Resistance to Fusarium langsethiae in Norwegian oats- SafeOats

Over the recent decades, the Norwegian cereal industry has had major practical and financial challenges associated with the occurrence of Fusarium and mycotoxins in cereal grains. From 2011, payment reductions to farmers were implemented for oat grain lots with high levels of deoxynivalenol (DON). However, HT-2 and T-2-toxins (HT2+T2), produced by Fusarium langsethiae, are considerably more toxic than DON. The SafeOats project has given new insight into the biology of F. langsethiae and HT2+T2 accumulation in oats. Knowledge developed in this project will facilitate the choice of relevant control measures to reduce the mycotoxin contamination of oats. SafeOats has also developed resistance screening methods to facilitate the phase-out of F. langsethiae susceptible germplasm. The results from SafeOats will benefit consumers nationally and internationally by providing tools to increase the share of high quality grain into the food and feed industry. The following ranking of oat varieties, according to mycotoxin content, has so far been observed in non-inoculated field trials: Vinger has been identified as a variety with low or moderate mycotoxin content (both DON and HT2+T2), whereas relatively high DON contents have been detected for Belinda. Odal have low (or moderate) content of DON, however the HT2+T2 content have been relatively high. A mathematical model for the estimation of the phenological growth stage of oats has been developed based on agronomic and weather data. The model can be used to estimate the appropriate timing of fungicide treatments that can reduce the risk of Fusarium and mycotoxin contamination in oats. Greenhouse studies showed that oat grains harvested from plants inoculated with F. langsethiae at heading, flowering or dough stage had higher levels of F. langsethiae DNA and HT2+T2 compared to grains harvested from plants inoculated at booting or early milk. This indicates that inoculations in the period around flowering results in acceptable levels of F. langsethiae and HT2+T2. The resistant variety Vinger had a stronger upregulation of two genes involved in signal transduction and disease resistance after inoculation with F. langsethiae and F. graminearum, compared to the more susceptible cultivar Belinda. These results may be of relevance in the further breeding for increased resistance to Fusarium spp. in oats. Field trials with six oat varieties, spray-inoculated with F. langsethiae at three growth stages (heading, anthesis, early milk stage), have been conducted over four years (2016-2019). The results resemble those from natural infection with Odal, Bessin and Belinda showing higher susceptibility than the more resistant varieties Hurum, Vinger and Haga. The results point to spray inoculation at anthesis as the most promising stage for reliable field testing with F. langsethiae. Field trials with 26-36 varieties and breeding lines have been conducted over three years (2017- 2019). Results from a total of five inoculated experiments show good correspondence with naturally infected fields with Odal as the most susceptible variety for F. langsethiae. Comparison of the variety rankings after inoculation with F. graminearum and F. langsethiae show a reasonable correspondence for most varieties, but with a clear exception for Odal, which is highly susceptible to F. langsethiae but relatively resistant to F. graminearum. Removal of small grains can reduce the content of mycotoxins in grain lots. In our experiments, the levels of HT2+T2 and EnnB were reduced by approx. 50 % after removal of small kernels (15-20% reduction in grain weight), thus contributing to improved grain quality. The incidence of F. langsethiae in 196 seed lots of selected oat varieties harvested in 2016, 2017 and 2018 was screened on growth medium (agar). The highest average infection levels were recorded in the varieties Belinda and Odal, whereas the lowest infection level was found in the variety Vinger. Quantification of F. langsethiae DNA by qPCR showed a similar ranking of varieties, which coincides with variety ranking in field trials. Results from germination analysis of naturally infected seed samples does not indicate any germination damage from F. langsethiae. However, in pathogenicity tests we observed that F. langsethiae can cause poor root development. Transmission of F. langsethiae from germinating seeds to seedlings have not been detected. Our studies indicate that ranking of oat varieties according to content of F. langsethiae and HT2+T2 not always corresponds with the ranking for F. graminearum and DON. Separate tests are therefore necessary to determine the risk for HT2+T2 toxins in oats.

SafeOats har utviklet metoder for å kartlegge resistens mot Fusarium langsethiae og HT2+T2 toksiner i havre. Dette er metoder som kan benyttes i planteforedlingen og som gjør det mulig å fase ut genotyper med høy risiko for mykotoksiner. SafeOats har kartlagt og formidlet informasjon om resistens mot Fusarium/mykotoksiner i havresorter. Denne informasjon benyttes av Plantesortsnemda ved godkjenning av nye havresorter. SafeOats har vist at utsortering av smått korn kan redusere innholdet av mykotoksiner. Metoden gjør det mulig å redusere forekomst av mykotoksiner i ubearbeidet havre som skal brukes til mat og fôr. Resultater oppnådd i SafeOats kan bidra til at havresorter som foredles frem, oppformeres og dyrkes i framtida har en lavere risiko for å få angrep av Fusarium enn mange av de havresortene som dominerer markedet i dag. Effekten av dette vil være at nivåene av mykotoksiner i korn til mat og fôr reduseres, noe som vil gi en helsegevinst for både mennesker og dyr.

Over the recent decades, the Norwegian cereal industry has had major practical and financial challenges associated with the occurrence of Fusarium and mycotoxins in cereal grains. From 2011, payment reductions to farmers were implemented for oat grain lots with high levels of deoxynivalenol (DON). However, according to preliminary results by Norwegian Institute of Bioeconomy Research (NIBIO), the Norwegian University of Life Sciences (NMBU) and the Norwegian plant breeding company, Graminor, certain oat varieties with generally medium or low DON contamination, may contain high levels of HT-2 and T-2-toxins (HT2+T2). These mycotoxins, formed by Fusarium langsethiae, are considerably more toxic than DON. The concentrations of HT2+T2 in Norwegian cereals were extraordinarily high in 2014, a year with growth conditions favouring development of HT2+T2. This coincided with a doubling of the market share for 'Odal', a variety ranked as especially prone to HT2+T2 in preliminary studies, but among the most resistant for F. graminearum and DON. Resistance to F. langsethiae is not included in the variety screening. SafeOats will develop resistance screening methods in collaboration with the main Norwegian and Swedish breeding companies, thus facilitating the phase-out of susceptible germplasm. The project will approach breeding by revealing gene expression pathways for Fusarium resistance in oats. Furthermore, SafeOats will provide information whether there are varietal differences concerning the content of mycotoxins in different size fractions of oat grains, and whether seed borne inoculum might be a source of F. langsethiae infections. SafeOats will give new insight into the biology of F. langsethiae and HT2+T2 accumulation in oats, and thus facilitate the choice of relevant control measures. The results from SafeOats will benefit consumers nationally and internationally by providing tools to increase the share of high quality grain into the food and feed industry.