Citrus is the second-largest fruit crop in China. It is cultivated in over 20 provinces with an area of approximately 2.5 million ha. There are an abundant and excellent variety of resources in China. Fruit decay is a common disease during postharvest transportation and storage. Generally, the decay rate is 20% to 30%, and sometimes it can reach up to 50%, which causes serious postharvest economic losses. Therefore, disease control is vital for the postharvest period of citrus fruit.
Considering the significant economic losses caused by postharvest diseases, the identification and prevention of citrus postharvest diseases is fundamental to the citrus industry. Decayed citrus fruit from four citrus varieties—Satsuma mandarin (Citrus unshiu), Ponkan (Citrus reticulata Blanco cv. Ponkan), Nanfeng mandarin (C. reticulata cv. nanfengmiju), and Sugar orange (C. reticulata Blanco) showing soft rot and sogginess on their surfaces and covered with white mycelia were collected from storage rooms in seven provinces. The pathogens were isolated and their pathogenicity was tested.
The fungal strains were identified as Lasiodiplodia pseudotheobromae based on their morphological and molecular characteristics. The strains could infect wounded citrus fruit and cause decay within two days post inoculation, but could not infect unwounded fruit. This is the first report of citrus fruit decay caused by L. pseudotheobromae in China.
"It is difficult to evaluate the harm of this fungus to citrus fruit during the growth and storage period." the scientists at Huazhong Agricultural University of Wuhan (China) explain. "Although the fungus can artificially infect citrus twigs and leaves and produce pycnidia, whether it can infect citrus in the field is still unknown. Due to its wide host range, the primary inocula of this disease might also come from other plants in the surrounding area. At the same time, since the fungus has also been found to be an endophyte in several tropical and subtropical trees, whether it could endogenously grow in citrus trees should also be investigated. Further research is needed to clarify the primary inocula and the inoculum source of the disease".
Source: Chen Jianghua, Zhu Zihang, Fu Yanping, Cheng Jiasen, Xie Jiatao, Lin Yang, 'Identification of Lasiodiplodia pseudotheobromae Causing Fruit Rot of Citrus in China', 2021, Plants, 10(2), 202.