Seed biopriming and spraying at fruit set for the management of chilli anthracnose caused by Colletotrichum capsicii (Sydow) Butler and Bisby

Abstract

The study entitled ‘Seed biopriming and spraying at fruit set for the management of chilli anthracnose caused by Colletotrichum capsici (Sydow.) Butler and Bisby’ was conducted at College of Agriculture, Vellayani and Coconut Research Station (CRS), Balaramapuram during 2017- 2019 with the objective to study the seed borne nature of chilli anthracnose/fruit rot caused by Colletotrichum capsici and the effect of seed biopriming and spraying during fruit set for its management. Samples of chilli seeds were collected from five agro-ecological zones of Kerala viz. Northern, High range, Central, Special problem and Southern zones. The lowest percentage of infection was found in seed samples collected from Vellayani (6.62) and the highest in Parassala (43.33). Both externally and internally seed borne fungi and bacteria were isolated from the infected seeds. Fruit rot samples were collected from five locations of Kerala viz. Vellayani, Kumarakom, Thrissur, Wayanad and Kasargod. Five isolates (C1 to C5) of C. capsici were obtained. Vellyani isolate (C1) was the most virulent isolate which recorded a lesion size of 3.81 cm in detached fruit assay at seven days after inoculation (DAI). The isolate C1 was used for further studies. Six biocontrol agents viz. Trichoderma viride (KAU isolate), Pseudomonas fluorescens PN 026 (KAU isolate), Bacillus subtilis VLY 62 Bacillus pumilus VLY 17, Bacillus amyloliquefaciens VLY 24 and Piriformospora indica were screened in vitro against C. capsici using dual culture method. B. amyloliquefaciens recorded the highest percentage suppression of mycelial growth of C. capsici (62.96) followed by B. subtilis (56.30) and T. viride (51.85). P. fluorescens did not show the mycelial growth suppression of C. capsici. In vitro assays on chilli fruits revealed that B. amyloliquefaciens was most effective in controlling fruit rot with a lesion size of 2.71 cm 10 DAI followed by B. subtilis (lesion size - 2.97 cm) and T. viride (lesion size – 3.81 cm). Peroxidase and polyphenol oxidase activities were also higher in B. amyloliquefaceins treated chilli fruits before and after treatment. Standardization of priming techniques revealed that soaking of seeds for 1 h was found effective for T. viride and 4 h for other biocontrol agents. The effective soaking durations were followed for the respective treatments in further in vivo studies. Based on the in vitro assays, the best three treatments viz., B. amyloliquefaciens, B. subtilis and T. viride were taken for in vivo studies. In vivo evaluation of seed biopriming on the control of fruit rot revealed that the lowest disease severity was recorded in B. subtilis (PDI – 37.19) followed by B. amyloliquefaciens and T. viride (PDI in both - 40.00). The severity of anthracnose in leaves was lowest in B. subtilis (PDI – 10.60) which was on par with T. viride (PDI – 11.30) and B. amyloliquefaciens (PDI – 11.90). The number of fruits per plant, 100 seed weight and seed yield per plant were higher in T. viride. In vivo studies on the effect of seed biopriming and spraying during fruit set recorded the lowest disease severity for B. amyloliquefaciens (PDI – 28.13 at 15 DAI) which was on par with carbendazim 0.1 per cent (PDI - 29.38) and was followed by B. subtilis (PDI - 31.25) and T. viride (PDI - 32.5). The severity of anthracnose in leaves was lowest in B. subtilis (PDI - 8.00) which was on par with B. amyloliquefaciens (PDI - 8.10) and T. viride (PDI - 8.50). The number of fruits per plant, 100 seed weight and seed yield per plant were highest in T. viride treated plants. Thus, the present study indicated that seed biopriming and spraying with B. amyloliquefaciens VLY 24 at fruit set was found to be the most effective for the management of fruit rot / anthracnose of chilli which could be used as an ecofriendly measure to produce safe-to-eat crop.