Effects of rhizobacteria on soybean cyst nematode, Heterodera glycines

Rhizobacteria were isolated from the rhizoplane and rhizosphere of soybean plants From fields in Arkansas and tested for their effect on numbers of so ybean cyst nematode (Heterodera glycines). In initial greenhouse tests in h eat-treated silt loam soil, 138 of the 201 bacterial isolates tested had no influence on numbers of cysts and eggs + second-stage juveniles (J2) of H glycines 36 reduced (suppressive isolates) and 27 increased (enhancing isol ates) numbers of cysts and (or) eggs + J2 when compared to the controls (P less than or equal to 0.05). When 20 suppressive and five enhancing isolate s were retested in the same soil, the results were highly variable and inco nclusive. The 25 isolates were then evaluated in vitro for their effects On eggs and J2 of H. glycines. No clear relationship was detected between the inhibition of egg hatch or immobilization of J2 in vitro and antagonistic activity toward nematodes in vivo. Amendment of the soil with 0.1% (w/w) pe ptone or casein hydrolysate did not improve the effects of suppressive isol ates on numbers of H. glycines. Nineteen of the 25 isolates were identified based on analysis of fatty acid methyl esters, and they are in 11 differen t genera.