Abstract
Two hundred and twenty-five Diaporthe isolates were collected from 2005 to 2019 in almond orchards showing twig cankers and shoot blight symptoms in five different regions across Spain. Multilocus DNA sequence analysis with five loci (ITS, tub, tef-1α, cal and his), allowed the identification of four known Diaporthe species, namely: D. amygdali, D. eres, D. foeniculina and D. phaseolorum. Moreover, a novel phylogenetic species, D. mediterranea, was described. Diaporthe amygdali was the most prevalent species, due to the largest number of isolates (85.3%) obtained from all sampled regions. The second most frequent species was D. foeniculina (10.2%), followed by D. mediterranea (3.6%), D. eres and D. phaseolorum, each with only one isolate. Pathogenicity tests were performed using one-year-old almond twigs cv. Vayro and representative isolates of the different species. Except for D. foeniculina and D. phaseolorum, all Diaporthe species were able to cause lesions significantly different from those developed on the uninoculated controls. Diaporthe mediterranea caused the most severe symptoms. These results confirm D. amygdali as a key pathogen of almonds in Spain. Moreover, the new species, D. mediterranea, should also be considered as a potential important causal agent of twig cankers and shoot blight on this crop.
Highlights
The worldwide cultivated area for almond (Prunus dulcis (Mill.) D.A
maximum parsimony (MP) analyses were performed in MEGA X with the tree Bisection and reconnection (TBR) algorithm, where gaps were treated as missing data
Control twigs were compared with the inoculated ones considering individual isolates, and different species were compared with D. amygdali using the Wilcoxon rank sum test (p < 0.01)
Summary
The worldwide cultivated area for almond (Prunus dulcis (Mill.) D.A. Webb) is over 2,000,000 ha. Diogo et al [8] examined Diaporthe isolates from almond and other Prunus species in Portugal through combining morphology, pathogenicity data and a phylogenetic study based only on ITS sequences. These authors concluded that D. amygdali was the main species on almond, reported. In Spain, the studies of Tuset and Portilla [9] and Tuset et al [10] described almond diseases and australafricana and D. novem, based on multi-gene, ITS, tef-1α and cal sequence analyses Information about the Diaporthe species causing twig cankers and shoot blight of almonds in Spain
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