Karakterisasi beberapa genotipe cabai (Capsicum spp.) dan mekanisme ketahanannya terhadap begomovirus penyebab penyakit daun keriting kuning

Abstract

The plant breeding program to develop resistant plants of Begomovirus is needed to characterize of pepper germplasm. The activities followed by study on resistance mechanism based on information of structural and biochemical resistance against Begomovirus and their vector Bemisia tabaci. Pepper yellow leaf curl virus (PYLCV) belongs to the genus of Begomovirus, the family members of Geminiviridae. The virus has been reported as the causal agent of yellow leaf curl disease in pepper and transmitted by an insect vector, B. tabaci Genn. Evaluation of genotypes characters showed that the morphological characters of leaves, stems, flowers, and fruits can be distinguished among the genotypes of pepper. There are significant differences among pepper genotypes for the following variables: height of dicotomous, plant height, canopy width, stem diameter, leaves length and width, and flowering times. Dendrogram analysis based on qualitative characters involving 29 genotypes classifies the genotypes into 4 different groups. Most of the genotypes belong to group I, genotypes IPB C15 and IPB C63 are in group II, IPB C12 genotype in group III, whereas IPB C20 and IPB C21 are in group IV. All genotypes are included in C. annuum, except IPB C63 genotype which belongs to C. frutescens. Capsicum species differs in the form of leaves, number of flowers at per node, the position of flowers, fruit color intermediate, and plants canopy. Resistance response of the genotypes was identified based on the measurement of disease intensity. IPB C12 genotype is resistant; IPB C10 and IPB C14 genotypes are moderately resistant; IPB C15, IPB C26, and 35C2 genotypes are susceptible. PYLCV detection using PCR technique has successfully amplified 780 bp-sized Begomovirus-specific DNA fragments. Dot blot hybridization is capable to detect PYLCV in resistant and moderately resistant genotypes to a dilution level of 1: 10, whereas susceptible genotypes can reach up to 1: 100 dilution level. Susceptible genotype tended to have a Begomovirus concentrations higher than genotypes resistant or moderate resistant. Genotypes resistance to Begomovirus is associated with structure of plants i.e. density of trichome and arrangement of palisade cells. An increased accumulation of salicylic acid and peroxidase enzyme activity are detected in Begomovirus-inoculated plants, 120 hours after inoculation. Based on the correlation among characters in pepper genotypes, it can be concluded that there is a correlation between the mechanisms of structural and biochemical resistance of plants following Begomovirus infection. Longer palisade cells will lead to thicker leaf and more accumulation of salicylic acid. Trichome density and palisade cells position are the structural barrier in the mechanism of pepper resistance to B. tabaci. Resistance mechanism to Begomovirus is the result of the width of palisade cells, increased accumulation of salicylic acid, and increased activity of peroxidase enzymes. There is a correlation between the structural and biochemical mechanisms to Begomovirus, with a positive correlation between the lengths of palisade cells and salicylic acid accumulation.