粟种子和花序的新发现揭示粟在传播中的表型分异

New empirical evidence from ancient foxtail millet seeds and panicles reveals phenotype divergence during its dispersal

晚全新世粟的传播是史前食品全球化的重要组成部分,对欧亚大陆农业生产体系、先民食物组成以及文明发展进程产生深远影响.但是粟传播的时间、路线和模式并不清晰,而且很少有研究涉及粟在传播过程中表型对新环境的响应和适应,以及这类表型变化可能产生的农业效应.本文根据245个粟直接测年数据的贝叶斯年代模型分析结果,提出粟向我国西部传播的"西北线"和"西南线",明确粟非"波浪式推进"的传播模式.分析有明显降水梯度的28个遗址中12977粒成熟炭化粟种子的测量值,发现距今5165年以来粟在适应不同降水背景下,各遗址间种子群体存在复杂的无规律的差异,但总体上种子尺寸和形状中值波动较小,缺乏指向性变化趋势,基于此提出该时间段粟产量增加主要依靠种子粒数增加而非单粒种子尺寸增大的新认识.另外,遗址五堡和米兰干燥粟种子测量结果也支持种子表型性状多样化但总体相对稳定的结论.但五堡粟花序尺寸小,呈直立柱状,而米兰粟花序大,呈纺锤弯曲形态,有复杂的分枝结构.这些被发现的完整干燥粟花序,突破了以往只依靠种子来推测粟表型多样化表现的有限认识,为揭示粟表型分化及其产生的农业效应提供了极为关键的实证材料.

Foxtail millet is one of the earliest domesticated cereal crops in the world.Its domestication has been traced back to the early Holocene(10,000–8000 cal a BP),first appearing in the basins of the Yellow River and Western Liao River[1].Dryland farming dominated by foxtail millet was ultimately established in the Central Plains during the middle Holocene(6000–5500 cal a BP)[2].This agricultural system served as the vital subsistence basis for demographic growth,a rise in urbanization,and the formation and continuous development of Chinese civilization.This cereal had traditionally been a major and valuable staple-food crop in northern China.In the late Holocene,along with human migration and innovative agricultural technology communication,foxtail millet cultivation expanded outward on a large scale and to a wide range of new habitats far away from its original center of domestication[3].