Screening soybean germplasm for resistance to rust disease and pod shattering

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JUNE, 2016
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Soybean production has suffered yield losses from 10 to 80 % due to rust disease. Host plant resistance has been found to be the best control strategy. These experiments were conducted to determine the presence of the rust resistance gene(s) and evaluate them on the field for P. pachyrhizi, pod shattering, lodging and yield potential. Thirty four soybeans accessions consisting of 32 breeding lines and two local varieties from Ghana were used. Screening for presence of rust resistance gene(s) was done using simple sequence repeat (SSR) makers. The field experiment was laid out in randomized complete block design (RCBD) with three replications. Soybean genotypes were evaluated for rust resistance under natural epiphytotic condition. Lodging was scored using IITA descriptors. Pod shattering screening was done using oven dry method in the laboratory. Days to 50 % flowering, nodule count, plant height, days to maturity, seeds per 100 pods, 1000 seed weight and grain yield were recorded. SSR markers revealed genotypes SIT-E TGx1990-3F, SIT-M TGx1987-91F, SIT-M TGx1989-45F and SIT-E TGx1988-5F to have multiple resistance genes Rpp1, Rpp2 and Rpp3, however genotype TGx1909-3F was identified not to have resistance gene. Out of the 34 soybean genotypes, SIT-M TGx1989-45F, SIT-M TGx1987-40F, SIT-E TGx1990-3F and SIT-M TGx1987-91F were found to be highly resistant to rust disease during phenotypic screening. It was revealed that 53 % of the genotypes showed erectness to lodging. Six genotypes, namely SIT-M TGx1904-6F, SIT-E TGx1835-10E, SIT-M TGx1987-40F, TGx1903-7F, SIT-E TGx1448-2E and ANIDASO were found to be moderately resistant to pod shattering. Genotype SIT-E TGx1989-45F was superior in terms of yield. Genotypes observed to have resistance gene(s) (Rpp1, Rpp2, Rpp3, Rpp4 and Rpp5) to soybean rust could further be exploited and used in breeding programme. Further studies should be conducted to verify the genotype or varieties known to have some level of resistance to rust, shattering and lodging is stable/durable or not.
Thesis submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture of the College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, in partial fulfilment of the requirements for the award of Master of Philosophy Degree in Agronomy (Plant Breeding),