4. A statistical evaluation of the classification of rice cultivars into hsien and keng subspecies

K.S. Cheng

Yunnan Academy of Agricultural Sciences, Kunming, China

Classification is of fundamental importance in the utilization of genetic resources. The rice cultivars of Asia including the "Javanica" and other ecotypes of Morinaga (1968) can be classified into two subspecies of Oryza sativa L., i.e., subsp. hsien Ting and subsp. keng Ting (Cheng et al. 1984). To reconfirm this assertion, a total of 209 rice cultivars from various Asian countries situated between Burma and Iran, which were considered as atypical by Glaszmann (1984), were made available through the courtesy of IRRI and were used for this study. They were evaluated by using our criteria based on six characters listed in Table 1. The sum of scores for the six characters was used for classification as follows: Varieties with a score sum <8 were considered as hsein (H), 9-13 mostly as hsien-cline (H'), 14-17 mostly as keng-cline (K'), and >16 as keng (K).

Table 1. Six characters and their scores used for classification.

==============================================================================
Character                                     Score/character state
                      --------------------------------------------------------
                        0           1            2         3            4
==============================================================================
Glume hairiness      Short,     Short, less    Nearly     Long,       Long
                     regular    regular        glabrous  irregular  overlapped

Phenol reaction       Dark        Light       Very light  Trace        None

Interval between 1st
and 2nd node of       1.5          2.0           2.5        3.0         3.5
panicle axis, cm

Glume color        Greenish      Whitish      Yellowish    Light       Green
at heading           white        green         green      green

Leaf pubescence    Very dense     Dense        Medium       Few          No

Length-width ratio    4.0          3.5           3.0         2.5         2.0
of spikelets
==============================================================================
On the basis of this analysis, 97 of the 209 atypical varieties were classified as hsien (H), 55 as keng (K). Of the rest, 34 were classified as hsien-cline (H') and 23 as keng-cline (K'). To evaluate the relative magnitude of differences between the four types, the mean score-values of respective characters for the four types were subjected to analysis of variance (Table 2). The results showed that the differences between H' and K' were not significant while those between H and H', as well as those between K and K', were significant.

Table 2. analysis of variance of mean character scores for variety-groups, H, H',K', and K.

==========================================================
Variance due to             df            MS
==========================================================
   Pooled analysis
Variety-group               3            4.60**
Character                   5            0.231
Interaction                15            0.376
   First partition
K-H                         1            13.25**
K'-H'                       1            0.499
(K-K')-(H'-H)               1            0.037
Interaction                15            0.376
   Second partition
(K+K')-(H+H')               1            9.45**
K-K'                        1            1.77*
H'-H                        1            2.57*
Interaction                15            0.376
==========================================================
*,** Significant at 5% and 1% levels, respectively.

The taxonomic distances (Sokal and Sneath 1963) based on the score-values were also computed. The distance was greatest between H and K (2.45), followed by that between H and K' (1.51) and that between H' and K (1.46), while that between H' and K' was smallest (0.59). These data show that a continuous array of intergrades occurs between the two subspecies, hsien and keng, but a majority of varieties can be regarded as belonging to either of the two subspecies.

These observations based on six characters and those by Glaszmann based on isozyme variations appear to agree in recognizing that varieites from high altitude, many of upland varieties, so-called the Bulus from Java, and many of the "Sadri" and "Basmati" varieties, belong to subsp. keng. Most of varieties with sickle-shaped grain were keng or keng-cline types although their grain shape was quite slender.

References

Cheng, K.S., X. K. Wang, J.W. Zhou, Y.X. Lu, J. Lou and N.W. Huang, 1984. Studies on indigenous rices in Yunnan and their utilization, II. A revised classification of Asian cultivated rice (in Chinese) Acta Agronomica Sinica 10:271-280.

Glaszmann, J.C. 1984. The overall genetic organization of Oryza sativa L. as perceived through isozyme study. IRRI Seminar paper (mimeogr.).

Morinaga, T. 1968. Origina and geographical distribution of Japanese rice. JARQ 3:1-15.

Sokal, R.R. and P.H.A. Sneath 1963. Principles of Numerical Taxonomy. Freeman, San Francisco.