Alessandro Nicoli

Resistance of advanced common bean lines to Fusarium root rot

Fusarium root rot (FRR) is a distributed disease of common beans in Brazil. Our main aim was to verify if there are genotypes, mainly advanced lines from the common bean breeding program with levels of resistance to FRR similar to those of the line A-300. We also compared three developmental stages for FRR assessment. Genotypes of six classes were evaluated in greenhouse and field experiments. In greenhouse, substrate was infested with chlamydospores. In field, genotypes were screened in area infested with Fusarium solani f. sp. phaseoli. Plants were rated for disease at V3, R5 and R7 stages. Correlation among area under the disease progress curve (AUDPC) in greenhouse and in the field experiments was significant. Genotypes were ranked into four groups based on AUDPC. Sixteen advanced lines were as resistant to FRR as A-300. Correlation between the disease rating at R5 stages and AUDPC was higher than those among AUDPC and either disease rating at V3 or R7 in all experiments. Our results indicate that there are advanced lines with levels of FRR resistance similar to those of A-300 and that the FRR assessment at the R5 stage is more appropriated than at either V3 or R7.

Black mildew disease on the neotropical medicinal shrub Pothomorphe umbellata in Brazil, caused by Irenopsis tortuosa var. potomorphes

A black mildew disease caused by Irenopsis tortuosa var. potomorphes (Meliolales) was observed on leaves of the neotropical medicinal shrub Pothomorphe umbellata collected in a stretch of Atlantic rain forest in the municipality of Viçosa, Minas Gerais, Brazil. This is the fourth record of Irenopsis tortuosa var. potomorphes on Pothomorphe umbellata and the first record of this fungus in Brazil.

Phylogenetic placement of the genus Anhellia and the description of A. nectandrae sp. nov.

The phylogenetic position of a new species of Anhellia (Myriangiales) was investigated by analysis of nucleotide sequences of ribosomal large subunit (LSU) and ITS regions. The new sequence was aligned with 28 sequences obtained from GenBank, including four species of Davidiellaceae (Capnodiales) used as outgroup. This study is the first attempt to resolve the placement of the genus Anhellia within Myriangiales. The genus Anhellia was strongly supported in Myriangiaceae by phylogenetic analyses. In addition, A. nectandrae sp. nov., collected on Nectandra rigida from a fragment of Atlantic forest in Brazil, is described, illustrated and a table with morphological features to all known Anhellia species is provided.

Chlamydospore concentration for assessment of Fusarium root rot on common bean

Fusarium root rot caused by Fusarium solani f. sp. phaseoli (Fsp) is widely distributed in Latin America. Experiments involving artificial inoculations could be better compared whether the number of Fsp infective propagules is well quantified by using chlamydospores. This study aimed to define the adequate concentration of chlamydospores of Fsp for assessment of the disease severity under controlled conditions. In greenhouse, two experiments were performed, where common bean susceptible genotypes were sown in a substrate infested with 0, 1000, 2000, 3000, 4000, 5000 or 6000 chlamydospores g-1 of substrate. Plants were rated for disease severity at 30 d after emergence. Linear response plateau was used to represent the relationship between disease severity and concentration of chlamydospores in the substrate. According to our results, concentrations between 4500 and 5000 chlamydospores g-1 of substrate maximizes the disease severity and can be recommended to evaluate large-scale screenings of bean germplasm.