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20201
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Subject: Plant Pathology × Author: Amrinder Kaur × End date: 2020 × Type: Thesis ×
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    ThesisItemOpen Access
    DIVERSITY AND ECO-FRIENDLY MANAGEMENT OF Helminthosporium spp. OCCURRING ON BARLEY AND OTHER GRAMINACEOUS HOSTS
    (Punjab Agricultural University, Ludhiana, 2020) Amrinder Kaur; Vineet Kuma
    Cereal crops all around the world are reported to be attacked by number of pathogenic microbes, among which the diseases incited by Helminthosporium species are economically very important. Among the 50 diseased samples collected during the survey from the various wheat, barley and oat growing areas of Punjab and adjoining states, Bipolaris sorokiniana was present in all the isolates from barley, wheat and Phalaris minor, while Drechslera avenae was found to be associated with the isolates from oats. All the cultures varied significantly with respect to their morphological traits. Total 12 isolates out of 50 were having greyish black growth of the mycelium on the PDA medium while, 34 and 4 isolates were whitish grey and greyish white, respectively. The pattern and margins of growth in most of the isolates were found to be raised and irregular, respectively. Three types of conidial shapes were recorded in all the isolates viz., oblong, elliptical and slightly curved with maximum conidial germination (95.70%) shown by isolate Bsb1 followed by Bsb42 (92.80%) and Bsw23 (91.28%) and it was minimum in isolate Bsb40 (51.20%) followed by Bsp33 (52.40%). All the 50 isolates were pathogenic towards their susceptible check PL426 (barley), HD-2329 (wheat), OL-9 (oats) and Phalaris minor. Minimum incubation period (2days), maximum no. of lesions per leaf (9.29), maximum size of lesions (9.30 mm2) and highest terminal disease severity score (89) were recorded with isolate Bsb1 from barley, followed by Bsw23 from wheat. The cross- infectivity of representative isolates of each host from each group viz., Bsb1 (barley), Bsw23 (wheat), Bsp34 (P.minor) and Da46 (oats) tested on different hosts revealed that all these isolates were found to be cross-infective on different graminaceous hosts except sorghum, rice and different weed hosts. Molecular variability studied among all the 50 isolates using ten different SSR markers revealed that primer BS 065 and BS 027 were found to be highly polymorphic as compared to other primers and thus can be used further for genetic diversity studies. Maximum melanin (µg/g of mycelium) production was recorded in the isolate Bsb1 (2.58 µg/g) followed by isolate Bsp34 (2.52 µg/g) and Bsw23 (2.49 µg/g) at 25°C, whereas, decrease in the trend of melanin production was observed at lower and higher temperature of 15°C and 35°C, respectively as compared to 25°C and 30°C. Among the different barley genotypes screened under field conditions, five genotypes (BL-1309, BL-1313, BL-1532, BL- 1562 and PL891) were found resistant and thirty three genotypes exhibited moderately resistant reaction to foliar blight pathogen. Considering the harmful effects of only use of fungicidal sprays, an eco-friendly approach was followed to manage foliar blight of barley. Maximum per cent growth inhibition (65.48%) under in vitro conditions was recorded with neem @15% followed by tulsi (45.37%) at the same concentration. Propiconazole 25EC @0.1% (standard chemical check) exhibited 100% mycelial growth inhibition as compared to the different botanicals tested and among bio-agents, T. harzianum exhibited 60.82% growth inhibition of the pathogen followed by T. viride as compared to the control. When these promising botanicals and bio-control agent were tested under field conditions for the management of foliar blight of barley, maximum per cent disease control (48.78%) was recorded with neem as compared to control. Among the different SAR chemicals tested under pot house conditions on two barley cultivars, PL 426 and PL807, maximum disease control (50.96%) was observed when the plants were sprayed with salicylic acid @ 0.03%, followed by 41.90% with BABA @ 0.3%. The promising doses of these SAR chemicals when tested under field conditions were found to be effective in controlling the disease upto 40 – 50% in susceptible cultivar PL 426 and upto 45 to 58% in the moderately resistant cultivar PL 807, as compared to the control and an increase was noticed in activity of defense enzyme (PAL) and phenol content of moderately resistant (PL807) and susceptible (PL 426) barley genotypes inoculated with the spore suspension of B. sorokiniana, however the increase was more pronounced in all the treatments in PL 807 as compared to the susceptible check PL 426. Thus, these disease management strategies could be further incorporated in IPM programmes for effective management of foliar blight disease of barley.