Abstract
Willow (Salix) is one of the most important ornamental tree species in landscape plants. One species, Salix matsudana, is widely used as a shade tree and border tree because of its soft branches and plump crown. Some varieties of S. matsudana were salt tolerant and could grow normally in coastal regions. However, the molecular mechanisms of salt tolerance for S. matsudana have been less clear. Here, we addressed this issue by performing a mapping experiment containing 195 intraspecific F1 progeny of S. matsudana, derived from salt-sensitive ‘yanjiang’ and salt-tolerant ‘9901’, grown by cuttings in a 100 mM NaCl solution. Growth performance of these progeny under salt stress was investigated, displaying marked genotypic variability with the coefficients of variance of 28.64–86.11% in shoot and root growth traits. We further mapped specific QTLs contributing to these differences to the Salix genome. Of the 204 QTLs identified, a few were detected to explain a remarkably larger portion of the phenotypic variation than many others. Many detected QTLs were found to reside in the region of candidate genes of known biological function. The discovery of growth QTLs expressed under salt stress provides important information for marker-assisted breeding of salt tolerant Salix varieties and founds the basis for the application of S. matsudana in coastal afforestation.
Highlights
Willows (Salix), originated from China, have a wide distribution and strong adaptability.[1]
Results from QTL mapping for the F1 hybrid population of S. matsudana under salt stress showed that a total of 204 QTLs were detected for 15 growth traits with the LODs of 43.00 and the contributions of 49.90% (Table 3)
Among the 15 growth traits, 3 QTLs on linkage group 18 were related with expand leaf number (ELN), with the contributions of 51.20%, 50.40% and 48.70%, respectively (Figure[2] and Table 3); 3 QTLs on linkage group 13 were related with nonexpand leaf number (NELN), with the contributions of 55.40%, 55.20% and 54.90%, respectively (Figure 2 and Table 3); 1 QTL related with total root number (TRN) were found on linkage groups 3 and 16, with the contributions of 55.10% and 55.70%, respectively (Figure 2 and Table 3)
Summary
Willows (Salix), originated from China, have a wide distribution and strong adaptability.[1]. Some varieties of willows are widely planted in ecological environment construction of coastal areas and have showed good growth traits. Because of their greening roles, willows have received considerable attention of genetic research. Hoglund et al have detected major QTLs for insect resistance in S. viminalis using SNP markers, with the contribution of 18%.6. One major QTL and 14 small QTLs have been found in the backcross population of S. viminalis × S. schwerinii and S. viminalis using SSR and SNP markers.[7] All of the above studies have helped to reveal the genomic locations of genes controlling important traits of willow, and provide important references for marker-assisted breeding of willow.
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