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Title: The effects of Potyvirus resistance on Maize lethal necrosis (MLN)
Maize lethal necrosis (MLN) is a viral disease of corn currently affecting farmers in East and Central Africa. MLN is caused by a combined infection of Maize chlorotic mottle virus (MCMV) and any virus in the potyviridae family. In East Africa, MLN is caused by a combined infection of MCMV and Sugarcane Mosaic virus (SCMV). This study aimed at utilizing available potyvirus resistance sources to control MLN and link potyvirus resistance with white maize endosperm color preferred by consumers in Sub Saharan Africa (SSA). The studies used Recombinant inbred lines (RILs) with different QTL for potyvirus resistance on chromosome 3, 6 and 10 derived from Oh1VI, a line known for multi-virus resistance, and screened them against MLN using artificial inoculation and natural infestation. Significant differences among genotypes and QTL groups were detected at P=0.05 when screened in the growth chamber and under natural infection. The QTL combination of 3, 6 and 10 was the best for MLN control as reflected by low MLN scores. The study also selected for genetic linkage between potyvirus resistance and white endosperm color to bring resistance into the white maize background preferred by farmers and consumers in SSA. The study used a yellow resistant line Pa405 and white susceptible lines CML 333 and CML 277 to generate 900 F2 progenies which were screened using short sequence repeats (SSR) markers to select for recombinants with white endosperm and potyvirus resistance. Twenty one (21) recombinants were selected, self-pollinated, and progenies from 6 recombinants were screened for resistance to SCMV and MDMV. All 6 progenies were resistant to MDMV and 4 recombinants were segregating for resistance to SCMV, suggesting that coupling phase recombination was established in these families. Recovered recombinants can be used in breeding programs for introgression of potyvirus resistance into the preferred food-grade genetic backgrounds in SSA. Results from this study provide useful baseline information for MLN control through potyvirus resistance in Sub Saharan Africa.