Relative resistance of sorghum varieties as revealed by variation in biological fitness parameters of the sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae)

A study was conducted using life table parameters to assess the relative resistance in eleven botswana sorghum varieties all local, namely ‘town’, ‘PMK 132’, ‘PL 174’, ‘PsA 158’, ‘PsA 161’, ‘PMK 110’, ‘PL 177’ ‘PMK 109’, 'sephala’, ‘PMK 108’ and ‘PMK 129’ against sugarcane aphid Melanaphis sacchari (Zehntner). biological fitness of the aphid was determined using population and life table parameters: developmental rate, fecundity and survival, longevity/lifespan, intrinsic rate increase (rm), net reproduction rate (Ro), generation time (T), doubling time (DT) as well as finite rate of increase (λ). Life table and population parameters of the aphids varied significantly among varieties. A significant reduction in fecundity and survival rate was observed in ‘town’, ‘PL 174’ and ‘PMK 132’. In addition aphid life table analysis showed significantly lower net reproduction rate (Ro), intrinsic rate of increase (rm), finite rate of increase (λ) and prolonged generation time (T) and doubling time (DT) on ‘town’, ‘PL 174’ and ‘PMK 132’compared to others. the negative impact of ‘town’, ‘PL 174’ and ‘PMK 132’ on biological fitness of M. sacchari suggest antibiosis mechanism of resistance in these varieties.