Morphological and Physiological Variation among Species of the GenusEchinochloain Northern Greece

The variability of 12Echinochloapopulations with respect to certain morphological and physiological characteristics, sensitivity to certain POST rice herbicides, and activity of selected enzymes was studied. Three distinct groups (each one represented by four populations from different areas) were studied:E. crus-galli,E. oryzoides, andE. phyllopogon. All theE. oryzoidesandE. phyllopogonpopulations showed earlier seed germination and higher germination percentages than theE. crus-gallipopulations. All theE. oryzoidesandE. phyllopogonpopulations showed reduced susceptibility to propanil, cyhalofop, clefoxydim, and bispyribac compared with theE. crus-gallipopulations. With respect to plant prostrateness, the species order, averaged over the four populations, wasE. crus-galliprostrate >E. oryzoidesrelatively erect >Ε. phyllopogon phyllopogon. erect, while the species order with respect to leaf length and tillering ability wasE. crus-galli ≥ E. oryzoides>Ε. phyllopogon. Regarding leaf width, time of panicle emergence, height, and biomass accumulation, the order wasE. crus-galli > E. oryzoides> Ε.phyllopogon, while that of seed weight, length and width wasE. oryzoides> Ε.phyllopogon > E. crus-galli. The order of species susceptibility (averaged over the four populations) to most of the herbicide treatments wasE. crus-galli>E. oryzoides>E. phyllopogon, which was exactly the opposite of that relating to their antioxidant enzyme activity. Finally, the order of herbicide efficacy, averaged over allEchinochloapopulations, was penoxsulam > clefoxydim > bispyribac > cyhalofop > propanil. Variability in a number of traits among the most commonEchinochloaspecies of rice fields in northern Greece as a result of different adaptive strategies of each species may be related to differential sensitivity to herbicides. This variability should be taken into account for the elaboration of effective weed management programs in rice. Where mixed populations of these species are present in a field, difficulties may arise in the successful chemical control of theEchinochloacomplex in rice due to species differences in biology and herbicide sensitivity.