Relative competitive ability of rice with strawhull and blackhull red rice biotypes

Authors: NOHATTO, MARCOS - Federal University Of Pelotas; AGOSTINETTO, DIRCEU - Federal University Of Pelotas; Gealy, David; DE AVILA, LUIS - Federal University Of Pelotas; DA SILVA, BRUNO - Federal University Of Pelotas; WESTENDORFF, NIXON DA ROSA - Federal University Of Pelotas

Submitted to: Científica: Revista de Ciências Agrárias
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2015
Publication Date: 3/31/2016
Citation: Nohatto, M.A., Agostinetto, D., Gealy, D.R., De Avila, L.A., Da Silva, B.M., Westendorff, N. 2016. Relative competitive ability of rice with strawhull and blackhull red rice biotypes. Científica: Revista de Ciências Agrárias. 4:176-184. doi: org/10.15361/1984-5529.2016v44n2p176-184.

Interpretive Summary: Competitive interactions between weeds and crops depend upon the species of the weeds and crop. Weedy red rice is a major weed pest of rice in the southern U.S. In this study, we evaluated the competitive ability of a common commercial rice variety against the two predominant and genetically diverse weedy red rice biotypes (strawhull or blackhull) in the southern USA. Experiments were conducted in greenhouse pots in Stuttgart, Arkansas, to determine the relative competitive effects of rice against these red rice biotypes, and between the two red rice biotypes. We planted the rice and red rice plants in mixtures at five different plant ratios, which were 16:0, 12:4, 8:8, 4:12 and 0:16 plants of rice:red rice or red rice:red rice. Plant stem dry weight, leaf area, and height were recorded. Both the strawhull and blackhull red rice biotypes grew aggressively, easily out-competing the CL 142 AR commercial rice variety, and the blackhull biotype was more competitive than the strawhull biotype. Thus, this rice variety was highly susceptible to competition from the diverse red rice biotypes tested. However, the red rice biotypes were predominantly susceptible to competition from each other, and not to the commercial rice. These results are consistent with reports from rice farmers and managers that red rice is among the most competitive and devastating weeds afflicting their fields in the southern USA, and highlights the need for continued, aggressive management of red rice in rice and its rotational crops.

Technical Abstract: Weed interference depends largely upon the species composition of the weed community and an ability to compete with the cultured crop. Weedy red rice is a major weed pest of rice in the southern U.S. The focus of this study was to evaluate the competitive ability of rice against common, genetically diverse populations of red rice (strawhull or blackhull). The experiments were conducted in a greenhouse from January to August 2013, at the United States Department of Agriculture, Agricultural Research Service, Dale Bumpers National Rice Research Center (USDA-ARS/DBNRRC) in Stuttgart, Arkansas. The experimental design was completely randomized with four replications. Treatments consisted of rice:red rice or red rice:red rice plant ratios of 100:0, 75:25, 50:50, 25:75 and 0:100%. The plant growth variables shoot dry weight, leaf area, and height were evaluated. Results show that both the strawhull and blackhull red rice biotypes were more competitive than CL 142 AR rice. Overall, the competitive ability of the blackhull red rice was greater compared with the strawhull red rice. Interspecific competition was most damaging for rice, whereas intraspecific competition was most damaging for the two red rice biotypes.