Breeding for multiple resistant hybrids in chilli (Capsicum annuum L.) against leaf curl viral disease and bacterial wilt

Abstract

Chilli (Capsicum annuum L.) is one of the most economically important vegetable crops cultivated in warm humid tropics of India, but its production is hindered by various biotic stresses, particularly the diseases such as chilli leaf curl viral disease and bacterial wilt. These diseases are potential enough to drastically reduce both the yield as well as the quality of produce. The management measures are often ineffective in controlling the disease as the pathogen survives in the alternative host, plant debris or in the soil. Therefore, utilizing host plant resistance is the most viable and sustainable approach to manage these diseases. In this context, the present investigation entitled Breeding for multiple resistant hybrids in chilli (Capsicum annum L.) against leaf curl viral disease and bacterial wilt" was carried out at the Department of Vegetable Science, College of Agriculture, Vellanikkara, with the objective of identifying high yielding disease resistant parental lines and developing hybrids with resistance to both chilli leaf curl viral disease and bacterial wilt. The study was conducted in three experiments viz., evaluation of parental genotypes, development of F hybrids and evaluation of Fi hybrids for yield and resistant characters. Ninety-two chilli genotypes were evaluated along with the check varieties Anugraha and Ujwala for their resistance to leafcurl viral disease and bacterial wilt as well as for their yield potential. The genotypes studied exhibited significant variation for all the traits observed and some ofthe promising genotypes identified were LC 84 (plant height), AVPP 0512 (fruit set percentage), IC 363993 (days to first flowering and fruiting), EC 628901 (days to maturity of fruit), IC 561626 (fruit length), LC 111 (I) (fruit width), AVPP 905 (fruit weight), LC 10/2 (fruits per plant and fruit yield per plant) and LC 23 (dry matter content). High genotypic coefficient ofvariation and phenotypic coefficient of variation was observed for several traits, including fruit width, fruit wall thickness, fruit length, fruit yield per plant, fruit weight, fruits per plant, fruit set percentage, dry matter content, fruit bearing period, ascorbic acid content, capsaicin and oleoresin. Traits such as days to first flowering, days to fruiting, fruit width, fruit wall thickness, fruit bearing period, days to fruit maturity, fruit length, fruit width, fruit number, fruit yield, fruit set percentage, ascorbic acid, capsaicin and oleoresin exhibited both high heritability and high genetic advance. Hence, these

chara cters can be im pro ved by selection as it show ed additive inherita nce. T he chara cters nam ely fru its pe r plant, fru it beari ng pe riod , fru it w eight, plan t heigh t and fru it set percentage show ed a signi fi cant positive dir ect infl uence on fru it yield per plant and sign ifi cant po sitive corr elation at the genotyp ic level. T herefo re, selectin g the genotyp es based on these tr aits w ould be effective in cro p im pro vem ent pro gr amm es targeting the yield. T he genetic diversity ana lysis identifi ed nin e distinct cl usters am ong the 94 genotyp es. C luster VIll , w ith 20 genoty pes, w as the largest and the sm allest w as cl uster IX w ith tw o genotyp es. T he sm allest inter cluster distance w as fo und betw een the clusters V II and vm, indicating close genetic relationships. The largest inter-cluster distance was observed between clusters V and IX, suggesting that genotypes from these clusters might provide valuable genetic diversity for breeding programs aimed at heterotic progeny. The genotypes were also ranked based on the economic characters to identify the best performers. In the field evaluation, twelve genotypes were found resistant to leaf curl virus and thirty-four genotypes showed moderate resistance to leaf curl virus. Whereas, for bacterial wilt, most of the genotypes were found resistant, it may be due to the lack of bacterial inoculum in the soil. Further, the genotypes identified from the parental screening were tested under artificial inoculation conditions to assess their reaction to both diseases. In the artificial screening, five genotypes were found resistant and five were found moderately resistant to bacterial wilt. With respect to leaf curl virus, ten genotypes were found moderately resistant, eight were moderately susceptible, and sixteen were classified as susceptible. Accordingly, the high yielding genotypes namely LC 10/1, LC 10/5, AVPP 0105, Ujwala, Chivar I and EC 566920 that got favourable ranking and demonstrated resistant reactions were selected as parents for subsequent hybridization programme. Eighteen F, hybrids were developed by crossing the bacterial wilt resistant lines vi:::., Ujwala, Chivar 1 and EC 566920 and moderately resistant leaf curl genotypes, LC 10/5, LC 10/1 and AVPP 0105 in partial diallel design and the hybrids were evaluated in open field and rain shelter for vegetative traits, yield, and disease resistance. Based on the per se performance in open field, several hybrids showed superior agronomic traits, such as Ujwala x AVPP 0105 for plant height, Chivar I x LC 10/1 for days to first flowering, AVPP 0105 x Ujwala for fruit length, EC 566920 x AVPP 0105 for

fru it w idth, C hivar 1 x LC 10 /5 fo r fru its per plant and A VP P O 10 5 x EC 566920 fo r fruit weight and yield per plant. On estimation of heterosis in field evaluation, high estimates of Standard Heterosis (SH) and Heterobeltiosis (HB) was exhibited by the hybrids AVPP 0105 x Ujwala for fruit length, EC 566920 LC 10/5 for fruit wall thickness and Chivar 1 x LC 10/5 for fruit number. A high estimate of all the three heterosis was found in the hybrids, AVPP O 105 x EC 566920, LC 10/5 x Ujwala and LC IO /I x Chivar I for fruit weight and the AVPP 0105 EC 566920 exhibited highest heterosis for yield per plant. In rain shelter, the best hybrid found was Chivar l x LC IO/I for plant height, EC 566920 AVPP 0105 for fiuit set percentage, LC 10/5 EC 566920 for fruit length, EC 566920 x AVPP O I 05 for fruit width, LC I 0/5 x Chivar I for fruit weight, LC 10/5 EC 566920 for fruits per plant and fruit yield per plant. A high estimates of SH for fruit length, fruit number and fruit yield were exhibited by the hybrid LC 10/5 x EC 566920. While the hybrids LC 10/5 Chivar I exhibited high estimates for three types of heterosis for fruit weight. Combining ability analysis revealed that in open field, Ujwala and LC 10/5 were good combiners for fruit yield and fruit number per plant. Other good combiners included EC 566920 for fruit length and LC I 0/5 for fruit weight. In rain shelter, the parent LC 10/5 was identified as good combiner for fruit yield and fruit weight, LC 10/5 and Ujwala for fruits per plant, EC 566920 and AVPP 0105 were found to be good combiners for fruit length. The specific combining ability of the hybrids showed that significant positive SCA effects for fruit yield per plant was exhibited by the hybrid AVPP 0105 x EC 566920 (135.93) being the highest followed by Chivar 1 x LC 10/5 (72.42), AVPP 0105 Ujwala (57.49), LC 10/5 Chivar 1 (16.25) and LC 10/1 Chivar 1(15.54) in open field. While, the cross LC 10/1 x Ujwala showed the highest significant SCA for fruit yield per plant (70.49) followed by the crosses Chivar 1 x LC 10/5 (60.90), LC 10/5 x EC 566920 (57.67), Ujwala x AVPP 0105 (47.19), AVPP 0105 x EC 566920 (15.99) and Chivar I x LC 10/1 (14.91) in rain shelter. Four crosses namely AVPP 0105 x EC 566920 (21.46), Chivar 1 x LC 10/5 (17.25), AVPP 0105 x Ujwala (4.95) and LC 10/5 x EC 566920 (2.86) showed significant positive SCA for the trait fruit number per plant in open field condition and the crosses LC 10/5 EC 566920 (17.58), Chivar 1 x LC 10/5 (15.38), Ujwala x AVPP 0105 (10.54), AVPP 0105

x EC 566920(6.56), LC 10/1 x Ujwala (5.81) and Ujwala x 10/5 (5.55) showed significant positive SCA for fruit number in rain shelter condition The performance ofhybrids towards bacterial wilt resistance showed that three hybrids (LC 10/5 x Ujwala, AVPP 0105 x Ujwala and AVPP 0105 x EC 566920) were found resistant and five hybrids viz., Ujwala LC 10/5, Chivar I LC 10/5, Chivar I x AVPP 0I05, EC 566920 x AVPP 0105, LC IO /1 x EC 566920 were moderately resistant. No hybrids showed resistance to leaf curl virus but seven hybrids namely Ujwala LC 10/5, Ujwala LC 10 /1, Ujwala AVPP 0105, Chivar 1 LC 10 /I, Chivar I x AVPP 0105, LC IO /I x Ujwala, LC IO /I x Chivar I exhibited moderate susceptibility in both field and rain shelter evaluations to leaf curl resistance. Molecular characterization of the hybrids for disease resistance was done with the reported SSR marker CAMS 451 for bacterial wilt resistance and SSR markers viz., CA 516044 and PAU-LC-343-1 for leaf curl virus resistance after its validation in parental lines. The bacterial wilt marker was found positive in the hybrids Ujwala x LC 10/5, Ujwala x AVPP O I 05, Chivar I x LC 10/5, Chivar I x AVPP 0105, LC 10/5 x Ujwala, LC 10/5 Chivar I, LC 10/5 x EC 566920, AVPP 0105 Ujwala, AVPP 0105 Chivar I and AVPP 0105 EC 566920. The leaf curl virus marker PAU-LC-343-1 only showed polymorphism between resistant and susceptible parental lines and it was found positive for the hybrids AVPP 0105 Ujwala, Ujwala LC 10/5, LC 10/5 Ujwala, Chivar 1 Ujwala, LC 10 /1 Ujwala, Chivar 1 LC 10/5, LC 10/5 EC 566920, Ujwala x Chivar I, Ujwala AVPPO I 05, LC 10/5 Chivar t, LC I 0/5 x EC 566920 which indicated the presence of the leaf curl virus resistant gene though they were found moderately susceptible in phenotypic evaluation. Out of the eighteen hybrids evaluated, seven hybrids viz., Ujwala x LC 10/5, Ujwala x AVPP 0105, Chivar l x LC 10/5, LC 10/5 x Ujwala, LC 10/5 Chivar 1, LC 10/5 x EC 566920 and AVPP 0105 x Ujwala showed positive results for both bacterial wilt and leaf curl virus markers, indicating the presence of the respective resistant genes. In addition to their disease resistance, these hybrids also demonstrated superior field performance, making them promising candidates for further development. Therefore, the present study could identify high-yielding hybrids with improved resistance to bacterial wilt and leaf curl virus resistance. Several hybrids demonstrated high levels of heterosis for fruit yield which explains the dominant gene action

prim ari ly infl uences th is tr ait. T he G C A an d SC A variances w ere signi fi can t fo r all the char acters exam in ed in the stu dy. T his highl ights the signi fi cance of both additive and non-additive vari ance in expressing these tra its, suggestin g tha t integr ated breedin g stra tegies such as hybrid developm ent and pur e lin e breeding should be em ployed to effectively harn ess bo th typ es of genetic variability . Th e pro mi sing parents identifi ed in the stu dy w ill se rve as valuable genetic resour ces fo r tra it-specifi c cro p im pro vem ent pro gra m m es in chili. T he identifi ed hybri ds can be fu rt her advanced to success ive genera tions to validate resistance and the supe rior hybri ds can be selected fo r advanced yield trials.