Effects of sowing mixed crops of resistant and susceptible cultivars of soybean on crop yield, the population dynamics of key insect pests and insect community diversity
Author of the article:SHEN Fang-Yuan；ZHANG Yi-Fei；GAO Fan-Qi；XIAO Zi-Jin；LI Li-Kun；CHEN Fa-Jun
Author's Workplace： Insect-information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China; Guangdong Key Laboratory of Sugarcane Improvement & Biorefinery, Guangdong Bioengineering Institute (Guangzhou Sugarcane Industry Research Institute, Guangzhou 510316, China; College of Agriculture, Nanjing Agricultural University, Nanjing 210095, China
Key Words：soybean; seed-mixed sowing with resistant and susceptible cultivars; population dynamics of insect pests; insect community diversity; yield; control damage and protect production
Abstract：
[Objectives] To identify the optimal ratio of resistant (R) and susceptible (S) soybean cultivars that should be sown to reduce insect pest numbers and maximize crop yield, thereby achieving the maximum possible soybean yield without pesticide use. [Methods] Different ratios of soybean varieties that were either resistant (cv. Lamar) or susceptible (cv. JLNMH) to Spodoptera litura were sown (R and S monocultures plus four mixed crops; 90% R and 10% S (9R1S), 80% R and 20% S (8R2S), 70% R and 30% S (7R3S), and 50% R and 50% S (5R5S)), to determine the effects of each seed ratio on soybean yield, the population dynamics of key insect pests (S. litura and Megacopta cribraria) and insect community diversity. [Results] There was no significant difference in the number of individual S. litura and M. cribraria per 100 plants among the different sowing treatments, but all treatments had significantly fewer of these species than the S monoculture. The insect community diversity index (H) and evenness index (E) of the 8R2S, 9R1S and R treatments were significantly higher than those of the other treatments, whereas the dominance index (C) of these three treatments were significantly lower than those of the other treatments. In addition, the insect community richness index (D) was lower when greater proportions of the sensitive cultivar were sown, and the richness index (D) of the 8R2S, 9R1S and R treatments was significantly higher than that of the S treatment. Sowing different cultivars significantly affected the dry weight of grain per 100 plants but there was no obvious effect on the 1000-grain dry weight. The R and 9R1S treatments had the highest grain dry weight per 100 plants, and this tended to increase with the proportion of resistant cultivar sown. [Conclusion] Sowing a mixture of resistant and susceptible cultivars can efficiently reduce the abundance of major soybean pests, and sowing ≥ 80% of the resistant variety significantly improves the diversity, evenness and richness of the insect community, and soybean yield. Consequently, we recommend sowing > 80% resistant soybean seed to control soybean pests and improve yield.