Abstract:

【Objective】 Weedy rice poses a significant threat to rice production in direct-seeded rice fields, resulting in substantial yield losses. Analyzing the occurrence patterns, diversity changes, and genetic evolution of weedy rice populations in these fields is crucial for managing agricultural ecosystems effectively and preventing weedy rice disasters.【Methods】 This study conducted a continuous three-year fixed-site survey of weedy rice populations in new direct-seeded rice field ecosystems. Through targeted sampling, phenotypic characterization, and population genetic structure analysis using liquid chip technology, we examined the scale of damage, ecological types, and genetic diversity evolution of weedy rice populations. 【Results】 In direct-seeded rice fields, the weedy rice population increased annually, with densities of 345.6 plants/m², 512.4 plants/m², and 600.1 plants/m², respectively. Phenotypic diversity showed a consistent upward trend, with Shannon-Wiener (H') indices of 0.530, 0.762, and 0.852, and Simpson (D) indices of 0.340, 0.227, and 0.164. Genetic diversity (Pi) initially increased and then declined over the three years, with values of 0.2097, 0.2530, and 0.1493, respectively. At the population genetic structure level, both principal component analysis (PCA) and phylogenetic tree analysis consistently indicated that weedy rice was not directly related to locally cultivated rice. Weedy rice samples from different years were distributed across major clustering branches. Various types of weedy rice underwent natural selection due to the cold environment and competition with direct-seeded rice, leading to a survival-of-the-fittest scenario. This process results in rapid convergence, increased genetic diversity, alterations in population genetic structure, and the emergence of adaptive types.【Conclusion】 Weedy rice invasion in direct-seeded rice fields leads to rapid population expansion and diversity increase, escalating the disaster index swiftly. Genetic diversity and population genetic structure are highly sensitive to selection pressure, suggesting that harmful adapted weedy rice types are established early in their invasion into direct-seeded rice field ecosystems.

Key words: weedy rice, direct seeded rice, weed infestation, population genetic structure, genetic diversity

摘要：

【目的】 杂草稻造成直播稻田水稻产量损失严重。对直播稻田中杂草稻种群的发生规律、多样性变化和遗传演变的解析，对农田生态系统管理和杂草稻灾害的防控具有重要意义。【方法】 连续三年对新开直播稻田生态系统中杂草稻种群进行追踪调查。通过定点追踪取样、特征表型鉴定和基于液相芯片的群体遗传结构鉴定，分析杂草稻群体的危害规模、生态类型及其遗传多样性演变。【结果】 水稻直播生产方式下杂草稻数量逐年增加，分别为345.6株/m²、512.4株/m²、600.1株/m²。表型多样性也呈逐年上升趋势，香农指数分别为0.530、0.762、0.852；辛普森指数分别为0.340、0.227、0.164。杂草稻群体的基因多样性（Pi）在三年间呈现先升高后降低的趋势，分别为0.2097、0.2530、0.1493。在群体遗传结构层面，主成分分析与进化树分析结果均显示杂草稻与当地种植的栽培稻没有直接的亲缘关系。不同年度间采集的杂草稻样品在各大聚类分支上均有分布。不同类型杂草稻在高纬度冷凉环境以及与直播稻竞争的双重选择压力下优胜劣汰，导致群体遗传多样性增加后迅速收敛，群体遗传结构随之改变，适应性类型崛起。【结论】 在直播稻新开田生态系统中，杂草稻入侵后群体规模与多样性迅速上升，导致灾害指数迅速增加。基因多样性与群体遗传结构对选择压力高度敏感，产生危害的适应类型杂草稻在入侵直播稻田生态系统伊始就已经奠定。

关键词: 杂草稻, 直播稻, 草害, 群体遗传结构, 遗传多样性