Diversity of Red Rice in Arkansas

Red rice is a troublesome weed in rice-growing areas of the southern U.S. Red rice in Arkansas may be diverse enough to warrant some adjustments in weed control programs. A study was conducted at the Rice Research and Extension Center (RREC), Stuttgart, Ark., in 2003 to determine the phenotypic diversity of red rice in Arkansas. One hundred thirty-six red rice accessions were collected from 26 rice-growing counties of Arkansas in summer 2002. Red rice seedlings were transplanted to the field on 12 May 2003. Data were collected on various morphological variables of red rice. Besides the two major hull colors, straw and black, other hull colors were also observed including brown and orange. There was no difference in plant height (overall mean = 53 in.) and tiller number (overall mean = 93) among strawhull accessions. Seed yield decreased with decreasing latitude in strawhull types. Among blackhull accessions, those from the east-central part of the state produced the most tillers (116) but were the shortest (52.5 in.) plants. Blackhull accessions from central Arkansas had the highest seed yield (196 g/plant). Phenotypic diversity was documented in red rice accessions from different regions based on hull color, presence of awns, height, tillering capacity, flowering, and seed yield. INTRODUCTION Red rice is a troublesome weed in the southern U.S. Red rice and cultivated white rice belong to the same genus and species. Due to similarity in their biology and physiology, red rice is difficult to control with traditional rice herbicides. For instance, both red rice and cultivated rice produce an enzyme, aryl acylamidase, that metabolizes propanil, which is one of the most commonly used herbicides in rice (Hoagland, 1978).