Studies on diversity analysis of collar rot pathogen (Phytophthora cactorum) of apple and its management
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Date
2014
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Publisher
YSPU
Abstract
The present investigations entitled “Studies on diversity analysis of collar rot pathogen (Phytophthora
cactorum) of apple and its management” was conducted in the laboratories and experimental farm of the
Department of Plant Pathology during year 2011-2013. During the survey of the disease, highest average
disease incidence was recorded in district Mandi (9.31%) while, it was minimum (3.86%) in district Kinnaur. In
the standardization of isolation technique experiment, baiting with sunhemp seeds in pond water for 96 h
yielded growth of P. cactorum in all five plates. Variability was recorded in sporangial shape and size of the
isolates as shape varied from ovoid, globose to ellipsoid with isolate PC 13 showing ellipsoid shape, isolate PC 3, PC 16 and PC 26 showing globose shape while, sporangium of all other isolates were ovoid shaped. Mycelial growth pattern in the culture were also variable with chrysanthemum like or radiate to slightly radiate growth pattern. Colonies of PC 6 and PC 20 were slightly submerged and it was submerged in isolate PC 11 and PC 22 while, colonies of rest of the isolates were with dense aerial or sparse aerial mycelium. Similarly, variability was also noticed in pathogenicity the different isolates. Polymorphic fragments generated by PCR using four primers were 12/12 with OPA 1, 11/11 with OPA 2, 7/7 with OPA 13 and 12/12 with OPA 16 showing 100 per cent polymorphism and the genetic polymorphism ranged from 17 to 70 per cent. Among ten pollinizer cultivars of apple evaluated for source of resistance, Stark Spur Golden showed maximum tolerance as minimum seedling mortality of 15.11 per cent. Among non-systemic fungicides tested in vitro, mancozeb was highly efficacious and gave 97.62 per cent mycelial inhibition of test pathogen followed by metiram (91.39%). Among the six combi-fungicides, cymoxanil + mancozeb (Curzate M) and metalaxyl + mancozeb (Matco) were most effective 97.87 per cent mycelial inhibition. Under pot conditions, metalaxyl + mancozeb and cymoxanil + mancozeb were best and statistically at par with each other. Water extract of mustard cake and Eucalyptus leaves were the most effective and significantly superior treatments among botanicals under in vitro and in vivo conditions. Trichoderma harzianum 1 resulted in maximum growth inhibition (52.96%) and minimum disease incidence of 20.0 per cent. Three most effective antagonists were found compatible with all three fungicides and botanicals. Under integrated management studies, maximum disease control of 99.16 and 99.15 per cent in disease incidence and severity, respectively was achieved with treatments C1E2B1 (Curzate M + Mustard cake +T. harzianum) and C2E2B1 (Matco + Mustard cake + T. harzianum). Maximum increase in shoot length (48.6 cm) was also recorded in the treatment combination C2E2B1 (Matco + Mustard cake + T. harzianum).
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Keywords
diseases, apples, fungi, pathogens, biological phenomena, planting, irrigation, fungicides, biological development, biochemical compounds