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Materials and methods

Two separate experiments were conducted. In the first experiment, seven cultivars, namely Hongwangmai, Ninchun No.10 and Mianyang No.11 from China, Sv 85131 from Sweden, Haruhikari from Japan, Chinese Spring and Cheyenne were used. In the second experiment, the Cheyenne disomic substitution lines in Chinese Spring and their parents, maintained by the Plant Genetics and Breeding Laboratory of Tottori University Japan, were employed. Planting was done in vinyl pots (diameter 8.3 cm x height 44.0 cm) filled with vermiculite. The pots were placed at 22C in a dark room. Twenty wheat seeds were sown in each pot at a depth of 15 cm. Water potential was adjusted to -0.18 MPa. Treatments were arranged in a complete randomized design with 5 replications. Final coleoptile length was measured after cessation of elongation, 12 days after sowing. Data were evaluated by analysis of variance and means were tested for significance by the Duncan Multiple Range Test.


Results and discussion

In the first experiment, varietal differences in the final coleoptile length were, invariably, significant and each cultivar had a characteristic final coleoptile length (Table 1). Hongwangmai, which has been successfully used in deep sowing cultivation in the Loess Plateau in China, had the longest coleoptile, while Cheyenne had the shortest. Relationship between the final coleoptile length and emergence under deep sowing showed a highly positive correlation (Matsui 1998). Furthermore, the final coleoptile length of Chinese Spring, grown under deep sowing condition, was about twice that under shallow sowing reported by Allan and Vogel (1964). Therefore, the results confirmed that the final coleoptile length is more suitable criterion of tolerance to deep sowing than coleoptile length reported by several workers (Burleigh et al. 1965; Feather et al. 1 968; Nayyar and Josum 1978; Sunderman 1964).

The difference in final coleoptile length between Chinese Spring (recipient) and Cheyenne (donor) was highly significant. In the second experiment, fifteen of the 21 substitution lines had significantly shorter, coleoptiles than Chinese Spring (Table 2). However, four substitutions of the chromosomes 1A, 4A, 5A and 5B, of the 15 lines resulted in remarkable reductions in the final coleoptile length (Table 2). On the other hand, substitution of the chromosome 4D showed the longest final coleoptile length. These results indicate that the final coleoptile length is controlled by many genes. And, the most influential genes are located on the 5 chromosomes. Repressor genes of final coleoptile elongation are located on the chromosome 4D of Chinese Spring, while stimulatory genes reside on the chromosomes 1A, 4A, 5A and 5B. Allan and Vogel (1964), based on F₂ monosomic analysis involving Chinese Spring monosomic series with Norin 10-Brevor and Olympia, concluded that genes promoting coleoptile elongation are located on the chromosomes, 1A, 2A, 3A, 5A, 6A, 2B and 2D, while inhibitory genes reside on the chromosomes 4A, 7A and 6D.

This study suggests that the final coleoptile length is interactively influenced by many genes. Furthermore, the results, in conformity with those of Allan and Vogel (1964), emphasize the importance of the A genome in controlling coleoptile length. However, contrary to their findings, the results in the present study indicate the importance of chromosomes 4A, 5B and 4D. This discrepancy may be attributed to differences in the donor cultivars used and /or to the method of assessment. Allan and Vogel (1964) used Norin 10-Brevor and Olympia, while the cultivar Cheyenne was used in this study. Finally, the study implies the possibility of development of cultivars with longer coleoptiles by manipulating the inhibitory genes on the 4D chromosome.

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