Phenylalanine ammonia-lyase gene expression in apricot cultivars grafted onto different Prunus rootstocks

The incorporation of new apricot cultivars from foreign sources in diverse Spanish regions need the study of their environmental adaptation and graft compatibility behavior with different roostocks. Grafting compatibility with new scion cultivars has a direct impact on different tree characteristics such as yield, fruit quality, efficiency and premature mortality of trees. Hence, the fast evaluation of the relationship between scion and rootstock before releasing new cultivars on the market is very important to increase the efficiency. In this study, the determination of graft compatibility was carried out in 13 cultivars introduced by different breeding programs, grafted onto two different Prunus rootstocks, 'Marianna2624' (Prunus cerasifera × Prunus musoniana) and 'Miragreen' (Prunus cerasifera × Prunus davidiana). Vegetative parameters (graft length, number of leaves) and the analysis of the phenylalanine ammonia-lyase (PAL) gene expression were performed in the different grafting combinations three months after grafting. It is known that PAL genes (PAL1 and PAL2) were differentially regulated under the stock-scion interactions between graft partners of different degree of compatibility. The results obtained showed a lower graft growth and higher expression level of PAL1 for the cultivars grafted on the rootstock 'Marianna2624' in comparison to 'Miragreen' which indicated a higher level of enzymatic activity and a higher level of incompatibility. The results will provide knowledge about the state of the unions at early stages of development providing information about the most suitable combinations to establish in the field.