Design and validation of a robust multiplex polymerase chain reaction assay for MAT idiomorph within the Fusarium fujikuroi species complex

The secondary metabolites from Beauveria bassiana PQ2 inhibit the growth and spore germination of Gibberella moniliformis LIA

Fungal secondary metabolites with antimicrobial properties are used for biological pest control. Their production is influenced by several factors as environment, host, and culture conditions. In the present work, the secondary metabolites from fermented extracts of Beauveria bassiana PQ2 were tested as antifungal agents against Gibberella moniliformis LIA. The L18 (21 × 37) orthogonal array from Taguchi methodology was used to assess 8 parameters (pH, agitation, sucrose, yeast extract, KH2PO4, MgSO4, NH4NO3, and CaCl2) in B. bassiana PQ2 submerged fermentation. The ability of the fermented extracts to slow down the growth rate of G. moniliformis LIA was evaluated. The results from 18 trials were analyzed by Statistica 7 software by evaluating the signal-to-noise ratio (S/N) to find the lower-the-better condition. Optimal culture conditions were pH, 5; agitation, 250 rpm; sucrose, 37.5 g/L-1; yeast extract, 10 g/L-1; KH2PO4, 0.8 g/L-1; MgSO4, 1.2 g/L-1; NH4NO3, 0.1 g/L-1; and CaCl2, 0.4 g/L-1, being the agitation at the highest level the most significant factor. The optimal conditions were validated in a sparged bottle bioreactor resulting in a higher S/N value (12.48) compared to the estimate. The extract obtained has the capacity to inhibit the germination of G. moniliformis spores at 24 h. HPLC-ESI-MS2 allowed to identify the water-soluble red pigment as oosporein (m/z 304.9). The secondary metabolites from B. bassiana PQ2 are a suitable alternative to control the growth and sporulation of G. moniliformis.

Weeds Harbor Fusarium Species that Cause Malformation Disease of Economically Important Trees in Western Mexico

Mango malformation disease (MMD) caused by Fusarium spp. is an important limiting factor in most production areas worldwide. Fusarium mexicanum and F. pseudocircinatum have been reported as causing MMD in Mexico. These two pathogens also cause a similar disease in Swietenia macrophylla (big-leaf mahogany malformation disease) in central western Mexico, and F. pseudocircinatum was recently reported as causing malformation disease in Tabebuia rosea (rosy trumpet) in the same region. These studies suggest that additional plant species, including weeds, might be hosts of these pathogens. The role that weed hosts might have in the disease cycle is unknown. The objectives of this work were to recover Fusarium isolates from understory vegetation in mango orchards with MMD, identify the Fusarium isolates through DNA sequence data, and determine whether F. mexicanum is capable of inducing disease in the weedy legume Senna uniflora (oneleaf senna). Additional objectives in this work were to compare Fusarium isolates recovered from weeds and mango trees in the same orchards by characterizing their phylogenetic relationships, assessing in vitro production of mycotoxins, and identifying their mating type idiomorph. A total of 59 Fusarium isolates from five species complexes were recovered from apical and lateral buds from four weed species. Two of the species within the F. fujikuroi species complex are known to cause MMD in Mexico. Trichothecene production was detected in five isolates, including F. sulawense and F. irregulare in the F. incarnatum-equiseti species complex and F. boothii in the F. sambucinum species complex. Both mating types were present among mango and weed isolates. This is the first report of herbaceous hosts harboring Fusarium species that cause mango malformation in Mexico. The information provided should prove valuable for further study of the epidemiological role of weeds in MMD and help manage the disease.

Malformation Disease in Tabebuia rosea (Rosy Trumpet) Caused by Fusarium pseudocircinatum in Mexico

Tabebuia rosea (rosy trumpet) is an economically important neotropical tree in Mexico that is highly valued for the quality of its wood, which is used for furniture, crafts, and packing, and for its use as an ornamental and shade tree in parks and gardens. During surveys conducted in the lower Balsas River Basin region in the states of Guerrero and Michoacán, symptoms of floral malformation were detected in T. rosea trees. The main objectives of this study were to describe this new disease, to determine its causal agent, and to identify it using DNA sequence data. A second set of objectives was to analyze the phylogenetic relationship of the causal agent to Fusarium spp. associated with Swietenia macrophylla trees with malformation surveyed in the same region and to compare mycotoxin production and the mating type idiomorphs of fusaria recovered from T. rosea and S. macrophylla. Tabebuia rosea showed malformed inflorescences with multiple tightly curled shoots and shortened internodes. A total of 31 Fusarium isolates recovered from symptomatic T. rosea (n = 20) and S. macrophylla (n = 11) trees were identified by molecular analysis as Fusarium pseudocircinatum. Pathogenicity tests showed that isolates of F. pseudocircinatum recovered from T. rosea induced malformation in inoculated T. rosea seedlings. Eighteen F. pseudocircinatum isolates were tested for their ability to produce mycotoxins and other secondary metabolites. Moniliformin, fusaric acid, bikaverin, beauvericin, aurofusarin. and 8-O-methylbostrycoidin were produced by at least one strain of the 18 isolates tested. A multiplex PCR assay for mating type idiomorph revealed that 22 F. pseudocircinatum isolates were MAT1-1 and that 9 were MAT1-2. Here, we report a new disease of T. rosea in Mexico caused by F. pseudocircinatum.

The Genome of Banana Leaf Blight Pathogen Fusarium sacchari str. FS66 Harbors Widespread Gene Transfer From Fusarium oxysporum

Fusarium species have been identified as pathogens causing many different plant diseases, and here we report an emerging banana leaf blight (BLB) caused by F. sacchari (Fs) discovered in Guangdong, China. From the symptomatic tissues collected in the field, a fungal isolate was obtained, which induced similar symptoms on healthy banana seedlings after inoculation. Koch's postulates were fulfilled after the re-isolation of the pathogen. Phylogenetic analysis on two gene segments and the whole genome sequence identified the pathogen belonging to Fs and named as Fs str. FS66. A 45.74 Mb genome of FS66 was acquired through de novo assembly using long-read sequencing data, and its contig N50 (1.97 Mb) is more than 10-fold larger than the previously available genome in the species. Based on transcriptome sequencing and ab initio gene annotation, a total of 14,486 protein-encoding genes and 418 non-coding RNAs were predicted. A total of 48 metabolite biosynthetic gene clusters including the fusaric acid biosynthesis gene cluster were predicted in silico in the FS66 genome. Comparison between FS66 and other 11 Fusarium genomes identified tens to hundreds of genes specifically gained and lost in FS66, including some previously correlated with Fusarium pathogenicity. The FS66 genome also harbors widespread gene transfer on the core chromosomes putatively from F. oxysporum species complex (FOSC), including 30 involved in Fusarium pathogenicity/virulence. This study not only reports the BLB caused by Fs, but also provides important information and clues for further understanding of the genome evolution among pathogenic Fusarium species.

Genetic diversity of Fusarium pseudocircinatum in the central western region of Mexico: the case of big-leaf mahogany malformation disease

Fusarium pseudocircinatum is the main causal agent of big-leaf mahogany malformation disease (BLMMD) of mahogany (Swietenia macrophylla) in Mexico. Although, BLMMD is the most important disease for this high-value timber species, there is a lack of information on the genetic variation present in geographically diverse isolates of F. pseudocircinatum. The objective of this study was to determine the genetic diversity of populations of F. pseudocircinatum causing BLMMD in the central western region of Mexico. A total of 611 big-leaf mahogany trees were inspected at eight sites in four states (Colima, Guerrero, Jalisco and Michoacán); of these, 42.7% showed malformation symptoms similar to those of BLMMD. Of 374 Fusarium isolates that were recovered, 277 were identified as F. pseudocircinatum, 56 were F. mexicanum, and 41 were Fusarium spp. An ISSR analysis of the F. pseudocircinatum isolates generated 51 bands of which 38 were polymorphic (76.8%) with a mean of 17 bands per primer. A total of 87 multilocus genotypes (MLGs) were identified. Nei's genetic diversity analysis showed that the isolates had a high genetic diversity average (0.147), with values ranging from 0.070 to 0.365 depending of the geographical location. An analysis of molecular variance revealed that the variation within the populations was low (27.36%), while the variation within MLGs was significant (72.64%), indicating genetic flow. Overall, the genetic variability of F. pseudocircinatum populations was high and the MLGs from Colima (Colima) and Gabriel Zamora (Michoacán) were placed centrally, which possibly is evidence of ancestry and indicates its dispersion routes in the central western region of Mexico.