Fusaric acid is a crucial factor in the disturbance of leaf water imbalance in Fusarium-infected banana plants.

Fusarium wilt of banana is caused by Fusarium oxysporum f. sp. cubense infection. The initial chlorosis symptoms occur progressively from lower to upper leaves, with wilt symptoms subsequently occurring in the whole plant. To determine the effect of the pathogen infection on the gas exchange characteristics and water content in banana leaves, hydroponic experiments with pathogen inoculation were conducted in a greenhouse. Compared with control plants, infected banana seedlings showed a higher leaf temperature as determined by thermal imaging. Reduced stomatal conductance (g(s)) and transpiration rate (E) in infected plants resulted in lower levels of water loss than in control plants. Water potential in heavily diseased plants (II) was significantly reduced and the E/g(s) ratio was higher than in noninfected plants, indicating the occurrence of uncontrolled water loss not regulated by stomata in diseased plants. As no pathogen colonies were detected from the infected plant leaves, the crude toxin was extracted from the pathogen culture and evaluated about the effect on banana plant to further investigate the probable reason of these physiological changes in Fusarium-infected banana leaf. The phytotoxin fusaric acid (FA) was found in the crude toxin, and both crude toxin and pure FA had similar effects as the pathogen infection on the physiological changes in banana leaf. Additionally, FA was present at all positions in diseased plants and its concentration was positively correlated with the incidence of disease symptoms. Taken together, these observations indicated that FA secreted by the pathogen is an important factor involved in the disturbance of leaf temperature, resulting in uncontrolled leaf water loss and electrolyte leakage due to damaging the cell membrane. In conclusion, FA plays a critical role in accelerating the development of Fusarium wilt in banana plants by acting as a phytotoxin.

Dong X ，Ling N ，Wang M ，Shen Q ，Guo S ... -  《-》

Fusaric acid accelerates the senescence of leaf in banana when infected by Fusarium.

Dong X ，Xiong Y ，Ling N ，Shen Q ，Guo S ... -  《-》

Water balance altered in cucumber plants infected with Fusarium oxysporum f. sp. cucumerinum.

Wang M ，Sun Y ，Sun G ，Liu X ，Zhai L ，Shen Q ，Guo S ... -  《Scientific Reports》

Contamination of bananas with beauvericin and fusaric acid produced by Fusarium oxysporum f. sp. cubense.

Li C ，Zuo C ，Deng G ，Kuang R ，Yang Q ，Hu C ，Sheng O ，Zhang S ，Ma L ，Wei Y ，Yang J ，Liu S ，Biswas MK ，Viljoen A ，Yi G ... -  《PLoS One》

Thermographic visualization of leaf response in cucumber plants infected with the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum.

Infection with the soil-borne pathogen Fusarium oxysporum f. sp. cucumerinum (FOC), which causes Fusarium wilt of cucumber plants, might result in changes in plant transpiration and water status within leaves. To monitor leaf response in cucumber infected with FOC, digital infrared thermography (DIT) was employed to detect changes in leaf temperature. During the early stages of FOC infection, stomata closure was induced by ABA in leaves, resulting in a decreased transpiration rate and increased leaf temperature. Subsequently, cell death occurred, accompanied by water loss, resulting in a little decrease in leaf temperature. A negative correlation between transpiration rate and leaf temperature was existed. But leaf temperature exhibited a special pattern with different disease severity on light-dark cycle. Lightly wilted leaves had a higher temperature in light and a lower temperature in dark than did in healthy leaves. We identified that the water loss from wilted leaves was regulated not by stomata but rather by cells damage caused by pathogen infection. Finally, water balance in infected plants became disordered and dead tissue was dehydrated, so leaf temperature increased again. These data suggest that membrane injury caused by FOC infection induces uncontrolled water loss from damaged cells and an imbalance in leaf water status, and ultimately accelerate plant wilting. Combining detection of the temperature response of leaves to light-dark conditions, DIT not only permits noninvasive detection and indirect visualization of the development of the soil-borne disease Fusarium wilt, but also demonstrates certain internal metabolic processes correlative with water status.

Wang M ，Ling N ，Dong X ，Zhu Y ，Shen Q ，Guo S ... -  《-》