| Most of land available for poplar afforestation in China is arid,cold,saline-alkali and other difficult site,breeding new poplar varieties including fast-growing,high-quality,drought-resistant and cold-resistant is an important way to meet the cost-saving and efficiency-increasing needs of poplar plantation in China.Three P.simonii clones(‘1-XY',‘XY-5',‘ZL3')and seven P.nigra clones(‘N188',‘N020',‘N139',‘N151',‘N429',‘N430')were selected as parents,and 1910 individuals of 8 hybrid combinations were obtained through artificial control-pollination.Ground diameter of biennial seedlings,as well as leaf morphological characters(leaf area,leaf perimeter,leaf length,leaf width,petiole)of annual seedlings were measured,and parameters such as coefficient of variation(CV),hereditary(h~2),genetic gain(G),combining ability(CA)were calculated.The incidence of leaf diseases in the hybrid progeny population was calculated by field investigation,The morbidity and disease index of the 8 hybrid combinations were calculated to explore the range and severity of diseases among the 8 hybrid combinations.In addition,leaf profile models of 8 hybrid combinations were constructed by Leaf Analyser.Principal component analysis(PCA)on leaf shape variation of hybrid progeny was conducted based on Leaf Analyser,and main leaf morphological characters that affect leaf shape variation were analyzed.Morpho J was used to build a leaf morphological feature model based on the Procrustes fit.The morphological variation of leaf shape was analyzed,and the proportion of morphological variation from different shape in the overall morphological variation was determined.The main results are as follows:(1)Genetic variation of ground diameter:the range of the two-year average mean ground diameter between 8 hybrid combinations weas from 2.71 cm to 3.60 cm,and the hybrid combinations with large diameter growth were‘1-XY×N188',‘ZL-3×N188',‘ZL-3×N429'.The variation coefficient of 8 hybrid combinations ranged from 42.85%to 52.38%,indicating that there was a large variation of each hybrid combination in ground diameter.The generalized heritability of the ground diameter of 8 hybird combinations was 0.81,showing that the ground diameter were greatly influenced by genetic factors and could be the basis for selection.The genetic gain of the hybrid combinations was above 50%,and the traits of the hybrid progeny were well performance.(2)Genetic variation of leaf traits:the mean leaf area,mean leaf perimeter,mean leaf length,mean leaf width and mean petiole length of‘ZL-3×N430'were the largest in 8combinations.The maximum single leaf appeared in‘ZL-3×N188'.The variation coefficient of leaf area ranged from 25.47%to 39.29%,leaf perimeter from 13.93%to 21.72%,leaf length from 11.34%to 18.56%,leaf width from 13.62%to 20.95%,and petiole length from 15.09%to26.83%.The results of variance analysis of leaf traits showed that the differences of leaf traits between hybrid combinations were extremely significant,and the mean value of leaf traits was close to that of the male parent.The generalized heritability of hybrids in leaf area,leaf perimeter,leaf length,leaf width and petiole length were 0.88,0.91,0.89,0.86 and 0.97,respectively,indicating that the leaf traits were mainly controlled by genetic factors.(3)Appearance of leaf diseases:field investigation of leaf diseases in the hybrids showed that the black spot disease[Marssonina.brunnea(Ell.et Ev.)Sacc.]occurred in a large proportion with obvious symptoms and was relatively serious.The incidence of black spot disease was above 50%in all combinations.The combinations with higher incidence of black spot disease were‘XY-5×N188',‘ZL-3×N430'and‘1-XY×N139'.The hybrids with lower incidence were‘1-XY×N151',‘1-XY×N188',‘ZL-3×N429'.The results showed that‘XY-5×N188'had the most serious incidence,was 85.72%,and the disease index reached 54.37%.Hybrid combinations‘1-XY×N151',‘1-XY×N188'and‘ZL-3×N429'were both with light symptoms and degree of morbidity,which the incidences were 53.11%,53.21%and 55.37%,the disease indexes were 28.82%,28.33%and 30.76%,respectively.(4)Leaf morphological variation analysis:Leaf morphological variation principal component analysis results based on Leaf Analyser showed that leaf area size was the first principal component affecting leaf-shape variation in 8 hybrid combinations,and its contribution to leaf morphological variation in 8 hybrid combinations was over 60%.According to the first principal component image of hybrid progeny,the morphological characteristics of leaves with larger leaf area are more similar to leaves of P.nigra,while leaves with smaller leaf area are more similar to leaves of P.simonii.Other main components that affect leaf morphological variation were leaf aspect ratio,leaf tip and leaf base morphology,leaf symmetry.Leaf morphological variation analysis based on Morpho J showed that the main source of leaf morphological variation in 8 hybrid combinations was rounded leaf,triangular leaf,rhombus leaf and obovate leaf,which account for more than 70%of total leaf morphological variance. |
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