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Downy mildew of cucurbits is a disease caused by the Oomycete Pseudoperonospora cubensis. It can cause considerable losses in cucurbit crops. Phylogenetic studies point to the existence of cryptic species of Pseudoperonospora. The objective of this study was to determine, the phylogeny of Pseudoperonospora species affecting cucurbits in different regions of Brazil. For this, leaves with symptoms of downy mildew were collected in areas of cucurbits production in the states of Pernambuco, Minas Gerais, Ceará, and the Distrito Federal. For phylogenetic analyses, DNA extraction was performed, and PCR reactions were carried out using primers DC-6 and LR-0, Cox2-F and Cox2-RC4, OomCox1-levup and OomCox1-levlo, FM79-C1 and FMPHY-10b, for amplification of the internal transcribed spacer (ITS) region, the mitochondrial cytochrome c oxidase subunit II (cox2), the mitochondrial cytochrome c oxidase subunit I (cox1) and cox2-cox1 intergenic spacer respectively. The nucleotide sequences were analyzed, edited, and aligned to perform Bayesian Inference analysis. The results of the phylogenetic analyses presented in the cox2-cox1-cox2_1-ITS concatenated tree indicate that in Brazil, the downy mildew of cucurbits is caused by phylogenetically distinct lineages of P. cubensis. [ABSTRACT FROM AUTHOR]

Verticillium dahliae is a soil-borne fungal pathogen responsible for vascular wilt diseases in more than 300 dicotyledonous species, including solanaceous vegetable crops. In this study, a collection of 89 Brazilian V. dahliae isolates was characterized by combing molecular information for mating type and physiological race determination, as well as via virulence bioassays employing a set of differentials. Based on the virulence assays, three isolates were classified as race 1, 76 were classified as race 2, whereas ten isolates did not cause any symptom on the tested cultivars." In race-specific detection, a total of six isolates were identified as race 1, 70 as race 2, and 13 isolates displayed no amplicon with any primer set employed. Therefore, V. dahliae race 2 isolates are currently ubiquitous across major Solanaceae-producing areas in Brazil. Both MAT idiomorphs were detected, but a larger number of the V. dahliae isolates displayed the MAT1–1 (82%) pattern in our molecular analyses. The simultaneous presence of both MAT idiomorphs opens the possibility of sporadic events of sexual reproduction among V. dahliae populations from Brazil, enabling the potential emergence of either new recombinant isolates with broader host ranges or novel physiological races. Our results clearly indicated the need to intensify the search for effective sources of resistance to V. dahliae race 2 in tomato breeding programs under Brazilian conditions. [ABSTRACT FROM AUTHOR]

Sixty-seven isolates of Rhizoctonia obtained from potato stems and tubers in the main potato growing regions of Brazil between 2013 and 2014 were analyzed for their molecular and pathogenicity characteristics. Using phylogenetic analysis of the internal transcribed spacer region of ribosomal DNA, 49 isolates were identified as R. solani and 18 isolates as binucleate Rhizoctonia (BNR). Twenty-five isolates (37.3%) belonged to anastomosis group (AG)-3 PT, 20 (29.9%) to AG-4 HGI, 15 (22.4%) to AG-R, three (4.5%) to AG-2-1, three (4.5%) to AG-A, and one (1.5%) to AG-1 IB. Most of the AG-3 PT, AG-4 HGI, AG-A and AG-R isolates, and all isolates of AG-2-1 and AG-1 IB were obtained from tubers with black scurf symptoms. AG-4 HGI isolates were widely distributed and recovered from six out of seven Brazilian states, including 11 potato-growing fields. All isolates were pathogenic to potato, causing necrotic lesions on subterraneous stems, but there were differences in aggressiveness among different AGs. AG-4 HGI was significantly more aggressive to potato plants than other AGs. To our knowledge, this is the first detailed report of the AG composition of Rhizoctonia populations causing potato diseases in different Brazilian regions. [ABSTRACT FROM AUTHOR]

The tree was rooted with the species Pseudoperonospora humuli Original article has been updated. 1 Symptoms of downy mildew of cucurbits on different hosts in Brazil. a-b, Cucumis sativus. c-d, Cucumis melo. e-f, Cucurbita moschata. g-h, Cucumis anguria Figure 2: Phylogenetic tree obtained by Bayesian Inference of the concatenated cox2, cox2-1, cox1 and ITS regions. [Extracted from the article]

The use of resistant cultivars is one of the most efficient strategies for reducing the amount of pesticides in agricultural crops. Several species of the Solanaceae and Cucurbitaceae families are susceptible to diseases caused by Phytophthora capsici isolates. Even though sources of resistance have been identified in other host plants, reports of resistance to P. capsici in cultivated and wild tomato species [genus Solanum (section Lycopersicon)] germplasm are yet scarce. The main objective of the present work was to characterize the reaction of 244 Solanum ( Lycopersicon) accessions to P. capsici under controlled greenhouse experiments. In the first set of experiments, tomato seedlings were inoculated at the collar area with a 3 mL of a spore suspension (2 × 10 zoospores mL). Disease incidence (dead plants/total plants) was assessed 14 days after inoculation. The accessions were separated in five well-defined reaction groups: highly resistant (HR), resistant (R), moderately susceptible (MR), susceptible (S), and highly susceptible (HS). The reaction of a group of the ten accessions with the highest levels of resistance was then evaluated against a collection of five P. capsici isolates. Differential reaction was observed among accessions and isolates. The resistant response was host species-dependent with susceptibility being more often found in S. peruvianum accessions, whereas sources of resistance were identified more frequently among accessions of the cultivated tomato ( S. lycopersicum). [ABSTRACT FROM AUTHOR]