旱地小麦理想株型与生长冗余

自1968年Donald提出作物理想株型(ideotype)以来,众多学者在如何减少生长冗余、塑造理想株型方面做了大量努力,在旱地小麦育种策略和栽培管理模式创新方面取得了一定进展。而该方面的进展有限,不同领域的研究者对理想株型和生长冗余的认识存在严重分歧。综述了近年来旱地小麦理想株型研究进展,以过去20年黄土高原雨养农业区的观测数据为主进行了集成分析,将产量分别与根系生物量、地上生物量和株高等指标进行回归分析,勾画了旱地小麦在根系、茎秆和分蘖等器官中生长冗余的演变趋势,对生长冗余产生的生态学机制展开了分析,并对理想株型与生长冗余的互作关系进行了讨论。已有的研究进展表明,旱地小麦理想株型演变是一个不断消减生长冗余,但又无法完全消除冗余的复杂过程,一定程度的冗余存在是理想株型发生的物质基础。旱地小麦理想株型育种必须以基因型和环境互作关系为基础,通过减少个体间的竞争强度和个体大小不整齐性,促进物质和能量更多地向籽粒迁移,最终提高种群产量。综上所述,旱地小麦理想株型选择需建立在生长冗余理论基础上,根据生态学基本原理对基因型和表现型进行耦合分析与选择权衡。

Plant ideotype and growth redundancy in dryland wheats

Since Donald proposed ideotype breeding in 1968, agronomists and breeders have endeavoured to develop ideotype-oriented breeding methods to improve the dryland wheat production. Several scholars have discussed methods to reduce growth redundancy and improve the ideotype of crops, and have made some progress on dryland wheat breeding strategies and model innovation for cultivation management. Nevertheless, the evaluation of crop ideotype is not the same in different ecological zones, and progress on a specific crop ideotype for a particular ecological zone is not universally accepted. In this paper, the recent progress in ideotype research for the dryland wheat is reviewed and the evolutionary trend in growth redundancy in roots, stems and tiller number studied. At the same time, based on the data that has been collected under rainfed agricultural systems on Loess Plateau over the past two decades, we conducted regression analysis between root biomass, above-ground biomass, height and yield. On the Loess Plateau, spring wheat still has a high root/shoot ratio and removal of some root biomass can improve seed production, implying that there is a high incidence of growth redundancy in modern crop cultivars. The excessive growth of individual organs results in decreased yields. Further ecological mechanism of growth redundancy and interaction between ideotype and growth redundancy were also discussed. Research has shown that growth redundancy can be gradually eliminated in ideotype succession process, but can''t be completely eliminated. A certain extent of the growth redundancy is the basic material for the ideotype. Over the long course of evolution from wild diploid and tetraploid, to modern hexaploid genotypes, spring wheat has been evolving from the high root/shoot ratio to the low root/shoot ratio, and this crop type could contribute to the increased yield of hexaploid wheat. We point out that the direction of dryland wheat ideotype breeding in the future should focus on the interaction between genotype of the wheat and its environment, reducing the intensity of competition among individuals and size inequality, promoting photosynthesis products that are deposited in the grain, and finally improving the population production. In summary, the interaction between a dryland wheat ideotype and growth redundancy is very complex. Selecting a dryland wheat ideotype should be based on the growth redundancy theory. Future breeding should be based on the basic principles of ecology, coupling the genotype and phenotype of dryland wheat, and then trade-off selection. The research focuses should move from research dealing with drought-resistance physiological genetics to the current ones dealing with crops ideotype. We believe that the theoretical and applied perspectives for the improvement of wheat production in the future will encompass the following: (1) The combination of the various morphological-physiological traits into one plant type; (2) The increase in the above-ground biomass and hence harvest index by selecting for small root systems and optimum resource allocation patterns; and (3) Selection and maintenance of weak competitors in population. Finally, the cooperative strategy that maximizes the population''s grain production, although clearly desirable in agriculture, is not evolutionarily stable.