title: Method for selection of soybeans tolerant to seed cracking under chilling temperatures.
abstract: In Hokkaido, northern Japan, soybean [Glycine max (L.) Merr.] crops are damaged by cold weather. Chilling temperatures result in the appearance of cracking seeds (CS) in soybean crops, especially those grown in eastern and northern Hokkaido. Seed coats of CS are severely split on the dorsal side, and the cotyledons are exposed and frequently separated. CS occurrence causes unstable production because these seeds have no commodity value. However, little is known about the CS phenomenon. The aims of this study were to identify the cold-sensitive stage associated with CS occurrence and to develop a method to select CS-tolerant lines. First, we examined the relationship between chilling temperatures after flowering and CS occurrence in field tests. The average temperature 14 to 21 days after flowering was negatively correlated with the rate of CS. Second, we evaluated differences in CS tolerance among soybean cultivars and breeding lines in field tests. 'Toyohomare' and 'Toiku-238' were more CS-tolerant than 'Yukihomare' and 'Toyomusume'. Third, we developed a selection method in which plants were subjected to 21-day chilling-temperature treatment from 10 days after flowering in a phytotron. This enabled comparisons of CS tolerance among cultivars. This selection method will be useful for breeding CS-tolerant soybeans.
authors.affiliation: Hokkaido Research Organization Tokachi Agricultural Experiment Station , 2, Minami 9 sen, Shinsei, Memuro, Kasai, Hokkaido 082-0081 , Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Yamaguchi
authors.affiliation: Hokkaido Research Organization Tokachi Agricultural Experiment Station , 2, Minami 9 sen, Shinsei, Memuro, Kasai, Hokkaido 082-0081 , Japan ; Present address: Hokkaido Research Organization Agricultural Department , Higashi 6 sen Kita 15 Gou, Naganuma, Yubari, Hokkaido 069-1395, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamazaki
authors.affiliation: Hokkaido Research Organization Tokachi Agricultural Experiment Station , 2, Minami 9 sen, Shinsei, Memuro, Kasai, Hokkaido 082-0081 , Japan ; Present address: Hokkaido Research Organization Kitami Agricultural Experiment Station , Yayoi 52, Kunneppu, Tokoro, Hokkaido 099-1496, Japan.
authors.forename: Shizen
authors.initials: S
authors.lastname: Ohnishi
authors.affiliation: Hokkaido Research Organization Tokachi Agricultural Experiment Station , 2, Minami 9 sen, Shinsei, Memuro, Kasai, Hokkaido 082-0081 , Japan ; Present address: Hokkaido Research Organization Central Agricultural Experiment Station , Higashi 6 sen Kita 15 Gou, Naganuma, Yubari, Hokkaido 069-1395, Japan.
authors.forename: Chika
authors.initials: C
authors.lastname: Suzuki
authors.affiliation: Hokkaido Research Organization Tokachi Agricultural Experiment Station , 2, Minami 9 sen, Shinsei, Memuro, Kasai, Hokkaido 082-0081 , Japan ; Present address: Hokkaido Research Organization Kitami Agricultural Experiment Station , Yayoi 52, Kunneppu, Tokoro, Hokkaido 099-1496, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Hagihara
authors.affiliation: Hokkaido Research Organization Tokachi Agricultural Experiment Station , 2, Minami 9 sen, Shinsei, Memuro, Kasai, Hokkaido 082-0081 , Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Miyoshi
authors.affiliation: Faculty of Agriculture and Life Science, Hirosaki University , 3 Bunkyo, Hirosaki, Aomori 036-8561 , Japan.
authors.forename: Mineo
authors.initials: M
authors.lastname: Senda
keywords: cold damage; cracking seed; selection method; soybean