A new interspecific pear cultivar Yutaka: highly resistant to the two major diseases scab and black spot on Asian pears

Abstract

Scab, caused by Venturia nashicola, is the most important disease of Asian pears. In Japan, the most popular and widely grown pear cultivar (cv.) Kousui is resistant to black spot, caused by the Japanese pear pathotype of Alternaria alternata, but highly susceptible to scab. Recently, a new interspecific pear cv. Yutaka carrying high fruit quality was registered officially after a cross between the Chinese pear cv. Hongli and the Japanese pear cv. Housui. Accordingly, tests were conducted to assess resistance of cv. Yutaka to scab, black spot and anthracnose. When conidial suspensions of V. nashicola were spray inoculated onto potted trees, leaves of cv. Yutaka showed no disease symptoms although severe scab development was recorded on the susceptible reference cv. Kousui. Furthermore, neither black spot symptoms nor necrosis formation were observed when leaves of cv. Yutaka were inoculated with conidial suspensions of the A. alternata Japanese pear pathotype or treated with a culture filtrate containing the host-specific AK-toxin of this pathogen, respectively. These results strongly indicate that cv. Yutaka is highly resistant to scab and black spot. Inoculation tests also suggested the potential high levels of resistance of cv. Yutaka to anthracnose caused by Colletotrichum gloeosporioides sensu lato. The introduction of this new pear cultivar will reduce fungicide applications in pear orchards and thus lower the risk of fungicide resistance development in these pathogens.