Identification of AFLP Markers Associated with Embryonic Root Development in Populus tomentosa Carr

Embryonic root (radicle) development in the mature embryo following germination is essential for the formation of the root organ in plants. In this study a phenotype described by a lack of proper radicle development was identified in an intraspecific hybrid of Populus tomentosa Carr.. Association of this trait with Amplified Fragment Length Polymorphisms (AFLPs) markers was investigated in a segregating F₁ population generated by intraspecific-controlled crossing between a highly fertile female P. tomentosa clone “5082” and a male P. tomentosa clone “JY”. A total of 3193 seeds were obtained, and the rate of germination found to be 48.74% at 15 to 20 days. 376 (24%) of seedlings were shown to lack a root organ following visual assessment of the developing radicle. Genetic regulation of this trait appeared to be via a single dominant gene or a set of tightly linked genes, based on the 3:1 ratio of the rooting versus nonrooting seed embryos. A Bulked Segregant Analysis approach using 5600 AFLP markers was applied to this population and revealed 2 AFLP markers, EcoRI + _GAG/ Mse I + _AAT-492 and EcoRI + _GAG/Mse I + _CCA-502, that were associated with the radicle development-controlling locus in P. tomentosa. The AFLP markers identified have potential for application in hybrid breeding via marker assisted selection, and provide a starting point for map based cloning of the radical development-controlling gene.