Competitive ability of rice cultivars against weeds: role of growth physiology and phenolic allelopathy
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Date
2008-01
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The present study was conducted in the Crop Research Center and Plant Physiology Department of G. B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand, with an objective to elucidate the competitive ability of five rice cultivars viz. Sarju 52, Narendra 359, Pant Dhan 12, Pant Dhan 16 and VL Dhan 206 against weeds, with an emphasis on the role of growth physiology and phenolic allelopathy.The experiment was conducted during rainy season of 2006 and 2007, in a split plot design with three replication. The treatments consisted of Weedy, Hand weeding, Butachlor. Morphological parameters such as plant height, tiller number, leaf number, as well as leaf growth parameters, grain yield and panical number; physiological parameters such as RGR, RLGR, RLAGR, LAR, SLW and NAR, was measured at different time intervals dry matter production. Biochemical parameter such as phenol content and profiling through HPLC were carried out at different growth. The effect of different phenolics alone or in combination and the water-soluble extracts of root and shoot tissuses of rice on germination and seedling growth of six weed species were analyzed in petri-dishes under laboratory conditions. Among the different phenolics, p- hydroxybenzoic acid and gallic acid had maximum inhibitory effect on weed seed germination. Inhibition of germination was greater when the phenolics were used in different combination than when used individually. Among shoot and root extract, the shoot extract of varieties PD12 and PD16 had maximum inhibitory effect on germination and seedling growth of all the six weed species under study. Among the five rice cultivars, PD 12, PD 16 & Narendra 359 were found to be highly competitive while VL Dhan & Sarju 52 were less competitive cultivars, as evident from their CWCI. VL Dhan is a taller variety & has lower yield potential while PD 12, PD 16, Sarju 52 and Narendra 359 are semi-dwarf varieties and had higher yield potential. The higher biomass at early vegetative stage contributes to their competitive ability so that PD 12 and PD 16 are more competitive cultivars than Narendra 359 and Sarju 52 while; VL Dhan was the least competitive cultivar. PD 12 & PD 16 had higher tiller number at 30 DAT, which contributes to their competitiveness, which was not true for VL Dhan. PD 12, PD 16 and Narendra 359 had more leaf area at 30 DAT hence a higher vegetative vigor than Sarju 52 and VL Dhan. There was no correlation of RGR & NAR with competitive ability. RGR & NAR of both the years was highest for the variety VL Dhan at 45-60 & 30-45 DAT respectively, while rest of the four varieties had similar RGR & NAR. The total phenol content was higher in the varieties PD 12 and PD 16 and it was higher in the root tissue than in the shoot tissue. The phenolic profiling through HPLC revealed that gallic acid, resorcinol, p-hydroxybenzoic acid, caffeic acid, syringic acid and vanillic acid were among the major phenolics present in the rice varieties. Protein profiling revealed no difference among the varieties, as the banding pattern was same for all the cultivars in both the years.
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Thesis-PhD
Keywords
competitive ability, rice, cultivars, weeds, weed control, plant physiology, phenolic compounds, allelopathy