Reaction of Peanut Cultivars to Tomato Spotted Wilt Virus (TSWV) Under Field Conditions and Their Response to Mechanical Inoculation by TSWV Under Greenhouse Conditions

Spotted wilt virus disease caused by Tomato spotted wilt tospovirus (TSWV) has become a limiting factor in peanut (Arachis hypogaea L.) production in the Southwest region of the U.S. Selected peanut cultivars (Okrun, Southwest Runner, Tamrun-98, Tamrun-96, Georgia Green, Tamrun OL-02, Tamrun OL-01, and Georgia Hi Oleic) were evaluated for reaction to TSWV in field plots in 2001, 2002, and 2003. Field plots were located near Pearsall, TX, where TSWV is endemic. In 2001, at 72 days post planting (DPP), incidence of TSWV was significantly (P , 0.05) higher in Southwest runner, Okrun, and Tamrun98 than the other cultivars except Tamrun OL-02 in the test. In 2002, disease incidence of TSWV was low and thus only one reading was taken at 135 DPP where the cultivars Georgia Green and Georgia Hi Oleic exhibited the least incidence of spotted wilt. In 2003, at 58 DPP, Georgia Green, and Georgia Hi Oleic showed the lowest incidence of spotted wilt compared with other cultivars. The response of the eight peanut cultivars to TSWV following mechanical inoculation with TSWV at three plant ages was evaluated under greenhouse conditions. Disease severity index (DSI) and plant growth parameters such as root length, root volume, plant height, and fresh weight were determined. ELISA values (as indicative of the relative presence of TSWV), and relative water content were also determined to show the impact of TSWV infections in inoculated plants. Reductions in most plant growth parameters were observed when plants were inoculated with TSWV at five days post-planting, than twelve and nineteen days post-planting inoculation. Positive values of correlation coefficient (CC) between DSI and root volume or root length in the cultivars Georgia Hi Oleic, Georgia Green, Tamrun-96 and Tamrun OL-01 indicate resistance or tolerance to mechanical inoculation with TSWV. Negative values of CC between DSI and root length or root volume in the cultivars Tamrun-98, Tamrun OL-02, Southwest Runner, and Okrun provide evidence for their susceptibility to TSWV. Comparison of results obtained from the field with those from greenhouse evaluations suggest that Georgia Hi Oleic, Georgia Green, Tamrun-96 and Tamrun OL-01 cultivars are useful as potential tools for management of TSWV in peanut for the Southwestern United States.