STUDIES ON SEED BORNE FUNGI IN GROUNDNUT
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Date
2019
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Acharya N G Ranga Agricultural University, Guntur
Abstract
The present investigation was carried out in the laboratory of Department of Seed Science and Technology, Advanced Post Graduate Centre, and RARS, Lam, Guntur, Andhra Pradesh during 2018-2019 to detect and isolate seed borne mycoflora of groundnut, to study the impact of Aspergillus spp. on seed quality parameters and management of Aspergillus spp. in groundnut.
A total of 11 farmers’ saved seed samples of groundnut were collected from three different districts in Andhra Pradesh and 13 genotypes were collected from ARS, Kadiri and RARS, Tirupathi. The farmers’ saved seed samples were analysed for seed borne mycoflora by standard blotter method, deep freezing blotter method, 2, 4-D blotter method, agar plate method with PDA and paper towel method. A total of eight fungal species belonging to seven genera were found to be associated with the seed of groundnut. Among these fungi, the mean incidence of A. niger was highest followed by A. flavus, while that of Penicillium sp. was found to be the lowest in all the detection methods.
Agar plate method was found to be efficient in isolation of A. niger, A. flavus, Rhizopus and Fusarium. 2, 4-D blotter method was found to be efficient for isolation of Macrophomina phaseolina and Alternaria. Standard blotter method was found to be better for isolation of Sclerotium. Deep freezing blotter method was found to be efficient for isolation of Penicillium.
Of all the five methods tested, agar plate method with PDA was found to be superior in recording maximum incidence of mycoflora from all the test samples, while rolled paper towel method was found to be least effective for the detection of seed borne fungi. Samples collected from farmers of Guduru village of Nellore district were found to be highly infected with different mycoflora followed by samples collected from the farmers of Cherukupalli village of Guntur district while samples collected from the farmers of Yazili village of Guntur district were least infected with seed mycoflora.
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Studies on the location of seedborne fungi in the groundnut by component plating revealed that seed coat is the most infected part followed by cotyledons. A. niger remained the most frequently occurring fungus in both seed coat and cotyledons where as in case of embryo Fusarium followed M. phaseolina remained predominant.
The impact of major seed borne fungi, A. niger and A. flavus on seed quality and biochemical characters of different genotypes was observed. Both these fungi caused reduction in all seed quality and biochemical characters except in per cent disease incidence and total phenol contents where an increasing trend is observed. Between these two fungi A. niger resulted in maximum changes in seed quality and biochemical characters over control.
The results indicated that on an average, A. niger caused 25.14, 25.18, 43.99, 22.55 and 41.46 per cent reduction in seed germination, seedling length and seedling vigour index I, seedling dry weight and seedling vigour index II, respectively over control. Similarly A. flavus caused 22.38, 24.23, 41.18, 18.62 and 36.93 per cent reduction in seed germination, seedling length and seedling vigour index I, seedling dry weight and seedling vigour index II, respectively over control. The per cent infection increased from 8.87 in control to 42.23 and 40.94 in seeds inoculated with A. niger and A. flavus, respectively.
On an average A. niger caused 8.82, 21.79 and 1.65 per cent decrease in protein, total sugar and oil contents and 13.22 per cent increase in total phenol content over control. Similarly A. flavus also caused 7.10, 12.08 and 1.33 per cent reduction in protein, total sugar, and oil contents and 11.69 per cent increase of phenol content over control.
A total of eight treatments comprising of four fungicides viz., mancozeb, carbendazim, tebuconazole, carboxin+thiram and two bio-control agents viz., Trichoderma viride and Pseudomona fluorescens were evaluated against A. niger and A. flavus under in vitro conditions using rolled paper towel method. In case of A. niger inoculated seed, tebuconazole @ 1 g kg-1 seed recorded highest germination of 91.04% and lowest per cent disease incidence of 4.10 followed by carbendazim @ 2 g kg-1 seed. Highest seedling length (18.44 cm), seedling vigour index I (1660), seedling dry weight (0.22 g) and seedling vigour index II (19.48) was recorded in carbendazim @ 2 g kg-1 seed followed by carboxin+thiram @ 2 g kg-1 seed and mancozeb @ 3 g kg-1 seed. Similarly, in case of A. flavus inoculated seed, tebuconazole @ 1 g kg-1 seed recorded highest germination of 91.00% and lowest per cent disease incidence of 3.88 followed by carbendazim @ 2 g kg-1 seed. Highest seedling length (18.93 cm), seedling vigour index I (1716), seedling dry weight (0.23 g) and seedling vigour index II (20.60) was recorded in carbendazim @ 2 g kg-1 seed followed by carboxin+thiram @ 2 g kg-1 seed and mancozeb @ 3 g kg-1 seed.
Based on the results obtained it is concluded that seed treatment with tebuconazole @ 1 g kg-1 or carbendazim @ 2 g kg-1 efficiently controls the seed borne infection of A. niger and A. flavus in groundnut.
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D5771
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