HomeIAMURE International Journal of Ecology and Conservationvol. 19 no. 1 (2016)

Incidence, Growth, and Agronomic Characteristics of Weedy Rice Variants from Iloilo Province, Philippines under Field and Screenhouse Conditions

Dindo King M. Donayre | Edwin C. Martin | Madonna C. Casimero



Weedy rice (Oryza sativa L.) is one of the major weed species that associates and competes with cultivated rice (Oryza sativa L.). When left uncontrolled, it can significantly reduce yield of cultivated rice as well as the quality of its harvested grains. Te occurrence of weedy rice had been reported by farmers of Iloilo Province as seed contaminants. Despite the report, however, no study had been done exploring and understanding the presence of weedy rice in ricefields of the province. This study was done to investigate the incidence, growth, and agronomic characteristics of the existing variants. Field surveys and collection of weedy rice samples were conducted in rice fields of Iloilo Province. Laboratory and pot experiments were conducted at Philippine Rice Research Institute, Maligaya, Science City of Muñoz, Nueva Ecija, Philippines. In the survey, eight weedy rice variants with distinct agronomic and morphologic characteristics were identified. Among ricefield areas surveyed, Pototan (75%) had the highest incidence followed by Dingle (34%), Barotac Nuevo (33%), and Dumangas (31%). Zarraga and the rest of the municipalities surveyed had a low incidence of weedy rice ranging from 1 to 3%. Te density of weedy rice in the ricefields was 4 to 6 plants m-2. Based on grain characteristics, eight variants were found and designated as WR-ILO 1, WR-ILO 2, WR-ILO 3, WR-ILO 4, WR-ILO 5, WR-ILO 6, WR-ILO 7, and WR-ILO 8. WR-ILO 1 was the most common variant observed in ricefields followed by WR-ILO 5 and WR-ILO 4. Ricefields of Barotac Nuevo registered the most number of weedy rice variants collected. Under field and screenhouse conditions, all variants were taller, matured earlier, and had fewer panicles plant-1 as compared to cultivated rice varieties. Shattering was only observed in WR-ILO 2, WR-ILO 3, and WR-ILO 8 while awns were only present in WR-ILO 1, WR-ILO 3, WR-ILO 4, and WR-ILO 8. Other agronomic and yield parameters were observed to be variable among the variants and had distinct differences compared to PSB Rc14 and PSB Rc82.