Selection and polymorphism of Pasteuria penetrans isolates in relation to Meloidogyne spp. from coffee

Abstract

Abstract Pasteuria penetrans isolates from different geographical areas were tested for the ability of endospores to attach to secondstage juveniles and to colonise females of different populations of Meloidogyne spp. from coffee and other crops. Our results confirm that the spore attachment test cannot be used as the only criterion for screening for the efficiency of the bacterial isolate against nematodes. The percentage of females infected with the bacteria and the endospore concentration in 100 macerated females were the best approaches for screening the highly pathogenic isolates. Using these parameters, it was possible to select some isolates for M. javanica and M. arenaria race 2; one isolate, P12, for the three populations of M. paranaensis, and isolate P10 for the four races of M. incognita from coffee. The isolates exhibited poor pathogenicity on M. hapla, M. exigua, M. graminicola and M. mayaguensis. There was clear evidence that the greatest parasitism occurred when the isolates of P.penetrans were exposed to species of Meloidogyne that were genetically close to that from which the bacteria populations had been originally isolated. The dendrogram obtained from attachment of 18 P. penetrans isolates on 13 Meloidogyne spp. populations clearly defined subgroups of the bacteria related to their geographical origin. RAPD analyses were used for fingerprinting the genomes of P.penetrans isolates. Twenty 10-mer oligonucleotide primers of arbitrary sequence revealed 145 scorable binary characters. Cluster analysis showed a low (61%) to high (80%) level of genetic similarity among the isolates and that phenetic groups were sometimes related to pathogenicity.