Classification and Diversity of Echinochloa in Paddy Fields of Main Agricultural Regions in China

The seeds of 206 Echinochloa samples from paddy regions of 15 provinces and one municipality of China were sown in the same cultivation environment and their offspring were obtained. We measured 21 morphological traits of the 206 Echinochloa offspring samples. Based on these 21 traits, cluster analysis and principal component analysis (PCA) were conducted. Results showed that:(1) Eights groups were identified from these 206 samples, corresponding to E. frumentaceae (2 samples), E. oryzoides (5 samples), E. crus-galli var. praticola (6 samples), E. glabrescens (14 samples), E. colona (2 samples), E. caudate (16 samples), E. cruspavonis (8 samples), E. crus-galli complex (150 samples including E. crus-galli var. crus-galli, var. mitis, var. breviseta and var. zelayensis) and three other samples, accounting for 0.97%, 0.97%, 2.42%, 2.91%, 3.88%, 7.77%, 6.80%, 72.81% and 1.46%, respectively. Echinochloa crus-galli and its varieties were the main taxa of the genus in the main paddy regions of China;(2) Analysis of variance showed that the main quantitative traits for identifying the eight groups of Echinochloa included leaf length, leaf width, panicle length, raceme length, awn length of spikelet, spikelet length, length of first glume/spikelet length, diameter of main stem, and individual height;(3) A key to the eight groups was given based on their morphological differences;(4) Taxonomically, E. crus-galli var. praticola was suggested as an independent species from the E. crus-galli complex due to its simple racemes, awnless spikelets, wider leaves, higher individuals, and purple spikelets.