Comparison of 2,4-D and dicamba treatments for embryo development and plant regeneration in crosses between Lolium multiflorum Lam. and Dactylis glomerata L.

BY：Toshinori Komatsu, Kazuhiro Uchiyama, Akira Arakawa, Kazuhiro Tase We compared the effects of 2,4-dichlorophenoxy acetic acid (2,4-D) and 6-dichloro-2-methoxybenzoic acid (dicamba) treatments on embryo development and plant regeneration in crosses between Lolium multiflorum Lam. and Dactylis glomerata L. Two embryos (1.1% of pollinated florets) were obtained after 2,4-D treatment for 2 days. They germinated on hormone-free Murashige and Skoog (MS) medium containing 1 g L−1 yeast extract, 70 g L−1 sucrose and 6 g L−1 agar, and developed into green seedlings. dicamba treatment for 2 days gave higher frequencies of embryo development (4.3% of pollinated florets) than did 2,4-D treatment, but only one embryo (0.4% of pollinated florets) germinated on hormone-free MS agar medium, and no seedling was obtained. These results show that 2,4-D is more effective than dicamba at producing F1 hybrids on hormone-free MS agar medium. The F1 plant was intermediate between the parents in height, inflorescence morphology and lower leaf appearance. The folding of leaves in young shoots and the number of glumes resembled those of D. glomerata. Anthers did not dehisce. The F1 plant was an aneuploid with 26 chromosomes. The mean chromosome association was 0.04 trivalents, 10.36 bivalents and 5.16 univalents at metaphase I in pollen mother cells.

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