufipogon accessions (wild rice) had resistant disease score of 0 and showing no symptoms of blast at all; while MR219, UKMRC2, UKMRC9, UKMRC10 and UKMRC11 were found to be moderately resistant with a disease score of 3 or 5 and Mahsuri along with MR264 with a disease score of 7 or 9 was the most susceptible. The same 51 SNP markers were used to study the blast disease resistance in two 4-way F4 segregating populations (F1 dan F4 populations derived from a cross between rice genotype Tetep (highly resistant), Teqing (moderately resistant) and UKMRC2 (moderately resistant)) that were earlier challenged with blast disease using all the six local isolates under rice field condition. SNP data analysis showed the consistent blast resistant alleles for SNPs representing Pi54 and Pita on chromosome 11 and 12 respectively. Qgene analysis revealed LOD score of 14 for both QTLs with phenotypic variations of 72.4% and 56.6% for Pita and Pi54 respectively in the 4-way F4 population. Pita was mapped to a region of 312 kb on Chromosome 12 flanked by SNPs Pita-10 and Pita-3 while Pi54 was mapped to a region of 175 kb on chromosome 11 flanked by SNPs Pi54-3 and Pi54-19. These SNPs were also used for studying sequence variation of genes conferring resistance against fungi M. oryzae where two and three sequence variants were identified on chromosome 11 and 12 respectively which can be used for generating functional SNPs. Pita and Pi54 which conferred resistance against all six of the blast isolates may be involved in the defense response against a broad spectrum of isolates. These two genes also might have an important role in putative durable resistance while the other genes (Pi9, Pi5, Pib, Piz) may only be involved in limited defense responses with varying degrees of race specificity. This genetic study of blast resistance on Malaysian high yielding rice varieties could be used as basic information in developing blast disease resistance rice cultivars in the future.,Certification of Masters/Doctoral Thesis is not available,Ph.D.
Pages:	182
Call Number:	SB608.R5M537 2019 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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