Variation in Oryza perennis I
Oryza perennis における変異 I
In the genus Oryza some of the wild species so closely resemble cultivated rice O. sativa, that they are popularly called wild rice. The taxonomy of the Asian wild ricer has been found to be difficult and a provisional classification is to group the assemblage under two specific names, O. perennis Moench emend. Sampath and O. ruipogon Griffith (Sampath)1' . Since the first species is the probable ancestor of cultivated rice, natural variation in the Asian population is of interest. A collection
... of wild rices from different countries is being built up and the study relates to the variations found in the collections which were originally classified as O. perennis. Materials and Methods The samples secured from different sources were grown every year, and seeds of representative plants retained for the next generation. The plants were grown in a low-lying area during the main season from July to December, and duplicates were maintained in pots. There is a certain amount of cross pollination between the cultures, and with two exceptions discussed later, the off-type plants were weeded out. The collection comprised of three samples from Orissa (from local pond, from Ku fang in the Mahanadi delta and from Jeypore tract) and one each from Chanda District, Madhya-Pradesh, and from Assam. Outside India, one sample was secured from each of the following countries; Ceylon, Malaya, Thailand, Cambodia, Philippines, Taiwan and New Guinea. The original collection from Malaya proved to be heterozygous and only some plants were selected for use in this study. A typical O. perennis from Africa, classified under the subspecies " Barthii " was used as a standard for comparison with Asian forms. The two exceptions to the above procedure in selection were the following. One O. perennis-like plant was picked out from a wild rice collection from Mali Republic of Africa, and another such from a West African collection. These are designated as Nat. cross Mali and Nat. cross Af. 26. The morphological characters were recorded from typical healthy plants. Pollen studies included estimate of sterility as seen in iodine mounts and size uniformity as measured by ocular micrometer. The details of chromosome pairing at meiosis were recorded from propiono-carmine smears of the P. M. C. Observations The morphological characters recorded were the following. Vegetative; emergence of bud whether piercing leaf . sheath or not, habit in general, distribution of anthocyanin pigmentation in various parts, ligule size and flag leaf position. Characters recorded were, whether fully exserted panicle is open or compact, spikelet dimensions, anther length, and ripening colour of the hull.