%0 Journal Article
%T Chromosomal Location of HCA1 and HCA2, Hybrid Chlorosis Genes in Rice
%A Katsuyuki Ichitani
%A Yuma Takemoto
%A Kotaro Iiyama
%A Satoru Taura
%A Muneharu Sato
%J International Journal of Plant Genomics
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/649081
%X Many postzygotic reproductive barrier forms have been reported in plants: hybrid weakness, hybrid necrosis, and hybrid chlorosis. In this study, linkage analysis of the genes causing hybrid chlorosis in F2 generation in rice, HCA1 and HCA2, was performed. HCA1 and HCA2 are located respectively on the distal regions of the short arms of chromosomes 12 and 11. These regions are known to be highly conserved as a duplicated chromosomal segment. The molecular mechanism causing F2 chlorosis deduced from the location of the two genes was discussed. The possibility of the introgression of the chromosomal segments encompassing HCA1 and/or HCA2 was also discussed from the viewpoint of Indica-Japonica differentiation. 1. Introduction Many post-zygotic reproductive barrier forms have been reported in plants [1]: hybrid weakness, hybrid necrosis, and hybrid chlorosis. The latter has been observed often in the F1 generation from crosses among wheat (Triticum aestivum L.) and its relatives [2¨C6]. This phenomenon resulted from the complementary action of a pair of dominant genes. Research for distribution of these genes contributed greatly to the study of the origin of wheat. Hybrid chlorosis in F2 generation has been reported only in rice (Oryza sativa L.) [7] and interspecific crosses among Melilotus species [8]. Sato et al. [7] incidentally found a case of hybrid chlorosis in the F2 population from a cross between two Japanese native cultivars: J-147 and J-321. Its first symptom was discoloration of the second or third leaf (Figure 1). The yellowish part expanded gradually. Then the whole plant died within 20 days [9], yielding no seed. The phenomenon was caused by a set of mutually independent duplicated recessive genes, named hca-1 and hca-2 by Sato and Morishima [9]. According to the new gene nomenclature system for rice [10], we changed our description of the gene symbols, as shown in Table 1. Table 1: Gene symbols frequently used in this study according to the new gene nomenclature system for rice [ 10]. Figure 1: Hybrid chlorosis caused by hca1-1 and hca2-1. Seedlings in an F 4 line from the cross between J-147 and IR24 are shown 10 days after sowing date. A chlorotic plant is located at the center. The neighboring green plants are normal. Rice is classified into two types: Indica-type and Japonica-type. Sato and Morishima [9] examined the distribution of HCA1 and HCA2. The experimentally obtained results can be summarized as follows. (1) The hca2-1 gene is widely distributed in native Japonica-type cultivars, whereas many Indica-type cultivars carry its
%U http://www.hindawi.com/journals/ijpg/2012/649081/