Abstract:【Objective】The Actinidia chinensis is the most mature domesticated species of thegenus Actinidia. More than 100 commercially valuable cultivars have been developed. However, few studies have evaluated the drought resistance of different kiwifruit cultivars based on the leaf morphology and microstructure. This research aims to evaluate the drought resistance of different kiwifruit cultivars by observing and analyzing characteristics such as leaf morphology, anatomical structure, stomata, epidermis, and trichomes. Key indicators for evaluating the drought resistance of kiwifruit cultivars and assessing their drought resistance will be identified. 【Methods】We selected a total of 12 kiwifruit cultivars (belonging to Actinidia chinensis var. chinensis and Actinidia chinensis var. deliciosa), including ‘Donghong’, ‘Guihai No.4’, ‘Hort 16A’, ‘Jintao’, ‘Jinyan’, ‘Jīn méi’, ‘Jinxia’, ‘Cuiyu’, ‘Jīn měi’, ‘Jinkui’, ‘Hayward’, and ‘Xuxiang’, as our observation subjects. We employed the multifunctional image analysis method, paraffin sectioning method, and scanning electron microscopy technique to observe and record the leaf morphology, anatomical structure, stomata, and epidermal trichomes of the 12 kiwifruit cultivars. A total of 24 traits (designated as X1-X24) were documented. Subsequently, we conducted variance analysis to compare the significant differences among the 24 traits across different cultivars. Then, using principal component analysis, we identified the key traits related to drought resistance from the original set of indicators. Finally, we employed the membership function method to comprehensively evaluate the drought resistance of different kiwifruit cultivars. 【Results】There are significant differences in leaf morphology, anatomical structure, stomatal apparatus, and the hair of the epidermis among different kiwifruit cultivars. Morphologically, the leaf shape is heart-shaped or oval shaped, leaf length (X1) ranged from 10.94 cm to 17.28 cm, leaf width (X2) ranged from 11.39 cm to 16.35 cm, leaf shape index (X3) ranged from 0.93 cm to 1.06 cm, petiole length (X4) ranged from 6.87 cm to 15.91 cm, petiole diameter (X5) and leaf area (X6) ranged from 3.51 mm to 4.58 mm and from 95.03 cm2 to 208.36 cm2 . For stomatal apparatus, the length (X7) ranged from 18.77μm to 29.21 μm, the width (X8) ranged from 12.64 μm to 18.57 μm, the macroaxis (X9) ranged from 8.46 μm to 16.31 μm, and the density (X10) between 168.70 to 339.63 per square millimeter. In the villi of lower epidermis, all cultivars have fluff, the length (X11) ranged from 249.41 μm~324.10 μm, the pedestal density (X12) between 9.37 to 31.83 pedestals per square millimeter, the villus densit (X13) between 54.93 to 113.95 roots per square millimeter, and the number of villis per pedestal (X14) between 5.57 to 7.30. Anatomical structures, these cultivars have similar anatomical characteristics. The structure of the leaves from the lower epidermis to the upper epidermis is composed of lower epidermal cells, sponge tissue, palisade tissue, and upper epidermal cells. Calcium oxalate crystals are scattered in the mesophyll cells. The leaf veins mainly form protrusions on the lower epidermis, which are vascular bundles, thin-walled tissues, and mechanical tissues from the inside out. Lateral vein diameter (X15) ranged from 595.04 μm to 860.71 μm, leaf thickness (X16) ranged from 177.68 μm to 264.53 μm, thickness of upper epidermis cell (X17) ranged from 15.36 μm to 23.37 μm, the first layer of palisade tissue cell density (X18) between 75.33 to 113.00 per square millimeter, thickness of lower epidermis cell (X19) ranged from 10.03 μm to 20.35 μm, thickness of palisade tissue (X20) ranged from 75.16 μm to 123.60 μm, thickness of spongy tissue (X21) ranged from 49.81μm to85.68μm, the ratio of X20 to X21 (X22) ranged from 1.19 to 2.16, tightness of leaf tissue structure (X23) ranged from 0.41 to 0.52, Looseness of leaf tissue structure (X24) ranged from 0.24 to 0.36. The coefficient of variation (CV) of the 24 traits ranged from 8.04% to 35.80%, and the correlation analysis showed that there were significant or extremely significant correlations among the different traits. Principal component analysis showed that the cumulative contribution rate of the first 7 principal components reached 93.046%, effectively retaining most of the information of the 24 indicators. Eight key drought-resistance indicators were selected, they were X2(leaf width), X3(leaf shape index), X9(macroaxis), X14(number of villis per pedestal), X17(thickness of upper epidermis cell), X19(thickness of lower epidermis cell), X22(thickness of palisade tissue/thickness of spongy tissue), and X23(tightness of leaf tissue structure). Furthermore, the drought resistance of different cultivars was compared by subordinate function method, drought resistance is: ‘Xuxiang’ > ‘Jīn měi’> ‘Jinxia’ > ‘Hayward’ > ‘Jinyan’ > ‘Jinkui’ > ‘Jīn méi’> ‘Donghong’ > ‘Cuiyu’ > ‘Jintao’ > ‘GuihaiNo.4’> Hort16A. 【Conclusion】The differences of leaf morphology, stomata, epidermal hair and anatomical structure of different kiwifruit cultivars were revealed. Leaf width, leaf shape index, stomatal length axis, number of villis per pedestal, thickness of upper epidermis, thickness of lower epidermis cell, thickness of palisade tissue/thickness of spongy tissue, and tightness of leaf tissue structure were selected to evaluate drought resistance. The drought-resistant cultivars such as ‘Xuxiang’, ‘Jinmei’ and ‘Jinxia’ were screened by the method of subordinate function analysis, which provided reference for genetic breeding, variety selection and production management in the future.
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