Fusarium wilt of banana caused by the soil-borne fungi Fusarium oxysporum f. sp. cubense, Tropical Race 4 (Foc TR4) (Syn. Fusarium odoratissimum), is a major threat to the global banana industry. Aiming to identify predisposing soil factors for Fusarium wilt of banana (FWB) TR4, the 23 physical and chemical soil properties were studied in three commercial banana farms in La Guajira, Colombia. Disturbed and undisturbed soil samples were collected from areas affected by the disease (affected plots) and disease-free areas (healthy plots). Five repetitions per farm were considered, with a total sample of n = 30. The data were analyzed using one-way analysis of variance (ANOVA). Subsequently, the debiased sparse partial correlation (DSPC) algorithm was applied. Organic matter (OM), pH, calcium (Ca), magnesium (Mg), zinc (Zn), and cation-exchange capacity on the exchange complex (ECEC), showed significant differences between the affected and healthy plots. In addition, the bulk density and saturated hydraulic conductivity (HC) were associated suggesting that physical attributes, such as soil compaction and poor drainage, create favorable conditions for FWB. According to the DSPC algorithm, the HC variable presented a grade of 5 and an intermediation of 14.67, which indicates that it has significant associations with BD, sand, porosity, ECEC, and OM and plays a critical role in the connection of other variables in the network and the differentiation of healthy and affected plots. These findings establish a baseline of information under field conditions in Colombia, which can be used to design soil management strategies to mitigate the detrimental effects of Foc TR4 by creating less favorable conditions for the pathogen.

Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4) (Syn. Fusarium odoratissimum) is a devastating soil-borne pathogen that infects the roots of banana plants and causes Fusarium wilt disease. Colombia is one of the world’s leading banana producers; therefore, new uncontrolled outbreaks could have serious consequences. Despite this, little is known about the susceptibility of Musaceae lands in Colombia to Foc TR4. This work presents a pioneering study on the susceptibility of Colombian soils to Foc TR4. For this, a study was carried out to characterize climatic, edaphic, and density factors of Musaceae productive systems at the Colombian level, articulated with expert criteria to map and define areas with different levels of susceptibility to Foc R4T. These criteria are typically selected based on the existing scientific literature, consultation with domain experts, and consideration of established methods for assessing soil health and disease susceptibility in Musaceae plantations. By joining the analyzed susceptibility factors, differentiated areas were generated that imply a greater or lesser predisposition to the disease. Subsequently, a validation of the classification was made with Random Forest. The results indicate that at the level of climate, soil, and farm density as a fit factor, practically 50% of the cultivated territory of Musaceae are areas high and very highly susceptible to the pathogen (572,000 km²). The results showed that from the total Musaceae area, Antioquia, Bolívar, Chocó, and Santander turned out to be the departments with the highest proportion of very high susceptibility class of the production farms. The analysis of Random Forest classification performance shows that the model has a relatively low out-of-bag (OOB) error rate (0.023). The study on the susceptibility is highly novel and original, as it represents the first systematic investigation of Foc TR4 susceptibility in Colombian soils. This paper provides important insights into the susceptibility of Musaceae lands in Colombia to Foc TR4. The study highlights the need for ongoing monitoring, containment, and control measures to prevent the spread of this deadly pathogen and protect Colombia’s important banana industry.

Banana, the main export fruit for Colombia, is threatened by Fusarium wilt (FWB), caused by Fusarium oxysporum f. sp. cubense (Foc), tropical race 4 (TR4). Pathogen containment through disinfecting tools, machinery, shoes, and any means that may carry contaminated soil particles with proper disinfectants is at the forefront of disease management. In this study, the biocide efficacy of 10 commercial quaternary ammonium compounds (QACs) products and one based on glutaraldehyde (GA) were evaluated on both reproductive structures (microconidia and macroconidia) and survival spores (chlamydospores) of Foc TR4 (strain 140038) isolated from La Guajira, Colombia. QACs were evaluated at 1200 ppm and two exposure times: <1 and 15 min in the absence or presence of soil. For GA disinfectant, four different concentrations (500, 800, 1200, and 2000 ppm) were evaluated at both contact times in the presence of soil. In the absence of soil, all QACs showed 100% biocidal efficiency against microconidia, macroconidia, and chlamydospores at both <1 and 15 min. The presence of soil decreased the efficacy of disinfectants, but some of them, such as QAC3_1st, QAC7_4th, and QAC5_4th, showed 98%, 98%, and 100% efficacy against Foc TR4 chlamydospores, respectively, after <1 min of contact time. For instance, the GA-based disinfectant was able to eliminate all Foc TR4 propagules after 15 min for all concentrations tested.

Fusarium wilt of banana (FWB) is the most limiting disease in this crop. The phytosanitary emergency caused by FWB since 2019 in Colombia has required the development of ecofriendly control methods. The aim of this study was to test the effectiveness of microbial-based biofungicides against FWB caused by Fusarium oxysporum f. sp. cubense race 1 (Foc R1) and correlate such effect with plant physiological parameters. Five Trichoderma (T1 to T4 and T9) and four Bacillus (T5 to T8)-based biofungicides were evaluated in pot experiments. In vitro, dual confrontation tests were also carried out to test whether the in vitro effects on Foc growth were consistent with the in vivo effects. While Trichoderma-based T3, T4, and T9, and Bacillus-based T8, significantly reduced the growth of Foc R1 in vitro, Trichoderma-based T1, T3, T4, and T9 temporarily reduced the Foc population in the soil. However, the incidence progress of FWB was significantly reduced by Bacterial-based T7 (74% efficacy) and Trichoderma-based T2 (50% efficacy). The molecular analysis showed that T7 prevented the inner tissue colonization by Foc R1 in 80% of inoculated plants. The T2, T4, T7, and T9 treatments mitigated the negative effects caused by Foc R1 on plant physiology and growth. Our data allowed us to identify three promising treatments to control FWB, reducing the progress of the disease, delaying the colonization of inner tissue, and mitigating physiological damages. Further studies should be addressed to determine the modes of action of the biocontrol agents against Foc and validate the utilization in the field.

El aguacate ha sido plantado y consumido desde hace más de nueve mil años sobre la Tierra, sin embargo, solo hacia finales del siglo XX se dio un aumento sostenido de su cultivo y producción, que sobrepasó, en 2018, los 5,6 millones de toneladas. Además ha adquirido una gran valor en la dieta humana para su consumo en fresco debido a sus calidades nutricionales y organolépticas. No obstante, la composición y las cualidades nutricionales de los frutos son muy variables, pues dependen del clima, el suelo, la temperatura, la humedad, la cantidad de lluvia durante el desarrollo del fruto y las prácticas de manejo del cultivo, además de las diferencias genotípicas entre cultivares. Dado que Colombia aún no cuenta con toda la información técnica necesaria para acompañar el incremento de nuevas áreas de cultivo y salvaguardar las actuales, este manual compendia una cantidad importante de temas clave para su cultivo.