Photosynthetic Changes In Wheat Cultivars With Contrasting Levels Of Resistance To Blast

Wheat blast, caused byPyricularia oryzae, is currently the main disease that threat to food security and wheat production in the world. This study investigated the photosynthetic responses of wheat plants from cultivars BR-18 (moderately resistant) and BRS-Guamirim (susceptible), differing in their levels of resistance to blast, by using leaf gas exchange and rapid light curves analysis focusing primarily on the asymptomatic (AS) and symptomatic (S) phases of disease development. The photosynthetic capacity of plants from cultivar BRS-Guamirim was compromised by diffusional CO(2)limitations and inefficient photoprotection mechanism at the AS phase of blast due to reductions in CO(2)assimilation, stomatal conductance, transpiration rate and fluorescent quantum efficiency (F-v/F-m). For cultivar BR-18, the loss in photosynthesis was minimized due to an efficient control in the regulated energy dissipation [Y(NPQ)] avoiding losses by latent heat [Y(NO)]. Additionally,F-v/F(m)was a promissory physiological indicator of blast during its AS phase while Y(NPQ) and Y(NO) were more sensitive at the S phase of the disease. In conclusion, the physiological parametersF(v)/F-m, Y(NQP) and Y(NO) can be used as physiological markers in wheat breeding programs seeking in the development of cultivars resistant to blast.