Origin of cytoplasm substituted rice cultivars found in Japan

Abstract

Genetic variation of Japanese rice cultivars were examined. Five of 450 lowland cultivars and another five of 200 upland cultivars were determined as the indica type by using isozyme genotypes and the remainder were of the japonica type. The major characteristics of these indica cultivars, revealed a slender shape of grains, a short apiculus hair length, a positive allele for Ph reaction, and allele-3 for the Pgd1 locus. Three of these indica cultivars showed a non-deletion ORF100, which is essential to the japonica-type plastid. The plastid subtype identity (PS-ID) sequences of these plastids is 6C7A, which is also a japonica-specific repeat unit. Thus, these cultivars were concluded to be naturally generated cytoplasm substituted lines. These plastids were introduced into a indica genetic background from japonica cultivars grown elsewhere. The rest of the indica cultivars revealed a deletion-type ORF100 and plastid subtype 8C8A, both of which are indica-specific. These cultivars carried indica-type allelic constitutions for diagnostic isozyme loci. However, other characters were identical to the cytoplasm-substituted cultivars in Japan. In East and Southeast Asia, cultivars carrying a indica-type nuclear genotype with a japonica-type plastid are restricted to Aus cultivars in the Bengal region. Genetic and historical records suggest that Japanese indica cultivars and the Aus cultivars are closely related. The Aus cultivars acquire necessary genetic constitutions from both indica and japonica cultivars through naturally occurring out-crossing to adapt to a particular cultivation condition in the region. The wide adaptability enabled them to be introduced into a northern region like Japan.

Origin of Weedy Rice Grown in Bhutan and the Force of Genetic Diversity

“…A particular lowland cultivar in Japan was classified as japonica type by multi-locus analysis for isozymes, but carried indica cytoplasm. In another case, indica cultivars in Japan were found to carry japonica cytoplasm (Ishikawa et al 2002b). Based on the unique isozyme allele and the historical record, the origin of indica cultivars was concluded to be India.…”

“…Nuclear and cytoplasm genotypes enabled us to find a particular cultivar form carrying a different set of nuclear and cytoplasm types (Ishikawa et al 2002b). A particular lowland cultivar in Japan was classified as japonica type by multi-locus analysis for isozymes, but carried indica cytoplasm.…”

Genetic Erosion from Modern Varieties into Traditional Upland Rice Cultivars (Oryza sativa L.) in Northern Thailand

“…Our previous report described that spontaneous out-crossing events might take part in generation of new ecospecies (Ishikawa et al 2002b). Even in Japanese lowland rice strains, we can detect nuclear-cytoplasmic substituted strains.…”

Genetic polymorphisms in Japanese fragrant landraces and novel fragrant allele domesticated in northern Japan

“…Of these, 17 were non-Japanese fragrant landraces, 25 were Japanese non-fragrant cultivars including elite cultivars such as ‘Koshihikari’, and 40 were Japanese fragrant landraces included five non-scented ones. Overseas category included Meragome originated in Kagoshima which is an indica cultivars known as Daitoumai-group introduced into Japan in the middle age (Ishikawa 2002a, Ogawa and Itani 2008). Thus, this landrace was categorized as a non-Japanese landrace.…”

“…The eastern group distributed in Hokuriku, Kanto, and Tohoku, was characterized by early heading, short panicles, low yield, a fine culm and a propensity to lodge, relative to the western group distributed in Kinki, Shikoku, and Kyushu. Like red rice, they soon disappeared from the general market and the fields used for growing them were resown with modern cultivars over the last 100 years (Arashi 1975, Ishikawa et al 2002a, 2002b, Itani 2002a, Tabuchi et al 2007). Although landraces including fragrant landraces were displaced by modern cultivars they may retain a number of potentially valuable traits that have been lost in modern cultivars (Arashi 1975).…”