Seed orchards play a critical role in reforestation, but often struggle to consistently produce enough seed. A mixture of the less polar gibberellins, GA₄ and GA₇, has been shown to promote flowering in Pinaceae species, but the responses vary significantly based on species, genotype and provenance, application method, timing and dosage. Previous studies with lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) suggest that the response to exogenous GA_4/7 varied among genotypes. Gibberellins also play a critical role in seed development and germination but it remains unclear how exogenous GA_4/7 will affect seed quality. We used 25 lodgepole pine genotypes in a commercial seed orchard in Alberta, Canada to explore the impact of genotype and geographic origin on the efficacy and optimal timing of GA_4/7 stem injections to promote female cone bud initiation, cones and seed production. Overall, we found that GA_4/7 stem injections promoted female conelets in 40% of genotypes included in this study. For these 10 genotypes, we found that the latitude of their provenance was positively correlated with later effective application times. Of the remaining 15 genotypes, five were hypersensitive to exogenous GA_4/7 showing needle discolouration and loss, and 10 genotypes showed no response. In general, stem-injected GA_4/7 did not affect the number of seeds per cone while two genotypes showed a reduced seed yield and one genotype showed increased seed yield per cone. Seed weights were not affected by the stem-injected GA_4/7, while the July application date resulted in higher germination rates compared to control trees.

中文翻译：

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基因型和亲本来源对黑松种子园GA 4/7茎注射效率和最佳时机的影响

种子园在造林中起着至关重要的作用，但经常难以持续产生足够的种子。极性较小的赤霉素GA ₄和GA ₇的混合物已显示可促进松科植物的开花，但响应因物种，基因型和来源，施用方法，时间和剂量而异。与黑松先前的研究（松扭叶松Dougl。变种宽叶地松）表明，外源GA响应_4/7基因型各不相同。赤霉素在种子发育和发芽中也起着至关重要的作用，但尚不清楚外源GA _4/7如何产生会影响种子质量。我们在加拿大艾伯塔省的一家商业种子园中使用了25种lodgepine松树基因型，以探讨基因型和地理起源对GA _4/7茎注射的功效和最佳时机的影响，以促进雌性锥芽的萌芽，穗和种子的产生。总的来说，我们发现GA _4/7茎注射可促进本研究中40％的基因型的雌性小球状。对于这10个基因型，我们发现其来源的纬度与以后的有效应用时间呈正相关。在其余的15个基因型中，有5个对外源GA _4/7过敏，显示针变色和丢失，还有10个基因型无反应。一般而言，茎注射GA _4/7两种基因型均显示出籽粒产量降低，而一种基因型则显示出每锥粒种子产量的增加。种子重量不受茎注射的GA _4/7的影响，而7月的施用日期导致种子发芽率高于对照树。