Dataset of banana leaves and stem images for object detection, classification and segmentation: A case of Tanzania

Banana is among major crops cultivated by most smallholder farmers in Tanzania and other parts of Africa. This crop is very important in the household economy as well as food security since it serves as both food and cash crops. Despite these benefits, the majority of smallholder farmers are experiencing low yields which are attributed to diseases. The most problematic diseases are Black Sigatoka and Fusarium Wilt Race 1. Black Sigatoka is a disease that produces spots on the leaves of bananas and is caused by an air-borne fungus called Pseudocercospora fijiensis, formerly known as Mycosphaerella fijiensis. Fusarium Wilt Race 1 disease is one of the most destructive banana diseases that is caused by a soil-borne fungus called Fusarium oxysporum f.sp. Cubense (Foc). The dataset of curated banana crop image is presented in this article. Images of both healthy and diseased banana leaves and stems were taken in Tanzania and are included in the dataset. Smartphone cameras were used to take pictures of the banana leaves and stems. The dataset is the largest publicly accessible dataset for banana leaves and stems and includes 16,092 images. The dataset is significant and can be used to develop machine learning models for early detection of diseases affecting bananas. This dataset can be used for a number of computer vision applications, including object detection, classification, and image segmentation. The motivation for generating this dataset is to contribute to developing machine learning tools and spur innovations that will help to address the issue of crop diseases and help to eradicate the problem of food security in Africa.

Protein compounds of Bacillus subtilis with in vitro antifungal activity against Pseudocercospora fijiensis (Morelet)

The metabolites of Bacillus subtilis CCIBP-M27 were evaluated as an antagonist of Pseudocercospora fijiensis. The culture filtrate did not inhibit ascospore germination but significantly reduced conidial germination and mycelial growth. Through microscopic analysis, deformations were observed as vacuolization and swelling in P. fijiensis mycelia when exposed to culture filtrate during 48 h. A similar response was induced by peptide-type compounds found on Bacillus subtilis CCIBP-M27 culture filtrate. The results obtained suggest that the in vitro antifungal effect of the strain CCIBP-M27 against P. fijiensis is related to the action of diffused metabolites such as proteins or peptide substances.

Effect of Bacillus pumilus CCIBP-C5 on Musa-Pseudocercospora fijiensis interaction

The effect of antifungal activity of culture filtrate (CF) of Bacillus pumilus strain CCIBP-C5, an isolate from a phyllosphere of banana (Musa) leaves, was determined on Pseudocercospora fijiensis challenged banana plants. The CF was shown to decrease the fungal biomass and induce changes in banana plant. In this sense, at 70 days post inoculation (dpi), a lower infection index as well as a decrease in fungal biomass after 6 dpi was obtained in treated plants with respect to control ones. At the same time, changes in the activities of several enzymes related to plant defense responses, such as phenylalanine ammonia lyase, chitinases, β-1,3-glucanases and peroxidases were observed. These results indicate that B. pumilus CCIBP-C5 has a potential role for biological control of P. fijiensis possibly due to the production of antifungal metabolites.

Transcriptome sequencing of Mycosphaerella fijiensis during association with Musa acuminata reveals candidate pathogenicity genes

BACKGROUND

Mycosphaerella fijiensis, causative agent of the black Sigatoka disease of banana, is considered the most economically damaging banana disease. Despite its importance, the genetics of pathogenicity are poorly understood. Previous studies have characterized polyketide pathways with possible roles in pathogenicity. To identify additional candidate pathogenicity genes, we compared the transcriptome of this fungus during the necrotrophic phase of infection with that during saprophytic growth in medium.

RESULTS

Transcriptome analysis was conducted, and the functions of differentially expressed genes were predicted by identifying conserved domains, Gene Ontology (GO) annotation and GO enrichment analysis, Carbohydrate-Active EnZymes (CAZy) annotation, and identification of genes encoding effector-like proteins. The analysis showed that genes commonly involved in secondary metabolism have higher expression in infected leaf tissue, including genes encoding cytochrome P450s, short-chain dehydrogenases, and oxidoreductases in the 2-oxoglutarate and Fe(II)-dependent oxygenase superfamily. Other pathogenicity-related genes with higher expression in infected leaf tissue include genes encoding salicylate hydroxylase-like proteins, hydrophobic surface binding proteins, CFEM domain-containing proteins, and genes encoding secreted cysteine-rich proteins characteristic of effectors. More genes encoding amino acid transporters, oligopeptide transporters, peptidases, proteases, proteinases, sugar transporters, and proteins containing Domain of Unknown Function (DUF) 3328 had higher expression in infected leaf tissue, while more genes encoding inhibitors of peptidases and proteinases had higher expression in medium. Sixteen gene clusters with higher expression in leaf tissue were identified including clusters for the synthesis of a non-ribosomal peptide. A cluster encoding a novel fusicoccane was also identified. Two putative dispensable scaffolds were identified with a large proportion of genes with higher expression in infected leaf tissue, suggesting that they may play a role in pathogenicity. For two other scaffolds, no transcripts were detected in either condition, and PCR assays support the hypothesis that at least one of these scaffolds corresponds to a dispensable chromosome that is not required for survival or pathogenicity.

CONCLUSIONS

Our study revealed major changes in the transcriptome of Mycosphaerella fijiensis, when associating with its host compared to during saprophytic growth in medium. This analysis identified putative pathogenicity genes and also provides support for the existence of dispensable chromosomes in this fungus.

Comparative analysis of the in vitro and in planta secretomes from Mycosphaerella fijiensis isolates

Black Sigatoka, a devastating disease of bananas and plantains worldwide, is caused by the fungus Mycosphaerella fijiensis. Several banana cultivars such as 'Yangambi Km 5' and Calcutta IV, have been known to be resistant to the fungus, but the resistance has been broken in 'Yangambi Km 5' in Costa Rica. Since the resistance of this variety still persists in Mexico, the aim of this study was to compare the in vitro and in planta secretomes from two avirulent and virulent M. fijiensis isolates using proteomics and bioinformatics approaches. We aimed to identify differentially expressed proteins in fungal isolates that differ in pathogenicity and that might be responsible for breaking the resistance in 'Yangambi Km 5'. We were able to identify 90 protein spots in the secretomes of fungal isolates encoding 42 unique proteins and 35 differential spots between them. Proteins involved in carbohydrate transport and metabolism were more prevalent. Several proteases, pathogenicity-related, ROS detoxification and unknown proteins were also highly or specifically expressed by the virulent isolate in vitro or during in planta infection. An unknown protein representing a virulence factor candidate was also identified. These results demonstrated that the secretome reflects major differences between both M. fijiensis isolates.

Selection ofMycosphaerella fijiensis-resistant cell lines from micro-cross sections of banana and plantain

Anin vitro selection system using microcross sections of banana and plantain cultivars belonging to AAA and AAB genomic groups were used to produce plants resistant against the Black Sigatoka disease. The fungus resistant plantlets were obtained in a double selection system. This involved in a first step the use of a fungal crude filtrate and in the second step the purified host-specific toxin 2,4,8-trihydroxytetralone extracted from the fungusMycosphaerella fijiensis (M. fijiensis), the causal agent of Black Sigatoka disease. Resistant plantlets obtained from the double selection system were inoculated with conidia ofM. fijiensis in a growth chamber to reproduce Black Sigatoka symptoms. Compared to non-treated control plantlets, which were highly susceptible to the fungus, 10.7-19.3% toxin-resistant plantlets which arose from tissues that went through the double selection system were resistant againstM. fijiensis. This technique of using micro-cross sections for selection on fungal toxins seems to be amenable to differentMusa genotypes for the production of fungus-resistant plants.