Histological and Gene Expression Analyses in Banana Reveals the Pathogenic Differences between Races 1 and 4 of Banana Fusarium Wilt Pathogen

Abstract

Fusarium oxysporum f. sp. cubense, the causative agent of Panama disease, is classified into three races: Foc1, Foc2, and Foc4. However, the histological characteristics, the accumulation of fusaric acid (FA), and resistant gene expression in banana infected with different races remain unclear. In this study, we compared the infection processes, FA contents, and gene expression levels in a Cavendish banana cultivar (Musa AAA Brazilian) inoculated with Foc1 and Foc4. Results showed that Foc4 can rapidly extend from the roots to the leaves, whereas Foc1 expands slowly from the roots to the rhizomes but cannot expand further upward. In addition, the colonization of plants by Foc4 was significantly higher compared with Foc1, as was the content of FA in those infected plant tissues. We observed that a large amount of starch granules was produced in the rhizomes and the number of starch granules was significantly higher after infection with Foc1 than after infection with Foc4. We further found that starch has an important inhibitory effect on the phytotoxicity induced by FA, thus leading to more resistance to the pathogens in the plants with high amounts of starch accumulation than in those with a low amount of starch accumulation. Moreover, the expression levels of 10 defense-related genes were analyzed and the results showed that the induction levels of those genes were higher after infection with Foc1 than after infection with Foc4. These results suggest that the observed differences in the invasion of host tissues and FA accumulation, and the number of starch granules and expression of defense-related genes, may contribute to a difference in virulence between the two races and the resulting difference in host resistance response, respectively.

Control of Panama disease of banana by intercropping with Chinese chive (Allium tuberosum Rottler): cultivar differences

“…The strain was maintained in Potato Dextrose Agar (PDA), and the inocula were cultured in PDA at 25°C in darkness. PDA medium was prepared and sterilized by autoclaving at 121°C for 20 min (Dong et al, 2019).…”

“…However, this crop production is severely hampered by Panama disease (also known as Fusarium wilt disease) caused by Fusarium oxysporum f. sp. cubense race 4 (FOC) (Segura et al, 2018), leading to extensive failure of commercial plantations in all bananaproducing areas, including Asia, Central and South America, Africa, and Australia (Ploetz et al, 2015;Xue et al, 2015;Dong et al, 2019). The soil-borne fungal pathogen colonizes and occludes the host xylem to cause vascular wilt (Butler, 2013;Ploetz et al, 2015;Dong et al, 2019).…”

Comparison transcriptome analysis revealed resistance differences of Cavendish bananas to Fusarium oxysporum f.sp. cubense race1 and race4

“…(VCG01221) and Foc4 XJZ2 (VCG01216) strains were used for the inoculation experiments, and the inoculation protocol referred to a previous method [4].…”

“…The Foc1 resistant cultivar 'Cavendish' (AAA) subgroup has dominated banana exports since the 1960s, thereby becoming the major commercial variety in the world [3]. The Cavendish banana variety 'Brazilian' can be infected by Foc1 and Foc4 during interaction with Foc, but it is resistant to Foc1 and susceptible to Foc4 [4][5][6][7]. Many researchers have focused on discovering the reason for the difference between the resistance to Foc1 and Foc4.…”

Comparison transcriptome analysis revealed resistance differences of Cavendish bananas to Fusarium oxysporum f.sp. cubense race1 and race4

“…The Foc1 resistant cultivar 'Cavendish' (AAA) subgroup has dominated banana exports since the 1960s, thereby becoming the major commercial variety in the world [3]. The Cavendish banana variety 'Brazilian' can be infected by Foc1 and Foc4, but it is resistant to Foc1 and susceptible to Foc4 [4][5][6][7]. Many researchers have focused on discovering the reason for the difference between the resistance to Foc1 and Foc4.…”