S01 - Session P9 - I - Genetic mapping of the unique photosynthetic stem of the wild almond Prunus arabica (Olivier) Meikle

Authors: Hillel Brukental *, Irit Bar- Ya'akov, Adi Doron-Faigenboim, Rotem Harel Beja, Tamar Azoulay- Shemer, Doron Holland

Almond ( Prunus dulcis (Mill.) D. A. Webb) is a major deciduous fruit tree crop worldwide. During dormancy under warmer temperatures and inadequate chilling hours, the plant metabolic activity increases and may lead to carbohydrate deficiency. P. arabica (Olivier) Meikle is a bushy wild almond species known for its green, unbarked stem, which stays green even during the dormancy period. Our study revealed that P. arabica green stems assimilate significantly high rates of CO 2 during the winter as compared with P. dulcis cv. Um el Fahem (U.E.F), and may improve carbohydrate status throughout dormancy. To uncover the genetic inheritance and mechanism behind the P. arabica Stem Photosynthetic Capability (SPC), a segregating F1 population was generated by crossing P. arabica to U.E.F. The genomes of both parents were sequenced and a single nucleotide polymorphism (SNP) calling identified 4,887 informative SNPs for genotyping. A robust genetic map for U.E.F and P. arabica was constructed (971 and 571 markers, respectively). QTL mapping and association study for the SPC phenotype revealed a major QTL (log of odd (LOD)=20.8) on chromosome 7, and another minor but significant QTL on chromosome 1 (LOD=3.9). As expected, the P. arabica allele in the current loci significantly increased the SPC phenotype. Finally, a list of 73 candidate genes was generated. This work sets the stage for future research on the mechanism regulating the SPC trait, how it affects the tree's physiology, and its importance for breeding new cultivars better adapted to high winter temperatures.