Variation of vascular bundle system corresponds to indica, tropical- and temperate-japonica differentiation of Asian Rice (Oryza sativa L.)

Variation of the vascular bundle system in 83 Asian rice cultivars and its usefulness in the distinction of the 3 types, indica, tropical-japonica and temperate-japonica were investigated. The 83 cultivars were classified int o 46 indica and 37 japonica cultivars by the discriminant function, D-1, ba sed on the data of phenol reaction, sensitivity to KClO3 and apiculus hair length. Next, the 37 japonica cultivars were subdivided into 8 tropical- an d 29 temperate-japonica using the score of D-2 which was computed from the ratio of length to width of the kernel, alkali digestibility and mesocotyl length. The number of vascular bundles(Vb) in the peduncle and the ratio of Vb to rachis branches(Rb)(V/R ratio) differed among the 3 types; the indic a and tropical-japonica cultivars had more Vbs and showed a higher V/R rati o than the temperate-japonica cultivars. Then, the new discriminant functio n(D-3) for identification of indica and japonica and D-4 for that of tropic al - and temperate-japonica were calculated based on Vb, Rb and V/R ratio. D-3 and D-4 improved the precision of distinguishing indica from japonica, and tropical- from temperate-japonica; the probability of misclassification decreased from 1.4% (D-1) to 0.7% (D-3), and from 4.8% (D-2) to 0.4% (D-4) , respectively. In conclusion, the variation of vascular bundle system was a highly useful character for identification of Asian rice cultivars.