Phenotypic characterization of <i>Echinochloa</i> species in California rice

Abstract Two independent greenhouse experiments were conducted in December 2020 and July 2021 in Davis, CA to characterize Echinochloa crus‐galli (L.) P. Beauv., Echinochloa colona (L.) Link, Echinochloa oryzicola (Vasinger) Vasinger and Echinochloa walteri (Pursh) A. Heller found in California rice systems based on their morphological traits. Phenotypic data was collected on 10 vegetative traits including plant height, number of tillers, flag leaf length, flag leaf width, flag leaf angle, the colour of leaf sheath, leaf blade colour, internode colour, node colour, growth habit and nine reproductive traits including number of days to heading, number of panicles, length of panicle, length of panicle branches, seeds per panicle, panicle weight, seed colour, awn length and awn pattern. High plasticity was observed in all species characterized in both experiments for both vegetative and reproductive traits, indicating potential inter‐specific hybridization. Awn length, days to heading, length of the panicle, length of the panicle branches, plant height, flag leaf angle, and growth habit were significantly higher in the fall experiment for all species indicating photoperiod could play a role in the expression of these traits. Also, high variation was observed for plant height, number of tillers, awn length, panicle weight, seeds/panicle, length of panicle branch, and number of panicles for all species in both experiments. The results from this study indicate morphological diversity currently present in Echinochloa species could contribute to their adaptation to selection pressure imposed by different management tools in California, emphasizing the need for a diversified management approach to effectively control this weed species.