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During the winter, there is a high occurrence of downy mildew on lettuce caused by Bremia lactucae. This oomycete shows variability in virulence, so understanding the genetic structure of the pathogen population becomes essential for obtaining resistant cultivars. Thus, the objective of this study was to determine sexual compatibility in Brazilian populations of B. lactucae and investigate the occurrence of sexual reproduction of the pathogen on lettuce (Lactuca sativa) and prickly lettuce (Lactuca serriola). Leaf samples were collected in 33 municipalities in seven Brazilian states. The virulence structure of the populations was monitored using the EU‐C sextet code. B. lactucae populations from the states of São Paulo, Paraná, Rio de Janeiro, and Rio Grande do Sul shared six of the 15 virulence factors evaluated. Twenty‐five virulence phenotypes (v‐phenotypes) were found, with the sextet codes 31‐00‐02, 31‐16‐02, 31‐24‐02, and 31‐01‐02 being more frequent. The predominance of some v‐ phenotypes indicates that clonal reproduction is still the main form of B. lactucae propagation. The genes and resistance factors of the cultivars Argelès (Dm38), Balesta, and Bartoli are recommended as suitable sources of lettuce resistance in Brazil. Natural occurrence of oospores was detected in most sampled locations, in lettuce and prickly lettuce plants. Virulence variability of Brazilian isolates is the result of the pathogen's ability to reproduce both sexually and asexually, with a prevalence of homothallic isolates; although the majority were of the predominant B2 mating type, there was a high incidence of predominant B1 in addition to B1 = B2. [ABSTRACT FROM AUTHOR]

The okra (Abelmoschus esculentus L. Moench) is one of the most important vegetables in the world and is a popular food item in many tropical and subtropical countries. Besides its cultivation for fresh consumption, okra also has potential industrial uses. Nonetheless, pests and diseases remain the most damaging factors affecting its crop yield. Among these, root-knot nematodes are the main pests limiting okra production. This study aimed to determine the responses of plant species of the Malvaceae family to Meloidogyne incognita and M. enterolobii rootknot nematodes and to also assess the compatibility of the same with the okra commercial 'Colhe Bem IAC'. Resistance was evaluated using the reproduction factor in two commercial okra cultivars ('Colhe Bem IAC' and 'Santa Cruz 47'), five cotton (Gossypium hirsutum L.) plant genotypes (PRO 277, IAC 29-233, PR 136, IAC 24, and IAC 03-979), and vinagreira (Hibiscus sabdariffa L.) Other resistance-related traits measured were the percentage of healing, plant height, root length, rootstock stem diameter, scion stem diameter, number of leaves, total fresh weight and fresh weight of the scion, rootstock, and root parts. While the cotton and vinagreira genotypes tested were resistant to both species of nematodes, okra cultivars were not. The okra, however, showed successful adaptation to grafting, which may offer an important physical resistance against attacks by root-knot nematodes, while vinagreira showed the greatest potential for use as rootstock for protecting okra crops. [ABSTRACT FROM AUTHOR]