African oil palm (Elaeis guineensis Jacq.) is considered the most productive oleaginous crop due to its high oil production per hectare. In April 2015, E. guineensis leaves showing elliptical necrotic spots with yellowish halo were observed in a commercial plantation in Moju, Pará state, Brazil. A synematous fungus was consistently observed associated with the necrotic spots. The aim of this study was to identify this fungus associated with E. guineensis in Brazil. Based on morphology and DNA sequence data of the internal transcribed spacer rDNA, the fungus was identified as Helminthosporiella stilbacea. Helmintosporiella stilbacea has been reported associated with leaf spots on E. guineensis in Africa, Ghana, Sudan and Zambia. To the best of our knowledge, this is the first report of H. stilbacea associated with E. guineensis in Brazil.

No abstract

Soybean root and stem rot caused by the oomycete Phytophthora sojae is a destructive disease worldwide that can affect plants at any growth stage. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the population of P. sojae regarding the dynamics of avirulence genes capable of overcoming resistance genes (Rps) is important to reduce yield losses and to enhance the effectiveness of the Rps genes. Forty isolates of P. sojae sampled from a region of high incidence of soybean root and stem rot in Brazil were characterized using 14 soybean differentials and 28 pathotypes were identified. Compared to a study conducted a decade ago there was a major shift in pathotype diversity and complexity towards both higher numbers of different pathotypes and of avirulence genes in a given individual in the current population of P. sojae. Breeding programs aiming at developing soybean cultivars with resistance to root and stem rot should consider the high variability in the population of P. sojae and seek for strategic deployment of genes and germplasm.

No abstract

During March 2016, leaf blight, followed by death, was observed on yard-long bean plants (Vigna unguiculata subsp. sesquipedalis) in Brazil. Based on morphological characteristics and phylogenetic analysis, the pathogen was identified as Rhizoctonia solani AG-1 IA. Koch's postulates were fulfilled. All accessions studied were classified as susceptible. This is the first report of Rhizoctonia solani AG1-IA infecting yard-long bean.

Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. cubense ( Foc), is considered one of the most destructive diseases of bananas in Brazil. In this study, a collection of 194 monosporic isolates from several banana-producing regions located in different climatic zones along a south-to-north transect in Brazil was formed to assess the genetic structure of the population of Foc. The isolates underwent pathogenicity tests, PCR diagnosis for the detection of tropical race 4, and screening of SIX homolog genes that produce putative effector proteins. The vegetative compatibility group (VCG) of 119 isolates was determined by pairing against 17 internationally known VCG-tester strains. A group of 158 isolates was selected for simple sequence repeat (SSR) genotyping. There was moderate diversity of Foc in Brazil. Eight VCGs were identified: 0120, 0122, 0124, 0125, 0128, 01215, 01220, and 01222, of which 78% of isolates belong to a single VCG, whereas 22% of isolates are assigned to multiple VCGs, belonging to complexes of VCGs. The distribution of VCGs is uneven and independent of the banana genotype. The isolates of a VCG shared a similar profile of SIX homologs, but there was no association with geographic region. Four SSR loci were polymorphic, and, on average, 7.5 alleles were detected per locus. Thirty-five multilocus genotypes (MLGs) were identified. There was no association between VCG and MLGs, and no genetic structure of the population of Foc in Brazil was detected.

Cycas revoluta Thunberg, which belongs to the Cycadaceae family, is also known as sago palm, King Sago Palm, and Sago Cycad (Figure 1a). This cycad is native to Japan, where it grows mainly on steep limestone cliffs and rocks overhanging the shoreline, as well as in sparse forests under heavy shade (Whitelock, 2002). This small palm-like tree is used as an ornamental plant in several countries. Humans have consumed it for food for nearly 7000 years, in addition to using it for alcoholic beverages, medicine, and other purposes (Whitelock, 2002).Cycads are rarely affected by the disease, except for seedlings, and most diseases are caused by fungi (Whitelock, 2002). Among other fungi that cause leaf spots on sago palm, some members of Sporocadaceae might be listed, such as Pestalotia cycadis, Pestalotiopsis leprogena, Pestalotiopsis uvicola, Pestalotiopsis vismiae, Pestalotiopsis glandicola and Pestalotiopsis guepinii (Farr & Rossman, 2022).Based on the characteristics of the conidia, Steyaert (1949) separated Pestalotia into two further genera, Pestalotiopsis and Truncatella.Briefly, Pestalotia is distinguished by having conidia with six cells.Truncatella has conidia with only four cells, while Pestalotiopsis possesses conidia with five cells. Maharachchikumbura et al. (2014) split Pestalotiopsis into three genera, namely Neopestalotiopsis, Pestalotiopsis and Pseudopestalotiopsis.

Soybean root rot disease caused by the oomycete Phytophthora sojae is particularly destructive, once it is a host-specific pathogen that can infect and kill soybean plants at any stage of growth. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the adaptability of P. sojae population to resistance genes (Rps) is extremely important not only from an epidemiological point of view but mainly for the management of the disease and durability of the Rps genes. We investigated the pathotypes of 40 isolates of P. sojae, sampled from the region with a higher incidence of soybean root rot in Brazil, using a set of 14 soybean differentials. The first study investigating pathotype diversity in Brazil was published in 2013. A decade later, we are reporting a major shift in pathotype diversity and complexity. This information can be useful for breeding programs aiming at developing soybean cultivars with resistance to root and stem rot and optimize the usage of genes and germplasm.