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Rice stripe necrosis virus (RSNV) is the causal agent of the disease 'rice crinkling' and is transmitted by the protozoan Polymyxa graminis. Although genetic resistance has been explored, no resistant commercial cultivars are currently available. Oryza glaberrima has been identified as a promising source of resistance. However, it remains unclear whether this resistance is effective against the virus, the vector, or both, as well as whether it can be transferred to Oryza sativa cultivars. Disease‐resistant genotypes are primarily selected through visual observations of symptom expression. The absence of a severity scale for RSNV makes this process difficult, and relying solely on visual assessments can introduce subjectivity. We developed a severity scale and a reverse transcripiton‐quantitative PCR (RT‐qPCR) assay for screening resistance levels in rice genotypes against RSNV and its vector and to analyse the genetic variability of RSNV isolates. To achieve absolute quantification, experiments were conducted using O. glaberrima and three O. sativa cultivars. Inoculation occurred naturally using soil from an area with a history of the disease. Visual symptoms were recorded and disease intensity was evaluated. Subsequently, total nucleic acid extraction was performed on the samples and viral and vector loads were quantified through RT‐qPCR and qPCR, respectively. To characterize the virus variability, symptomatic rice samples were collected in the 2021/2022 crop season. RT‐PCR was conducted to amplify the coat protein gene of RSNV, and molecular variability descriptors were analysed. [ABSTRACT FROM AUTHOR]

Embrapa has led breeding programs for irrigated and upland rice (Oryza sativa L.) since 1977, generating a large amount of pedigree and phenotypic data. However, there were no systematic standards for data recording nor long‐term data preservation and reuse strategies. With the new aim of making data reuse practical, we recovered all data available and structured it into the Embrapa Rice Breeding Dataset (ERBD). In its current version, the ERBD includes 20,504 crosses involving 9,974 parents, the pedigrees of most of the 4,532 inbred lines that took part in advanced field trials, and phenotypic data from 2,711 field trials (1,118 irrigated, 1,593 upland trials), representing 226,458 field plots. Those trials were conducted over 38 years (1982–2019), in 247 locations, in latitudes ranging from 3°N to 33°S. Phenotypic traits included grain yield, days to flowering, plant height, canopy lodging, and five important fungal diseases: leaf blast, panicle blast, brown spot, leaf scald, and grain discoloration. The total number of data points surpasses 1.27 million. Descriptive statistics were computed over the dataset, split by cropping systems (irrigated or upland). The mean heritability of grain yield was high for both systems, at around.7, whereas the mean coefficient of variation was 13.9% for irrigated trials and 18.7% for upland trials. The ERBD offers the possibility of conducting studies on different aspects of rice breeding and genetics, including genetic gain, G×E analysis, genome‐wide association studies and genomic prediction. Core Ideas: Historical datasets are useful for genetic research and development of breeding tools.Phenotypic data from crop breeding programs connect elite genotypes with target environments.Converting available records in analyzable format is a worthwhile investment. [ABSTRACT FROM AUTHOR]

Background: The necessity of a competent vector for transmission is a primary ecological factor driving the host range expansion of plant arthropod-borne viruses, with vectors playing an essential role in disease emergence. Cassava begomoviruses severely constrain cassava production in Africa. Curiously, begomoviruses have never been reported in cassava in South America, the center of origin for this crop. It has been hypothesized that the absence of a competent vector in cassava is the reason why begomoviruses have not emerged in South America., Methods: We performed a country-wide whitefly diversity study in cassava in Brazil. Adults and/or nymphs of whiteflies were collected from sixty-six cassava fields in the main agroecological zones of the country. A total of 1,385 individuals were genotyped based on mitochondrial cytochrome oxidase I sequences., Results: A high species richness was observed, with five previously described species and two putative new ones. The prevalent species were Tetraleurodes acaciae and Bemisia tuberculata , representing over 75% of the analyzed individuals. Although we detected, for the first time, the presence of Bemisia tabaci Middle East-Asia Minor 1 ( Bt MEAM1) colonizing cassava in Brazil, it was not prevalent. The species composition varied across regions, with fields in the Northeast region showing a higher diversity. These results expand our knowledge of whitefly diversity in cassava and support the hypothesis that begomovirus epidemics have not occurred in cassava in Brazil due to the absence of competent vector populations. However, they indicate an ongoing adaptation process of Bt MEAM1 to cassava, increasing the likelihood of begomovirus emergence in this crop., Competing Interests: The authors declare there are no competing interests., (©2021 Xavier et al.)