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Late blight is caused by the oomycete Phytophthora infestans, and it is the most devastating disease of potato in Southern Brazil. The objective of this work was to evaluate the variability of P. infestans isolates collected from potatoes in Rio Grande do Sul (RS), Paraná (PR) and Santa Catarina (SC) states for their mating type (MT) and virulence. One hundred and twenty-eight isolates of P. infestans were collected between 2010 and 2012. They were characterized for mating type and subsequently evaluated for virulence/avirulence using a differential series of 11 potato clones. The virulence study was conducted in vitro by the leaf disc method, where the potato clones were inoculated with each isolate. Seventy-six isolates were identified as MTA2, 24 as MTA1, 17 as MTA1A2 and 11 as self-fertile. In addition, 79 pathotypes of P. infestans were detected in the survey and the largest number of races was identified in RS. The most frequent pathotypes identified were '14' and '21' and the vast majority of isolates overcame the R7 resistance gene, followed by the R3, R1 and R11 genes. Smaller numbers of virulent isolates were detected to the clones carrying the R5, R2 and R9 genes. Higher percentages of virulent and complex isolates were identified in the MTA2. High indices of diversity were observed in populations grouped by mating type and by state of collection. The highest value of the Gleason index HGR = (0.95) was obtained for the isolates from PR. Higher complex P. infestans populations were found in RS, and the least complex population was in PR. [ABSTRACT FROM AUTHOR]

One hundred seven samples of potato tubers and roots were collected from different commercial potato fields of the Southern Brazilian states, Rio Grande do Sul (RS), Santa Catarina (SC), and Paraná (PR) in order to evaluate the occurrence, geographical distribution, and morphological characterization of lesion nematode (Pratylenchus sp.). Pratylenchus brachyurus was detected in 21.5% of the collected potato samples corresponding to 23.94, 21.02, and 13.33% of samples obtained in RS, PR, and SC states, respectively. Subsequently, nine commercial potato cultivars were evaluated for resistance to P. brachyurus in greenhouse at 25°C ± 5°C. Among the genotypes tested, the cultivars 'Bel', 'Eliza', 'Cris', and 'Clara' were immune to P. brachyurus. On the other hand, 'Catucha', 'Ana', 'Cota', and 'Agata' cultivars were resistant, and 'Asterix' behaved as susceptible to this lesion nematode species. [ABSTRACT FROM AUTHOR]

Summary: The rice root-knot nematode, Meloidogyne graminicola , has been reported in Southeast Asia, China, India, South Africa, USA, Brazil, and other countries. Recent surveys in Southern Brazil showed that M. graminicola was widespread in irrigated rice in Rio Grande do Sul, Santa Catarina and Paraná states, and the presence of a species complex with a predominance of M. graminicola (Est VS1 = G1) and other variants showing similar esterase phenotypes (Est G2 = R2, G3 = R3). Meloidogyne oryzae (Est O1) and M. ottersoni (Est Ot0) were also part of this complex and were recently re-described and detected on rice. The present study provides an integrative taxonomy approach of the typical and atypical populations of M. graminicola on the basis of morphological, morphometric and molecular data. Considering morphological and morphometric features, the two atypical populations (Est G2 and G3) are in close agreement with the description of M. graminicola. Based on the molecular characterisation, populations G1, G2 and G3 were successfully amplified by M. graminicola SCAR markers, although the specificity of these markers was questioned. Phylogenetic relationships complemented and confirmed the other studies. In maximum likelihood analysis of ITS, D2-D3 rRNA and COXII -16S rRNA sequences, all populations of M. graminicola from different esterase phenotypes clustered together with other M. graminicola populations, thus confirming that these enzyme phenotypes (G1, G2 and G3) are related to the same species. A high level of intraspecific variability was detected among all populations, but no correlation between genetic variability and geographic origins occurred. [ABSTRACT FROM AUTHOR]

The frequency of root-knot nematode (Meloidogyne spp.) occurrence on fig (Ficus carica L.) and weed plants was evaluated in different orchards in Rio Grande do Sul State, southern of Brazil. In the samples where root-knot was detected, species characterization was differentiated by electrophoresis using the isoenzymes esterase (Est) and malatedesydrogenase (Mdh). The nematode was detected in all fig plant samples and two Meloidogyne species were identified: M. incognita with the phenotypes (Est/Mdh) I1/N1, I2/N1, S1/N1 and or S2/N1 in all fig orchards and M. javanica (J2/ N1) in only one orchard associated with M. incognita I1/N1. In the weeds collected under the canopy of fig trees, six host plants (Sida rhombifolia, Ipomoea nil, Commelina benghalensis, Asclepias curassavica, Solanum americanum and Ageratum conyzoides) of Meloidogyne spp. were identified. The frequency of Meloidogyne species in the weed samples was variable. The isoenzyme phenotypes corresponded to M. incognita (Est I1, I2, S1), M. javanica (Est J3 and J2), M. arenaria (Est A2), and M. ethiopica (Est E3). Among these weed plants, Sida rhombifolia was the species with major root gall presence in the weed hosts. The phenotypes I1, I2 and S1 of M. incognita and J2 of M. javanica, were also detected in fig trees, which is highly important to crop management. [ABSTRACT FROM AUTHOR]