8. Genetic diversity of weedy rice in Malaysia

Duncan A. Vaughan, 1 H. Watanabe2 ,Abdullah Md. Zain 3and K. Okuno1

1)NIAR. 2-1-2 Kannondai. T.sukuba 305. Japan

2) JIRCAS. Tsukuba 305. Japan

3) Rice Research Center, MARDI. Seberang Perai. Malaysia

     Weedy rice has recently become one of the major weeds in two of the main rice production areas of Malaysia. Tanjung Karang and MLJDA. We randomly sampled weedy rice from across the entire range of its distribution in these two rice growing areas. 49 samples of weedy rice were analysed from MUDA and 37 from Tanjung Karang. DNA was extracted from each sample and was subjected to RAPD analysis. Polymorphic bands were scored and cluster analysis was performed on the data. Wards coefficient of similarity was measured.
    For samples from MUDA 18 polymorphic bands were scored using 12 primers (Fig. 1). For samples from Tanjung Karang, 24 polymorphic bands were scored using 12 primers (Fig. 2). Samples from MUDA showed no clear groupings. However, samples from Tanjung Karang fell into 2 groups with the same number of samples in each group. The phenol test. a test which is indicative of Indica and Japonica races (Oka 1988). was performed on all samples and the results are shown (Table 1 ). The weedy rice samples did have different reactions to phenol and in Tanjung Karang the number of sample which reacted or did not react were almost equal in number. However, the two groups revealed by cluster analysis of RAPD data of samples from Tanjung Karang did not correspond to the groups by phenol test. It seems possible in Tanjung Karang. where weedy rice was a problem for many years, that the early stages of differentiation have been revealed by RAPD analysis, which is a method sensitive to small differences between samples at the DNA level. Wards coefficient of discrimination

Fig. 1. Dendrogram showing cluster analysis of DNA polymorphism revealed by RAPD

                                            analysis of weedy rice from MUDA Wards coefficient of discrimination
Fig. 2. Dendrogram showing cluster analysis of DNA polymorphism revealed by RAPD
analysis of weedy rice ( *) from Tanjung Karang and cultigen (MR84X)(* ).
 Table 1. Phenol reaction of weedy rices in Malaysia
 
Sampling location Number of plants Positive Negative
MUDA 31 4
Tanjung Karang

Cluster 1

 17

9

 14 

5
Cluster 2 8 9

Plants with a dark hull were excluded.

Reference

Oka, H. I., 1988. Origin of Cultivated Rice. Elsevier/Japan Sci. Soc. Press. Amsterdam/Tokyo, 254pp.