In Vitro Quantitative Resistance Components in Wheat Plants to Fusarium Head Blight

Abstract

Background: In vitro tools have proved to be very useful in identifying quantitative resistance in wheat to Fusarium Head Blight (FHB) infection. However, there is a need to understand how the different in vitro and in planta tests correlate to describe the level of wheat resistance to FHB infection. Objective and Methods: We evaluated the correlation between in vitro symptom assessment using nine quantitative resistance criteria and in planta disease severity for Type II resistance assessment using a set of 16 FHB isolates across two widely grown Syrian wheat cultivars: Cham1 (durum) and Cham6 (bread). Results: Cultivar differences after inoculation with fungal isolates in seedlings and adult plants relative to the controls were detected. There were significant differences in the resistance of two wheat cultivars as measured by adult FHB resistance, Latent Period (LP) of detached leaf inoculation and standardized Area Under Disease Progress Curve (AUDPCstandard) of modified Petri-dish inoculation. Correlation coefficients between FHB severity and the two in vitro components LP and AUDPCstandard were significant (r=0.545 with p<0.05, and r=0.659 with p<0.01, respectively). No significant differences in the resistance of Cham6 and Cham1 were indicated for the other seven in vitro components: incubation period and lesion length of detached leaf inoculation, germination rate reduction and coleoptile length reduction of modified Petri-dish inoculation and lesion length of clip-dipping inoculation and percentage of infected seedlings of foliar-spraying and pin-point inoculations. Results from these seven components were not correlated with adult FHB resistance. Longer latent period and less AUDPCstandard were related to greater FHB disease-type II resistance. Conclusion: LP and AUDPCstandard are indicators of mechanisms of resistance occurring in the whole plant during FHB infection. Therefore, the idea of using in vitro components is based on their predictive ability of in planta adult FHB resistance.