Quiescent Infection of Flowers by the Causal Agents of Loquat Fruit Rot, Neopestalotiopsis sp. and Pestalotiopsis sp. 

Shunsuke Nozawa, Masayuki Komine, Yoshiki Takata, Keisuke Uchikawa, Yasuhiro Suga, and Kyoko Watanabe

Loquat fruit rot, caused by Pestalotiopsis sensu lato, is a key problem for loquat producers in Nagasaki Prefecture, the area with the highest loquat fruit production in Japan. In a previous study, it was postulated that fruit rot pathogens latently infect flowers, with the corresponding disease symptoms occurring in wounded fruits. To reveal whether the pathogens responsible for the development of fruit rot disease are found in the asymptomatic flowers and immature fruits of loquat trees, we sprayed a conidial suspension of nitrate-nonutilizing mutants, containing strains derived from pathogenic Neopestalotiopsis sp. (TAP18N004) and Pestalotiopsis sp. (TAP18N010), onto the flowers of “Mogi” and “Nagasaki-wase” trees. Both inoculated mutants were reisolated using selective media (minimal media with chlorate) from the part of the asymptomatic immature fruit that includes the flower apex. Symptoms were observed in the mature fruits of both cultivars, and mutants were specifically detected in the symptomatic tissues of all rotted fruits. Additionally, all reisolated mutants were reconfirmed by assessing corresponding nitrate auxotrophy characteristics. Thus, it was revealed that both fruit rot pathogens that latently infect loquat flowers can cause fruit rot after maturation.

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https://doi.org/10.1094/PHYTOFR-03-23-0037-SC