Abstract
Orobanche minor seedlings were attached onto red clover (Trifolium pretense) roots grown in rhizotrons. Approximately 30% of the O. minor seedlings formed tubercles on red clover roots 2 weeks after attachment. Root primordia were appeared on the surface of the tubercles, and crown roots were developed 19 days after attachement. A shoot bud was differentiated from the crown roots 5 weeks after attachment. O. minor parasitism induced little morphological changes in red clover roots during the development process from tubercle formation (de-differentiation) to shoot bud formation (re-differentiation). These observations suggest that O. minor produces growth regulators in its own metabolism to control its differentiation. In addition, the crown roots and the shoot bud were differentiated without the seed embryo of O. minor, suggesting that the developmental process seems to be the process of adventitious root and shoot formation. To investigate the involvement of phytohormone homeostasis in the differentiation process, the endogenous levels of various plant hormones during the developmental process from seed germination to flowering were measured. Furthermore, gene expression involved in the developmental process of O. minor has been extensively studied with the next-generation sequencing platform.
