Association between microsatellite markers and rice response to the rice blast pathogen Magnaporthe oryzae in selected Zambian rice genotypes
Keywords:Magnaporthe oryzae, Polymorphic information content (PIC), Simple sequence repeats (SSRs)
Magnaporthe oryzae, the rice blast disease pathogen is estimated to cause losses of up to 30% in rice production worldwide, yet its impact on rice production in Zambia remains unknown. Symptomatic rice leaf tissue collected from rice fields in Mongu District of Zambia was cultured on oatmeal agar medium and fungal colonies were purified and identified through leaf lesions and conidia using published keys. An M. oryzae isolate from this study was used to challenge twenty-eight selected Zambian rice genotypes to determine their responses to infection with the pathogen estimated by lesion numbers and sizes. Twelve of the genotypes (42.8%) were highly resistant (HR) with 1 to 2 lesions per cm2, 6 (21.4%) were moderately resistant with mean lesion numbers of 3 to 4 per cm2 while 10 (35.7%) were susceptible with lesion numbers above 5 per cm2 of leaf tissue. Polymerase chain reaction (PCR)-amplification of rice genomic DNA extracted from the 28 genotypes using selected microsatellite marker primers revealed a moderate genetic diversity with three of them showing significant genetic diversity. Allelic diversity among the selected genotypes was also confirmed from a calculated mean polymorphic information content of 0.8. A correlation between 8 of the microsatellite markers in some of the rice genotypes and their resistance response to M. oryzae was also established. Results show that some of the analysed rice genotypes have a significant potential for use as a genetic resource in breeding for varieties that are resistant to the rice blast pathogen for Zambian farmers.