Exploitation of cytoplasmic genetic male sterility (CGMS)system i chilli (Capsicum annuum L.)for the development of hybrids resistant to bacterial wilt

Abstract

Chilli botanically known as Capsicum annuum (2n=24, Solanaceae) is an important vegetable crop extensively cultivated in tropical and subtropical parts of the world. However, the crop faces major challenges due to its small flower size which complicates hybrid seed production and susceptibility to various biotic stresses, both of which restrict its yield potential. Developing host plant resistance to bacterial wilt through heterosis breeding using cytoplasmic gentic male sterility system and identified resistance sources is an effective method to mitigate the biotic stress and to realise the yield potential in chilli. With this context the current study entitled as “Exploitation of Cytoplasmic Genetic Male Sterility (CGMS) System in Chilli (Capsicum annuum L.) for the development of hybrids resistant to bacterial wilt” was carried out at the department of vegetable science during May 2022-Novemener 2024. Initially 17 chilli genotypes comprised of seven male sterile, maintainer and 10 restorer lines were evaluated at department of Vegetable Science, College of Agriculture, Vellanikkara, during May 2022-23. The statistical analysis of various characters exhibited significant differences among lines and restorer lines. The analysis on pollen sterility revealed that four lines were completely sterile, two were partially sterile and one line was found partially fertile throughout growing period. Among the lines, the highest plant height was recorded in VI046838 (116.66 cm), while VI060627 exhibited earliness in terms of days to flowering (24.56 days), fruiting (28.46 days), and maturity (44.30 days). Superior mean performance for fruit traits such as fruit weight, fruit length, fruit wall thickness, and fruit width was observed in VI046838. The mean performance of the genotypes for yield and quality parameters revealed notable differences. Fruit set percentage and fruit- bearing period were highest in AVPP9907, with values of 73.77% and 119.96 days, respectively. The highest fruit yield per plant and number of seeds were recorded in VI060629. The highest value of ascorbic acid observed in AVPP9907 (213.82 mg/100 g). Significant differences were also noted for oleoresin content, with AVPP9907 recording the highest value (18.10 %). Under field screening for bacterial wilt incidence, three genotypes were resistant, three were susceptible, and VI046838 was moderately susceptible. However, none of the seven genotypes showed resistance under artificial inoculation. Out of 10 restorer lines, AVPP9905 was found to be superior for multiple traits, including, days to first flowering, fruit weight, fruit length, fruit-bearing duration, number of fruits per plant, and overall yield. Chivar-1 showed the highest ascorbic acid content (197.83 mg/100 g), while LC 217 recorded the highest oleoresin content (18.37%). Highest capsaicin content was observed in AVPP9703 (1.06%). Bacterial wilt screening among the restorer lines revealed that seven were resistant, two were susceptible, and one was moderately resistant. High genotypic and phenotypic coefficient of variation was observed for fruit per plant, fruit length, fruit set percentage, fruit bearing period, fruit width, fruit wall thickness. Path analysis of the characters revealed that fruits per plant, fruit set percentage, and fruit bearing had a direct positive effect on yield, Twenty-four hybrids were produced from a cross involving 3 × 8 (L × T) mating design as a part of the second experiment. In third experiment Parents and hybrids, along with the standard check Sierra were evaluated for various characters. The ANOVA for combining ability revelated presence of significant general combining ability for parents and specific combining ability for hybrids. Predominance of non additive gene action was evident for almost all the characters under study. Significant heterosis was observed for most of the quantitative traits. Yield and contributing characters showed significant difference among parents, hybrids and check. The hybrid AVPP0516 × Anugraha exhibited the highest mean fruits per plant (179.65) and yield per plant (822.12 g). AVPP0517 was the best combiner for fruits per plant, Among the testers significantly highest positive GCA for yield per plant was noticed in Ujwala. In lines, AVPP9907 had highest GCA for yield per plant. Among the testers, Ujwala had maximum GCA for yield per plant. Regarding biochemical characters, VI059328 recorded highest GCA for ascorbic acid, Chivar-1 for oleoresin and AVPP9703 had highest GCA for capsaicin content. AVPP0516 × Anugraha, AVPP0517 × VI059328, and AVPP9907 × Ujwala were best combiner for yield per plant. For fruit setting percentage, highest SCA was observed in the cross AVPP0516 × LC 217. Highest SCA for ascorbic acid was observed in the hybrid AVPP0516 × VI059328. AVPP0517 × Ujwala exhibited maximum SCA for oleoresin. On estimation of heterosis for number of fruits per plant, the hybrid AVPP0516×Anugraha recorded superiority in terms of relative heterosis (137.88%), heterobeltiosis (102.26%) and standard heterosis (212.71%). Artificial screening of hybrids revealed that AVPP0517 × VI059328 was highly resistant, with a disease incidence of 10.05%, followed by AVPP0516 × Anugraha (10.35%) and AVPP0517 × EC566920 (11.50%). The reported DNA marker for bacterial wilt resistance was validated using the parental lines and their hybrids. The primer CAMS 451 exhibited polymorphism, producing the expected band size of 220 bp for susceptible genotypes and 210 bp for resistant genotypes. All 24 hybrids tested positive for the marker and were confirmed to be heterozygous in nature. The study stands out for the successful development of three promising F1 hybrids, namely, AVPP0516 × Anugraha, AVPP0517 × VI059328, and AVPP9907 × Ujwala. Based on their mean performance, combining ability, and heterosis, they were recognized as potential genotypes for further evaluation and utilization in breeding programs. Exceptional standard heterosis and resistance to bacterial wilt were also observed in four hybrid, AVPP0516 × Ujwala, AVPP0517 × Anugraha, AVPP0517 × Ujwala, and AVPP9907 × Anugraha which are potential candidates for replicated and multilocational testing under bacterial wilt prone zones in Kerala.