Effects of resistant and susceptible rubber germplasms on development, reproduction and protective enzyme activities of Eotetranychus sexmaculatus (Acari: Tetranychidae).

Abstract

Systematic research or technical support regarding rubber germplasm resistance against mites was not performed yet. To develop a preliminary understanding of the mite-resistance mechanisms of rubber germplasms, stably resistant rubber germplasms were obtained, the development and reproduction of Eotetranychus sexmaculatus that fed on leaves of resistant and susceptible rubber germplasms were examined in the laboratory, and the activities of protective enzymes in this mite species were also compared. The results indicated that: (1) among the 23 rubber core germplasms identified, five (IRCI12, Reyan87-6-5, IAN717, RRIM600 and RRIC52) steadily developed resistance to E. sexmaculatus; (2) E. sexmaculatus that fed on the highly resistant germplasm IRCI12 did not complete development and reproduction-the female adults laid only 4.90 eggs on average, and none of these eggs hatched; (3) the resistant germplasms extended the duration of each developmental stage, reduced the fecundity, egg hatchability, and female offspring percentage, and significantly decreased the offspring survival rate compared with the susceptible germplasms; and (4) during each developmental stage of the mites that fed on resistant rubber germplasms, decreased activities (by 0.25-fold to 0.63-fold times) of the protective enzymes peroxidase, ascorbate peroxidase, polyphenol oxidase, superoxide dismutase and catalase were observed compared with those in the mites that fed on susceptible rubber germplasms (P<0.05). These findings may explain why E. sexmaculatus did not complete their development and reproduction on the resistant rubber germplasms. This study lays a foundation for elucidation of the mechanism of rubber resistance to mites and provides experimental material and technical support for the breeding of mite-resistant rubber plants.