Soybean anthracnose

Thais R. Boufleur

Luiz de Queiroz College of Agriculture (ESALQ), University of São Paulo, Brazil

Soybean (Glycine max) anthracnose is caused by several Colletotrichum species, including C. truncatum, C. destructivum, C. coccodes, C. chlorophyti, C. gloeosporioides, C. incanum, C. plurivorum, C. sojae, C. musicola and C. brevisporum; being C. truncatum the most studied species until now.

The dissemination of the disease to new areas occurs mainly by contaminated soybean seeds, and there are evidences of off-season survival due the production of fungal resistance structures, called microsclerotia. Anthracnose symptoms can appear since the sowing until the final reproductive stages of soybean in the field. It is known that Colletotrichum species can go through a quiescent phase in the plant, but differences in timing of appearance of the disease are not yet fully understood.

Typical soybean anthracnose symptoms are pre and post-emergence damping-off; irregular, dark and depressed lesions that can appear in all the tissues of the plant and dark lesions on laminar veins on leaves. The consequence of those symptoms are the reduction of stand, early defoliation and opening of pods; all of those causing significant reduction of soybean production in years with warm and humid conditions, when anthracnose can reach up to 100% of incidence. 

Figure 1: Typical symptoms and signs of C. truncatum on soybean. Infected seed (A); irregular, dark and depressed lesions on cotyledons, leaves, petiole, stem and pods (B; D-E); premature opening of pods with infected seeds (C). (Boufleur et al., 2021).

Control measures for soybean anthracnose should start with sowing disease-free seeds, and the application of cultural practices like crop rotation. Some chemical molecules are available to be used alone or in mixtures, that can be used on seed treatments and spraying of plants. However, several studies on the efficiency of the chemical control showed the lack of efficiency of some of those, and therefore they need to be constantly updated. Besides the potential of destruction and the increasing reports of the disease in soybean production regions all over the world, until now there are no breaded soybean cultivars resistant to anthracnose.

A lot of effort still needs to be done to better understand the complexity of this disease and the role of all the Colletotrichum species reported until now associated with soybean.

More information about soybean anthracnose and questions that still need to be answered can be found at Boufleur et al., 2021.

References

Boufleur, TR, Ciampi‐Guillardi, M, Tikami, Í, et al. Soybean anthracnose caused by Colletotrichum species: Current status and future prospects. Mol Plant Pathol. 2021; 22: 393– 409. https://doi.org/10.1111/mpp.13036

PLOS ONE: Metabarcoding Analysis of Fungal Diversity in the Phyllosphere and Carposphere of Olive Olea europaea

PLOS ONE: Metabarcoding Analysis of Fungal Diversity in the Phyllosphere and Carposphere of Olive Olea europaea.

 

Abstract

The fungal diversity associated with leaves, flowers and fruits of olive (Olea europaea) was investigated in different phenological stages (May, June, October and December) using an implemented metabarcoding approach. It consisted of the 454 pyrosequencing of the fungal ITS2 region and the subsequent phylogenetic analysis of relevant genera along with validated reference sequences. Most sequences were identified up to the species level or were associated with a restricted number of related taxa enabling supported speculations regarding their biological role. Analyses revealed a rich fungal community with 195 different OTUs. Ascomycota was the dominating phyla representing 93.6% of the total number of detected sequences followed by unidentified fungi (3.6%) and Basidiomycota (2.8%). A higher level of diversity was revealed for leaves compared to flowers and fruits. Among plant pathogens the genus Colletotrichum represented by three species (Cgodetiae synCclavatumCacutatum s.s and Ckarstii) was the most abundant on ripe fruits but it was also detected in other organs. Pseudocercospora cladosporioides was detected with a high frequency in all leaf samples and to a less extent in ripe fruits. A much lower relative frequency was revealed for Spilocaea oleagina and for other putative pathogens including Fusarium spp., Neofusicoccum spp., and Alternaria spp. Among non-pathogen taxaAureobasidium pullulans, the species complex of Cladosporium cladosporioides and Devriesia spp. were the most represented. This study highlights the existence of a complex fungal consortium including both phytopathogenic and potentially antagonistic microorganisms that can have a significant impact on olive productions.