Abstract
AbstractThe genus Echinochloa constitutes some of the most prominent weed species found in rice (Oryza sativa L.) production worldwide. The taxonomy of Echinochloa is complex due to its morphological variations. The morphophysiological diversity and taxonomic characteristics of Echinochloa ecotypes infesting rice fields in Texas are unknown. A total of 54 Echinochloa ecotypes collected during late-season field surveys in 2015 and 2016 were characterized in a common garden in 2017. Plants were characterized for 14 morphophysiological traits, including stem angle; stem color; plant height; leaf color; leaf texture; flag leaf length, width, and angle; days to flowering; panicle length; plant biomass; seed shattering; seed yield; and seed dormancy. Principal component analysis indicated that 4 (plant height, flag leaf length, seed shattering, and seed germination) of the 14 phenological traits characterized here had significantly contributed to the overall morphological diversity of Echinochloa spp. Results showed wide interpopulation diversity for the measured traits among the E. colona ecotypes, as well as diverse intrapopulation variability in all three Echinochloa species studied, including barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.], junglerice [Echinochloa colona (L.) Link], and rough barnyardgrass [Echinochloa muricata (P. Beauv.) Fernald]. Taxonomical classification revealed that the collection consisted of three Echinochloa species, with E. colona being the most dominant (96%), followed by E. crus-galli (2%), and E. muricata (2%). Correlation analysis of morphophysiological traits and resistance status to commonly used preemergence (clomazone, quinclorac) and postemergence herbicides (propanil, quinclorac, imazethapyr, and fenoxaprop-ethyl) failed to show any significant association. Findings from this study provided novel insights into the morphophysiological characteristics of Echinochloa ecotypes in rice production in Texas. The morphological diversity currently present in Echinochloa ecotypes could contribute to their adaptation to selection pressure imposed by different management tools, emphasizing the need for a diversified management approach to effectively control this weed species.
Highlights
The genus Echinochloa contains the most troublesome weeds of rice (Oryza sativa L.) production systems worldwide
Sensitivity of the collected Echinochloa ecotypes to five different herbicides commonly used in Texas rice production was evaluated in a parallel study (Liu 2018)
Based on the taxonomic characteristics of the plants, 52 of the total 54 ecotypes studied were identified as E. colona and 1 each as E. crus-galli and E. muricata (Table 1; Figure 2)
Summary
The genus Echinochloa contains the most troublesome weeds of rice (Oryza sativa L.) production systems worldwide. It comprises about 50 species, most of which are found in the tropics (Michael 1983). Echinochloa crus-galli is an annual grass weed that mimics rice, especially at the seedling stage. By the time it can be differentiated from rice, crop yield loss may have already occurred (Holm et al 1977) It is an erect-growing plant, reaching up to 2 m tall. Echinochloa colona, a species like E. crus-galli in appearance, is an annual grass weed, but has a prostrate growth habit, with plants growing up to 0.6-m tall (Hruševar et al 2015). Echinochloa colona and E. crus-galli can flower throughout the year, whereas E. muricata usually
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