Genetic Diversity in Purple Nutsedge (Cyperus rotundusL.) and Yellow Nutsedge (Cyperus esculentusL.)

Abstract

Differential susceptibility of nutsedge biotypes ( Cyperus sp.) to Puccinia canaliculata, a rust fungus registered as a bioherbicide, exists. In an attempt to understand the possible genetic basis of this difference, RAPD (random amplified polymorphic DNA) analysis was used to study genetic variation within collections of purple nutsedge ( Cyperus rotundus ) and yellow nutsedge ( Cyperus esculentus ) samples obtained from different geographical locations. Expectedly, purple nutsedge genotypes differed significantly from yellow nutsedge genotypes. Purple nutsedge samples, however, showed very limited intraspecific variation, with most showing no differences. In contrast, yellow nutsedge samples showed a wide range of variation. The RAPD technique revealed a far greater level of variation in nine Californian samples than was previously shown by isozyme analysis, raising questions about the method of dispersal of this species. The uniformity of RAPD patterns in most purple nutsedge samples suggests that purple nutsedge plants may form large regional clones that are most likely propagated by asexual means. In contrast, however, the extensive variation exhibited by the yellow nutsedge samples may be attributable to dispersal by seeds produced as a consequence of sexual reproduction. These results have implications for biological control of these weed species.