ABSTRACT
The development and reproduction of the citrus leafminer (CLM), Phyllocnistis citrella Stainton, were evaluated in six citrus genotypes in order to identify genotypes with resistance traits that could be applied in a program for the development of citrus varieties resistant to the citrus leafminer. Tests were conducted under controlled laboratory conditions (25 ± 1ºC, 70 ± 10 percent RH, and 14h photophase). Seedlings of each genotype tested were infested with eggs obtained from a stock colony of CLM maintained on 'Cravo' lemon (Citrus limonia L. Osbeck), and the duration and survival of the eggs, larval and pupal stages, pupal size and weight, fecundity and longevity of adults, and sex ratio were evaluated. No influence was observed on the duration and survival of eggs, larvae and pupae of P. citrella. However, pupae obtained in the hybrid C x R4 were significantly smaller and lighter than pupae from the remaining treatments. Adult females from the hybrids C x R4 and C x R315 were the least fecund. However, the lowest value for the corrected reproductive potential (CRP) was recorded in the hybrid C x R315, suggesting that this genotype is the least favorable for the development and reproduction of CLM. On the other hand, the highest CRP value obtained in the 'Rugoso' lemon confirms the susceptibility of this genotype, indicating it as the most suitable for CLM.
Subject(s)
Animals , Citrus/genetics , Citrus/parasitology , Disease Resistance/genetics , Lepidoptera , GenotypeABSTRACT
Changes in the agroecosystem with the increase of green cane harvesting in Brazil affected the insect populations associated to this crop, and secondary pests like the spittlebug Mahanarva fimbriolata Stål, became much more important. Many studies have demonstrated the active role played by silicon in plant defense against herbivory. The objective of this study was to evaluate the effects of silicon applications on the biology of the spittlebug reared on two resistant (SP79-1011 and SP80-1816) and one susceptible (SP81-3250) sugarcane cultivars. Sugarcane plants were grown under greenhouse conditions and submitted to different treatments: with and without silicon fertilizer in two different soil type (sandy and clay soil). The newly hatched nymphs were transferred to sugarcane roots and placed into boxes with lids, to keep a moistened and dark environment favoring their growth and maintenance of the root system, providing food access to the developing nymphs. After emergence, adult males and females were placed in cages for mating and oviposition. The silicon absorbed and accumulated in the plant caused an increase in nymphal mortality, and depending on the sugarcane cultivar tested this element also provided an increase in the duration of the nymphal stage and a decrease in the longevity of males and females. 'SP79-1011' presented the highest silicon content in leaves, and M. fimbriolata had the highest nymph mortality and the shortest female longevity. The pre-oviposition period, fecundity and egg viability were not affected by the silicon content in plants or the cultivar used.