Abstract The factors responsible for yield progress can be analysed through yield determinant frameworks. These conceptual models consider factors such as crop growth dynamics, partitioning of vegetative and reproductive biomass and yield components to provide insights into the factors responsible for observed genetic gains and opportunities for future gains. The aim of this study was to use direct cultivar comparison to assess the rate of genetic gain in the CSIRO (Australia) cotton breeding program, and to understand how factors within a conceptual yield determinant framework relate to yield performance. Using field experimentation, yield progress of 16.1 kg lint ha−1 y−1 was observed in ten cultivars released between 1968 and 2012. This study identified that selection pressure has resulted in improvements in total dry matter (TDM), harvest index (HI), lint percentage and carbon assimilation. While gains have been made in these four parameters, improvements in lint yield have largely been driven by altering HI through increasing lint percentage. Although improvements have been made in TDM, the reproductive allocation of total biomass and the amount and efficiency of light capture has not been altered in modern cultivars. Future gains in lint yield will require the concurrent maintenance of harvest index while producing larger plants with more fruiting branches that capture more incident radiation with increased efficiency. As the collection of phenotype data such as biomass, boll number, boll size and radiation use efficiency at the scale required in a commercial breeding program is largely aspirational, we conclude in the short term improvements may be achieved through direct selection for yield. Future efforts should be placed in increasing early season growth rates, and in the longer term enhancing carbon assimilation rates. Importantly, due to trait associations and the effects of trade-offs between functional components, factors within a conceptual framework must not be considered in isolation.

中文翻译：

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导致陆地棉新品种产量提高的因素

摘要 影响产量进展的因素可以通过产量决定因素框架进行分析。这些概念模型考虑了作物生长动态、营养和繁殖生物量的划分以及产量成分等因素，以深入了解导致观察到的遗传收益和未来收益机会的因素。本研究的目的是使用直接品种比较来评估 CSIRO（澳大利亚）棉花育种计划中的遗传增益率，并了解概念性产量决定因素框架内的因素如何与产量表现相关。通过田间试验，在 1968 年至 2012 年间发布的 10 个栽培品种中观察到 16.1 kg 皮棉 ha−1 y−1 的产量进展。这项研究确定选择压力导致总干物质 (TDM) 的改善，收获指数 (HI)、皮棉百分比和碳同化。虽然在这四个参数方面取得了进步，但皮棉产量的提高主要是通过增加皮棉百分比来改变 HI 的。尽管在 TDM 中进行了改进，但现代栽培品种中总生物量的繁殖分配以及光捕获的数量和效率并未改变。皮棉产量的未来收益将需要同时保持收获指数，同时生产具有更多果枝的更大植物，以更高的效率捕获更多入射辐射。由于商业育种计划所需规模的生物量、铃数、铃大小和辐射利用效率等表型数据的收集在很大程度上是有抱负的，我们得出的结论是，短期内可以通过直接选择产量来实现改进。未来的努力应该放在提高早季增长率，并从长远来看提高碳同化率。重要的是，由于特征关联和功能组件之间权衡的影响，不能孤立地考虑概念框架内的因素。