II. Record

Proceedings of the 17th Wheat Genetics Symposium of Japan

The 17th Wheat Genetics Symposium of Japan was held at Faculty of Agriculture, Kyoto University on Oct 9 and 10, 1982. The followings are the abstracts of the invited and contributed presentations. In addition to these contribution, slide demonstrations were presented by Dr. I. Nishiyama entitling 'Genetical utilization of the interspecific cross incompatibility', and by Drs S. Ohta and S. Sakamoto entitling' Botanical expedition to Greece'.

Genetical analyses of dwarfism in common wheat

T. SASAKUMA and N. IZUMI

Kihara Inst. Biol. Res., Yokohama, and Obihiro Univ. Hokkaido. Japan

Characterization, mode of gene action, and gene localization of a dwarf wheat variety, Aibian-I were investigated, which was obtained from Shei-Beii Agricultural Academy (San-Shi, China).

Aibian-I is a weak winter type wheat showing 32 cm height on average with normal size (7.2 cm on average) of spike on the reduced length of internodes. The number of node is not different from those of other varieties. The number of spikelets per spike is, also, comparable to other conventional varieties. It flowers without complete head emergence, but bears almost full set of seeds.

Numerical analysis was conducted in 40 common wheat lines, including Aibian-I and 29 semi-dwarf varieties which were obtained from Japan, England, Holland, West Germany, USA, and Canada, on 25 quontitative characters. A dendrogram was drawn which classified them into four groups. The first group consists of 10 lines including four Canadian winter wheat varieties and experimental lines of Chinese Spring, Tve, macha and spelta. The second one includes most of semi-dwarf conventional varieties. Dwarf Bezostaya (a dwarf strain originally from USSR) was included into this group together with conventional varieties like Nugaines (USA), Hobbit (England), and Horoshiri (Japan). The third one is characteristic to include breeding parental lines of semi-dwarfness like Daruma, and Norin-10. Sonora-64, Norin-61, and Feilder were combined with these lines. The forth consisted of only one line of Aibian-I, which was combined with other groups at most distance in the dendrogram. This result suggest that Aibian-I has different genetic components from others, and that there are some genetical differentiation of plant structure between the most of conventional varieties and their breeding parents.

F₂ segregation and monosomic analysis of Aibian-I showed that its dwarfness was controled a complete dominant single gene located on chromosome 4D. This fact also indicates that this dwarf gene is completely different from those of Norin-10, although one of them are located on 4D (GALE 1975). A dwarf wheat Tom Thumb is reported to have a incomplete dominant gene on chromosome 4A (MORRIS et al. 1975). Since nine induced dwarf or semi-dwarf genes were so-far identified including induced mutations (reviewed by KONZAK 1975, 1980), the dwarf gene of Aibian-I could be designated as Rht₁₀ located on chromosome 4D (probablly 4D^s by a preliminary examination of telocentric mapping).

Sensitivity test of gibberellic acid was applied to seedlings of Aibian-I, which indicated that it was insensitive to GA₃, and that the sesitivity segregated in the same fashon as dwarfness in F₂ generation.

Since Aibian-I has potential characters for wheat breeding like complete fertility, strong straw and stable dwarfness, the isogenic line and chromosome substitution line in Chinese Spring background are now being established as well as the introduction of the dwarf gene into the conventional varieties. Plants of these backcrosses at B₃ generation had 40-50 cm height with completely emmerged head on strong straw having complete fertility.

Fig.1 Distribution frequency in F₂ population Ai-bian I x Chinease Spring