Researchers present new data on pod anomaly

With field experiments installed in Sorriso and Nova Mutum, researchers from the MT Foundation have already made some progress on the subject of 'soybean pod anomaly and stem breakage'. The problem has been occurring for four harvests, especially in crops along the BR-163 axis, and has been monitored by a network made up of research institutions, genetic improvement companies, consultancies and seed companies since the 2021/22 harvest.

Results recently obtained by the institution indicate a 50% frequency of occurrence of the fungal complex Diaphorte/Phomopsis; and 61% of the fungus of the genus Colletotrichum spp, the causal agent of anthracnose, both in the soybean stem and pod. The sample collection strategy sought to consider the most contrasting scenarios: symptomatic plants for anomaly and failure in each of the cultivars, the sensitive and the less sensitive (not necessarily immune to each problem), as well as healthy plants in the same cultivars.

This generated the necessary basis of comparison that research needs to take the next step towards understanding the causes of the two problems. The results indicated the presence of Diaphorte in situations in which there were no external symptoms of breakage and anomaly, nor the presence of stretch marks.

Karla Kudlawiec (in the photo above), researcher in the area of ​​Phytopathology and Biologicals at Fundação MT and one of those responsible for the experiments, highlights that the results of the molecular analyzes are now being awaited.

“We will also continue with the collection and evaluation over time of materials sown at other times and verify the frequency of occurrence of these main pathogens. Furthermore, we continue to investigate whether both the stem breakage and the pod anomaly are caused by the same agent or whether they are different things”, he defines.

The molecular part will help to understand which species are involved and which factors can modulate the occurrence or not of the problem, since the analyzes found the fungus Diaphorte even when there were no symptoms. The researcher adds that, although this line of research is the most studied at the moment, other lines that involve the interaction with plant nutrition and plant hypersensitivity responses are still being evaluated, since the MT Foundation has several tests that can contribute with more answers.

2022/23 harvest scenario

So far in the 2022/23 harvest, both the incidence and severity of symptoms of pod anomaly and stem breakage are lower compared to the last harvest. However, researchers warn that nothing prevents this scenario from changing, and the problem is already progressing.

“In general, at our station in Sorriso and in the commercial crops that we had reports from producers, the symptoms in this harvest appeared at the R6 stage, different from last year which was at R5 and R5.4”, explains Felipe Araújo, Phytotechnics researcher and also responsible for the experiments.

The differences, according to experts, may be related to the climatic conditions of the current cycle, with phenological stages lasting longer and thus symptoms being observed later. Another possibility suggested for the lower severity of symptoms could be, on the part of the producer, the use of genetic materials that are less sensitive to the problem. Furthermore, by building more robust fungicide programs, which take into account not only the selection of products but also the addition of more products at each timing, and the extension of the period of coverage of the crop by the program.

At this point, there is also positive news highlighted by researchers. In Fundação MT's anomaly and breakage trials, fungicides are also evaluated to mitigate the problem and the results vary from 4% to 24% incidence with the use of fungicides and without applications, respectively.

“Several mixtures involving different chemical groups are showing positive results, as well as multi-site fungicides are also adding positively”, reports Karla.

Cultivar Grandes Culturas Magazine 281

In an article published in issue 281 of Revista Cultivar Grandes Culturas, researchers had presented a similar conclusion (Carolina Cardoso Deuner, Monikéli Aparecida da Silva, Flávia Elis de Mello, Sandra Marisa Mathioni, Victoria Oasis Regis Lessa Matos, Gustavo Cruz and Ricardo Francisco Desjardins Antunes) .

On page 28, they pointed out:

"As a result of the experiment, it was found that, after isolating the pathogens from the pods with symptoms of the anomaly, there was the presence of the fungus cercospora in 98% of the pods, 45% of Colletrotrichum and 33% of Phomopsis.

For the seeds that were inside the pods, the presence of the fungus was detected cercospora in 27% of the seeds, Macrophomina in 11%, Phomopsis in 9%, Fusarium in 7%, Colletotrichum in 1% and Corynespora by 1%.

Therefore, fungi cercospora, Colletotrichum e Phomopsis were detected in both pods and seeds.

In several experiments, in which other samples were analyzed, the results of sequencing the ITS region confirmed the gender for all fungal isolates.

In the pod samples, it was found that 48% were identified as the fungus Colletotrichum, 33% as cercospora, 16% with Phomopsis and 4% with Corynespora.

Given the similar results of the two experiments, even though they were carried out independently by the institutions, it is noted that there are pathogens such as Colletotrichum, cercospora e Phomopsis that occurred in both experiments, indicating that these fungi may be associated with the pod anomaly problem."

O Material published in the magazine Cultivar Grandes Culturas can be read here.