Abstract
Weedy rice (Oryza sativa f. spontaneae) is a recently emerged major threat in many rice-growing areas in tropical Asia including Sri Lanka since 1990s. Though there are scientific investigations on origin, diversity, distribution and controlling technique of weedy rice in regional and global scales, studies on the interactions between weedy rice and cultivated rice varieties under local situations are limited. A green-house experiment was conducted at the Open University, Nawala, Sri Lanka (30oC, 40% humidity) in 2015 using an improved-cultivated rice variety (Bg379-2) with varying percentages of cultivated: a black-hulled weedy rice bio-type (0, 20, 40, 60 80 100 /pot). Influence of weedy rice on growth and yield of Bg379-2 was assessed by measuring plant height and number of tillers through 2, 4, 6 and 8 weekly. Dry shoot-and root- biomass of uprooted plants at 8 weeks after sowing (8WAS)were determined through oven-dried to a constant weight at70 o C for 72 hrs and weighed to the nearest 0.01 g. Yield components of Bg379-2 including mean weight of 100 grains/plant, number of panicles/plant, number of grains/panicle and yield weight/plant were calculated. Data were statistically analyzed using SAS Ver. 9.0. Significant interactions between weedy rice bio-type and Bg379-2 were apparent after 6 weeks after sowing (WAS). A yield loss of 30% was observed even at a percentage of 20 of weedy rice at 20 /pot. The competition of weedy rice resulted in 90% loss of yield of variety Bg379-2at 80% plants/pot. For the purpose of generalization, further research is recommended to determine the effect of weedy rice density on growth and yield components of different new improved rice varieties. KEYWORDS: Competition, Oryza sativa f. spontaneae, Yield loss, Sri Lanka, Weedy rice
Highlights
Rice (Oryza sativa L.) is one of the major staple food crops cultivated throughout the world and is mainly important in Asia where approximately 90 % of world’s rice is produced and consumed (Zeigler and Barclay, 2008)
The improved-cultivated rice variety Bg379-2 and black-hulled weedy rice (WR) bio-type collected from Ampara District in Southern Province of Sri Lanka served as experimental material
The experiment included a total of six treatments and each treatment was represented by five replicates of nine plants which were arranged in a random complete design
Summary
Rice (Oryza sativa L.) is one of the major staple food crops cultivated throughout the world and is mainly important in Asia where approximately 90 % of world’s rice is produced and consumed (Zeigler and Barclay, 2008). The growth and competitive ability of weedy rice vary considerably among populations due to differences in plant height, leaf area or biomass (Chauhan and Johnson, 2010a). Abud (1989) reported that density of 11 weedy rice plants m2 led to considerable yield loss of 43%.
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