Graft compatibility between new red apricot cultivars and different Prunus rootstocks

Apricot production is limited by the soil conditions of the different growing Spanish Mediterranean areas, such as heavy, calcareous soils with iron chlorosis and waterlogging problems. Graft incompatibility between most popular Prunus rootstocks and apricot cultivars is also one of the major problems for rootstock usage and improvement. To overcome this problem, a wide array of species have been used as rootstocks, such as apricot, peach, and plum seedlings or interspecific hybrids. However, the introduction of new apricot cultivars and rootstocks requires knowledge of the extent and nature of (in)-compatibility reactions before releasing these cultivars on the market, providing both growers and nurseries with valuable information about the risk of the weakness of the graft interface and breakage of the rootstock/scion union. In this study, the evaluation of graft compatibility was carried out in new red apricot cultivars (6 cultivars introduced by different breeding programs) grafted onto four different 'Prunus' rootstocks, 'Marianna2624' (Prunus cerasifera x Prunus musoniana), 'Miragreen' (Prunus cerasifera x Prunus davidiana), 'Mirared' (P. cerasifera x Nemared) and 'Monctlar' (peach seedling). Phenotyping of graft compatibility was done at different time points, one and three months after grafting and one year after grafting in Mediterranean conditions. Anatomical and cytomorphological characteristics related to graft incompatibility were evaluated for all scion/rootstock combinations. In addition, the induction of the expression of transcripts encoding phenylalanine ammonia-lyase (PAL) was also measured by qRT_PCR. The results highlighted that 'Miragreen' and 'Mirared' might be potential commercial rootstocks for the red apricot industry.