Analysis of spatial and temporal variation of the farmers' rice variety Tai Nguyen under changing cropping systems in the Mekong Delta, Viet Nam
2006
Tin, H.Q. (Mekong Delta Development and Research Institute, Can Tho University, Can Tho City (Vietnam)) | De, N.N. | van Treuren, R. | Visser, L.
On-farm management of crop diversity forms a dynamic contribution to conservation of plant genetic resources. A case study looked at the differences between populations of the popular photo-sensitive farmers' variety Tai Nguyen sampled in six locations in the Mekong Delta in Viet Nam, and into the changes of this variety over time as a result of evolving cropping systems. In 1997, on-farm cultivation of four populations and a gene bank accession corresponding to one of the four populations, but acquired six years earlier, was carried out in each of the collaborating communities and at the gene bank premises. Flowering time, plant height and leaf length varied between populations over time and place. In 2000, AFLP analysis was performed on samples newly obtained from these sites and from two additional sites, and compared with two gene bank accessions of Tai Nguyen acquired nine years earlier, as well as with three other farmers' varieties from the same sites. Apart from two populations, no major genotypic variation could be observed. Of all 267 Tai Nguyen plants analyzed, 151 exhibited an identical AFLP profile. Off-types identified by the farmers prior to the AFLP analysis accounted for 65% of the genotypically deviant individuals. No genotypic changes were noted between the two gene bank accessions and the dominant genotype in the farmer populations. It is concluded that the majority of Tai Nguyen populations have not undergone genetic changes based on comparison of germplasm obtained at different sites with different agro-ecosystems, nor when comparing germplasm obtained over a period characterized by major changes in cropping systems. The popular and dominant farmers' variety Tai Nguyen is highly homogeneous and has been efficiently maintained on-farm
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