Effects of different maize hybrids (inbreds) on the growth, development and population dynamics ofRhopalosiphum maidisFitch

The corn leaf aphid, Rhopalosiphum maidis (Fitch), an important agricultural piercing-sucking pest on corn, has caused more and more severe damage to corn production in recent years. Moreover, the characteristics of R. maidis such as rapid reproductive speed, short generation period, transmitting plant virus and easily generating insecticide resistance made it difficult to manage in the field. Host plants play a vital role in the development and fecundity of insect pests, including R. Maidis. In order to provide a foundation for resistant identification and molecular mechanism of resistance, it is very important to assess the effect of host plants on growth and development of R. Maidis. In the present study, the time-specific life table of R. maidis on 8 maize hybrids (inbreds) was constructed at the constant temperature of 23 °C, relative humidity of 85% and photoperiod of 16L: 8D. The results showed that the durations of the 1st instar nymph of R. maidis on the 4 maize hybrids, Zhengdan 958, Xundan 20, Xianyu 335 and Liangyu 88, were longer than those on the 4 maize inbreds, 87-1, Pugai 340-1-1, Han 21 and Qi 319, most interestingly, these kinds of differences of developmental periods among 8 hybrids (inbreds) minished gradually with the growth of R. maidis. Furthermore, the adult longevities were 14. 00 d on 87-1, 14. 64 d on Pugai 340-1-1, 13. 15 d on Han 21 and 14. 04 d on Qi 319, which were longer than that on 4 maize hybrids, and the corresponding generation periods on 4 maize inbreds were all longer than those on 4 maize hybrids as well. The survival rates of R. maidis at diverse development stages on the 4 maize inbreds were significantly lower than those on 4 maize hybrids. In addition, the fecundities of aphids on different corn hybrids (inbreds) differed significantly, with the maximum fecundity of 64. 40 on Qi 319, followed by on Pugai 340-1-1 with 56. 53 and on 87-1 with 55.8, which were much higher than those on other corn hybrids (inbreds), and the minimum fecundity was 19. 93 on Xundan 20. Although R. maidis could grow and reproduce successfully on all tested 8 maize hybrids (inbreds) in experimental condition, the life table parameters were different on these maize hybrids (inbreds). As an important life table parameter, the innate capacity for increase (rm) of R. maidis on 87-1, Pugai 340-1-1, Han 21 and Qi 319 were 0. 31, 0. 29, 0. 28 and 0. 34, respectively, which were higher significantly than those on 4 hybrids. Compared to the other 4 life table parameters of aphids on 4 inbreds, the net reproductive rate (R0) and finite rate of increase (λ) of the R. maidis on 4 hybrids were much lower while mean generation time (T) and doubling time (t) were notably longer. All these results indicated that R. maidis feeding on maize hybids have lower survival rate, longer developmental periods at nymphal stage, shorter adult longevities and lower fecundities at adult stage in contrast with the maize inbreds, and the 4 hybrids affect the development and breeding of R. maidis, consistent with the population dynamics of R. maidis in the field of 8 maize hybids (inbreds).