Physiological behavior and nutritional status of almond scion-rootstock combinations in a high-density planting system under warm Mediterranean conditions

Abstract

• High-density planting with new almond cultivars and Prunus rootstocks in warm area. • SPAD and Fv/Fm affected by the scion-rootstock combinations and the monitoring year. • Significant differences in mineral status among almond cultivars on Prunus rootstocks. • DOP analysis demonstrated low values on less vigorous rootstock R40 than Garnem. • R40 suitable for high-density with medium canopy and balanced nutritional status. • Guara, Lauranne and Tuono on R40 best choice for physiological and mineral parameters. Nowadays, the new tendency for a high-density plantings system for almond requires smaller and more efficient canopies. In this way, appropriate scion-rootstock combination is an important factor in adapting to local conditions and specific training systems. This investigation was dedicated to identify the most suitable scion-rootstock combination for high-density planting of almond under warm Mediterranean conditions. Four almond cultivars ‘Lauranne’, ‘Tuono’, ‘Guara’ and ‘Belona’ budded on two Prunus rootstocks ‘Garnem’ and ‘Rootpac-40′ (R40) and planted at 2m×4m spacing were followed for five successive years. Measurements focused on physiological parameters and the mineral foliar analysis. As a result, strong variability between the scion-rootstock combinations of almond was observed. For all surveyed parameters, significant effects of rootstock, cultivar, and year and their interactions were recorded. Less tree vigor was induced by ‘R40’ with similar medium tree vigor obtained with ‘Lauranne’, ‘Tuono’, and ‘Belona’ cultivars, whereas ‘Guara’ performed the lowest vigor. A significant yearly difference in vigor level could be related to local conditions and crop yield with negative impact during warm and drought year. For physiological parameters, SPAD and quantum yield Fv/Fm values were significantly affected by the scion-rootstock combinations and the monitoring year. ‘Belona’ and ‘Tuono’ performed high SPAD and Fv/Fm values on ‘Garnem’ and ‘Lauranne’ and ‘Guara’ showed the high SPAD and Fv/Fm values on ‘R40’. Mineral tree status revealed differences in leaf macronutrient and micronutrient content for almond cultivars on Prunus rootstocks. Optimal macro elements contents ​​were detected for ‘Guara’ and ‘Lauranne’ on ‘R40’. However, variable microelements contents were observed within different combinations. DOP analysis demonstrated low values on ‘R40’ with the best-balanced and highest imbalanced nutritional status (average ∑DOP index) performed by ‘Lauranne’/‘R40’ and ‘Belona’/‘R40’, respectively. In conclusion, less vigorous rootstock ‘R40’ seems to perform well in high-density planting almond orchards in a warm area. Their best performances were associated with ‘Guara’, ‘Lauranne’ and ‘Tuono’. These scion-rootstock combinations inducing size-controlling effect could be considered to implement a new high-density planting system for almond in a warm area.