Prevalence, Agronomic Characteristics and Biology of Weedy Rice Biotypes of Nueva Ecija, Philippines

Abstract

A survey of different weedy rice biotypes was conducted in rice field areasof Nueva Ecija from CY 2004-2006 to determine their prevalence, agronomiccharacteristics and biology. Surveys and quadrat samplings were conducted inrandom alongside of the roads to gather data on prevalence, height, numberof panicles/plant and density/m of weedy rice as well as the cultivated onesthey were associated. Studies on seed germination test, biology and agronomical characteristics of different weedy rice biotypes were also conducted at thelaboratory and screenhouse of Crop Protection Division, Philippine Rice ResearchInstitute. Five weedy rice biotypes designated as WR-NE 1, WR-NE 2, WR-NE3, WR-NE 4 and WR-NE 5 were found distributed almost everywhere in ricefields of Nueva Ecija. Among the biotypes, WR-NE 1 was the most common inmany rice fields. Prevalence of all biotypes around the province ranged from 1to 17%. In the field, all biotypes were found taller but had fewer panicles plantthan cultivated rice varieties. In the laboratory, all weedy rice biotypes emergedearlier than PSB Rc82 and IR64. Under screenhouse condition, all weedy ricebiotypes were taller, produced more leaves and culms plant than the cultivatedrice. WR-NE 5 was the tallest biotype while WR-NE 1 and WR-NE 2 had themost number of leaves and culms plant-1-1. All biotypes matured earlier but hadno seed shattering characteristics. The biotypes had comparable values in termsof flag leaf areas and LAI/plant with PSB Rc82. Shoot dry weight and number ofpanicles/plant of all biotypes was significantly higher than the control varieties.WR-NE 4 and WR-NE 5 had the longest panicles, longer and wider grains.Grains/panicle was highest in WR-NE 5 (102 grains/panicle). Grain lengthwidthratio (GLWR)of all biotypes, however,weresignificantly lowerthan thetwocontrolvarieties.WR-NE1 and WR-NE4 had the longest length of awnwhileWR-NE4 and WR-NE5 had the highest grain weight(both at 24 g/1000grains).The growthand developmentof the fiveweedyrice biotypes weremuchadvantageouscomparedto selected cultivarssuggesting their competitivenessandthreatin achieving the potential yield and quality of harvestedcultivatedrice. Keywords - Plant ecology, prevalence, agronomic characteristics, weed biology, biotype,Oryza sativa L., weedy rice, experimental design, Philippines