Variability and management of Colletotrichum gossypii Southw., the incitant of anthracnose disease of cotton
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Date
2023-03
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CCSHAU, Hisar
Abstract
The present investigation entitled, “Variability and management of Colletotrichum gossypii Southw., the incitant of anthracnose disease of cotton” was conducted during Kharif, 2020 and 2021 at CCS Haryana Agricultural University, Hisar. This investigation was aimed to study cultural, morphological and molecular variability among different isolates of Colletotrichum gossypii; to manage pathogen under in vitro and in vivo conditions and to screen cotton genotypes for disease resistance. Anthracnose disease of cotton caused by Colletotrichum gossypii is becoming serious impediment and limiting factor for reduced quality and quantity of produce. All the collected C. gossypii isolates showed a significant variation in cultural, morphological and molecular characteristics. The maximum mean radial growth was recorded for COG 5 isolate i.e., 52.20 mm, whereas minimum radial growth of 29.20 mm was recorded in COG 13 isolate. Most of the collected isolates have shown whitish-creamy and whitish to grey colony colour except COG 13 which showed whitish to pink colour. The size of conidia varied from 8.58-11.41 μm × 3.39-4.54 μm. The COG 5 isolate recorded maximum mycelial width (4.37 μm), while minimum mycelial width was observed in COG 13 (2.89 μm). ITS region, TUB region and species specific SNP primers successfully identified and confirmed C. gossypii, and ISSR primers grouped all isolates into two major clusters at a similarity coefficient of 0.67 depicting the genetic variability among 13 isolates of C. gossypii. The extract of garlic cloves recorded maximum growth inhibition (83.96%) under in vitro conditions. Trichoderma harzianum recorded maximum mycelium growth inhibition (65.37%) among five biological control agents. The maximum mean mycelial growth inhibition was recorded by azoxystrobin 18.2% + difenoconazole11.4% SC i.e., 90.48 per cent among all the seven evaluated fungicides. Amongst four tested fungicides under field conditions, maximum mean disease control during Kharif 2020 and 2021 was recorded by azoxystrobin 18.2% + difenoconazole 11.4% SC @ 0.1 % i.e. 78.21 and 75.80 per cent in RCH 773 and H1098i, correspondingly with highest cotton yield of 2590.26 and 2105.29 kg/ha in cotton cultivars RCH 773 and H1098i, respectively. The maximum disease control was recorded by garlic cloves extracts i.e. 62.50 and 60.92 per cent in RCH 773 and H1098i, respectively with maximum yield in RCH 773 (2436.62 kg/ha) and H1098i (2018.18 kg/ha) during Kharif, 2020 and 2021. Among all the 131 germplasm lines which were screened against cotton anthracnose disease, sixty four genotypes exhibited moderately resistant reaction.