Leaf surface characters related to resistance against pepper yellow leaf curl disease

Emergence of pepper yellow leaf curl disease, caused by the whitefly-transmitted geminivirus (WTG), was first reported in 1999 in Indonesia and, since then, the disease has become widespread across the country with the highest incidence and severity occurring in Central Java. Breeding programmes for WTG-resistant cultivars have been one of the major activities in regard to disease control strategy as host resistance to WTGs in commercial chili pepper cultivars is currently unavailable. We screened 27 chili germplasms using the insect vector Bemisia tabaci for virus transmission with a 24 h acquisition feeding period and a 48 h inoculation feeding period. Two accessions, 'IPBC12' and '35C2', were selected for further evaluation of leaf surface characters related to resistance. 'IPBC12' showed resistance to WTG infection, with low disease intensity, high trichome density, and thick epidermis and palisade layers. By contrast, '35C2' was considered susceptible, with high disease intensity, low trichome density, and thin epidermis and palisade layers. A correlation study indicated that disease intensity was significantly related with trichome density (r=-0.320). This result was strongly supported by the evidence that plants inoculated at the cotyledon stage were more susceptible than those inoculated at the 4-leaf or 6-leaf stage.