Why are There Indica Type and Japonica Type in Rice?——History of the Studies and a View for Origin of Two Types

On the bases of archaeological discoveries, the earliest domestication of rice has been confirmed in the middle and lower Changjiang River basin, while in the region wild rice populations are found in shallow swamps under a climate with freezing winter cold. These findings lead us to-examine the past ideas about domestication and differentiation of rice. Historically, in 1930s two sub-species, indica and japonica, were proposed on the basis of sterility in F1 hybrids between them. Soon after that, the two types were classified by the associations of a number of genetically independent traits. The characteristic associations of traits have been explained by the hybrid sterility or reproductive barriers which were assumed to comprise a set of duplicate recessive lethal genes and to be an inner genetic mechanism to lead to the varietal differentiations In 1980s, the hybrid sterility between Indica and Japonica types was analyzed, and Indica, Japonica, and wide-compatibility type which gives fertile hybrids when cross to Indica and Japonica types, are proved to contain an allele, S5＇, S5＇ and S5^n, respectively at a locus on chromosome 6. And those gametes having Sj allele are found to be partially aborted in the hybrid genotypes of S5＇/S5＇ while no gamete abortion occurs in S5＇/S5^n and S5＇/S5^n genotypes. Since then, the gene S5^n has been used in hybrid rice breeding to obtain fertile and vigorous hybrids between subspecies, and the long-disputed problem of hybrid sterility has been solved. Also in such studies the characteristic association of traits found in each of vadetal groups is better explained by founder effects. On the other hand, a large number of native cultivars of rice were surveyed with enzyme polymorphism in 1980s and later with molecular markers. As a result, profound genetic diversity is found in cultivated rice as well as in wild rice. These findings seem to lead us to the idea of multiple independent domestications of rice. However, before reaching such a conclusion, at least two factors, i.e., long-distance-dissemination of some genotypes and the possibilities of introgression by local wild rice to primitive cultivars need to be examined. Taking the two factors as well as the historical events into consideration, it is considered here that the perennial japonica cultivars which are close to wild rice in the Changjiang River basin were disseminated to East India through Assam or along the Bengal Bay, where they were transformed under the introgressions of local wild rice and formed a secondary center, from which some genotypes seem to be disseminated to colonies in Southeast Asia under the influence of Hinduism. Later some of the genotypes were introduced into China and constituted so called Indica type. This may be a reasonable picture for the varietal differentiation.

Progress on Transferring Elite Genes from Non-AA Genome Wild Rice into Oryza sativa through Interspecific Hybridization

The progress of research on transferring elite genes from non-AA genome wild rice into Oryza sativa through interspecific hybridization are in three respects, that is, breeding monosomic alien addition lines （MAALs）, constructing introgression lines （ILs） and analyzing the heredity of the characters and mapping the related genes. There are serious reproductive barriers, mainly incrossability and hybrid sterility, in the interspecific hybridization of O. sativa with non-AA genome wild rice. These are the ＇bottleneck＇ for transferring elite genes from wild rice to O. sativa. Combining traditional crossing method with biotechnique is a reliable way to overcome the reproductive barriers and to improve the utilizing efficiency of non-AA genome wild rice.

Song divergence indicates an unclear relationship between the Neotropical and Nearctic Horned Larks

Background:Some studies have indicated that the Horned Larks(Eremophila alpestris)should be considered as a species complex.Recently it split into four species or clades and seven subclades based on genetic,morphological,and biogeographic data.However,other aspects like song divergence have not been studied and several subspe-cies have not been evaluated,leading to important information gaps in this group of birds.In this work,we aimed to assess the differences in song traits and playback response between the Nearctic subclade and the Neotropical or Colombian subspecies E.a.peregrina.Methods:We compared six song traits between these groups and performed field playback experiments,to test the response of the Neotropical larks to both songs.We tested the difference in the variables for separate as well as by principal component analysis(PCA).Results:We found significant differences(p<0.05)in the individual song traits and the PCA analysis between the two groups.Further,the PCA analysis showed a clearer divergence of the Neotropical songs in comparison to the Nearctic songs of different locations within North America.Similarly,the playback analysis showed a significantly lower response of E.a.peregrina to the songs of the Nearctic larks.Conclusions:Besides this song divergence,there are important ecological and biogeographic differences between the Neotropical and Nearctic Horned Larks,that indicate an unclear relationship between these two groups.Thus,further morphological and genetic studies are required to clarify the taxonomy of the Neotropical Horned Lark and define if they share the same evolutionary history as the other subspecies of the Nearctic subclade.