| I. Research Notes F1 monosomic analysis of Triticum macha K. TSUNEWAKI and H. KIHARA National Institute of Genetics, Misima, Japan Gene analysis of Triticum macha is important, because it seems to be the most probable progenitor of hexaploid wheat (Kihara 1958). It is also known to have a normal allele of the third necrosis gene that has not yet been identified (Sachs 1954, Hermsen 1960). The authors studied this species by crossing it to 21 monosomic lines of Chinese Spring. F1 plants were grown in the green house under long day conditions and their chromosome numbers were determined in root-tip mitosis. Due to semi-lethality of the hybrids, only a few F2 seeds were produced, which did not allow to carry out the monosomic analysis to the F2 generation. The results obtained in the F1 generation are reported here. Number of disomic and monosomic F1 plants obtained and their phenotypes in respect to necrosis and some other characters are recorded in Table 1. Necrosis. In the F1 generation, all the disomics and 20 monosomics (except mono-XVI) were necrotic with the exception of a single mono-II plant that seemed to be not a typical plant originated from asynapsis in Chinese mono-II parent. On the other hand, F1 mono-XVI's were all normal. These findings indicate that chromosome XVI of Chinese Spring carries a necrosis gene, whose interaction with macha's genes causes necrosis and semilethality of the hybrids. As chromosome XVI belongs to D genome, the authors' finding confirms Sachs' conclusion that a necrosis gene should be present in the D-chromosome set of 6x wheats. Previously, Tsunewaki (1960) reported that Prelude and Kharkov carry Le1 gene on chromosome V and Le2 gene on chromosome XIII, respectively. Chinese Spring carries normal alleles of both genes. No homoeology exists between Le1, Le2 and the necrosis gene of the authors, because chromosomes V , XIII and XVI belong to the homoeologous groups 5, 2 and 3, respectively. |
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