Functional Analysis of MYB73 of Arabidopsis thaliana Against Bipolaris oryzae

Bipolaris oryzae is a severe rice disease,resulting in significant economic losses.MYB73 gene of Arabidopsis was isolated based on T-DNA insertion mutants whose lose-of-function mutant increased susceptibility to B.oryzae.Results of staining for H2O2 revealed that infection of incompatible B.oryzae caused much more strong brown patches on the leaves of myb73 mutant than those on the leaves of wild type.Expression of MYB73 gene was induced by B.oryzae.Its increased expression was severely impaired in the myb73 mutant.Expression of MYB73 was severely decreased in the npr1,jar1,eds5,and sid2 mutants,suggesting MYB73 gene participates in the jasmonate （JA） and salicylic acid （SA） signaling pathways.Expression of MYB73 who encoded an R2R3 MYB transcription factor was increased by SA,JA,and ethylene （ET） treatments.The cDNA full-length sequence of MYB73 was 960 bp and a protein with 320 amino acids was encoded.The predicted molecular weight of MYB73 was 34.85 kDa.The expression of MYB73 gene was induced within 24 h of the inoculation,however,the expression of PR1,PDF1.2 and NPR1 weren＇t changed.When B.oryzae successfully infected myb73 mutant plants,the expression of PR1,PDF1.2 and NPR1 were increased.Collectively,our results suggested that MYB73 is involved in NPR1-mediated SA and JA signaling pathways.

Characterizing and Estimating Fungal Disease Severity of Rice Brown Spot with Hyperspectral Reflectance Data

Large-scale farming of agriculture crops requires real-time detection of disease for field pest management. Hyperspectral remote sensing data generally have high spectral resolution, which could be very useful for detecting disease stress in green vegetation at the leaf and canopy levels. In this study, hyperspectral reflectances of rice in the laboratory and field were measured to characterize the spectral regions and wavebands, which were the most sensitive to rice brown spot infected by Bipolaris oryzae （Helminthosporium oryzae Breda. de Hann）. Leaf reflectance increased at the ranges of 450 to 500 nm and 630 to 680 nm with the increasing percentage of infected leaf surface, and decreased at the ranges of 520 to 580 nm, 760 to 790 nm, 1550 to 1750 nm, and 2080 to 2350 nm with the increasing percentage of infected leaf surface respectively. The sensitivity analysis and derivative technique were used to select the sensitive wavebands for the detection of rice brown spot infected by B. oryzae. Ratios of rice leaf reflectance were evaluated as indicators of brown spot. R669/R746 （the reflectance at 669 nm divided by the reflectance at 746 nm, the following ratios may be deduced by analogy）, R702/R718, R692/R530, R692/R732, R535/R746, R521/R718, and R569/R718 increased significantly as the incidence of rice brown spot increased regardless of whether it＇s at the leaf or canopy level. R702/R718, R692/R530, R692/R732 were the best three ratios for estimating the disease severity of rice brown spot at the leaf and canopy levels. This result not only confirms the capability of hyperspectral remote sensing data in characterizing crop disease for precision pest management in the real world, but also testifies that the ratios of crop reflectance is a useful method to estimate crop disease severity.