Efficient anther culture method of the japonica rice cultivar Koshihikari

The japonica rice cultivar Koshihikari has been used as the crossing parent for breeding of high-eating quality cultivars, An anther culture method has been developed to breed a new rice cultivar with in a short period, and several cultivars have been released in recent years. However, the efficiency of anther culture of Koshihikari was low. We developed a culture medium suitable for Koshihikari callus culture to increase the anther culture efficiency. The medium was a modification of the R2 medium, i.e., the concentrations of potassium nitrate (KNO3) and ammonium sulfate ((NH4)(2)SO4) in the R2 medium were diluted to 1/5, 5 mM aspartic acid and 5 mM glutamine were added, and the vitamins were replaced by those of B5 medium, We designated the medium as DKN (dilute KNO3) medium. The anthers of Koshihikari were cultured by using the three-step anther culture method in which DKN medium was used as the basal medium. The green plant regeneration rate per anther on DKN medium was 4.3 times (donor plants cultivated in green house) and 21.4 times (donor plants grown in field) higher than those on 1/2R2 medium which had been used for rice breeding by anther culture. It is concluded that the combination of the three-step anther culture method and DKN medium is efficient for anther culture of Koshihikari.