Effects of Temperature and Inoculation Timing on the Meloidogyne hapla/Corynebacterium insidiosum Complex in Alfalfa.

Hunt et al. (2) and Norton (4) showed that the northern root-knot nematode, Meloidogyne hap/a Chitwood, increased the incidence of bacterial wilt in alfalfa. Hunt et al. (2) also f o u n d t h e b a c t e r i a l wilt organism, Corynebacterium insidiosum (McCuU) H. L. Jens., in plant tissue that had been inoculated only with the bacteria. This would indicate that the role of M. hapla is something more than that of aiding the entry of bacteria through nematode-induced wounds. This study was designed (i) to determine bac ter ia l wilt incidence with M. hap/a inoculation before and after inoculation with C. insidiosum; and (ii) to determine the effect of temperature on susceptibility of alfalfa to bacterial wilt. Twelve-week-old 'Vernal,' 'Ranger,' and 'Moapa' alfalfa plants were transplanted (one plant/pot) into Provo sand in 15-cm diameter clay pots, and segregated into six equal 25-plant treatment groups. Treatments consisted of: (N) = plants inoculated with 200 M. hap/a larvae/plant; (B) = plants inoculated with 10 cc C. insidiosum suspension/plant (2); (NB1) = plants inoculated with 200 M. hapla larvae plus 10 cc C. insicliosum suspension/plant; (NB2) = plants inoculated with 200 M. hapla larvae; and after 30 days the plants were carefully washed free of soil, surface sterilized in 100 ppm s t r ep tomyc in sulfate solution, washed in distilled water, transplanted into sterile soil and inoculated with 10 cc C. insidiosum suspension; (NBa) = plants inoculated with 10 cc C. insidiosum suspension, and after 30 days the plants were carefully washed free of soil, surface sterilized in 100 ppm streptomycin