Leonardo Silva Boiteux

Cowpea ( Vigna unguiculata ) is an important field crop that exhibits a high level of adaptation to the semiarid regions of Brazil. Powdery mildew was previously considered a minor disease of cowpea in this region. However, the disease has become increasingly frequent and economically important following the expansion of cowpea cultivation into the Cerrado (savanna) region of central Brazil. Here, we characterised fungal isolates associated with powdery mildew signs and symptoms on cowpea plants. Morphological and phylogenetic analyses based on three genomic regions confirmed that the disease is caused by Erysiphe vignae . To the best of our knowledge, this is the first worldwide report of E. vignae causing powdery mildew on V. unguiculata .

Onion (Allium cepa) is a major source of rural income in the tropical semi-arid region of Northeast Brazil. Nevertheless, local farmers still depend heavily on imported hybrid seeds. We assessed genotype-by-environment (G×E) interaction and identified broadly adapted and more phenotypically stable onion hybrids originated from the Brazilian breeding program. Twelve experimental hybrids, two commercial hybrids and one open-pollinated cultivar were evaluated across eight semi-arid environments (Bahia and Pernambuco states) under a randomized complete block design with two replications. Marketable bulb yield was analyzed by combined ANOVA and by two stability approaches, Eberhart–Russell regression and AMMI biplot. In addition, marketable yield was also evaluated with a covariance adjustment using marketable stand as a covariate. Significant G×E interaction was detected, and both methods consistently highlighted two high-yielding hybrids (‘EPCEB20H037’ and ‘EHCEB21H0507’) as the ones with superior adaptation and more stable performances. These results support the use of locally developed onion hybrids to improve yield and reduce seed costs across the Brazilian semi-arid region.

Guava (Psidium guajava L.) is a Myrtaceae fruit species native to tropical and subtropical regions, widely recognized for its nutritional value and medicinal properties (Santos et al. 2022). It has...

Black root rot, caused by two Berkeleyomyces species ( B. basicola and B. rouxiae ), is a major disease of lettuce ( Lactuca sativa L.) in tropical areas. Nationwide surveys in Brazil indicated similar levels of incidence as well as an overlapping geographical distribution of B. basicola and B. rouxiae across major lettuce-producing areas. The most promising strategy for managing these polyphagous and aggressive pathogens is the deployment of genetic resistance. The heirloom cultivar ‘La Brillante’ displayed resistance to a broad range of isolates of both Berkeleyomyces species. However, to date, there is no information about the genetic control of B. basicola and B. rouxiae . Inheritance studies investigating the resistance of ‘La Brillante’ to isolates of both pathogens were conducted separately employing F ₂ populations derived from crosses with the highly susceptible cultivar ‘Elisa’. The hybrid origin of individual F ₁ plants was assessed via RAPD marker genotyping. Two bona-fide F ₁ plants were then selfed to obtain two independent F ₂ segregating populations. The contrasting parental cultivars and F ₂ seedlings were then separately inoculated with B. rouxiae (F ₂ population size = 247) and B. basicola (F ₂ population size = 166). Chi-square test was employed to assess the goodness of fit of the observed segregation patterns against each pathogen to the predicted Mendelian ratios. All ‘Elisa’ plants displayed highly susceptible reactions to both pathogens, whereas all ‘La Brillante’ plants were resistant even under harsh inoculation conditions, indicating high levels of penetrance of this trait. The F ₂ populations inoculated with either B. basicola or B. rouxiae displayed a good fit to 3:1 resistant/susceptible segregation ratios, indicating monogenic and dominant resistance to both pathogens. Additional experiments are necessary to verify whether the same gene/locus or distinct genes/loci are controlling the resistance to B. rouxiae and B. basicola . Nevertheless, this simple monogenic inheritance will facilitate the incorporation of these resistant traits into elite lettuce breeding lines and cultivars.

Beans (Phaseolus vulgaris and P. lunatus) are the major hosts of bean golden mosaic begomovirus (BGMV). Robust taxonomic criteria were established for Begomovirus species demarcation. However, DNA–A identities among BGMV isolates display a continuous variation (89–100%), which conflicts with the current concept of a single viral species. The diversity of 146 Brazilian isolates designated in the GenBank as BGMV was assessed by comparing their complete DNA–A sequences. The isolates were clustered into four groups, being discriminated mainly by their original Fabaceae hosts. Additional Sequence Demarcation Tool analyses indicated that BGMV-related viruses comprise two clear-cut groups: isolates reported infecting mainly P. vulgaris (identities of 96–97% to the reference NC_004042 isolate) and a group associated with P. lunatus (identities of 89–91%). Moreover, we recognized a distinct set of genomic features in the iterons and Rep-associated protein motifs across these two diversity groups. The host prevalence and genomic differences suggest that most P. lunatus isolates are currently misclassified as BGMV strains, being more likely samples of a closely related (but distinct) Begomovirus species. Hence, the implications of this BGMV diversity should be taken into consideration by classical and biotech breeding programs aiming for large-spectrum viral resistance in Phaseolus species.

Leandria momordicae Rangel is the etiological agent of net spot, which is a very important disease of cucumber (Cucumis sativus), chayote (Sicyos edule), and in other Cucurbitaceae species. Although this pathogen was described more than a century ago infecting Momordica charantia, its taxonomic positioning has not yet been clarified. Moreover, a standard isolate of this fungus is not available in any reference mycological collection. In this context, the aims of the present work were (i) to clarify the taxonomic position of the fungus via morphological and phylogenetic analyses; (ii) to deposit a neotype of L. momordicae in a public mycological collection; (iii) to provide the first DNA sequences of the pathogen in GenBank. The morphometrical characteristics of distinct L. momordicae isolates were similar to those originally described. The phylogenetic analyses were carried out using information of five genomic regions. Using the BLASTn algorithm, it was observed that the L. momordicae-derived sequences displayed higher identity levels to fungal sequences of the order Pleosporales, which were subsequently included in the analyses. All sequences from the nine isolates of L. momordicae grouped within a single phylogenetic clade distinct from the other taxa in Pleosporales. Therefore, it is suggested the establishment of a new family of Pleosporales to include L. momordicae to which the name Leandriaceae is proposed. In addition, an ex-neotype and a neotype were illustrated and deposited in the Herbarium of the Federal University of Viçosa (VIC4754) and in the culture collection "Octávio Almeida Drummond" (COAD3403). The present study reinforces the view that many "hidden" fungal taxa are yet to be discovery under Neotropical conditions.

A new alphasatellite was discovered via high-throughput sequencing in mixed infections with five distinct tomato-infecting begomoviruses in central Brazil, and the presence of this alphasatellite in tomato leaf samples was confirmed by PCR and Sanger sequencing. It has a circular genome of 1,321 nucleotides with typical features of alphasatellites belonging to the subfamily Geminialphasatellitinae, including a replication-associated hairpin sequence (TAGTATTAC) and an open reading frame encoding a replication-associated protein. Pairwise sequence comparisons and phylogenetic analysis indicated that this alphasatellite represents a new species, with 69–77% sequence identity to other members of the genus Clecrusatellite. Tomato golden vein virus (TGVV) was the only begomovirus present in all six positive samples. However, it was not possible to determine which of these viruses can function as a helper virus for the alphasatellite. The species name "Clecrusatellite solanumbrasiliensis" is proposed to classify this alphasatellite associated with endemic Brazilian begomoviruses. To our knowledge, this is the first report of a tomato-associated alphasatellite in the New World.