Diversity of Meloidogyne arenaria using morphological, cytological and molecular approaches

Thirteen Meloidogyne arenaria isolates representing two cytological types (3n = 51-56, 2n = 42-48) and four enzymatic phenotypes (esterase and malate dehydrogenase: A3N1, A2N1, A1N1, A2N3) were studied using different approaches. The analysis of molecular markers showed a high level of polymorphism among the isolates. The trees obtained with RAPID or ISSR polymorphisms showed concordant results and agree with morphological studies. By considering morphometrical and morphological features, it was possible to conclude that the isolate with enzymatic phenotype A2N3 race I was the M. arenaria described in 1949 by Chitwood and appearing clearly separated in the trees, as well as in the outgroups. The seven isolates with phenotype A2N1 from different localities and isolate A1N1 can be considered morphometrically typical of M. arenaria race 2 and they were apparently clustered by geographical origin. Morphologically, they differed from isolate A2N3 race 1. The two isolates with phenotype A3N1 appeared to be closely related to the isolate of M. morocciensis and, considering all of the features described for this species, were identified as such. The two isolates A2N3 race 2 were identified either as an atypical M. arenaria or an unidentified species (females and males having atypical stylets), and clustered together and separated from other M. arenaria isolates with high bootstrap support. The same M. arenaria isolates were tested with the species-specific molecular marker, type SCAR. A fragment of 420 bp was obtained for ten isolates of M. arenaria, including the atypical A2N3 race 2 and M. morocciensis. This fragment was not amplified for three typical A2N1 isolates of M. arenaria.