GENETIC-CHARACTERISTICS OF THE BREAKING S TRENGTH OF THE BASAL CULM RELATED TO LODGING RESISTANCE IN A CROSS BETWEEN KOSHIHIKARI AND CHUGOKU-117

In order to investigate the possibility of introducing lodging resista nce into long culm and ear weight type rice cultivars, we studied the genetic charactersitics of breaking strength related to lodging resist ance in a cross between Koshihikari and Chugoku 117 with small and lar ge section modulus, respectively, and their progenies. In the F-1 plan ts, the mean section modulus was much higher than that in Koshihikari, while the mean of the bending stress was higher than that in Chugoku 117 as well as that in Koshihikari. Consequently, the mean of the bend ing moment at breaking of the basal internode (M) in the F-1 populatio n was much higher than that in Koshihikari as well as Chugoku 117. The M in F-2 ranged widely from 800 to 2900 g cm, and eight plants of F-2 exceeded the maximum value of Chugoku 117. The section modulus in F-2 ranged widely from 8 to 25 mm(3) and showed a trimodal frequency dist ribution. The ratio of 30:92:28 did not fit the 1:2:1 expected for one -gene segregation. The section modulus showed a comparatively large he ritability value in the F-2 line, so this character was expected to be effective for selection. Dispite negative genotypic correlation betwe en section modulus and bending stress, three plants in the F-2 line ha d very high M values due to large section modulus and large bending st ress. The M and section modulus in the two F-3 lines were almost large , corresponding to the selected F-2 parental plants. From these result s, there is a possibility of introducing lodging resistance into long culm type cultivars by individual selection.