Common resistance to Fusarium head blight in Brazilian wheat cultivars

Abstract

Mycotoxin levels in Fusarium head blight (FHB) infections can be difficult to quantify.The relationship between mycotoxin and disease is not consistent and it is not clear if wheatpathogen interaction is of significance in regions where more than one Fusarium species with distinct trichothecene production ability co-exists. This study aimed to investigate whether a set of eight Brazilian wheat genotypes, varying in resistance according to classification by the breeder, exhibit a common or differential resistance to Fusarium graminearum (Fgra) (deoxynivalenolproducing) and Fusarium meridionale (nivalenol-producing) (Fmer) using full-spike and central spikelet inoculation (type II resistance). Fgra was generally more aggressive than Fmer based on the percentage of diseased spikes (99 and 84 %, respectively) and number of diseased spikelets (mean 2.8 and 2.0, respectively) below the central spikelet. The genotype-pathogen species interaction was not significant, but there were differences between the genotypes, with BRS 194 and BRS 327 being the least and most resistant, respectively, based on severity ratings. The incidence of Fusarium-damaged kernel (FDK, %) was not affected by species, but two genotypes , respectively, suggesting that Fgra is a more potent producer of trichothecene. Our data confirm prior resistance classifications by the breeders and suggest that the use of a single highly aggressive Fgra isolate may be sufficient for effective screening for FHB resistance. However, further studies are needed to elucidate the accumulation of resistance to trichothecene.

Fitness traits of deoxynivalenol and nivalenol-producing Fusarium graminearum species complex strains from wheat

“…We found that the species with the DON chemotype were generally more aggressive (higher area under severity curve) than the NIV ones, which is in agreement with our previous studies (Mendes et al 2018; Spolti et al 2012a). We could not compare statistically the effect of cultivar because the experiments were conducted at different times, and with different total time duration of the evaluations.…”

“…We could not compare statistically the effect of cultivar because the experiments were conducted at different times, and with different total time duration of the evaluations. Nevertheless, the area under the curve was in general higher for BRS 194, the susceptible one, compared with BRS Guamirim as shown earlier (Mendes et al 2018; Spolti et al 2012a). For the first time, we compared the two acetylates of DON within the Brazilian strains; while 15-ADON ( F. graminearum ) was the most aggressive in a susceptible cultivar, the 3-ADON ( F. austroamericanum ) was the most aggressive in the moderately resistant cultivar.…”

“…Deoxynivalenol (DON) is the most significant mycotoxin given its widespread occurrence at levels of concern to human and animal health (Tanaka et al 1988). However, nivalenol (NIV), another type-B trichothecene, has been found in commercial wheat samples from Brazil (Del Ponte et al 2015) and also in inoculations of wheat under controlled conditions (Mendes et al 2018; Nicolli et al 2015). A molecular survey conducted during the last decade showed that Fusarium graminearum (O’Donnell et al 2004), formerly lineage 7 (O’Donnell et al 2000), is the main (>85% frequency) F. graminearum species complex (FGSC) member causing FHB of wheat in Brazil (Del Ponte et al 2015).…”

“…Other FGSC members that occur at smaller frequency in wheat include F. cortaderiae and F. austroamericanum that possesses either 3ADON or NIV trichothecene genotype (Del Ponte et al 2015). Nivalenol, as well as 3-ADON strains within FGSC members are actually much less common in wheat grown in the Americas, especially in Brazil (Del Ponte et al 2015), but there are concerns about their ability to produce different or greater amount of trichothecenes (Mendes et al 2018; Umpiérrez-Failache et al 2013) and potential shifts in climate that may favor build up of inoculum of the currently minor species (Juroszek et al 2013; Vaughan et al 2016). In the state of Louisiana, U.S., NIV-type populations of F. graminearum , which were found at high frequency (79%) among isolates from small-grain-growing regions, accumulated four times less trichothecene toxin than DON types on inoculated wheat (Gale et al 2011).…”

The Influence of the Dilution Rate on the Aggressiveness of Inocula and the Expression of Resistance against Fusarium Head Blight in Wheat

“…It is possible that the stock suspension may either need dilution to reach the wanted conidium concentration (such as 5 × 10 5 conidia/mL) or must be concentrated when its density is too low. No details were given in the literature [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ], with the expression “adjusted” used in most cases. It appears that the researchers did not think that this practice could influence experimental results.…”