Abstract
‘Candidatus Phytoplasma prunorum’, the causal agent of European stone fruit yellows (ESFY), is one of the most important pathogens causing considerable economic losses in stone fruit orchards. This study evaluated trees infected and noninfected by phytoplasma ESFY of 16 apricot varieties grown in an orchard in Lednice (Czech Republic) between the years 2008-2014. Pomological traits, phenophases, pollen germination and seed viability were analysed as well as the presence of ‘Ca. P. prunorum’ in pollen, flower organs, fruit flesh, immature seeds and seedlings by nested PCR. One of the most detrimental impacts was the decreased fruit set of infected trees which occurred in 12 out of 16 studied varieties reaching an average fruit set decrease of 16.1%. Pollen germination rates also suffered, showing an average decrease by 11.78% in infected trees. In the analysis of some traits, overall significant differences were observed between the infected and noninfected trees. However, for all analysed traits in different varieties, both positive and negative influences of phytoplasma ESFY were observed. The presence of ‘Ca. P. prunorum’ in infected trees was confirmed in flower parts (only in peduncle in 70.2% of cases) and fruit parts (immature fruit flesh in 42.0% and milky kernels in 26.2% of cases), however, neither in seedlings nor in pollen.
Highlights
European stone fruit yellows (ESFY) phytoplasma (‘Candidatus Phytoplasma prunorum’) is an important agent of premature death of apricot trees (Gazel et al, 2009)
The risk factors of phytoplasma ESFY occurrence in different regions and orchards were assessed by Thébaud et al (2006), as well as by Ulubaş et al (2007) who reported the differences in ESFY phytoplasma occurrence in extensive and intensive orchards, when in the extensive orchard, the ESFY phytoplasma was detected in 54.8% of the analysed samples, while in the intensive orchard the ESFY phytoplasma was detected in only 3.2% of analysed samples
Late blooming of infected trees is a common symptom of ESFY phytoplasma infection (Chabrolin, 1924; Morvan, 1977), no information is available in the case of earlier blooming of infected trees
Summary
European stone fruit yellows (ESFY) phytoplasma (‘Candidatus Phytoplasma prunorum’) is an important agent of premature death of apricot trees (Gazel et al, 2009). Except from work of Gazel et al (2009), where the influence of phytoplasma ESFY on quantitative fruit traits, such as fruit size, titratable acidity, and total soluble solids content was studied out, detailed research on ESFY phytoplasma influence on qualitative and quantitative pomological traits of apricots has not been carried out. The level of influence on pomological traits and symptom manifestation might depend on the sensitivity of individual Prunus variety to phytoplasma ESFY (Jarausch, et al, 2000; Kison et al, 2001; Carraro et al, 2002; Nečas et al, 2015). Preliminary results were published in a previous study by Nečas et al (2008), there is no description of the pathogen occurrence in the various organs of the fruit trees
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