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Title: Management of Black Scurf of Potato by Commercial Biofertilizers and Asteraceous Weeds
Authors: Rafiq, Muhammad
Keywords: Plant Sciences
Plant Pathology
Issue Date: 2020
Publisher: University of the Punjab , Lahore
Abstract: Potato (Solanum tuberosum L.) is a widely cultivated crop in different agroclimatic conditions of Pakistan. Despite the ease in cultivation and fewer labor requirements, potato productivity in Pakistan is not at par with the world’s potato production. Among different biotic constraints, black scurf disease caused by the Rhizoctonia solani Kühn, is very common and destructive disease for potato production in Pakistan. Various conventional practices including application of chemical fungicides can help to lessen disease severity but still an effective control measure to completely manage this disease is unavailable. Thus, this study was conducted to examine the potential of commercially available biofertilizers and soil amendments using weeds biomass of family Asteraceae to manage black scurf disease. In vitro screening experiments for evaluation of antifungal activity of four asteraceous weeds revealed that different concentrations (1.56–200 mg mL–1 ) of the methanolic extracts (leaf, stem, root and fruit) of Silybum marianum L., Xanthium strumarium L., and Sonchus asper (L.) Hill significantly decreased the biomass of R. solani by 70–97%, 60–99% and 40–97%, respectively, while extracts of Carthamus oxycantha M. Bieb did not exhibit inhibitory activity against R. solani. Due to their best antifungal activity, leaf and root extracts of S. marianum and X. strumarium were partitioned using n-hexane, chloroform, ethyl acetate and n-butanol. Bioassays with 1.56–200 mg mL–1 concentrations of these fractions showed pronounced antifungal activity against R. solani. Different fractions of X. strumarium and S. marianum extracts reduced biomass of R. solani by 66–100% and 32–100%, respectively. GCMS analysis showed presence of a large number of compounds of diverse nature in these fractions. Among the major constituents, a few namely benzoic acid, 4-hydroxy3- methoxy-, methyl ester; 5-amino-8-hydroxyquinoline; pyridine, 2-pentyl-; glycerol; salicylic acid; cinnamic acid; xylitol and dodecanoic acid (lauric acid) were identified as potent antifungal with reference to literature. Host susceptibility of ten potato varieties against black scurf disease was assessed in a pot experiment. The results revealed four varieties (Ronoldo, Rubi, Challenge and Sadaf) as moderately resistant, three (SH-5, Sante and Astrex) as moderately susceptible and remaining three (Karoda, Mosica and Simply red) as 2 susceptible. Disease also reduced number and size of tubers, while the disease incidence showed negative (P ≤ 0.001) correlation with chlorophyll and protein contents, and activities of catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO) enzymes. For disease management, two potato varieties Karoda (moderately susceptible) and Sante (susceptible) were selected. Two commercially available biofertilizers viz. Fertibio and Feng Shou were applied to the soil either alone or in combination with dry biomass of X. strumarium and S. marianum to evaluate their disease managing potential. The highest disease pressure was observed in positive control (with R. solani only) where 100% and 90% disease incidence were recorded in Karoda and Sante, respectively. Chemical fungicide (ithiocarbamate) significantly reduced black scurf disease incidence to 44% and 36% in Karoda and Sante, respectively. Different doses of S. marianum dry biomass (0.5–1.5%) more effectively reduced disease incidence to 23–31% in Karoda, and 21–33% in Sante. Likewise, different doses (1– 3%) of X. strumarium dry biomass significantly decreased disease incidence to 29– 44% in Karoda and 24–36% in Sante. Fertibio was more effective than Feng Shou in alleviating stress of black scurf in potato. A 1.5% dose of S. marianum dry biomass in combination with Fertibio showed the highest management potential of black scurf disease in both the potato varieties, where disease incidence was significantly dropped to 10% in Karoda and in 6% in Sante. Plant physiological and biochemical attributes were significantly stimulated, while tuber’s weight, photosynthetic pigments, total protein content, and antioxidant enzymes (CAT, POX and PPO) exhibited positive correlation (P ≤ 0.001) with each other due to application of the plant dry biomass or the biofertilizers. The present study concludes that combined application of Fertibio and dry biomass of S. marianum can be used to manage black scurf disease of potato. Such eco-friendly biopesticides and botanical fungicides could be essential tools for management plant disease and yield improvement. Further studies are needed to investigate cost effectiveness, applicability, commercialization and safety of such biofungicides.
Gov't Doc #: 20703
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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