接ぎ木による開花誘導のアブラナ科作物の育種および採種への利用

Grafting-induced flowering has the potential to be applied to plant breeding and seed production, to shorten the time needed for floral induction, and to expand the environment in which seed production is possible. However, it is difficult to induce flowering by grafting in some crop species, which currently limits the use of this technique to specific plant species. We have established a technique for inducing flowering in cabbage (Brassica oleracea L.) by grafting, which had hitherto been considered difficult, by clarifying the causes of different flowering responses caused by various rootstocks. This article introduces the key factors for the floral induction of cabbage by grafting and its potential application to the breeding and seed production of cruciferous crops. It was observed that cabbage grafted onto B. oleracea rootstocks did not flower at all, while cabbage grafted onto some accessions of Raphanus sativus rootstocks did flower. Furthermore, the ability of R. sativus to induce flowering of grafted cabbage varied even within the species. Immunoblotting analysis of the FLOWERING LOCUS T (FT) protein, a main component of florigen, revealed that floral induction was quantitatively correlated with the level of accumulated FT protein in the grafted scion. It was concluded that increasing the total amount of FT protein produced in the rootstock is important for the stable floral induction of the grafted cabbage, and this can be accomplished by increasing FT transcription and the leaf area of the rootstock. Field cultivation experiments with cabbage progenies obtained by the grafting method indicated the direct applicability of this method to breeding and seed production in cruciferous crops.

研究紹介 (Research Report)