2021 Volume 2021 Issue 7 Pages 39-46
'Porosuke' is an early maturing and easy pellicle peeling (EPP) new cultivar of Japanese chestnut (Castanea crenata Sieb. et Zucc.) released in 2016 by the Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization (NIFTS) in Japan. ‘Porosuke’ originated from a cross between ‘550-40’ [290-5 (Moriwase × Kairyoutoyotama) × Kunimi] and 'Tanzawa' in 2004 at Tsukuba, NIFTS. It was selected in 2008 and subjected to the 7th national trial on chestnut as Kuri Tsukuba 41 from 2009, conducted at 15 experimental stations in 14 prefectures in Japan. It was registered as No.26828 under the Plant Variety Protection and Seed Act of Japan on May 29, 2018. The tree vigor is medium and tree form is intermediate between upright and spreading. The full bloom date of female flowers averaged June 3, at the same time as that for ‘Tanzawa’ and ‘Porotan’ in the national trial. The nut of ‘Porosuke’ ripened around late August to early September, and the harvest date averaged Sep. 2, earlier than that of ‘Porotan’, at the same time as that of ‘Tanzawa’. The yield of 6-7 years old trees was as high as those in ‘Tanzawa’ and 'Porotan'. The incidences of nut polyembryony, pericarp splitting and decayed nut in ‘Porosuke’ were comparable to those traits in ‘Tanzawa’. Injured nut by insect pests occurred frequently as in ‘Tanzawa’ and ‘Porotan’. Nut weight of ’Porosuke’ averaged about 19g, smaller than ‘Tanzawa’ and ‘Porotan’ nuts in the national trial. The nut uniformity was good. The specific gravity of ‘Porosuke’ nuts was comparable to those of ‘Tanzawa’ and ‘Porotan’ nuts. The kernels of ‘Porosuke’ nuts were yellow in color, medium in sweetness and flavor, medium-mealy in texture, and of good eating quality, comparable to those of ‘Tanzawa’ and ‘Porotan’ nuts. The pellicle is easy to peel, comparable to that of ‘Porotan’ chestnuts. ’Porosuke’ and ‘Porotan’ is cross-compatible reciprocally, therefore only EPP nuts are expected to be harvested from orchards, in which these two cultivars are planted. ‘Porosuke’ is expected to be cultivated as EPP cultivar, which extent supplying period of EPP nuts of Japanese chestnut than that of ‘Porotan’.
