Herrera Sara, Lora Jorge, Fadón Erica, Hedhly Afif, Alonso José Manuel, Hormaza José I, Rodrigo Javier
Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Departamento de Ciencia Vegetal, Zaragoza, Spain.
Instituto Agroalimentario de Aragón-IA2 (CITA-Universidad de Zaragoza), Zaragoza, Spain.
Front Plant Sci. 2022 Apr 7;13:842333. doi: 10.3389/fpls.2022.842333. eCollection 2022.
Dormancy is an adaptive strategy in plants to survive under unfavorable climatic conditions during winter. In temperate regions, most fruit trees need exposure to a certain period of low temperatures to overcome endodormancy. After endodormancy release, exposure to warm temperatures is needed to flower (ecodormancy). Chilling and heat requirements are genetically determined and, therefore, are specific for each species and cultivar. The lack of sufficient winter chilling can cause failures in flowering and fruiting, thereby compromising yield. Thus, the knowledge of the chilling and heat requirements is essential to optimize cultivar selection for different edaphoclimatic conditions. However, the lack of phenological or biological markers linked to the dormant and forcing periods makes it difficult to establish the end of endodormancy. This has led to indirect estimates that are usually not valid in different agroclimatic conditions. The increasing number of milder winters caused by climatic change and the continuous release of new cultivars emphasize the necessity of a proper biological marker linked to the endo- to ecodormancy transition for an accurate estimation of the agroclimatic requirements (AR) of each cultivar. In this work, male meiosis is evaluated as a biomarker to determine endodormancy release and to estimate both chilling and heat requirements in apricot. For this purpose, pollen development was characterized histochemically in 20 cultivars over 8 years, and the developmental stages were related to dormancy. Results were compared to three approaches that indirectly estimate the breaking of dormancy: an experimental methodology by evaluating bud growth in shoots collected periodically throughout the winter months and transferred to forcing chambers over 3 years, and two statistical approaches that relate seasonal temperatures and blooming dates in a series of 11-20 years by correlation and partial least square regression. The results disclose that male meiosis is a possible biomarker to determine the end of endodormancy and estimate AR in apricot.
休眠是植物在冬季不利气候条件下生存的一种适应性策略。在温带地区，大多数果树需要经历一定时期的低温才能打破内休眠。内休眠解除后，需要温暖的温度才能开花（生态休眠）。需冷量和需热量是由基因决定的，因此，每种物种和品种都有其特定的需求。缺乏足够的冬季低温会导致开花和结果失败，从而影响产量。因此，了解需冷量和需热量对于优化不同土壤气候条件下的品种选择至关重要。然而，由于缺乏与休眠期和催芽期相关的物候或生物学标记，难以确定内休眠的结束。这导致了间接估计，而这些估计在不同的农业气候条件下通常是无效的。气候变化导致暖冬数量增加，以及新品种的不断推出，凸显了需要一个与内休眠向生态休眠转变相关的合适生物学标记，以便准确估计每个品种的农业气候需求（AR）。在这项研究中，将雄配子减数分裂评估为一种生物标志物，用于确定杏树内休眠的解除以及估计需冷量和需热量。为此，在8年时间里对20个品种的花粉发育进行了组织化学特征分析，并将发育阶段与休眠相关联。将结果与三种间接估计休眠打破的方法进行了比较：一种是通过评估整个冬季定期采集的嫩枝上的芽生长情况，并在3年时间里将其转移到催芽室中的实验方法，以及两种通过相关性和偏最小二乘回归将11 - 20年系列中的季节温度和开花日期联系起来的统计方法。结果表明，雄配子减数分裂是确定杏树内休眠结束和估计农业气候需求的一种可能的生物标志物。
