Development of EST-SSR markers and association mapping with floral traits in Syringa oblata.

BACKGROUND: Lilac (Syringa oblata) is an important woody plant with high ornamental value. However, very limited genetic marker resources are currently available, and little is known about the genetic architecture of important ornamental traits for S. oblata, which is hindering its genetic studies. Therefore, it is of great significance to develop effective molecular markers and understand the genetic architecture of complex floral traits for the genetic research of S. oblata. RESULTS: In this study, a total of 10,988 SSRs were obtained from 9864 unigene sequences with an average of one SSR per 8.13 kb, of which di-nucleotide repeats were the dominant type (32.86%, 3611). A set of 2042 primer pairs were validated, out of which 932 (45.7%) exhibited successful amplifications, and 248 (12.1%) were polymorphic in eight S. oblata individuals. In addition, 30 polymorphic EST-SSR markers were further used to assess the genetic diversity and the population structure of 192 cultivated S. oblata individuals. Two hundred thirty-four alleles were detected, and the PIC values ranged from 0.23 to 0.88 with an average of 0.51, indicating a high level of genetic diversity within this cultivated population. The analysis of population structure showed two major subgroups in the association population. Finally, 20 significant associations were identified involving 17 markers with nine floral traits using the mixed linear model. Moreover, marker SO104, SO695 and SO790 had significant relationship with more than one trait. CONCLUSION: The results showed newly developed markers were valuable resource and provided powerful tools for genetic breeding of lilac. Beyond that, our study could serve an efficient foundation for further facilitate genetic improvement of floral traits for lilac.

[Increased Size of Epidermal Cells in Syringa josikaea Jacq. Smaller Leaf Side as an Adaptive Mechanism for Reducing Its Asymmetry].

Comparative study of quantitative anatomy of the epidermis in Syringa josikaea Jacq. leaf halves of different width was conducted in order to analyze the possible mechanism of formation of the value of fluctuating leaf asymmetry. A regular decrease in the density of main epidermal cells in the smaller leaf half compared with the bigger one was traced during leaf ontogeny. Stomatal index was equal in different-sized leaf halves. Adaptive response was found in fully formed leaves; it was aimed at reducing leaf blade fluctuating asymmetry by 23% on average and consisted of compensatory growth--further elongation of main epidermal cells in the smaller half of the leaf. It was concluded that the level of fluctuating leaf asymmetry in Hungary lilac is mainly due to a lower rate of cell division, as well as due to their greater elongation in the smaller half of adult leaf compared with the bigger half.

[Morphological-ecological characters and growth patterns of main tree species leaves in urban forest of Shenyang].

The study with statistic and multivariate analyses showed that the main meteorological factors affecting the growth and development rhythms of main tree species leaves in urban forest of Shenyang were > or = 5 degrees C accumulated temperature, accumulated sunshine hours, and mean temperature in the middle ten days of each phenological period. The meteorological factors needed by the tree species varied with their phenological period. Necessary low temperature and CI were required in germination period, and suitable WI and HI were needed in the growth period. The major quantitative morphological characters of 10 tree species in Shenyang urban forest were displayed in their leaf morphology and size, which decreased in the sequence of Lespedeza cyrtobotrya > Syringa oblata > Sophora japonica > Populus alba > Cornus alba > Lonicera maackii > Ligustrum obtusifolium > Fraxinus mandshurica > Prunus padus > Phellodondron amurense. As for the leaf area, it was decreased in the order of S. oblata > P. alba > P. amurense > P. padus > F. mandshurica > C. alba > L. cyrtobotrya > L. maackii > S. japonica > L. obtusifolium. The relationships of leaf length with leaf width, perimeter and area accorded with the model of y = ax(k), and the growth trend belonged to allometic type. The k value between leaf length and width of all test tree species except P. alba was lower than 1, and that between leaf length and perimeter was > 1 for P. amuresne, approximately 1 for P. alba, and < 1 for other tree species. As for the k value between leaf length and area, it was > 1 for all the tree species, with that of P. alba being 2. 1028. The increasing rate of leaf area was about 2 times higher than that of leaf length. An optimum regression assessment model of the 10 tree species leaf area was built and tested.