Analysis of shade-tolerance and determination of evaluation indicators of shade- tolerance in seedlings of Chrysanthemum grandiflorum and its closely related genera
菊花近缘种属植物幼苗耐阴特性分析及其评价指标的确定

Chrysanthemum (Chrysanthemum grandiflorum (Ramat.) Tzvel.) is one of the most important ornamentals, enjoying a major share of the cut flower and flowering pot plant market worldwide. The related taxa of Chrysanthemum have been shown to be tolerant to various biotic or abiotic stresses such as pest, fungi, drought or salt stress etc, so the useful gene can be used to the elite germplasm and new variety breeding of Chrysanthemum by interspecific hybridization or gene engineering. Several representative species of Chrysanthemum and its related genera, maintained at the Chrysanthemum Germplasm Resource Preserving Center, " Nanjing Agricultural University ", were used in this study. Seedlings of fifteen species from Dendrathema and Ajania generus such as D. makinoi, D.nankingense, D.indicum, D.yoshinaganthum, D. japonense, D.crassum, D.makinoi var. akasaense, D. okiense, D.vestitum, Ajania przewalskii, A. pacificum, A.shiwogiku, Artemisia vulgaris, A.abrotarum, A. japonicawere subjected to shading treatment. Morphological and physiological parameters including stem diameter, internode length, leaf width, leaf length, leaf thickness, leaf area, relative water content, chlorophyll content, net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), stomatal conductance (Gs) and transpiration rate (Tr) of seedlings were determined under non-shading, 60%, 78% and 95% shading rate, respectively. Our results showed that thirteen out of fifteen species including D. makinoi, D.nankingense, D.indicum, D.yoshinaganthum, D. japonense, D.crassum, D.makinoi var. akasaense, D. okiense, D.vestitum, Ajania przewalskii, A.shiwogiku, Artemisia vulgaris, A.abrotarum are shade-tolerant with longer leaf length, thiner leaf thick, higer chlorophyll content, no change of relative water content and intercellular CO2 concentration than that of control, while Ajania pacificum is sensitive to shade tolerance with abnormal phenotype such as the smallest leaf length and leaf area, the lowest chlorophyll content, the highest relative water content and intercellular CO2 concentration than its control, the sensitivity of the other one A. japonica to shade treatment was lower than that of Ajania pacificum but higher than that of the thirteen species. It suggests that most of the species from Chrysanthemum and Ajania are shade tolerant plants. The co-efficiency of different indexes was used to evaluate the shade tolerance of the plants. The shade tolerance of the tested 15 species was evaluated using the principle component analysis, regression analysis and hierarchical cluster analysis. The results showed that stem diameter (X2), leaf thickness (X10) and chlorophyll content (X16) under 78% shading, chlorophyll content (X15) under 60% shading, and leaf area (X13) and relative water content (X14) and intercellular CO2 concentration (X21) under 95% shading were suitable indexes for shading tolerance evaluation. The mathematical evaluation model for chrysanthemum shade-tolerance