Quorum sensing (QS) is often defined as a mechanism of microbial communication that can regulate microbial behaviors in accordance with population density. Much is known about QS mechanisms in bacteria, but fungal QS research is still in its infancy. In this study, the molecules constituting the volatolomes of the plant pathogenic fungi Fusarium culmorum and Cochliobolus sativus have been identified during culture conditions involving low and high spore concentrations, with the high concentration imitating overpopulation conditions (for QS stimulation). We determined that volatolomes emitted by these species in conditions of overpopulation have a negative impact on their mycelial growth, with some of the emitted molecules possibly acting as QSM. Candidate VOCs related to QS have then been identified by testing the effect of individual volatile organic compounds (VOCs) on mycelial growth of their emitting species. The antifungal effect observed for the volatolome of F. culmorum in the overpopulation condition could be attributed to ethyl acetate, 2-methylpropan-1-ol, 3-methylbutyl ethanoate, 3-methylbutan-1-ol, and pentan-1-ol, while it could be attributed to longifolene, 3-methylbutan-1-ol, 2-methylpropan-1-ol, and ethyl acetate for C. sativus in the overpopulation condition. This work could pave the way to a sustainable alternative to chemical fungicides.

Variations in banana susceptibility to crown rot disease have been observed but the molecular mechanisms underlying these quantitative host–pathogen relationships are still unknown. This study was designed to compare gene expression between crowns of banana fruit showing a high susceptibility (S⁺) and crowns showing a low susceptibility (S^–) to the disease. Comparisons were performed at two situation times: i) between crowns (S⁺ and S^–) collected 1 h before inoculation and ii) between crowns (S+ and S–) collected 13 days after inoculation. Gene expression comparisons were performed with cDNA-amplified fragment length polymorphism (AFLP) and results were confirmed by real-time reverse-transcription polymerase chain reaction. Among genes identified as differentially expressed between S⁺ and S^– crowns, two were involved in signal transduction, three in proteolytic machinery, two had similarity to pathogenesis-related protein 14, one to a CCR4-associated factor protein, and one to a cellulose synthase. Paradoxically, the overexpression of the cellulose synthase gene was associated with banana showing a high susceptibility in both pre- and post-inoculation situations. Finally, the cDNA-AFLP identified a gene that seems to be associated with the quantitative banana responses to crown rot disease; this gene encodes a dopamine-β-monooxygenase, which is involved in the catecholamine pathway. To our knowledge, this work is the first to address both pre- and post-infection gene expression with the same host–pathogen combination and distinct susceptibility levels.

Background and aims – While tropical forests play an important role in carbon sequestration, they are assumed to be sensitive to rising temperatures and prolonged drought. Plant functional traits are useful for understanding and predicting the effects of such changes in plant communities. Here, we analyse the variation of leaf traits of understory woody species of the Congo Basin rainforests over a 60-year period using herbaria as tools and we verify if this variation is potentially related to recent climate change. Material and methods – Leaves of five shrub species were collected in 2019–2022 in Congolese old-growth forests (Yangambi Biosphere Reserve, DR Congo) from different positions on the shrub. These leaves were compared with herbarium specimens collected in the same area before 1960. For both periods, we assessed leaf size, specific leaf area, stomatal size, and stomatal density for all species. Key results – The variability of the functional traits of the understory woody species are independent of the position of the leaves in the crown. This allows for the use of historic herbarium collections for trait analyses on tropical understory shrubs. The traits of the recently collected leaves were notably different from the traits of herbarium leaves collected in pre-1960: recent leaves were significantly larger, had a higher Specific Leaf Area, a smaller stomata pore length, and, apart from Coffea canephora, showed a lower stomatal density. Conclusion – The difference in traits over time is probably related to the increase in temperature and to atmospheric CO₂ concentration, as the average temperature at Yangambi over the past 60 years has shown an upward trend consistent with global increasing CO₂ levels, while the average annual rainfall has remained unchanged. Our results provide a first insight into the response of forest species to climate change in the Congo Basin forests, and on how the understory species and the ecosystem will react in the long term, when the temperature further increases.

Fat content (FC) and fatty acids (FA) are the most important traits in shea tree breeding, controlled by several genes with relatively small effects. Therefore, determining the genes involved in the biosynthesis of such traits is crucial for improving oil quantity and quality and for the domestication process of the species. To identify the quantitative trait nucleotides (QTNs) controlling FC and FA, we conducted a multi-locus genome-wide association study (GWAS) using six multi-locus GWAS methods for FC and FA in 122 superior shea trees (SSTs). SSTs were genotyped using DArTseq, resulting in 7,559 non-redundant single nucleotide polymorphism markers. Fat content varied from 36 to 58% with a mean of 50%. Fatty acid composition was 51.26 ± 4.21, 38.76 ± 4.67, 6.45 ± 0.76 and 3.53 ± 0.52% for oleic, stearic, linoleic and palmitic acids, respectively. A very high negative correlation coefficient (-0.98) was found between stearic and oleic acids. A total of 47 significant QTNs associated with fat-related traits were detected by the GWAS methods. Among these QTNs, 25 were identified as common QTNs based on their detection by multiple GWAS methods. Using the superior allele information of the 4 common QTNs associated with fat content in 17 high-fat and 21 low-fat SSTs, we found a higher percentage of superior alleles in SSTs with high FC (47.1%) than in SSTs with low FC (14.3%). Pathway analysis of the common QTNs identified 24 potential candidate genes likely involved in the biosynthesis of FC and FA composition in shea tree seeds. These findings will contribute to the discovery of the polygenic networks controlling FC in shea tree, improve our understanding of the genetic basis and regulation of FC, and be useful for molecular breeding of high-fat shea tree cultivars.

In Africa, rice has always been a staple food in some countries and the fastest growing food source there. In the Democratic Republic of Congo (DRC), in terms of cereal production, rice is ranked second after maize and is an important source of income for the rice farmer. The objective of this study was to analyze and understand consumers’ preferences and behaviors towards local and imported rice in the South Kivu and Tanganyika provinces, DRC. Data collected on 1565 rice-consuming households in eastern DRC showed that there is a great opportunity for the rice value chain and food policy development, and the promotion of local rice consumption. Consumers focus on local rice because it is cheaper, but it does not always meet their desired needs. Indeed, only urban consumers were more willing to pay for higher-quality rice. The development of the demand for local rice calls for strong investment in improving production, post-harvest practices, and market aspects. It was found that over 90% of rice consumers know about local rice production and over 84% have consumed it. In rural areas, there is typically lower consumption of imported rice. However, as households require more rice, they tend to rely more on imported varieties due to their availability in the market. The most preferred rice attributes were flavor, aroma, purity, swelling capacity, breakage rate, and whiteness. Therefore, rice producers should consider the habits and needs of consumers to improve market demand. In addition, good packaging, labeling, and marketing can also enhance local rice preference and competitiveness in South Kivu and Tanganyika provinces in eastern DRC. The findings of this study indicated that research aimed at improving local rice varieties with regard to yield, disease resistance, and organoleptic qualities could enable the population to consume more locally produced rice, which is often more affordable than imported rice. This could in turn significantly reduce the need for rice imports. These results suggest that research carried out to improve the yield and organoleptic qualities of local rice in this area can allow it to be more competitive on the market and can reduce the importation of rice.