Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz, 45662-000 Ilhéus, BA, Brazil.
Tree Physiol. 2010 Jan;30(1):56-67. doi: 10.1093/treephys/tpp101. Epub 2009 Dec 3.
In soil, anoxia conditions generated by waterlogging induce changes in genetic, morphological and physiological processes, altering the growth and development of plants. Mass propagation of cacao (Theobroma cacao L.) plantlets (clones) is affected by waterlogging caused by heavy rains and irrigation methods used to induce rooting. An experiment was undertaken to assess the effects of a 45-day flooding (anoxia) on physiological and morphological traits of 35 elite cacao genotypes, aiming at potentially identifying those with greater tolerance to flooding of the growth substrate. Eighteen fluorochrome-labeled microsatellite (SSR) primer pairs were used to assess genetic variability among clones, with 248 alleles being amplified and used to calculate similarity coefficients. The resulting dendrogram indicated the presence of four major groups, in which two represented 60% and 31% of the genotypes tested. A general trend toward high levels of heterozygosity was also found for physiological and morphological traits. The survival index (IS) for flood tolerance observed varied from 30 to 96%. Clones TSA-654, TSA-656, TSA-792, CA-1.4, CEPEC-2009 and PH-17 showed an IS value above 94%, whereas CEPEC-2010, CEPEC-2002, CA-7.1 and VB-903 clones were those mostly affected by waterlogging, with IS value below 56%. All genotypes displayed lenticel and adventitious root formation in response to waterlogging, although with different intensities. To determine whether patterns of physiological response could be associated with tolerance to anoxia, a similarity-grouping analysis was performed using the ratio between waterlogged and control values obtained for a series of physiological variables assessed. No specific pattern of physiological and morphological responses to waterlogging was strictly associated with survival of plantlets. However, results revealed by the dendrogram suggest that absence of leaf chlorosis may be a proper trait to indicate cacao clones with higher survival rates under flooding conditions. Consequences of these findings are discussed in the context of developing improved strategies for mass production of clones from elite cacao genotypes.
在土壤中，由积水引起的缺氧条件会导致遗传、形态和生理过程发生变化，从而改变植物的生长和发育。可可（Theobroma cacao L.）无性系（克隆）的大规模繁殖受到大雨引起的积水和用于诱导生根的灌溉方法的影响。进行了一项实验，以评估 45 天的水淹（缺氧）对 35 个精英可可基因型的生理和形态特征的影响，目的是潜在地鉴定那些对生长基质水淹具有更高耐受性的基因型。使用 18 对荧光标记的微卫星（SSR）引物对克隆进行遗传变异评估，扩增了 248 个等位基因，并用于计算相似系数。生成的聚类树状图表明存在四个主要组，其中两组代表了测试的基因型的 60%和 31%。还发现生理和形态特征的杂合度水平普遍较高。观察到的耐水淹生存指数（IS）变化范围为 30%至 96%。TSA-654、TSA-656、TSA-792、CA-1.4、CEPEC-2009 和 PH-17 等克隆的 IS 值高于 94%，而 CEPEC-2010、CEPEC-2002、CA-7.1 和 VB-903 克隆受水淹影响最大，IS 值低于 56%。所有基因型在水淹时都会形成皮孔和不定根，尽管强度不同。为了确定生理反应模式是否与对缺氧的耐受性相关，使用聚类分析对一系列评估的生理变量的水培和对照值之间的比值进行了相似性分组分析。没有特定的生理和形态对水淹的反应模式与幼苗的存活严格相关。然而，聚类树状图的结果表明，叶片失绿的缺失可能是一个合适的特征，表明在水淹条件下具有更高存活率的可可克隆。讨论了这些发现对开发从精英可可基因型大规模生产克隆的改进策略的影响。
