4. Relationship between chromosome number and plant characters in aneuploids of Oryza glaberrima

Koshun ISHIKI

Tropical Agriculture Research Center, 1-2 Ohwashi, Tsukuba, 305 Japan

Aneuploids generally show decreased vigor with increasing number of extra chromosomes. This relation in aneuploids of O. sativa has been observed by a few workers. Koga et al. (1967) and Watanabe et al. (1969) reported a close negative relation between chromosome number and seed fertility. The more the extra chromosomes, the lower the seed fertility, although there was a wide variation in plants with 2n=25 and 26. Most aneuploids with more than 27 chromosomes had nearly 0% seed fertility. Ramanujam (1937) and Watanabe et al. (1969) reported a close negative relation between chromosome number and plant height or culm length. The more the extra chromosomes, the shorter the plants.

The relationships between chromosome number and some metric characters in the aneuploi.ds of O. glaberrima Steud. were investigated by the present author. In the progeny of autotriploids, chromosome number ranged from 24 to 28, and a plant with 2n=28 was highly abnormal in morphological and reproductive features (Ishiki 1987, 1991). Correlations between chromosome number and some other characters observed in the progeny of autotriploids are given in Table 1. Chromosome number was negatively correlated with plant height, seed fertility, second internode length and panicle length. Similar negative correlations of chromosome number were observed with first internode length, "penultimate" (second from the top) leaf-blade length, spikelet number per panicle, and flag leaf-blade length. These correlations indicate that the more the extra chromosomes, the more abnormal the plants in morphological and reproductive features, in the same manner as reported in O. sativa. 

Table 1. Correlation coefficients (r) found between chromosome number and
some characters of aneuploids of O. glaberrima
===============================================================================
    Character                                      r
===============================================================================
Days to heading                                    0.12
Plant height                                      -0.67**
Panicle length                                    -0.53**
Neck-node diameter                                -0.15
First internode length                            -0.49*
Second internode length                           -0.55**
Panicle number per plant                          -0.13
Spikelet number per panicle                       -0.44*
Flag leaf-blade, length                           -0.44*
Flag leaf-blade, width                            -0.37
"Penultimate" leaf-blade, length                  -0.47*
"Penultimate" leaf-blade, width                   -0.29
Pollen stainability                               -0.34
Seed fertility, selfed                            -0.65**
Seed fertility, open                              -0.62**
===============================================================================
P<0.05, **P<0.01.
"Penultimate" leaf = Second leaf from the top.
References

Ishiki, K., 1987. Breeding of primary trisomics in African rice, Oryza glaberrima Steud- Ph. D. Dissertation, Osaka Prefecture Univ., 176pp.

Ishiki, K., 1991. Cytogenetical studies on African rice, Oryza glaberrima Steud- 3. Primary trisomics produced by pollinating autotriploid with diploid. Euphytica 55: 7-13.

Koga, Y., T. Nagamatsu and Y. Inoue, 1967. Studies on the crossing experiments between diploid and auto-triploid rice plants, Oryza sativa L., with special reference to the artificial culture of progeny plants and their chromosome numbers. Sci. Bull. Fac. Agr., Kyushu Univ. 23: 63-66. (in Jap. with Eng. summary)

Ramanujam, S., 1937. Cytogenetical studies in the Oryzeae- II. Cytogenetical behaviour of an autotriploid in rice (0ryza sativa L.). J. Genet. 35: 183-221.

Watanabe, Y., S. Ono, Y. Mukai and Y. Koga, 1969. Genetic and cytogenetic studies on the trisomic plants, Oryza sativa L. I. On the autotriploid plant and its progenies. Jpn. J. Breed. 19: 12-18.