CIRAD, UMR AGAP, F-33612 Cestas, France.
BMC Plant Biol. 2013 Aug 26;13:120. doi: 10.1186/1471-2229-13-120.
The genetic basis of growth traits has been widely studied in forest trees. Quantitative trait locus (QTL) studies have highlighted the presence of both stable and unstable genomic regions accounting for biomass production with respect to tree age and genetic background, but results remain scarce regarding the interplay between QTLs and the environment. In this study, our main objective was to dissect the genetic architecture of the growth trajectory with emphasis on genotype x environment interaction by measuring primary and secondary growth covering intervals connected with environmental variations.
Three different trials with the same family of Eucalyptus urophylla x E. grandis hybrids (with different genotypes) were planted in the Republic of Congo, corresponding to two QTL mapping experiments and one clonal test. Height and radial growths were monitored at regular intervals from the seedling stage to five years old. The correlation between growth increments and an aridity index revealed that growth before two years old (r = 0.5; 0.69) was more responsive to changes in water availability than late growth (r = 0.39; 0.42) for both height and circumference. We found a regular increase in heritability with time for cumulative growth for both height [0.06 - 0.33] and circumference [0.06 - 0.38]. Heritabilities for incremental growth were more heterogeneous over time even if ranges of variation were similar (height [0-0.31]; circumference [0.19 to 0.48]). Within the trials, QTL analysis revealed collocations between primary and secondary growth QTLs as well as between early growth increments and final growth QTLs. Between trials, few common QTLs were detected highlighting a strong environmental effect on the genetic architecture of growth, validated by significant QTL x E interactions.
These results suggest that early growth responses to water availability determine the genetic architecture of total growth at the mature stage and highlight the importance of considering growth as a composite trait (such as yields for annual plants) for a better understanding of its genetic bases.
生长性状的遗传基础已在林木中得到广泛研究。数量性状位点（QTL）研究强调了存在稳定和不稳定的基因组区域，这些区域与树木年龄和遗传背景有关，但关于 QTL 与环境之间的相互作用，结果仍然很少。在这项研究中，我们的主要目标是通过测量与环境变化相关的间隔内的初生和次生生长，剖析生长轨迹的遗传结构，重点关注基因型与环境互作。
在刚果共和国种植了具有相同桉树杂交种（不同基因型）的三个不同试验，对应于两个 QTL 作图实验和一个无性系试验。从幼苗阶段到五岁，定期监测高度和径向生长。生长增量与干旱指数之间的相关性表明，两岁之前的生长（r = 0.5；0.69）比后期生长（r = 0.39；0.42）对水分供应变化的响应更大，无论是高度还是周长。我们发现，对于高度[0.06-0.33]和周长[0.06-0.38]，累积生长的遗传力随时间呈规律增加。增量生长的遗传力随时间变化更加不均匀，即使变化范围相似（高度[0-0.31]；周长[0.19 至 0.48]）。在试验内，QTL 分析揭示了初生和次生生长 QTL 之间以及早期生长增量和最终生长 QTL 之间的空间定位。在试验之间，检测到很少的共同 QTL，强调了环境对生长遗传结构的强烈影响，这通过显著的 QTL x E 互作得到验证。
这些结果表明，早期生长对水分供应的响应决定了成熟阶段总生长的遗传结构，并强调了将生长视为复合性状（如一年生植物的产量）的重要性，以更好地理解其遗传基础。
