Genetik ketahanan cabai terhadap begomovirus penyebab penyakit daun keriting kuning dan arah pemuliaannya

Abstract

Begomovirus has been reported as the major pathogen for various important crops, including chilli pepper. Disease severity and yield loss caused by Begomovirus infection are affected by several factors, among others are plant varieties, viral strains and time of infection. The use of resistance varieties is considered as the most effective way to control the disease. Research activities were conducted to study the genetics of resistance of chilli pepper varieties to Pepper yellow leaf curl Begomovirus, in order to develop resistance chilli pepper varieties. Preliminary experiment was conducted to determine the transmission method using insect vector, Bemisia tabaci followed by determination of plant stage for inoculation of Begomovirus. Individual inoculation using 10 insects per plant with 24 h acquisition period and 48 h inoculation period on cotyledon stage was considered as the most effective and efficient way for Begomovirus transmission. Type of symptoms develop from Begomovirus infection can be differentiated into 5 groups, i.e (1) yellowing (2) yellowing and leaf curling (3) yellowing, leaf cupping with leaf curling, upward or downward, (4) yellowing, leaf cupping with leaf curling, upward and downward (5) yellowing, leaf curling, stunting. Twenty seven genotypes of chilli pepper were evaluated for their resistance based on score/type at symptoms and disease intensity. Disease intensity was ranged from 2.40% to 100% and they were group grouped into resistance (1 genotipe), moderate resistance (4 genotipes), moderate susceptible (4 genotipes), susceptible (8 genotipes) and highly susceptible (10 genotipes). Further analysis showed that resistance genotype (IPBC12) has more trichome than susceptible genotype (35C2) does salicylic acid contain was not significantly different between two genotypes, although Begomovirus infection could increase salicylic acid contain in resistance genotype. Genetic studies for resistance of chilli pepper to Yellow leaf curl Begomovirus was conducted using two methods, i.e. (1) analysis ofbasic population using six-population analysis and (2) analysis of random mating using diallel analysis. The result indicated that pepper resistance to Begomovirus was controlled by polygenes and there was extrachromosomal effect. The degree of dominance were over dominant. Gene action for resistance were additive, dominant and additive x additive interaction. However one population (IPBClO x IPBC14) showed additive gene action, dominant, additive x additive and dominant x dominant interaction. Estimation of broad-sense heritability were high but narrow-sense heritability were low to high. IPBC12 dan IPBC10 have the best combining ability for resistance to Begomovirus whereas IPBC14 have the highest yield. There are four crossing, i.e. IPBC10xIPBC12, IPBC12xIPBC14, IPBC14xIPBC18, dan IPBC18xIPBC26, that good combining ability and heterosis for resistance to Begomovirus and yield. Resistance verieties to Begomovirus could be established through hybrid cultivars to benefit the effect of dominance gene action. However, it could also be developed through open pollination using bulk or pedigree method.