Screening interspecific hybrids of Populus (P. ciliata x maximowiczii) using AFLP markers

Hybrids of Populus ciliata x maximowiczii are very vigorous and outperform both the parents in growth performance and yield. Genetic evaluation of 24 of these interspecific hybrids along with the two mother trees ( Populus ciliata), and five male-parent ( Populus maximowiczii) genotypes was carried out using the AFLP marker assay. Eight AFLP primer combinations detected 428 markers, of which 280 (66%) were polymorphic. Genetic relationships within the samples were evaluated by generating the similarity matrix based on Jaccard's coefficient. The phenetic dendrograms, as well as the PCO plots, separated the hybrids and the two parent species into three distinct clusters. The hybrids grouped closer to the P. ciliata (female parent) cluster as compared to the P. maximowiczii (male parent) cluster. The hybrid cluster contained internal groupings, which correlated to some extent with growth performance. The four best performing hybrids (42m1, 65m1, 23m2, Cm2-5-20/91) formed a distinct sub-cluster. Data from a single primer combination was sufficient for distinguishing the hybrids from the parents and assigning paternity. The hybrids showed 22 markers that were absent in P. ciliata but were monomorphically present in all the hybrids, suggesting outcrossing and common paternity. Further, these 22 markers were found in all the P. maximowiczii genotypes confirming it as the male parent. These male-specific markers can be converted to SCAR markers and used for rapid screening of the P.ciliata x maximowiczii hybrids. The primer combination E-AAC x M-CAA was identified as most suitable for ascertaining true hybridity. AFLP proves to be a useful tool for screening of P. ciliata x maximowiczii hybrids at the early stages of development.