Association genetics approach to identification of hybrids in pinus contorta - pinus banksiana complex

扭叶松天然杂种的正确鉴定。前大声。和班克夏木（P.banksiana Lamb.）（PCBC）对于评估其进化意义至关重要。尽管几十年来进行了大量的形态学、生物化学和分子生物学研究，但由于两个主要原因，从该杂交区鉴定杂交种仍然很困难。首先，经典的安德森杂种指数或类似的形态测量指数是基于杂种与其亲本物种之间的显著表型差异，但观察到的性状相关性和形态中介性可能源于进化现象（例如，两个孤立物种的祖先种群的残余），而不是杂交本身。其次，缺乏独特的分子标记的亲本基因型和PCBC群体之间的密切的遗传亲和力没有显着提高形态特征的能力，从亲本物种分离杂种。近年来，在包括松树在内的许多物种中发现了大量的单核苷酸多态性（SNP）标记，为全基因组关联研究开辟了新的前景。然而，由于大的基因组大小（约300亿bp）和快速衰减的连锁不平衡（在1000 bp或更快）在异交松，候选基因的方法是更适合这些针叶树。在这个建议中，我将开发一个“准全基因组”的耐旱性的混合指数，从负担得起的和丰富的SNP对明确的识别杂交种和亲本个体和PCBC复杂的人口。我将使用总树高作为替代品，以衡量表型变异之间的36个PCBC种群响应干旱。耐旱性的“准全基因组”杂交指数然后将被预测为在不同混合模型下跨所有SNP标记的基因型（育种）值的总和。拟议的关联遗传学方法来识别杂交种使用最新的混合模型的发展，允许结合信息的适应性性状与SNP标记，因此是一个重要的一步，解决了长期存在的问题的分类和使用的自然杂交种。

Correct identification of natural hybrids between Pinus contorta Dougl. ex Loud. and P. banksiana Lamb. (PCBC) is essential for assessing their evolutionary significance. Despite numerous morphological, biochemical and molecular studies conducted over decades, hybrids identification from this hybrid zone remains difficult for two main reasons. First, classic Anderson's hybrid index or similar morphometric indices are based on marked phenotypic differences between hybrids and their parental species but the observed character correlation and morphological intermediacy could arise from evolutionary phenomena (e.g., remnants of ancestral population of two isolated species) other than hybridization per se. Second, a lack of unique molecular markers for parental genotypes and the close genetic affinity among PCBC populations have not significantly improved the capability of morphological characters to separate hybrids from the parental species. Recent advances in discovery of vast numbers of single nucleotide polymorphism (SNP) markers in many species including pines have raised prospects of genomewide association studies. However, due to the large genome sizes (~30 billion bp) and rapid decay of linkage disequilibrium (within 1000 bp or faster) in outcrossing pines, a candidate gene approach is more appropriate for these conifers. In this proposal, I will develop a 'quais-genomewide' hybrid index for drought tolerance from affordable and abundant SNPs towards unambiguous identification of hybrids and parental individuals and populations in PCBC complex. I will use total tree height as a surrogate to measure phenotypic variation among 36 PCBC populations in response to drought. The 'quasi-genomewide' hybrid index for drought tolerance will be then predicted as the sum of genotypic (breeding) values across all SNP markers under different mixed models. The proposed association genetics approach to identification of hybrids uses the latest mixed-model developments that allow for combining the information of adaptive traits with SNP markers and thus is a major step towards resolving a longstanding issue of classification and use of natural hybrids.