No abstract

Evolution of almond planted area and production has been mainly due to the arrival of new cultivars and rootstocks that have contributed to improve agronomic characters such as yield, precocity and efficiency. In recent years, are becoming available new cultivars that have contributed to provide late blooming time and self-fertility, and with ease to adapt for mechanical harvest and high-density. However, there is scarcity of studies where the interaction of these new cultivars with hybrid rootstocks has been tested. The aim of this study was to assess the performance of Cadaman ® , Garnem ® , INRA GF-677, IRTA-1, IRTA-2, Ishtara ® , Adesoto, Rootpac ® 20, Rootpac ® 40, and Rootpac ® R rootstocks with two promising almond cultivars such as 'Marinada' and 'Vairo'. Bloom and nut ripening dates were affected by rootstock genotype. Both 'Marinada' and 'Vairo' cultivars showed low biennial bearing, with some differences among rootstocks, with IRTA-2 and Adesoto inducing the lowest values. On the other hand, Adesoto had higher number of suckers than the rest of the rootstocks. Garnem ® provided the biggest trees, followed by Cadaman ® , and then a third group which comprised IRTA-2 and INRA GF-677. Rootpac ® 20 was the most dwarfing rootstock, followed by IRTA-1, Adesoto, Ishtara ® , Rootpac ® R, and Rootpac ® 40. In terms of yield efficiency and partitioning index, IRTA-1, INRA GF-677, and Rootpac ® R were the ones with higher values. Differences in tree volume and vigor for these rootstocks suggested that INRA GF-677 would be a suitable rootstock for low-medium planting densities with wide spacings; whereas Rootpac ® R and IRTA-1 would be suitable rootstocks for medium-and high-density 2 plantings. Findings of this study showed dramatic differences in tree vigor, yield, kernel weight, yield efficiency, and partitioning index, which provide a wide range of options to deem for each cultivar in a particular climate and management.

Red leaf blotch (RLB) of almond, caused by Polystigma amygdalinum, is an important foliar disease of this nut tree in the Mediterranean basin and Middle East regions. In recent years, the incidence of this disease has increased in Spain corresponding to increases in the area of newly-planted orchards and the use of susceptible cultivars. In 2009, an experimental orchard including 21 almond cultivars was planted at Les Borges Blanques, Lleida, NE Spain. No fungicide treatments were applied during the 10-year experimental period (2009-2018) in order to allow natural disease development. Cultivar susceptibility to RLB was assessed each year, from 2011 to 2018, through visual observations of symptoms in naturally-infected trees. The experimental results led us to classify the cultivars into five susceptibility groups. The most susceptible were 'Tarraco', 'Guara', 'Tuono', 'Marinada', 'Desmayo Largueta', and 'Soleta', whereas 'Mardía' was the most tolerant. The annual incidence of disease was positively correlated with accumulated rainfall in spring, and especially in April, while it was negatively correlated with high spring and summer temperatures, especially in May. These findings could be used to improve disease management strategies by identifying the most susceptible cultivars and improving the timing of fungicide application.

No abstract

Red leaf blotch (RLB) disease of almond, caused by Polystigma amygdalinum, is an important foliar disease in most production regions of the Mediterranean basin and the Middle East because severe infections may cause a premature defoliation of the tree. Some key aspects on the epidemiology of P. amygdalinum were studied in multiyear trials in two almond-growing regions in Spain, which included the seasonal development of perithecia and production and germination of ascospores along with the disease incubation and plant infectivity periods. Our results showed that primary inoculum was available in extended periods (January to August). Significant differences in ascospore amounts among regions, higher in the southern Andalusia and lower in the northern Catalonia, and years of study were detected. The factors geographical location, sampling period, and evaluation year were found significant on the development of P. amygdalinum perithecia. Variable ascospore germination rates were observed from April to July: >15% but rarely exceeding 30%. The RLB infectivity period in Catalonia extended from March to mid-June, whereas in Andalusia it was from March to May. The incubation period was mainly in a range of 5 to 10 weeks in Catalonia. The environmental conditions of October to January influence the available ascospore amounts in the next season. RLB infection occurs in spring to summer when mean temperatures are in the range 10 to 20°C. These results represent the first step in developing a prediction model of the disease that might serve as a tool for the control of RLB.