Kiwifruit is a very important commercial crop in China, which is the largest producer of the fruit in the world. The rapid expansion of kiwifruit cultivated area has resulted in the spread of post-harvest rot diseases.
Rotten fruits can be divided into ripe rot and stem-end rot according to the infected symptoms. The typical symptoms of kiwifruit ripe rot were as follows: clear external symptoms of ripe rot were sometimes absent from the surface of the fruit, but a portion of the fruit surface collapsed. Water-soaked flesh tissue could be seen in the sunken area when the skin of the collapsed portion was peeled back. A milky-colored spot appeared in the flesh and developed concentrically as the fruit ripened.
Typical infected symptoms of kiwifruit stem-rot were as follows: the brown pubescent skin at the stem-end of the fruits became softer and lighter in color than the adjacent firm healthy tissues. When the skin was peeled, the affected flesh appeared water-soaked, disorganized, softer and lighter green than the healthy tissue. A scent of fermentation was often associated with rotted fruit.
Since 2014, Prof. ZHONG Caihong and Dr. LI Li from Wuhan Botanical Garden have been focusing on the research of kiwifruit postharvest rot. In order to clarify the pathogens which causing kiwifruit rot disease in China, several strains were isolated from rotten fruits (‘Jinyan’, ‘Hongyang’, ‘Jinkui’, ‘Guichang’ and ‘Qinmei’ cultivars), which was collected from Henan, Hubei, Chongqing, Jiangxi, Guizhou, Shanxi, Sichuan, Fujian, Anhui and Hunan Provinces during 2014-2015.
By using biological characteristics analysis, pathogenicity test and molecular sequencing, the research results showed that four species were responsible for kiwifruit rot disease in different regions of China. They were Phomopsis sp. (Diaporthe sp.), Botryosphaeria dothidea, Alternaria alternate and Pestalotiopsis sp. The species of pathogen detected in different regions were significantly distinct. Among them, Diaporthe actinidiae and Alternaria alternata was firstly reported as the pathogen causing kiwifruit postharvest rot in China.
These findings have important implications for resistance breeding and control of kiwifruit post-harvest rot in China. Considering the economic importance of kiwifruit in China and throughout the world, further study of kiwifruit rot is warranted.
Result were published in Plant Disease entitled “First Report of Diaporthe actinidiae Causing Stem-end Rot of Kiwifruit in Hunan and Hubei provinces, China” and “First Report of Alternaria alternata Causing Postharvest Rot of Kiwifruit in Shaanxi, Hubei and Sichuan provinces, China”.
It was supported by the Chinese Academy of Sciences Science and Technology Service Network Program and the Ministry of Agriculture's Crop Germplasm Resource Conservation and Utilization Project.
Rot symptoms on infected kiwifruit and Colony characteristics, conidia of A. alternata (Image by ZHONG’s group)
Stem rot symptoms on infected kiwifruit and Colony characteristics, conidia of D. actinidiae (Image by ZHONG’s group)
Molecular phylogenetic tree of A. alternata (Image by ZHONG’s group)