Graft Incompatibility Influence on Assimilating Pigments and Soluble Sugars Amount of some Pear (Pyrus sativa) Cultivars

Graft incompatibility in fruit trees is one of the greatest obstacles in rootstocks and cultivars breeding. The mechanism in which incompatibility is expressed is not yet fully understood and several hypotheses have been advanced in an attempt to explain it. In many cases (pear on quince grafts, apricot on Prunus grafts), incompatibility is manifested by the breaking of the trees at the point of the union particularly when they have been growing for some years. Many reports focus on this problem in order to understand the mechanisms of graft development. These reports refer to both cytological and biochemical responses occurring at an early phase in response to grafting, as well as to the consequences of these events on the future graft response. In this experiment, we tried to highlight how affinity between scion and rootstock can influence the photosynthetic apparatus and carbohydrates synthesis. The results showed that grafting affinity has an influence on total assimilating pigments content. Thus, on the pear cultivars grafted on an incompatible rootstock (cultivars/Cydonia oblonga) the total pigments content ratio (reported to the ungrafted rootstock) ranged between 0.58 and 0.69. However, the combinations had a ratio ranging between 0.79 and 0.98. Nevertheless, the assimilating pigments ratio reduction had no influence on photosynthetic rate. The soluble sugars amount was close in both variants (cultivars/Cydonia oblonga and cultivars/Pyrus sativa).