油茶'德油2号'和攸县油茶'攸杂2'正反交子代生长性状的遗传分析OA

[Objective]Camellia oleifera is a distinctive woody oilseed species native to China,valued for its exceptional nutritional and economic significance.Nevertheless,its hybrid breeding efficiency is constrained by factors such as complex genetic backgrounds,prolonged juvenile phases,and poorly understood inheritance patterns.This study systematically investigated the genetic variation and inheritance patterns of growth-related traits in reciprocal hybrids derived from C.oleifera cultivars'Deyou No.2'(DY2)and C.yunsienensis'Youza 2'(YZ2),with the aim of establishing a theoretical basis for optimizing parental selection strategies and facilitating early phenotypic prediction in hybrid offspring.[Method]Reciprocal crosses were performed using DY2(a high-yielding cultivar characterized by large fruit and thin pericarp)and YZ2(a wild superior genotype exhibiting spring flowering and anthracnose resistance)as parental lines.Two crossing combinations were established:the orthogonal group(DZ,DY2 ♀ × YZ2 ♂)and the reciprocal group(ZD,YZ2 ♀ × DY2 ♂),consisting of 749 and 569 progeny individuals,respectively.All plant materials were planted in 2019 at the C.oleifera Seedling Experimental Base of Central South University of Forestry and Technology(113.42°E,28.38°N)under standardized cultivation management practices.Eleven quantitative traits-namely leaf length(LL),leaf width(LW),leaf thickness(LT),leaf area(LA),leaf shape index(LSI),SPAD value(SV),shoot length(SL),shoot diameter(SD),branching angle(BA),trunk diameter(TD)and tree height(TH)—were measured during July-August 2022 in accordance with the Technical Specification for Investigation and Determination of Major Traits in C.oleifera(LY/T 2955-2018).Data were processed using Excel 16 and SPSS 26.0.Key genetic parameters,including coefficients of variation(CV),mid-parent heterosis(MPH),and relative genetic contribution of parents,were calculated.Cluster analysis(K-means)and normality tests(Kolmogorov-Smirnov)were conducted to assess trait distribution and genetic divergence.[Result](1)Trait variation and distribution:significant genetic variation was observed across all measured traits,with CV values ranging from 9.46％(SV in ZD)to 29.33％(SL in DZ).The average CV followed the order of SL＞LA＞TH＞TD＞BA＞LW＞SD＞LT＞LL＞LSI＞SV.Most traits exhibited continuous distribution patterns,consistent with polygenic inheritance.However,only SL(DZ,P=0.024;ZD,P=0.174),SD(DZ,P=0.200),and SV(DZ,P=0.200)showed approximately normal distributions;the remaining traits displayed significant skewness,likely due to directional selection or parental genetic dominance.(2)Reciprocal effects and genetic tendency:maternal influence was predominant for traits including LL,LSI,LT and SV.For instance,LT in DZ(0.34 mm)and ZD(0.32 mm)reflected mid-parent values(MPV 0.34 mm),with DZ exhibiting positive mid-parent heterosis(MPH 0.09％).Traits such as LW,SD and BA showed a paternal bias toward DY2;for example,LW in DZ(33.35 mm)was lower than that in the MPV(34.12 mm),with a CV of 11.75％.Conversely,LA,SL,TD and TH exhibited a directional trend toward YZ2,with LA in ZD displaying the highest MPH(10.41％).Tree-related traits(SL,TD,TH)showed negative MPH(e.g.,SL in DZ,-18.05％),indicating hybrid depression,whereas leaf-related traits demonstrated moderate heterosis(e.g.,LA in ZD,16.52 mm2 vs.MPV 14.96 mm2).(3)Correlation analysis:strong correlations were observed among leaf and tree traits.For instance,LL was positively correlated with LW(R=0.674,P＜0.01)and LA(R=0.765,P＜0.01).The SPAD value showed a significant positive correlation with LT(R=0.172,P＜0.01),suggesting that LT may serve as a potential proxy for photosynthetic efficiency.A significant negative correlation was found between LSI and LW(R=-0.603,P＜0.01),indicating morphological trade-offs in leaf structure.(4)Cluster analysis:the orthogonal progeny(DZ)were classified into three distinct clusters:Cluster 1,comprising 321 individuals,exhibited phenotypic characteristics similar to those of YZ2;Cluster 2,consisting of 182 individuals,aligned closely with DY2;Cluster 3,with 248 individuals,demonstrated inferior growth performance.In contrast,the reciprocal progeny(ZD)segregated into four clusters.Notably,Cluster 3(140 individuals)surpassed both parental lines in key tree traits,exhibiting greater TH(60.02 cm vs.54.97 cm in DY2)and TD(18.33 mm vs.15.86 mm in YZ2).[Conclusion]Reciprocal hybrids between C.oleifera DY2 and YZ2 display substantial genetic diversity.Maternal effects are predominant in determining leaf morphology,whereas paternal inheritance plays a more significant role in shaping tree architecture.The reciprocal cross(ZD)demonstrates superior performance in critical growth traits,particularly with Cluster 3,which showed enhanced TD and TH.These results highlight the potential for simultaneous selection of genetically correlated traits and provide valuable guidance for early-stage screening in hybrid breeding programs.Future research should incorporate fruit-related traits to assess the predictive validity of growth trait selection.