3. Karyotype analysis of Lu-Dao, an indigenous weedy rice germplasm found in Jiangsu, China

Zeng-Jian CHEN and Li-Hong ZHU

Department of Agronomy, Nanjing Agricultural University, Nanjing, China

Lu-Dao, discovered in the district of Lianyun Harbor of Jiangsu Province, China, in 1960's appears to be a weedy form of cultivated rice, 0. sativa subsp. japonica. So far, no consensus of opinions about its taxonomic status has been reached. It occurs spontaneously in moist places of mountainous areas and near paddy fields and water ponds, and is characterized by shattering panicles, long blackish awns, black-purple hulls and red grains at maturity. For karyotypic observations, its root-tips were fixed in 1:3 acetic-alcohol and smeared in 45% acetic carmine. The chromosome number of somatic cells is 24, although occasional cells with 2n= 36, 48 could also be observed. Karyotype analysis at mitotic prometaphase and early metaphase showed six metacentric (K1, K3, K6, K7, K8 and K11), four submetacentric (K2, K5, K9, and K12), one subtelocentric (K4) and one satellite (K1O) chromosomes (Table I and Fig. 1). It is evident that chromosome K 1 is the longest with RL 12.6 and chromosome K 12 is the shortest with RL 4.9.

Table 1.Mean values of relative length(RL) and arm ratio(AR) of
      chromosomes at prometaphase root-tip cells of Lu-Dao
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Chromosome                             RL                 AR1
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K1                                   12.6                 1.67m
K2                                   10.6                 1.84sm
K3                                   11.5                 1.23m
K4                                    9.3                 3.35st
K5                                    8.4                 1.81sm
K6                                    8.1                 1.16m
K7                                    7.0                 1.43m
K8                                    6.9                 1.32m
K9                                    7.3                 2.14sm
K 102                                 7.1                 3.84st
KII                                   6.5                 1.28m
K12                                   4.9                 1.96sm
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1.   AR: 1.0-1.7 m; 1.71-3.00 sm; 3.00-7.00 st.
2.    K10 was measured without the satellite.
Comparing the karyotypes of Lu-Dao with those of 0. perennis and 0. sativa (Kurata et al., 1981; 1984) showed general similarity except probably chromosome K1 which was metacentric in Lu-Dao, whereas submetacentric in those of perennis and sativa species. In addition, a secondary constriction in the long arm of


Fig. 1. Karyotype of Lu-Dao somatic-chromosomes at early metaphase.

chromosome K3 was found (Fig. 1), which should be the second chromosome if arranged by its relative length. According to Chen et al. (1982), secondary constriction could also be detected in the short arms of the second chromosome in the somatic cells of three wild rice species (0. rufipogon, 0. offlcinalis, 0. meyeriana) in China.

Giemsa C-bands and chromosome Giemsa regions could be formed by means of modified Giemsa banding technique in chroniosomes K1-K6, while only Giemsa regions appeared in other smaller chroniosomes K7-KI2. The banding characteristics of Lu-Dao somatic chromosomes at prometaphase seemed to be more diversified as compared with results obtained by previous authors (Chen et al. 1982; Kurata and Omura 1981, 1984).

References

Kurata, N. and T. Omura, 1981. Karyotype analysis in rice II. Identification of extra chromosomes in trisomic plants and banding structure on some chromosomes. Jpn. J. Genet. 56: 41-50.

_____, 1981. Chromosome analysis. In Biology of Rice, Tsunoda, S. and N. Takahashi, (eds.) Jpn. Sci. Soc. Press, Tokyo.

Chen, R. Y., W. Q. Song and X. L. Li, 1982. Studies on three different karyotypes of wild rice in China. Acta Botanica Sinica 23(4): 226-230.