Potential chromosomal introgression barriers revealed by linkage analysis in a hybrid of Pinus massoniana and P. hwangshanensis.
BACKGROUND
Exploring the genetic mechanisms underlying speciation is a hot topic in modern genetics and evolutionary studies. Distortion of marker transmission ratio is frequently ascribed to selection against alleles that cause hybrid incompatibility. The natural introgression between P. massoniana and P. hwangshanensis and their distribution ranges lead to the emergence of the two species as desirable organisms to study the genetic mechanisms for speciation.


RESULTS
Using seeds sampled from trees at different elevations, we consistently detected sharp decreases in seed germination rates of trees in the hybrid zone, which might be due largely to the hybrid incompatibility. A genetic map was established using 192 megagametophytes from a single tree in the hybrid zone of the two species. Segregation distortion analysis revealed that the percentage of significant-segregation-distortion (SSD) markers was extremely high, accounting for more than 25% of the segregating markers. The extension range, the distortion direction, and the distortion intensity of SSD markers also varied dramatically on different linkage groups.


CONCLUSIONS
In this study, we display the potential chromosomal introgression barriers between P. massoniana and P. hwangshanensis. Our study provides a valuable platform for conducting genome-wide association of hybrid incompatible QTLs and/or candidate genes with marker transmission ratio distortion in the hybrid.
Li
Shuxian
S
Nanjing Forestry University, China.
Chen
Ying
Y
Gao
Handong
H
Yin
Tongming
T
D054458:Amplified Fragment Length Polymorphism Analysis; D002678:Chimera / Q000235:genetics; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D018744:DNA, Plant / Q000235:genetics; D008040:Genetic Linkage; D005819:Genetic Markers; D049810:Genetic Speciation; D018525:Germination; D028223:Pinus / Q000235:genetics*; D017422:Sequence Analysis, DNA
D018744:DNA, Plant; D005819:Genetic Markers