Investigations were undertaken to identify the effect of temperature on the expression of a gene involved in melanin biosynthesis (Brn1) in the dark spored fungus Alternaria brassicicola causal agent of black spot of mustard and its association with the biology, virulence, and release of extracellular enzymes such as cellulase and amylase. The expression of genes Brn1, AbCbh7, Glycosyl hydrolase, responsible for melanin biosynthesis, cellulase, and amylase production, respectively was assessed after exposing the pathogen to 15, 25, and 35 °C temperature. Results revealed a reduction in both melanin biosynthesis and expression of Brn1 at 35 °C when compared to those at 25 °C. The expression of Glycosyl hydrolase also decreased at 35 °C, whereas AbCbh7 expression remained unaffected. However, with decrease in gene expression; extracellular release of cellulase and amylase by A. brassicicola increased at 35 °C, compared to 25 °C. Additionally, reduced mycelial growth and sporulation at warmer conditions were correlated with an increase in occurrence of multiple germ tube per spore. Such changes might represent a mechanism to compensate for the reduced radial growth as well as sporulation at warmer temperatures. Artificial inoculations of leaves of the susceptible variety Brassica juncea cv. Varuna with A. brassicicola at 35 °C also resulted in larger chlorotic zones than inoculations at cooler temperatures, indicating an increase in virulence of the pathogen possibly due to the enhanced release of extracellular enzymes as a result of reduced melanin production in the cell walls.

进行了调查，以确定温度对芥菜黑斑病黑孢菌真菌黑斑病念珠菌病原体中涉及黑色素生物合成基因（Brn1）表达的影响及其与生物学，毒力和细胞外酶释放的关系。例如纤维素酶和淀粉酶。将病原体暴露于15、25和35°C的温度后，分别评估负责黑色素生物合成，纤维素酶和淀粉酶生成的基因Brn1，AbCbh7，糖基水解酶的表达。结果显示，与25°C相比，在35°C时黑色素的生物合成和Brn1的表达均降低。糖基水解酶的表达在35°C时也下降，而AbCbh7表达仍然不受影响。然而，随着基因表达的减少；与25°C相比，在35°C时，A。brasicicola对纤维素酶和淀粉酶的胞外释放增加。另外，在较温暖的条件下，菌丝生长和孢子形成减少与每个孢子多个胚芽管的发生增加有关。这种变化可能代表了一种机制，可以补偿径向生长减少以及在温度较高时形成孢子的现象。易感品种芥菜叶片的人工接种。伐楼拿与A.甘蓝 与在较低温度下接种相比，在35°C下的接种也导致更大的褪绿区，这表明病原体的毒力增加可能是由于细胞壁黑色素生成减少导致细胞外酶释放增强所致。