ScienceAsia 28 (2002) : 227-239 |doi: 10.2306/scienceasia1513-1874.2002.28.227

Genetic Relationship among Exotic Soybean Introductions in Thailand: Consequence for Varietal Registration

Abul Kashem Chowdhury^a, Peerasak Srinives^b,*, Panie Tongpamnak^c, Panapa Saksoong^d and Presert Chatwachirawong^b

ABSTRACT: This research was designed to identify forty-eight exotic germplasm lines that were genetically and geographically distinct from the existing Thai soybean lines. Using 11 morphological descriptors, all genotypes were classified according to 37 morphological markers which allowed fully discrimination of the cultivars. Similarity indices between cultivars were calculated from 37 binary character states using Dice coefficient, which varied from 0.0 to 0.92 with an average of 0.449. The UPGMA cluster analysis revealed two groups, one formed by 32 cultivars and the other by the remaining 16 cultivars. DNA samples from forty-eight exotic soybean cultivars was examined to determine the efficiency of randomly amplified polymorphic DNA (RAPD) markers in identifying cultivars and determining level of genetic similarity. Out of 80 random primers, 37 generated highly reproducible polymorphic RAPD fragments. With these primers, 274 clear-cut RAPD markers were produced and only 85 (31%) were polymorphic, which indicated that high level of genetic similarities existed in these exotic cultivars. One to six alleles per primer were detected with a polymorphic information content varying from 0.04 to 0.50. The use of only 14 RAPD markers amplified from five primers was sufficient to identify uniquely all the cultivars, indicating that RAPD markers are efficient for use in genetic fingerprinting in soybean. Genetic similarities of 85 RAPD profiles were estimated via the DICE coefficient and then the data were processed using UPGMA clustering method. Each genotype was clearly identified and separated from the others. RAPD based dendrogram revealed that the 48 cultivars could be classified into four groups at 0.57 similarity scale, between which the similarity coefficient was as low as 0.51, even though the cultivars are morphologically or geographically very close. The Principal Component Analysis (PCA) yielded rather similar results to the UPGMA dendrogram. RAPD genetic similarity coefficients were correlated with morphological similarity coefficients (r = 0.241). Comparing agronomic performance and RAPD analysis via dendrogram, a total of 11 cultivars were ear-marked for crossing program. These genotypes can be useful to soybean breeders in Thailand who want to utilize genetically diverse introductions in soybean improvement.

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a Department of Genetics and Plant Breeding, Faculty of Agriculture, Patuakhali Science and Technology University, Patuakhali-8602, Bangladesh.
b Department of Agronomy, Faculty of Agriculture, Kasetsart University, Kamphaeng Saen, Nakhon Pathom 73140, Thailand.
c Central Laboratory and Greenhouse Complex, Kasetsart University Research and Development Institute, Kamphaeng Saen, Nakhon Pathom 73140, Thailand.
d Department of Genetics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.

*Corresponding author, E-mail: agrpss@ku.ac.th

Received 29 Oct 2001, Accepted 11 Dec 2001