Reaction of selected medium duration breeding lines to groundnut rosette disease in Malawi during the year 2017

Research work carried out to identify promising groundnut breeding lines with resistance to groundnut rosette disease. The experiment was carried out in Chitedze research station during the 2016-2017 growing season. The infector row technique was used to induce a high disease pressure. At sowing time, one infector row of susceptible cultivar was sown after every two contiguous rows of test lines, such that every test row was adjacent to one infector row. Six weeks before planting on the field, a large number of seedlings were raised in the green house and inoculated with Groundnut Rosette Virus (GRV), using a greenhouse culture of viruliferous aphids, which had been reared on GRV-infected plants. These were then transplanted into the infector rows at 1.5-2 m spacing. Each test line was assessed for disease incidence at 8 weeks and 12 weeks after sowing. The total number of plants in each plot and the number of plants showing rosette symptoms with severe stunting are counted and percentage of disease incidence computed. Plants showing severe symptoms are stunted and bushy in appearance due to reduced internodes length. Leaves of the infected plants are reduced in size and the plants do not produce pods. Breeding lines were considered resistant when no susceptible plants were found within the complete entry (0% incidence), highly susceptible when no resistant plants were present (100% incidence) and moderately resistant when at least one plant within the entry has mild symptoms (< 10% incidence). Experiment location on Google Map