Edwards Christine E, Ewers Brent E, Weinig Cynthia
Department of Botany, University of Wyoming, Laramie, WY, 82071, USA.
Current Address: Center for Conservation and Sustainable Development, Missouri Botanical Garden, PO Box 299, St. Louis, MO, 63166, USA.
BMC Plant Biol. 2016 Aug 24;16(1):185. doi: 10.1186/s12870-016-0876-3.
Plant performance in agricultural and natural settings varies with moisture availability, and understanding the range of potential drought responses and the underlying genetic architecture is important for understanding how plants will respond to both natural and artificial selection in various water regimes. Here, we raised genotypes of Brassica rapa under well-watered and drought treatments in the field. Our primary goal was to understand the genetic architecture and yield effects of different drought-escape and dehydration-avoidance strategies.
Drought treatments reduced soil moisture by 62 % of field capacity. Drought decreased biomass accumulation and fruit production by as much as 48 %, whereas instantaneous water-use efficiency and root:shoot ratio increased. Genotypes differed in the mean value of all traits and in the sensitivity of biomass accumulation, root:shoot ratio, and fruit production to drought. Bivariate correlations involving gas-exchange and phenology were largely constant across environments, whereas those involving root:shoot varied across treatments. Although root:shoot was typically unrelated to gas-exchange or yield under well-watered conditions, genotypes with low to moderate increases in root:shoot allocation in response to drought survived the growing season, maintained maximum photosynthesis levels, and produced more fruit than genotypes with the greatest root allocation under drought. QTL for gas-exchange and yield components (total biomass or fruit production) had common effects across environments while those for root:shoot were often environment-specific.
Increases in root allocation beyond those needed to survive and maintain favorable water relations came at the cost of fruit production. The environment-specific effects of root:shoot ratio on yield and the differential expression of QTL for this trait across water regimes have important implications for efforts to improve crops for drought resistance.
植物在农业和自然环境中的表现会因水分可利用性而有所不同，了解潜在干旱响应范围及其潜在的遗传结构对于理解植物在不同水分条件下如何响应自然选择和人工选择至关重要。在此，我们在田间对白菜型油菜的基因型进行了充分浇水和干旱处理。我们的主要目标是了解不同干旱逃避和脱水避免策略的遗传结构及产量效应。
干旱处理使土壤湿度降至田间持水量的62%。干旱使生物量积累和果实产量降低多达48%，而瞬时水分利用效率和根冠比增加。所有性状的平均值以及生物量积累、根冠比和果实产量对干旱的敏感性在基因型间存在差异。涉及气体交换和物候的双变量相关性在不同环境下基本保持不变，而涉及根冠比的相关性在不同处理间有所变化。尽管在充分浇水条件下根冠比通常与气体交换或产量无关，但在干旱条件下根冠比分配有低到中等增加的基因型在生长季节存活下来，维持了最大光合作用水平，并且比根分配最大的基因型结出更多果实。气体交换和产量构成因素（总生物量或果实产量）的QTL在不同环境下具有共同效应，而根冠比的QTL往往具有环境特异性。
根分配增加到超过生存和维持良好水分关系所需的水平是以果实产量为代价的。根冠比对产量的环境特异性影响以及该性状的QTL在不同水分条件下的差异表达对于改良作物抗旱性的努力具有重要意义。
