A new double low cultivar of winter rapeseed, 'Kirariboshi' [Brassica napus]

Glucosinolates are secondary plant metabolites found mainly in Brassicaceae. As a defense reaction mechanism to various injuries, glucosinolates are converted into highly reactive isothiocyanates and other products by endogenous myrosinase enzymes. However, a few glucosinolate breakdown products such as a nitrile are associated with toxic effects. So, utilization of rapeseed (Brassica napus) meals for animal feed has been limited despite that the seed contains about 40% proteins with a well-balanced amino acid composition. Since the discovery of the Polish cv. 'Bronowski' containing considerably reduced glucosinolates, low glucosinolate cultivars known as canola type, containing less than 30micro mol/g seeds in the meal have been bred throughout the world. 'Kirariboshi' is the forty-eighth cultivar in the Nourin series of winter rapeseed cultivar and the first one with canola quality in Japan. It was developed at the National Agricultural Research Center for the Tohoku Region, NARO, and its cultivar registration was carried out by the Ministry of Agriculture, Forestry and Fisheries (MAFF) in 2004. 'Kirariboshi' was selected from the progenies of the cross of 'Morikeil88/Karat.' with the aim of developing a new rapeseed cultivar with the following properties: Low glucosinolates and zero erucic acid content, high yield, resistance to sclerotinial disease, and adaptability to the Tohoku region of Japan. The major agronomic characteristics of 'Kirariboshi' are as follows. Its glucosinolate content is of the same level as canola cultivars. Like 'Asakano-natane', maturity is medium. Its yield ability is higher than that of 'Asakano-natane' and its resistance to sclerotinial disease and tolerance to cold and snow damage are stronger than those of 'Asakano-natane'. 'Kirariboshi' is well adapted to the south Tohoku region of Japan.