Epicuticular wax rice mutants show reduced resistance to rice water weevil (Lissorhoptrus oryzophilus) and fall armyworm (Spodoptera frugiperda)

Epicuticular waxes (EWs) on the aerial surfaces of many land plants offer protection from biotic and abiotic stresses. In rice mutations that reduce EWs have been previously reported. However, whether such mutations affect rice water weevil (RWW) and fall armyworm (FAW) performance has not been investigated yet. These pests cause significant economic problems in rice-producing areas of the United States. The aim of our study was to characterize the EWs of EW mutants and wild-type (WT) rice plants comparing the resistance of mutant and WT plants against RWW and FAW. We hypothesized that mutants with reduced EWs would have weaker resistance to pests than WT plants. Three mutant lines (6-1A, 7-17A, and 11-39A) and their WT parent (‘Sabine’) were used to test this hypothesis. Reduction in EWs significantly affected performance of insects in experiments conducted under greenhouse conditions. Experiments with RWWs were conducted in arenas in which females were given a choice of the mutants and the WT for oviposition. Number of first instars emerging from the three EW mutants was higher on the EW mutants than on WT plants with normal wax levels. In no-choice experiments using whole plants or detached leaves, weight gains of FAW on leaves were higher on the mutant lines than on the WT. These results indicate that EW traits are involved in rice resistance to weevils and armyworms. Understanding the plant traits that contribute to resistance to rice pests will be helpful for the development of resistant varieties for reducing pest insect damage.