An evaluation on resistance of spotted alfalfa aphid to different Medicago sativa cultivars

Theriaphis trifolii is a crucial pest in alfalfa field, which causes serious harm to alfalfa production in most areas in China. In our study, the feeding behavior of aphid were screened at the alfalfa seedling stage. The change of alfalfa biomass under aphid stress were estimated and the population dynamics of aphids was also assessed on different alfalfa cultivars. The results showed that the total duration of C wave and E1 wave on Gannong No.4 was the longest, being 179.52 and 27.24 min, respectively. The total duration of E2 wave was 29.49 min and it was significantly lower than that on the other four cultivars (P < 0.05). The E1 wave of the aphid in the Golden Empress and the Crown was significantly shorter than that on other cultivars (P < 0.05), while the total duration of E2 wave was significantly higher than that on other cultivars (P < 0.05). There was no significant difference in EPG (electronic penetration graph) between Zhongmu No.3 and MF4020 (P > 0.05). EPG technique on the alfalfa susceptibility to spotted alfalfa aphid were coincided with the approch of aphid abundance. The resistance level of alfalfa to aphid was ranked as the following: Gannong No.4 > Zhongmu No.3 > MF4020 > Golden Empress > Crown. The estimation of alfalfa biomass also indicated that Gannong No.4 and Zhongmu No.3 were both resistant cultivars which are suitable for extension in Ningxia practically.