Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2002
Publication Date: 9/1/2002
Citation: Mandal, B., Pappu, H.R., Culbreath, A.K., Holbrook Jr, C.C., Gorbet, D.W., Todd, J.W. 2002. Differential responses of selected peanut cultivars and breeding lines to mechanical inoculation of tomato spotted wilt virus. Plant Disease. 86:939-944. Interpretive Summary: Tomato spotted wilt virus (TSWV) is one of the most economically important diseases of peanut in Alabama, Florida, Georgia, Mississippi, North Carolina, and Texas. Annual losses of several million dollars were attributed to TSWV in Georgia alone. The most effective way to minimize losses to this disease is through development and deployment of disease resistant varieties. We used a highly efficient mechanical inoculation procedure in this study to evaluate the response of four peanut genotypes to TSWV. The breeding line C11-2-39 was observed to have the highest level of resistance to TSWV .Virus infection of this genotype tends to be localized resulting in fewer systemically infected plants. Field studies have also showed significantly lower incidence of TSWV in this breeding line in comparison to commonly grown varieties. The results of this study should aid in the development of peanut varieties with higher levels of resistance to this virus.
Technical Abstract: Screening of peanut germplasm for resistance to Tomato spotted wilt virus (TSWV) has been largely inefficient due to the lack of a screening technique based on mechanical transmission of the virus under controlled environmental conditions. We have studied the reaction of three peanut cultivars (Georgia Green, Georgia Runner, C-99R) and one breeding line (C11-2-39) using a highly efficient mechanical inoculation procedure. The disease response was studied at two temperature regimes, 25 to 30°C (low temperature) and 30 to 37°C (high temperature). Based on percent transmission, symptomatology, distribution of TSWV and relative levels of TSWV nucleocapsid (N) protein, Georgia Runner and Georgia Green were found to be susceptible whereas, C-99R and C11-2-39 were resistant. Of all the four genotypes tested, Cl1-2-39 had the highest level of resistance to TSWV. The results correlated with the field performance of the genotypes except in the case of Georgia Green which could not be distinguished from TSWV susceptible Georgia Runner. Exposure of the inoculated plants to higher temperature (30 to 37°C) resulted in a better resistant response as reflected by reduced systemic infection, localized symptom expression, restricted viral movement and reduced levels of TSWV antigen. This is the first report of differential response of peanut genotypes to TSWV using mechanical inoculation. The four peanut genotypes should be useful as reference 'standards' for the initial screening and identification of sources of TSWV resistance in peanut germplasm.