VARIETAL SCREENING BASED ON DEMOGRAPHIC PARAMETERS - RESISTANCE OF TEA TO BREVIPALPUS-PHOENICIS (ACARI, TENUIPALPIDAE)

Nest plant resistance to herbivores is usually measured by visual scre ening in the field, which is very expensive. We tested an alternative method using 26 varieties of tea, Camellia sinensis, selected from dif ferent geographical locations to screen for resistance against the red and black flat mite, Brevipalpus phoenicis (Geijskes); survival and l ogistically fixed net fecundity schedules (predicted number F-1 offspr ing) were compared. Survival schedules of the mites varied among the d ifferent varieties, as indicated by a change in the concavity of the s urvivorship curves and measured in terms of entropy. Varieties were cl assified according to their level of resistance/susceptibility based o n the number of predicted F-1 offspring. The level of susceptibility w as positively correlated with life expectancy and was negatively relat ed to entropy. Varieties that evolved from northeast India were consis tently less susceptible, which suggests that a search in this region t o identify genes for resistance might be useful for future breeding pr ograms.