Productivity and Yield Quality of Intersubspecies Crossing of Japonica-Indica

Abstract
In the middle of 1980s, rice self-sufficiency in Indonesia has been achieved, but the growth of rice production slowed down since the 1990s. Narrow genetic variability of released rice varieties contributed largely to the occurrence of leveling of potential rice yield over the past decades. To enlarge the genetic variability, an intersubspecies crossing of Koshihikari (japonica) and IR36 (indica) has been performed. Through this crossing, three high yielding and high yield quality promising lines of KI 37, KI 238, and KI 730 have been obtained. The objective of this study was to evaluate the superiorities of these lines through multi-location yield trials, pests, diseases, and grain qualities examinations. Examination methods used followed the release food crops variety procedure issued by the Indonesian Ministry of Agriculture. The result of examinations showed that the average yield of KI 730 was 7.47 t/ha, it was significantly higher than that of Ciherang (6,73 t/ha). KI 730 has a good grain quality, with translucent milled rice, a high percentage of milled rice (78.0%) and head rice (91.01%). The texture of its cooking rice was soft, sticky, with the amylose content of 20.41%. In addition, pests and diseases resistances of KI 730 were better than those of other lines tested. After evaluation by National Food Crops Release Variety Team, the KI 730 line was released as a national superior variety with the name of Tropiko. Tropiko should become an alternative variety to grow widely in order to increase national rice production and farmers income.