GENETIC DIVERSITY IN PURPLE NUTSEDGE (CYPERUS-ROTUNDUS L) AND YELLOW NUTSEDGE (CYPERUS-ESCULENTUS L)

Differential susceptibility of nutsedge biotypes (Cyperus sp.) to Pucc inia canaliculata, a rust fungus registered as a bioherbicide, exists. In an attempt to understand the possible genetic basis of this differ ence, RAPD (random amplified polymorphic DNA) analysis was used to stu dy genetic variation within collections of purple nutsedge (Cyperus ro tundus) and yellow nutsedge (Cyperus esculentus) samples obtained from different geographical locations. Expectedly, purple nutsedge genotyp es differed significantly from yellow nutsedge genotypes, Purple nutse dge samples, however, showed very limited intraspecific variation, wit h most showing no differences. In contrast, yellow nutsedge samples sh owed a wide range of variation. The RAPD technique revealed a far grea ter level of variation in nine Californian samples than was previously shown by isozyme analysis, raising questions about the method of disp ersal of this species, The uniformity of RAPD patterns in most purple nutsedge samples suggests that purple nutsedge plants may form large r egional clones that are most likely propagated by asexual means. In co ntrast, however, the extensive variation exhibited by the yellow nutse dge samples may be attributable to dispersal by seeds produced as a co nsequence of sexual reproduction. These results have implications for biological control of these weed species. (C) 1997 Academic Press.