Departamento de Ciências Agrárias, Ambientais e Biológicas, Universidade Federal do Recôncavo da Bahia, Cruz das Almas, Bahia, Brazil.
Departamento de Fitossanidade, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista "Júlio de Mesquita Filho, Jaboticabal, São Paulo, Brazil.
PLoS One. 2020 May 20;15(5):e0233014. doi: 10.1371/journal.pone.0233014. eCollection 2020.
Citrus trees produce flushes throughout the year, but there are no criteria established for a precise shoot monitoring in orchards under tropical climate. Methods for quantification of flush dynamics would be useful for horticultural and pest management studies because different insect vectors feed and reproduce on flushes. We estimated the minimum number and distribution of trees for sampling and determined the flushing pattern over time in 'Valencia Late' orange trees grafted onto 'Swingle' citrumelo rootstock. Shoots within a square frame (0.25 m2) on two sides of the canopy were counted and classified by their phenological stage. The minimum number of samples was estimated using the mean number of shoots and area under the flush shoot dynamics (AUFSD). The temporal and spatial distribution analysis was performed by Taylor's power law and by multiple correspondence analysis (MCA). Additionally, a shoot maturity index (SMI) based on visual qualitative assessment of flushes is proposed. Considering the mean number of shoots, it was necessary to sample two sides of 16 trees to reach a relative sampling error (Er) of 25%, whereas by the AUFSD, only five trees were necessary to reach an Er of 10%. Flushes were predominantly randomly distributed over time and space. Testing eight transects, sampled trees should be distributed throughout the block, avoiding sampling concentration in a certain area. MCA showed that the west side and the upper sampling positions of trees were more likely to be associated with younger shoots. AUFSD and the evaluation of both sides of the canopy yielded a smaller number of trees to be assessed. The SMI was a reliable metric to estimate the shoot phenology of orange trees, and correlated well (R2 > 70%) with the mean number of shoots within the square frame. Therefore, SMI has the potential to make shoot monitoring in the field more practical.
柑橘树全年都会抽梢，但在热带气候条件下，果园内还没有精确梢监测的标准。对抽梢动态进行量化的方法将有助于园艺和害虫管理研究，因为不同的昆虫传播媒介在抽梢上取食和繁殖。我们估计了采样所需的最小树木数量和分布，并确定了‘瓦伦西亚晚’甜橙嫁接到‘斯维格’克里曼丁橘砧木上的树体随时间的抽梢模式。在树冠两侧的正方形框架（0.25 平方米）内计算并按物候阶段对嫩梢进行分类。使用嫩梢动态的平均数量和面积（AUFSD）来估计最小样本量。通过泰勒幂定律和多元对应分析（MCA）进行时间和空间分布分析。此外，还提出了基于嫩梢视觉定性评估的嫩梢成熟指数（SMI）。考虑到平均嫩梢数量，需要对 16 棵树的两侧进行采样，才能达到相对采样误差（Er）为 25%，而根据 AUFSD，只需对 5 棵树进行采样，就能达到 Er 为 10%。抽梢在时间和空间上主要呈随机分布。通过测试 8 个样带，应在整个小区内分布采样树，避免在某个区域集中采样。MCA 表明，西侧面和树冠上部的采样位置更有可能与较年轻的嫩梢相关。AUFSD 和树冠两侧的评估产生了更少的树木需要进行评估。SMI 是一种可靠的指标，可以估计甜橙的嫩梢物候，与正方形框架内的平均嫩梢数量相关性很好（R2 > 70%）。因此，SMI 有可能使田间嫩梢监测更加实用。
