Vigor assessment of juvenile rubber tree clones in Northwestern São Paulo State, Brazil

ABSTRACT Besides rubber production, one of the main goals of the genetic improvement of rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.] is to develop vigorous clones. The objective of the present study was to evaluate the vigor of 34 elite juvenile rubber clones. To this end, three experiments were conducted in the municipality of Pontes Gestal, in the northwest region of the São Paulo State. Each experiment consisted of 10 treatments, and 2 controls in common to the 3 experiments. The experiments were arranged in the randomized block design, with three replications and ten plants per plot, in the 8 m x 2.5 m spacing. Individual and joint analyses of variance were performed. The means were compared using the Dunnett test at 5%. Significant effect of treatments was found in the three experiments and in the joint analysis. The most vigorous clones were not different from the controls in the comparison of means by the individual and joint analyses. The less vigorous clones were statistically different from the others and from the controls, reflecting this difference in the genetic variability observed. The breeding program must consider the lack of difference between the most vigorous clones and the controls when recombining superior clones, since genetic gain depends on variability.摘要：除橡胶生产外，巴西橡胶树（Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.）遗传改良的核心目标之一是培育高活力无性系（clone）。本研究旨在评估34个优良幼龄橡胶无性系的活力表现。为此，研究于圣保罗州西北部蓬蒂斯赫斯塔尔（Pontes Gestal）市开展了三组试验。每组试验包含10个处理，另有2个对照为三组试验共用。试验采用随机区组设计，设置3次重复，每小区种植10株植株，株行距为8 m × 2.5 m。本研究分别进行了单试验方差分析与联合方差分析，并采用Dunnett检验在5%显著性水平下对均值进行多重比较。三组单试验及联合方差分析均检测到处理间存在显著效应。单试验与联合均值比较结果显示，高活力无性系与对照间无显著差异。低活力无性系与其余无性系及对照均存在统计学差异，该结果反映了试验中观测到的遗传变异水平。由于遗传增益依赖于遗传变异，在开展优良无性系重组时，橡胶树遗传改良项目需考虑高活力无性系与对照间无显著差异这一现状。