A novel index to estimate the stress-physiological status in wheat and barley against Fusarium head blight pathogens

Wheat and barley can be massively invaded with Fusarium head blight (FHB) which results in decrease in grain weight and quality. Accurate evaluation of the stress-physiological status including quantitative resistance (QR) and aggressiveness in breeding programs is a key to selecting resistant cultivars. Out of several analyzed components, one or two metric components composing a disease index are commonly employed as a typical methodology to score FHB; however, this resistance index can not describe correctly and accurately the whole resistance in host plants. We have therefore assessed a novel index to estimate the physiological and pathogenic status in a set of diverse bread and durum wheat and barley cultivars under artificial infection with four Fusarium species. Eighteen QR components obtained under in vitro , growth camber and field conditions were evaluated and nine components at the earliest and latest growth stages were selected and combined in one index to score QR. This novel index was further investigated for its stability in the same fungi-seedling and -adult plants treated with silicon that reduced these nine pathogenic components forming this index. The scores of our index were highly significant and correlated with data of reductions resulted in silicon treatments across the bread and durum wheat and barley cultivars, thus it is suitable to be used for quantification of resistance in host plants and aggressiveness of Fusarium isolates. Findings show that the novel index analyzed in the present report captured key components of quantitative wheat and barley resistance. This index can be applied for screening the most aggressive isolates of different FHB species for FHB resistance breeding of wheat and barley. The mean of nine disease components is introduced in this paper as a new index for QR in plants and aggressiveness of fungi. Moreover, the novel index could be a starting point for more correct techniques for assessing on of the most damaging biotic stresses on cereals, FHB.