Combined effect of salt stress and Xanthomonas axonopodis pv citri on citrus (Citrus aurantifolia).

Xanthomonas axonopodis pv citri (Xac) and salt stress are two crucial hindrances to citrus production. The effect of continuous salt application and Xac infection in citrus has been investigated. Citrus plants were exposed to salt stress by irrigating with 50 mM, 100 mM, 150 mM, and 200 mM NaCl solution on weekly basis and challenged by Xac. Salt stress affected the defense response of Citrus plants to Xac and therefore lesion diameter and disease severity were gradually increased at higher salt concentration. Meanwhile, accumulation of Na+ and Cl- in the leaves were also increased with the increase of salt concentration. Besides, physiological performance (PP) of plants was estimated based on the parameters such as net assimilation rate, chlorophyll content, stomatal conductance, transpiration rate and intercellular CO2 concentration. The PP of sole Xac treated plants was gradually increased and maintained up to end of the experiment, whereas plants treated with Xac+50 mM and Xac+100 mM NaCl showed the highest PP up to 30 days after inoculation and then decreased. However, the PP of Xac+150 mM and Xac+200 mM NaCl treated plants gradually decreased till the end of experiment. Similarly, the PP of 200 mM NaCl treated plants declined continuously. Interestingly, the PP in 50 mM and 100 mM NaCl treated plants was higher initially and then decreased at 30 DAI to 40 DAI. This study revealed that citrus canker disease development was enhanced by salt stress. In addition, the physiological performance of the plants was enhanced by Xac and Xac + moderate salt stress but then demolished under severe salt stress.

Two new species of Xanthagaricus and some notes on Heinemannomyces from Asia.

Xanthagaricus flavosquamosus and X. necopinatus, two new species of Agaricaceae, are described and illustrated from Asia. Macroscopically, both species are closely related to each other, but there are obvious micromorphological and molecular differences between them. Morphological and phylogenetic data showed that the two new species are distinct from other known species of the genus Xanthagaricus. Xanthagaricus flavosquamosus from China is characterized by its small, yellow basidiomata, short clavate cheilocystidia, epithelial pileipellis, and verrucose basidiospores measuring 5-5.5 × 3-3.5 µm. Xanthagaricus necopinatus from Bangladesh is characterized by having small, yellow basidiomata, a fugacious annulus, clavate to narrowly clavate cheilocystidia, epithelial pileipellis, and rugulose-rough basidiospores measuring 4-5 × 2.7-3.2 µm. In addition to the new species, a Heinemannomyces collection from China is reported. Morphological data and molecular phylogenetic analyses fully support the Chinese collection being Heinemannomyces splendidissimus, a species of Agaricaceae, originally described from Southeast Asia. Detailed descriptions, color photos and illustrations of the three species are presented. A key to the genus Xanthagaricus occurring in Bangladesh and China is provided.