Development of a New Plant Growth Regulator, Inabenfide

Abstract

Inabenfide is a new plant growth regulator discovered and developed by Chugai Pharmaceutical Co. Ltd. The biggest change in rice culture in recent years in Japan has been the remarkable development in mechanization of rice-transplanting and rice harvesting. Thus, attention is being paid to development of seedling tough to withstanding mechanized transplantation and of culture techniques for preventing lodging of rice plants before harvesting. For these reasons, it has long been desired to establish good cultivation techniques or to develop plant growth regulation with the use of chemicals so that sufficiently tough seedlings and plants having good properties for mechanized harvesting can be realized. We have searched for several years to find compounds capable of regulating the growth of rice plants, and found that isonicotinanilide represented by the formula, 4′-chloro-2′-(α-hydroxybenzyl) isonicotinanilide (inabenfide, Seritard^®), has excellent growth regulating activity. The treatment of inabenfide in nursery boxes strongly controlled growth of rice seedling after treatments with 0.01 to 1g per box, and resulted in good seedlings. When inabenfide was treated on rice paddies at a rate of 2.4kg per ha on either the 62nd, 52nd, 42nd, 32nd, 22nd and 12th day before heading, the resultant growth showed shorter plants and less tendency to lodge. As a result, the yield also increased, as did the number of panicles, percentage of well ripening, and 1000-Kernel weight. On the other hand, a large number of official trials carried out in Japan since 1981 have demonstrated the effective qualities of inabenfide. It is now registered for agriculture use in Japan and under developing in some countries in Southeast Asia. The action sites of inabenfide is the inhibition of oxidation of ent-Kaurene, ent-Kaurenol and ent-Kaurenal in GA biosynthesis. Inabenfide has several favourable properties: It is low in acute mammalia toxicity and fish toxicity, causes no skin and eye irritation, has no impact on usefull insects and no phytotoxicity.