The Influence of Temperature on Development and Sex Differentiation of Meloidogyne graminis

Meloidogyne grarninis (Sledge and Golden) Whitehead on Cynodon sp. (var. 'Tifgreen' bermudagrass) was studied at four temperatures; 16, 21, 27, and 32 C. Both mode and rate of development were temperature dependent. Females developed more rapidly and in greater numbers at 27 C: saccate females exuding matrices were present 14 days following inoculation, eggs were laid after 21 days and newly-hatched larvae were present in the matrix at 25 days. Sex differentiation to males was 80% at 32 C and 4% at 27 C. No males were observed at 21 or 16 C. Developing males were present 14 days following inoculation and emerged from roots after 21 days at 32 C. In populations pre-exposed to 27 C then transferred to 32 C, the percentage of males ranged from 0 for 1 day exposure at the initial temperature to 45.5% after 5 days. After 11 days pre-exposure the recovery of males was 4.3%. Individuals interpreted to be male sex reversals and male intersexes were noted. Pre-exposure at 32 C for 1 or 2 days followed by 27 C produced 1-2% males, while exposure for 3 or more days at 32 C followed by 27 C produced 90% males.