New leaf and fruit disease of Juglans regia caused by Juglanconis juglandina in Xinjiang, China

Abstract

AbstractJuglans regia L. is an important and scarce natural resource that grows in the part of the western Tianshan Mountains and the Pamir Alai Mountains in Central Asia. They only distribute in Gongliu County, Yili, Xinjiang Uygur Autonomous Region in China. However, the healthy growth of J. regia was seriously affected by a fungal disease affecting leaves, branches and fruit in 2016. Sixty isolates were obtained from diseased branches, leaves and fruit collected. The pathogenicity of the isolates was confirmed by inoculating shoots and fruit collected from healthy J. regia in Gongliu County and by inoculating the leaves of J. regia seedlings. The pathogen was re‐isolated from all inoculated shoots, leaves and fruits, thereby fulfilling Koch's postulates. Furthermore, isolates from leaves were able to infect fruit and shoots and vice versa. The isolate 1429‐1 was more pathogenic to the branches than HG and HY, no significant difference between the other isolates from leaves and fruits. Based on morphological, cultural characteristics and multilocus analyses using the internal transcribed spacer region, the RNA polymerase II subunit 2 gene, the calmodulin gene, the guanine nucleotide‐binding protein subunit beta gene, the translation elongation factor 1‐alpha gene and the β‐tubulin gene sequences, the fungus was identified as Juglanconis juglandina. Although J. juglandina has been reported previously as the causal agent of stem disease, this is the first description of J. juglandina as the causal agent of a leaf and fruit disease of J. regia.