"Transcriptomic analysis of the Musa acuminata and Fusarium oxysporum f. sp. cubense interaction."
banana, RNAseq, Fusarium wilt, biotic stress, genetic resistance, genomics.
Banana (Musa spp.) is one of the world's most important consumed fruits and a basic component of the diet of millions of people. It is considered as an important source of carbohydrates, vitamins and minerals. Commercial bananas originate from crossings of two wild species, namely Musa acuminata (A) and Musa balbisiana (B). Cultivars that have uniform characteristics are divided into subgroups, which are typically limited in genetic variability. As such, commercial cultivars tend to be susceptible to attack by numerous pests and diseases, which are responsible for the greatest losses in the crop in yield and fruit quality. Fusarium wilt is a classic vascular wilt disease caused by the fungal pathogen Fusarium oxysporum f. sp. cubense (FOC). Losses can reach 100% of production in affected areas, with persistence of fungal chlamydospores in contaminated soil making land inappropriate for continued banana production. FOC is subdivided into four races, based on pathogenicity to different banana cultivars. Race 1 is pathogenic to Gros Michel (AAA), Silk and Pome (AAB) cultivars, race 2 is pathogenic to Bluggoe (ABB) cultivars, and race 4 is pathogenic to all subgroups and Cavendish (AAA). Race 4 is subdivided into tropical race 4 (TR4) and subtropical race 4 (STR4), as STR4 is pathogenic to 'Cavendish' cultivars only in subtropical regions and with less aggressiveness than TR4. The most efficient control measure is through genetic resistance, with genomics being one of the important tools for introgression of genes from wild and pathogen-resistant cultivars into commercial cultivars. Thus, the aim of this study is to identify and validate target genes involved in the resistance response in Musa during the interaction with the pathogen FOC STR4, via RNAseq analysis of M. acuminata subsp. burmannicoides var. 'Calcutta 4'. For this, two contrasting cultivars were employed for investigation of the interaction with FOC isolate CNPMF 218A previously identified as STR4: 'Calcutta 4' (a resistant wild genotype) and 'Prata-Anã' (a susceptible commercial genotype). Inoculation was performed using rice inoculated with FOC at a concentration of 106 CFU/g. Total RNA was extracted from root samples collected at 1, 2 and 4 days after inoculation (DAI) with the pathogen. Histological analyses were performed to investigate plant defense responses such as callose deposition and production of phenolic compounds, as well as to accompany the infection process of the STR4 isolate in both genotypes. It is expected that through RNAseq performed via Illumina Novaseq 6000 PE100 sequencing and gene mapping against the reference genome of M. acuminata ssp. malaccensis var. 'DH-Pahang', it will be possible to identify differentially expressed genes potentially involved in defense responses in ‘Calcutta 4, relevant for future breeding programs for the species in generation of new resistant genotypes.