Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2001
Publication Date: 4/1/2002
Citation: Estorninos, L.E., Gealy, D.R., Talbert, R.E. 2002. Growth response of rice (Oryza sativa) and red rice (O. sativa) in a replacement series study. Weed Technology. 16(2):401-406. Interpretive Summary: Red rice have been one of the most troublesome weeds in rice. Red rice belongs to the same species with cultivated rice so it is difficult to control. Red rice have shown competitiveness against cultivated rice because of its high tillering capacity and taller height. The growth response of two rice cultivars (cultivated rice) grown alone and in different planting mixture proportions with red rice was evaluated in the greenhouse at the Altheimer Laboratory, University of Arkansas, Fayetteville. Kaybonnet (medium height rice cultivar) was less competitive than PI 312777 (semi dwarf rice) against red rice. PI 312777 rice compensated its genetically short stature by producing more tillers, greater leaf area index, and shoot biomass compared to Kaybonnet whether planted alone or with red rice. On the other hand, the taller LA3 red rice produced more tillers, leaf area index, and shoot biomass than the medium height KatyRR red rice. Both red rice ecotypes limited the growth of Kaybonnet rice indicating that Kaybonnet had a disadvantage in capturing the resources for its growth even when the ratio of rice density was two times greater than KatyRR or LA3. PI 312777 produced more tillers and leaf area index than KatyRR and was as competitive as LA3. PI 312777 could have gained more resources at the expense of KatyRR while neither PI 312777 nor LA3 gained an advantage over the other. These results indicate that competitiveness of shorter rice cultivars with high tillering capacities, as demonstrated by PI 312777, could be as great or greater than that of taller red rice. The results suggest that high tillering capacity may be useful when breeding for rice cultivars that are competitive against weeds, and may help to improve the success of reduced herbicide rate programs.
Technical Abstract: A replacement series pot study was conducted in a greenhouse in 1998 and 1999 to evaluate the interference interactions between two rice cultivars and two red rice ecotypes. Plants were established in proportions of 3:0, 2:1, 1:2, and 0:3 (rice:red rice) plants per pot. Kaybonnet (commercial rice cultivar was dominated by both Katy RR (suspected rice:red rice cross) )and LA3 (tall red rice ecotype in tiller production, while PI 312777 (weed suppressive cultivar) was comparable with either KatyRR or LA3. Both KatyRR and LA3 reduced considerably the leaf area index (LAI) of Kaybonnet. In contrast, PI 312777 was comparable to that of KatyRR and LA3 red rice ecotypes. They further suggest that high tillering capacity, as demonstrated by PI 312777, should be considered when breeding for rice cultivars that are competitive against weeds. This agronomic characteristic of rice may improve the success of reduced herbicide rate application programs.