DataSheet_1_Genetic Dissection of Bloom Time in Low Chilling Sweet Cherry (Prunus avium L.) Using a Multi-Family QTL Approach.docx

Bloom time in sweet cherry (Prunus avium L.) is a highly heritable trait that varies between genotypes and depends on the environmental conditions. Bud-break occurs after chill and heat requirements of each genotype are fulfilled, and dormancy is released. Bloom time is a critical trait for fruit production as matching cultivar adaptation to the growing area is essential for adequate fruit set. Additionally, low chilling cultivars are of interest to extend sweet cherry production to warmer regions, and for the crop adaptation to increasing winter and spring temperatures. The aim of this work is to investigate the genetic control of this trait by analyzing multiple families derived from the low chilling and extra-early flowering local Spanish cultivar ‘Cristobalina’ and other cultivars with higher chilling requirements and medium to late bloom times. Bloom time evaluation in six related sweet cherry populations confirmed a high heritability of this trait, and skewed distribution toward late flowering, revealing possible dominance of the late bloom alleles. SNP genotyping of the six populations (n = 406) resulted in a consensus map of 1269 SNPs. Quantitative trait loci (QTL) analysis using the Bayesian approach implemented by FlexQTL™ software revealed two major QTLs on linkage groups 1 and 2 (qP-BT1.1m and qP-BT2.1m) that explained 47.6% of the phenotypic variation. The QTL on linkage group 1 was mapped to a 0.26 Mbp region that overlaps with the DORMANCY ASSOCIATED MADS-BOX (DAM) genes. This finding is consistent with peach results that indicate that these genes are major determinants of chilling requirement in Prunus. Haplotype analysis of the linkage group 1 and 2 QTL regions showed that ‘Cristobalina’ was the only cultivar tested that contributed early bloom time alleles for these two QTLs. This work contributes to knowledge of the genetic control of chilling requirement and bloom date and will enable marker-assisted selection for low chilling in sweet cherry breeding programs.

欧洲甜樱桃（Prunus avium L.）的开花期是一项高遗传力性状，其在不同基因型间存在显著差异，同时受环境条件调控。当各基因型满足需冷量与需热量要求后，芽即可萌发，此时休眠亦随之解除。开花期是果品生产的关键性状，因为品种适配栽培区域是保障良好坐果的必要前提。此外，低需冷量品种可助力甜樱桃栽培范围拓展至温暖区域，同时有助于作物适应冬春季气温升高的趋势。本研究旨在通过分析源自西班牙本地低需冷量、极早花品种‘Cristobalina’，以及其他需冷量较高、开花期中晚的品种的多个家系，解析该性状的遗传调控机制。对6个相关甜樱桃群体的开花期鉴定结果证实，该性状具有较高遗传力；群体表型呈偏向晚花的偏态分布，暗示晚花等位基因可能存在显性效应。对6个群体（样本量n=406）进行单核苷酸多态性（Single Nucleotide Polymorphism, SNP）基因分型后，构建了包含1269个SNP标记的整合遗传图谱。利用FlexQTL™软件实现的贝叶斯方法开展数量性状位点（Quantitative Trait Loci, QTL）分析，在第1和第2连锁群上鉴定到2个主效QTL（qP-BT1.1m和qP-BT2.1m），二者可解释47.6%的表型变异。第1连锁群上的QTL被定位至0.26 Mb的基因组区域，该区域与休眠相关MADS-box（DORMANCY ASSOCIATED MADS-BOX, DAM）基因簇重叠。这一发现与桃的相关研究结果一致，后者表明这类基因是李属植物需冷量的主要决定因子。对第1和第2连锁群QTL区域的单倍型分析显示，‘Cristobalina’是供试品种中唯一能为这两个QTL贡献早花等位基因的品种。本研究加深了对甜樱桃需冷量与开花期遗传调控机制的认知，可为甜樱桃育种项目中的低需冷量性状标记辅助选择提供理论支撑。