STUDIES ON ALTERNARIA BLOTCH OF APPLE AND ITS MANAGEMENT
| dc.contributor.advisor | GUPTA, A K | |
| dc.contributor.author | CHAUHAN, PRANEET | |
| dc.date.accessioned | 2018-12-22T07:26:26Z | |
| dc.date.available | 2018-12-22T07:26:26Z | |
| dc.date.issued | 2018-10 | |
| dc.description.abstract | ABSTRACT Alternaria blotch caused by Alternaria alternata f. sp. mali is one of the economically important disease of apple particularly in Himachal Pradesh. Therefore, the present investigations were undertaken with the objectives to record the prevalence of this disease; study the variability of causal agent Alternaria isolates and evolve effective disease management strategy through the use of fungicides, plant extracts, bioproducts, biocontrol agents and their combinations as well as host resistance during the year 2015-2017. Alternaria blotch of apple was found to occur in moderate to severe form in different apple growing areas of district Shimla of Himachal Pradesh. The mean disease incidence ranged from 11.00 to 50.00 per cent with maximum at Summerkot and minimum at Khadrala of district Shimla, while highest disease severity was recorded at Chaithla and lowest at Khadrala in the same district with an average of 6.20-27.57 per cent. Pathogenicity test revealed that symptoms appeared after 4 to 7 days of inoculation. Eleven isolates of Alternaria spp. were isolated from apple cv. Royal Delicious and fiveisolates were isolated from tomato, cabbage, marigold, carnation and pear. These isolates differed in their ability to produce typical symptoms. Morphological, cultural and molecular studies were made to ascertain the prevalence of variability among the isolates. Colonies varied in their cultural behaviour ranging from velvetty to cottony, mostly appressed, with regular to irregular margins. Colour of the colonies varied from light to dark olivaceous. The mean ,of the isolates was between 32.90 to 66.92 mm after 8 days of inoculation with highest growth in Isolate 1 on potato dextrose agar medium and lowest in Isolate 8 on Dimmick’s agar medium. Morphological studies revealed variations in their size, shape and septations of conidiophore and conidia. Maximum conidial size was 19.38-38.8× 9.90-20.7 μm and minimum was 9.9-23.8× 5.3-13.6 μm in Isolate 10 and Isolate 9, respectively. Isolates when tested for their pathogenic behaviour showed variation in incubation period, latent period and disease reaction. A positive reaction was observed on the susceptible apple cv. Royal Delicious during the leaf necrosis bioassay, demonstrating the host specific nature of the toxin. Molecular characterization of the seven isolates of Alternaria spp. showed 99-100% homology with Alternaria alternata, Alternaria mali and Alternaria spp. Phylogenetic tree depicted that all the isolates were closely clustered to Chinese isolates deposited earlier in the NCBI. The sixteen isolates of the Alternaria spp. were differentiated on the basis of location, host, cultural and morphological characteristics using RAPD markers. Leaves collected during autumn produced the maximum inoculum in the month of August i.e. 3.7 ×103conidia/ml whereas, the production of primary inoculum was least (1.8×103 conidia/ml) on the leaves during April. Alternaria alternata f.sp. mali infection on host physiology revealed that reducing and non reducing content were more in uninoculated plants in all the test cultivars with time lapse. Total phenolics content, polyphenol oxidase, peroxidase, PAL activity and ROS were more in inoculated plant during all the sampling hours in all the three test cultivars. Screening of cultivars revealed that only one cultivar Top Red Delicious showed highly susceptible reaction and Starking Delicious showed susceptible reaction. Six cultivars viz., Manchurian Crab, Tydeman’s Early Worcestor, Hardeman, Stark Spur Golden, Gold Spur and Scarlet Gala were found to be moderately susceptible at RHR&TS Mashobra while, two cultivars viz., Royal Delicious and Vance Delicious showed susceptible reaction at Nauni. Out of ten systemic and non-systemic fungicides evaluated under in vitro conditions, two fungicides viz., difenoconazole and propineb exhibited complete mycelial growth inhibition against the test pathogen. Amongst eight plant extracts tested under in vitro conditions, leaf extract of neem was found to be most effective with 72.89 per cent mycelial growth inhibition, while in case of bioproducts tested, Neemazal, cow urine and field formulation gave cent per cent mycelial growth inhibition. Under pot conditions, difenoconazole + propineb gave good disease control as compared to all other combinations. Among SAR chemicals tested, BABA @2000 ppm found to be the most effective in all the cultivars, with minimum disease severity rangingfrom 5.24-7.15per cent and maximum disease control rangingfrom 69.71-75.85per cent. In case ofSAR chemicaltreatments, there was an increasein reducing sugar and non reducing sugar over the untreated controlin all three cvs. of apple with maximum in salicylic acid and minmum in calcium carbonate treated leaves, respectively. Total phenol content in apple leaves after treatment with SAR inducers was found to be maximum in salicyclic acid treated leaves and minimum in calcium carbonate. Polyphenol oxidase, Peroxidase and PAL activity was found to be highest in salicyclic acid treated leaves in all the three cultivars. Production of Reactive oxygen species was found to highest in salicyclic acid treated leaves in all the three cvs. Among biocontrol agents, Pseudomonas flourescens @105cfu/ml found to be best in all the cvs. tested with minimum disease severity ranging from 1.90-13.33 per cent and maximum disease control ranging from 63.79-89.01 per cent. Maximum suppression of the primary inoculum was observed when the leaf litter was dipped in urea (50000 ppm) followed by difenoconazole (1000 ppm) and hexaconazole (1000 ppm). Under field conditions, the combination of difenoconazole and propineb was most effective(95.30%)in disease control, whileBacillus subtilis was found least effective (58.66%). | en_US |
| dc.identifier.uri | http://krishikosh.egranth.ac.in/handle/1/5810086230 | |
| dc.keywords | disease of apple,Alternaria blotch, diametric growth | en_US |
| dc.language.iso | en | en_US |
| dc.pages | 165+xi | en_US |
| dc.publisher | UHF, NAUNI | en_US |
| dc.sub | Plant Pathology | en_US |
| dc.subject | null | en_US |
| dc.theme | disease of apple,Alternaria blotch, diametric growth | en_US |
| dc.these.type | Ph.D | en_US |
| dc.title | STUDIES ON ALTERNARIA BLOTCH OF APPLE AND ITS MANAGEMENT | en_US |
| dc.type | Thesis | en_US |
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