Influence of bacterial leaf blight on the photosynthetic characteristics of resistant and susceptible rice

The effect of crop disease on photosynthetic characteristics is important for disease control. Two varieties, Shenzhou 98 and Neiwuyou 8015 with resistance and susceptibility to bacterial leaf blight (BLB), respectively, were selected, and the responses of the net photosynthetic rate (P-N) to active photon flux density (PPFD) and intercellular carbon dioxide concentration (C-i), as well as chlorophyll fluorescence, pigments and stomatal resistance (SR), were measured. The results showed that BLB infection greatly decreased the maximum photosynthetic rate (P-max), light saturation point (LSP), carboxylation efficiency (CE), maximal fluorescence (F-m) and actual photochemical efficiency of PSII (phi(PSII)) but increased the light compensation point (LCP) and dark respiratory rate (R-D), which suggested that the performance of rice photosynthesis was decreased by BLB infection. The BLB infection had a lower effect on resistant rice Shenzhou 98 than on susceptible rice Neiwuyou 8015. The reduction of pigment and increased SR caused by BLB infection may have resulted in the decline in the photosynthetic rate. Significant effects of the BLB infection were observed on chlorophyll fluorescence F-m and phi(PSII) in resistant and susceptible rice. These parameters may be useful for noninvasive monitoring of plant disease considering the negative effect caused by other stresses.