Diversidade de populações de Meloidogyne spp. e Pratylenchus spp. de diferentes regiões do sul do Brasil produtoras de batata e estudo da patogenicidade em Solanum spp.

Abstract

The Objectives of this study were i) to characterize root-knot nematodes (Meloidogyne spp.) and root-lesion nematodes (RLN) (Pratylenchus spp.) parasitizing potato crops in the states of Rio Grande do Sul (RS), Santa Catarina (SC) and Paraná (PR), southern Brazil; ii) to access the aggressiveness of Meloidogyne javanica populations on selected potato cultivars; iii) to evaluate the resistance of commercial cultivars and wild accessions of potato to Meloidogyne spp., and iv) to study the life cycle of M. javanica on resistant and susceptible potato genotypes. In this study, 47 and 27 populations of Meloidogyne spp., and Pratylenchus spp. were obtained, respectively. Meloidogyne populations were biochemically characterized using esterase isozyme (Est). A subset of twenty populations was further characterized molecularly by SCAR PCR and RAPD markers. Populations of Pratylenchus spp. were characterized by morphological and morphometric characters. Subsequently, the aggressiveness of four populations of M. javanica from RS, SC and PR were evaluated in the commercial potato cultivars BRS Clara and Agata. Subsequently, the reaction of nine commercial potato cultivars for resistance to Meloidogyne spp. and Pratylenchus brachyurus, and the resistance of 24 wild potato accessions to Meloidogyne javanica was evaluated in greenhouse conditions. Finally, the life cycle of M. javanica in a susceptible cultivar (BRS Ana) and other resistant wild potato (68-16) was investigated under controlled conditions (24°C ± 0,5°C; 14h light). Overall, Meloidogyne spp. was present at 42.34% of sampled sites, and M. javanica (Est J3) was the most frequent species. Forty-two populations of Meloidogyne with five different esterase phenotypes were obtained from RS state. M. javanica J2, J2a and J3 occurred on 3%, 12.1% and 100% of sampled sites, respectively. Forty-two populations of Meloidogyne with five different esterase (Est) phenotypes were obtained In the collected samples from RS. M. javanica Est J3, J2 and J2a occurred at 100, 3.0 and 12.1% of the samples, respectively. Moreover, two populations of M. incognita I2, and two populations of M. arenaria A2 (13.2% in total), were detected. In SC state, M. javanica (J3) was observed on 100% of sampled sites. In PR state, six populations of M. javanica (J3), one population of M. ethiopica (E3) and one population of M. incognita (I2) were observed, which corresponds to 85.7%, 14.3% and 14.3% of the total samples, respectively. The occurrence of Pratylenchus spp., was observed in 24.32% of the total samples. Among them, samples obtained from RS state, there were 17 populations identified as P. brachyurus (81%) and it was not 10 possible to characterize four populations (19%) by specific level. In SC and PR, P. brachyurus occurred in two and four samples, respectively, and was the only species identified. In the RAPD analysis, 317 and 435 reproducible amplified fragments were observed for the isolates whose percentage of polymorphisms varied from 13.9% within M. javanica populations and 27.1% between M. javanica and other Meloidogyne spp. In the phylogenetic analysis, there was three groups, in which 15 populations of M. javanica (J3) formed a major group; M. incognita (I2), M. ethiopica (E3), and M. arenaria (A2) formed a second group, and the third group formed by two populations of M. javanica (J2a) with a low intraspecific variability between them (9.47%). In the aggressiveness of M. javanica populations, there was significant interactions between potato cultivars and nematode populations according to total number of galls (roots and tubers), nematode reproduction factor, plant height and tuber weight. For the genetic screenings, most potato cultivars were susceptible to both Meloidogyne spp. and Pratylenchus brachyurus. Interesting, two accessions of wild potatoes (675 and 68-16) were resistant and one (51-9) moderately susceptible to M. javanica. Finally, we observed an extended life cycle of M. javanica in the resistant accession of wild potato compared to the susceptible potato cultivar BRS Ana.