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INTEGRATED MANAGEMENT OF BLACK SCURF OF POTATO

Naz, Farah (2006) INTEGRATED MANAGEMENT OF BLACK SCURF OF POTATO. PhD thesis, University of Arid Agriculture, Rawalpindi.

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Abstract

Black scurf caused by Rhizoctonia solani Kuhn is a serious disease in the eight potato (Solanum tuberosum L.) production agro-ecological zones of Pakistan. The management of this disease problem is difficult by single control measure because of its soil-borne nature and high degree of survival of this fungus. Therefore, control measures namely chemical, biological and cultural were first investigated individually and later on the best treatment evaluated out of each study were combined in the integrated disease management (IDM) investigations. To study the effect of graded soil-borne inoculum in causation of black scurf, three potato cultivars (cvs.) and two advanced lines were evaluated against three soil-borne inoculum levels, 10, 15 and 20 g of R. solani AG 3 isolate CL-58 (a known aggressive isolate). The disease was evaluated based on eyes germination inhibition, sprouts killing, stem canker index, stolon canker index, black scurf disease index and yield reduction (parameters). It was found that 20 g inoculum dose /pot (8"xll ") of the fungus is the best for the disease screening. Management of disease through determining level of susceptibility in 14 potato cultivars I advanced lines was investigated by using isolate CL-58 under greenhouse conditions against the same abovementioned disease symptoms. The overall reaction of cvs. / lines to the disease ranked cv Desiree as the susceptible and cv. Cardinal and line CIP-393574-61 resistant. Concurrently, 26 plant extracts were also screened in vitro. for their antifungal activity against R. solani. Seed diffusates of Brassica rapa (turnip), B. napus (canola) and Allium cepa (onion) appeared significantly (P<0.05) the most effective and they exhibited 100 % inhibition in radial mycelial growth of the fungus at all the concentrations i.e. 10, 50, and 100 g L-1 of the potato dextrose agar medium tested. Later-on, the efficacy of seed treatment with these plant extracts and chemicals, boric acid @ 3 %, Daconil @ 5g L-1 and mixture of I % acetic acid + 0.05 % zinc sulfate was studied under green house conditions. Tuber treatment with boric acid gave statistically significant protection to eyes and sprouts against soil-borne inoculum as compared to rest of the treatments. The effect of biofumigation canola B. napus as green manure (20 days old plants) and cover crop (60 days old root tissues in soil) was evaluated against soil-borne R. solani, to distinguish the efficacy of allelochemicals produced by glucosinolates hydrolysis following soil incorporation of tender and old root tissues of B. napus in black scurf management Soil incorporation with 20 days old canola crop gave significant protection against the fungus when compared with the plants following incorporation of 60 days old canola root tissues and inoculated control. The efficacy of soil application with microbial preparations viz. Trichoderma harzianum, effective microbe (EM) culture and biological potassium fertilizer (BPF) was also evaluated for the management of soil-borne inoculum of black scurf of potato by sowing cv. Desiree. Soil application with T. harzianum gave significant protection to eyes, sprouts and stolons, against soil-borne inoculum of the fungus which ultimately contributed to better crop stand and increased yield as compared to inoculated control and rest of the treatments. Accordingly, the best disease control measures evaluated in individual investigations were combined and their integrated effect was determined in solarized and non-solarized soil. Efficacy of seed treatment with boric acid, supplemented with biofumigation and soil application of T. harzianum in the IDM of black scurf pathogen conferred considerable protection to the eyes, sprouts, stems and stolons, which eventually, provided better crop stand and lower yield reduction (14.08%) as compared to 54.21, 41.24 and 32.41% reduction in yield respectively when these treatments were administered individually.

Item Type:Thesis (PhD)
Uncontrolled Keywords:black scurf, potato, rhizoctonia solani, solanum tuberosum l, integrated disease management, inoculum, desiree, cardinal, brassica rapa (turnip), b. napus (canola), allium cepa (onion), allelochemicals, trichoderma harzianum, biofumigation, boric acid
Subjects:Biological & Medical Sciences (c) > Medical Sciences (c2) > Pathology(c2.4)
ID Code:1409
Deposited By:Mr. Muhammad Asif
Deposited On:26 Feb 2007
Last Modified:04 Oct 2007 21:06

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