American chestnut (Castanea dentata) was a foundation species in the eastern United States until chestnut blight (Cryphonectria parasitica) infestation resulted in range-wide catastrophic reduction. Since 1983, The American Chestnut Foundation (TACF) has engaged in a breeding program aimed at restoring C. dentata to the wild. The primary goal has been to introduce blight resistance from Castanea mollissima while recovering a C. dentata phenotype via successive backcrosses. To diversify the genetic base, state chapters of TACF have been producing BC₃ and BC₄ (third and fourth backcross) lines using C. dentata from across its native range. This study focuses on morphology and chemistry of seeds, and morphology and early growth of seedlings derived from BC₃ and BC₄ trees selected for blight resistance in state chapters. Our primary comparisons were among backcross, pure C. mollissima, and pure C. dentata lines. Seed traits included a suite of morphological characters known to differ between C. dentata and C. mollissima, as well as dry matter, total carbohydrate, sugar, protein, lipid, and phenolic content. Seedling traits included variables such as stem basal diameter and height, leaf variables such as number and area, and relative growth in key parameters such as stem volume. C. mollissima lines tended to differ significantly from C. dentata and backcross lines in most parameters, while C. dentata and backcross types tended to overlap broadly in traits. These results suggest that seed and seedling characteristics of backcross hybrids studied here are likely to be sufficiently similar to C. dentata for use in restoration programs.

中文翻译：

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从回交抗性育种程序得出的杂交栗（Castanea spp。）种子和幼苗特征

美洲栗（Castanea dentata）是美国东部的基础物种，直到栗疫病（Cryphonectria parasitica）侵袭导致全范围的灾难性减少。自1983年以来，美国栗子基金会（TACF）从事了一项旨在将齿齿衣原恢复到野外的育种计划。主要目标是从栗木中引入抗白叶枯病，同时通过连续回交恢复齿状念珠菌表型。为了使遗传基础多样化，TACF的各州分会一直在使用齿状念珠菌生产BC ₃和BC ₄（第三回交和第四回交）品系。来自其本地范围。这项研究的重点是种子和种子的形态和化学性质，以及在各州章节中从抗白叶枯病的BC ₃和BC ₄树中选出的幼苗的形态和早期生长。我们的主要比较是回交，纯色梭状芽孢杆菌和纯齿状芽孢杆菌。种子性状包括一组齿状C. dentata和C. mollissima之间不同的形态特征，以及干物质，总碳水化合物，糖，蛋白质，脂质和酚类含量。幼苗性状包括变量，例如茎基部直径和高度，叶片变量，例如数量和面积，以及关键参数的相对生长，例如茎体积。在大多数参数上，C。mollissima品系趋向于与C. dentata和回交品系显着不同，而C. dentata和回交品型在性状上趋于广泛重叠。这些结果表明，本文研究的回交杂种的种子和幼苗特征可能与齿形衣原体足够相似，可用于恢复程序。