5. New characters for identification of Indica and Japonica rice T. fukuyama, H. sasahara and Y. fukuta

1) Faculty of Agriculture, Niigata University, Niigata, 950-21, Japan

2) Hokuriku National Agricultural Experiment Station, Joetsu, 943-01, Japan

 We have recently reported on the varietal variation in large vascular bundles (Vb) in the peduncle and that of primary rachis branches (Rb) in Asian rice cultivars. Cultivars from Japan had nearly equal numbers of Vb and Rb, while those from Nepal, Bangladesh and India had Vbs 1.4 to 2.2 times of the number of Rbs (Fukuyama and Takayama 1995). Huang (1988) also reported marked differences in the numbers of Vb between 10 Indica and 9 Japonica cultivars with the same number of Rb and proposed that the V/R was a new character to distinguish two types.

This study was undertaken to elucidate whether the variations of Vb-Rb system correspond to Indica-Japonica differentiation, or not. Eighty-three cultivars from Asian countries were investigated for the numbers of Vb in the peduncle, Rb number in rachis branches and ratio of Vb to Rb (V/R), phenol reaction of the hull (Ph), tolerance to KClO3 (K) and apiculus hair length (H).

At first, the 83 cultivars could be classified into 46 Indicas and 37 Japonicas following the Sato's discriminant function: Z=Ph+1.313K-0.82H-1.251 (Sato 1991). As shown in Table 1, Indica types possessed more Vbs (17.6 on the average) than Japonicas (13.0), while no difference was found in the number of Rb in two types. Most distinct difference was detected in V/R; 1.71 in Indica and 1.17 in Japonica types. The variation of V/R, however, somewhat overlapped between two types, and it was difficult to identify Indica and Japonica using only V/R ratio. As is well known, Indica type had longer apiculus hair and lower tolerance to KCl03.

Table 1. Probabilities of misclassification between Indica (46 cvs)

and Japonica (37 cvs) by different characters
Character Mean(delta) Indica Japonica Misclassification** P(%)
No. of vascular bundle(V) 17.6 (2.7 ) 13.0 (3.0 ) 20.9
No. of rachis branch(R) 10.4 (1.9 ) 11.2 (1.8 ) 42.1
V/R 1.71(0.16) 1.17(0.21) 6.7
Ap. hair length 0.50(0.13) 0.69(0.25) 30.2
KClO3 sensitivity 1.37(0.44) 0.21(0.20) 4.1
KClO3 sensitivity 0.96(0.70) -1.52(0.35)
**Probability was estimated by d/2delta .
Research Notes 49
Table 1 also shows the discriminant power among the characters investigated. The Indica and Japonica types could be best distinguished by the sensitivity to KC103, the probability of misclassification being 4.1%. It was followed by V/R (6.7%), the number of Vb (20.9%) and the apiculus hair length (30.2%). The number of Rb was useless for identification of Indicas and Japonicas.

Since Vb and V/R are differentiated between Indica and Japonica, the principal component analysis was conducted using two characters and also K and H. The first and second vectors showed 70% and 16.8% contributions to the total variance, respectively, and a scatter diagram of eighty-three cultivars is shown in Fig. 1. They were divided into 3 groups. One is Indica group and the remaining two may be temperate- and tropical-Japonicas. The classification of the latter two will need more detailed investigation using a number of cultivars, especially those of tropical-Japonica type.

From the present results, we propose here the utilization of Vb and V/R as new characters for identification of Indica and Japonica types, together with the characters of Ph, K and/or H. Since the numbers of Vb in the peduncle are easily countable with the aid of a magnifying glass with 10 or 15 times, it will be possible to obtain an information about Indica and Japonica types on the spot during collection tour.

Fig. 1. Scatter diagram of 83 Asian rice cultivars by the scores of the first (Zl) and
second (Z2) vectors of PCA. 50 Rice Genetics Newsletter Vol. 13

References 

Fukuyama, T. and T. Takayama, 1995. Variations of the vascular bundle system in Asian rice cultivars.

Euphytica 86:227-231. Huang, H., 1988. Japonica and indica differences in large vascular bundles in culm. Intl. Rice Res. Newsl. 13:1. Sato, Y.I., 1991. Variation in spikelet shape of the indica and japonica rice cultivars of Asian origin. Japan. J. Breed. 41:121-134.