Identification of Genetically Distinct Cassava Clones from On-Farm Plantations to Widen the Thai Cassava Breeding Gene Pool

Abstract

Cassava (Manihot esculenta Crantz) is one of the mostimportant economic crops in Thailand. However, the Thai cassava breeding gene pool wasgenetically narrow with only 11 distinct landraces. An attempt was made here tocharacterize 266cassava clones collected from 80 farms in eight provinces using 35 SSR markers.A total of 365polymorphic alleles were detected in the assayed samples. The molecularanalysis of variance revealed that a large SSR variance (19.8%) was presentamong the farm samples. The genetic relationships of the 266 farm samplesrevealed by the principal coordinate analysis confirmed the large SSRvariation observed among the collected cassava samples. The average dissimilarity (AD) of a cassava sample against the other 265samples was calculated and the AD values obtained ranged from 0.256 to 0.502with a mean of 0.319. Based on these AD values, a set of 50 unique cassavasamples with AD valuesof 0.346 or higher was assembled from the on-farm samples to widen the genetic baseof the Thai cassava breeding gene pool.