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Epidemiology and Management of Leaf Spot of Cotton Caused by Alternaria spp.

KrishiKosh

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Title Epidemiology and Management of Leaf Spot of Cotton Caused by Alternaria spp.
 
Creator Govindappa N. Hosagoudar
 
Contributor S.N. Chattannavar
 
Subject Plant Pathology
 
Description Cotton, does not need much emphasis as being the principal raw material for a
flourishing textile industry. The research studies revealed that the maximum
Alternaria leaf spot disease severity was recorded in Gulbarga, Yadagiri, Dharwad
and Raichur districts. Among 17 isolates, in morphological studies mean colony
diameter ranged between 60 mm (Hirebagevadi) to 84 mm (Bagalkot). The mycelial
width was larger in Kalmala (4.76 μm) and was least in Hattigudoor (2.53 μm). The
dimensions of conidia of Kalmala isolate showed maximum size of 43.98-76.89 x
8.43-18.70 μm and Annigeri isolate showed maximum beak length of 16.30 μm.
The temperature studies revealed that, the Hanumanamatti isolate (230.20 mg)
recorded maximum dry mycelial weight. The highest dry mycelial weight was
recorded at 30oC (252.38 mg) followed by 25oC (237.76 mg). The dry mycelial
weight was significantly superior at pH 7 (230.21 mg), followed by pH 8 (215.18
mg). RAPD analysis revealed the maximum genetic similarity of 93 per cent between
Gabbur (A7) and Sunkeshwarhal (A8) isolates, whereas the least similarity (40 per
cent) was between Hattigudoor (A9) and Yaragatti (A13). The isolates were made into
i.e., A cluster and B cluster.
Stepdown regression led to the equation as Y = – 235.94 + 9.89X1 – 11.84X2 +
1.89X3 + 0.64X4 – 1.23X6 with R2 value of 0.78 including variables maximum
temperature, minimum temperature, RH (morning), RH (evening) and rainy day.
Fungi viz., Alternaria spp., Fusarium spp., Helminthosporium spp., Aspergillus spp.,
Penicillium spp., Rhizopus spp. and Mucor spp. were detected in infected seeds and
survival studied for more than 14 months in refrigerator condition.
The maximum per cent avoidable yield loss was recorded in Propiconazole
(0.1%) at 35, 55, 75, 95, and 115 DAS. Yield reduction was 32.38 per cent in Bunny
Bt caused by Alternaria leaf spot. Seed Treatment (ST) of Vitavax power (0.3%) +
Foliar Spray (FS) with Propiconazole (0.1%) significantly lowered Alternaria leaf
spot per cent disease index. However, the ST of Vitavax power (0.3%) + FS with
Hexaconazole (0.1%) recorded highest incremental benefit: cost of 5.24. The T. viride
(TV-97), seed treatment (0.8%) + foliar spray (0.8%) and Propiconazole, FS (0.1%)
and both the treatments recorded highest and same incremental benefit: cost of 4.34.
 
Date 2016-07-25T13:51:58Z
2016-07-25T13:51:58Z
2012
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/69772
 
Format application/pdf