INVESTIGATIONS ON THE EFFECT OF SOME PLANT DEFENSE ACTIVATORS IN ONION AGAINST PURPLE BLOTCH DISEASE
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Date
2014-12
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UNIVERSITY OF HORTICULTURAL SCIENCES, BAGALKOT
Abstract
Onion (Allium cepa L.) is an important commercial vegetable crop of India grown for domestic and international market. Purple blotch disease caused by the fungus Alternaria porri (Ellis) Cif. is one of the serious onion production constraints in the country. At present, the management of this foliar disease under field situation mainly relies on frequent fungicidal sprays. However, due to hazardous nature of chemical pesticides there is a search for safer alternatives for managing pest and diseases and the present study was aimed at that.
Field experiments were conducted during Rabi 2013 at College of Horticulture, UHS campus, GKVK, Bengaluru, to test the effectiveness of some of the known plant defense activators viz., silicon, organic chemical compounds (INA and BABA) and biological defense activators on two varieties (Arka Kalyan and Bellary Red ) of onion against purple blotch disease.
Silicon was applied to soil at the time of planting or as foliar spray of soluble silicic acid to the plants. Silicon treatment significantly reduced purple blotch disease incidence and severity, and increased the average bulb weight and bulb yield when compared with untreated control or standard check (mancozeb @ 2.5 g L-1). Two foliar spryas of silicic acid @ 4 ml L-1 was the best treatment followed by silicon soil application @ 300 kg ha-1. Among the chemical plant defense activators like isonicotinic acid (INA) and beta amino butyric acid (BABA) tested at different concentrations reduced the incidence and severity of purple blotch disease and increased the yield significantly over control. Further, BABA 1.0 g L-1, BABA 0.5 g L-1, INA 100 mg L-1, INA 150 mg L-1 were better or on par with standard check (mancozeb 2.5 g L-1). Studies on the effect of PGPR and bioagents (Trichoderma harzianum, Pseudomonas fluorescens) indicated that these agents positively influenced plant height, number of leaves and yield in both the varieties and reduced the incidence and severity of purple blotch disease. Consortium of PGPR soil application @ 12 kg ha-1 + three sprays of PGPR @ 20 g L-1 proved the best.
Description
DEPARTMENT OF PLANT PATHOLOGY
COH, BENGALURU - 560 065
UNIVERSITY OF HORTICULTURAL SCIENCES
BAGALKOT
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