Seed-borne nature and management of Alternaria alternata (Fr.) Keissl., the cause of fruit rot in chilli (Capsicum annum L.)
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Date
2019-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Chilli (Capsicum annuum L.) is one of the most important commercial crops and highly valued for its flavour, colour as well as its antioxidant compounds. It is affected by many diseases such as damping off, powdery mildew, anthracnose, leaf spot and fruit rot. Fruit rot of chilli has been found to be quite serious and wide spread disease which causes significant losses in fruit production and seed quality. Investigations were undertaken to study the fruit rot, its pathogen and effect of seed-borne infection on seed quality parameters, detection, transmission, location of seed-borne inoculum in various seed components, persistence of pathogen on/in the seed and in vitro evaluation of fungicides against the
pathogen. The symptoms of disease appeared on all aerial plant parts. At the fruit setting stage severe fruit rot was observed. The fungus has also been found on seeds collected from infected fruits. The seeds from infected fruits were discoloured and covered with mycelial growth of
the fungus. On the basis of cultural and morphological characteristics, the fungus was identified as Alternaria alternata by ITCC, New Delhi. Spores of the fungus appeared in long chains on the surface of the seeds when observed under stereo binocular. The maximum radial
growth of the fungus was observed on Potato Dextrose Agar medium, at 25±1°C after 7 days of incubation. The fungus associated with the infected seeds reduced seed germination, adversely affected the seedling growth, seed weight & seed viability. The seedlings raised from infected seeds increased abnormal seedlings and exhibited seedling infection. Seed when stored at ambient storage conditions, the longevity of the fungus in seed went on reducing with the increase in storage period. Standard blotter method was found to be the best as it exhibited
maximum recovery of fungus from infected seeds as compared with other methods. The presence of fungal mycelium was observed in the seed coat, pericarp and endosperm. Seed components were invaded with the fungus leading to disintegration of the seed tissues. Seed treatment with fungicides (Thiram 75% DS; Mancozeb 63% +Carbendazim 12% WS; and Metiram 55% + Pyraclostrobin 5 % at 500 μgml-1) enhanced the seed germination, reduced abnormal seedlings and seedling infection. The fungicides when evaluated against A. alternata in vitro at different concentrations (25 μgml-1, 50 μgml-1, 75 μgml-1, 100 μgml-1) showed that all the fungicides used in the present investigation significantly inhibited the radial growth of the fungus, irrespective their concentration, as compared to check. However, Tebuconazole 25.9% EC; Trifloxystrobin 25% + Tebuconazole 50% WG; Thiram 75% DS at 50ppm, 75ppm , 100ppm and Azoxystrobin 11% + Tebuconazole 18.30% SC at 100 ppm and Captan 70%+ Hexaconazole 5% WP at 50ppm & 100ppm exhibited maximum growth inhibition of the fungus.
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