Search

Peach orchards in the northeast of Spain were severely affected in 2012 by a previously unreported disease in this area. The symptoms included early reddening, leaf curling, decline, abnormal fruits, and in some cases death of the peach trees. All the infected peach samples were positive for ‘Candidatus Phytoplasma pyri’, but none were infected by the ‘Ca. Phytoplasma prunorum’. In this work, potential vectors able to transmit ‘Ca. Phytoplasma pyri’ from pear to peach and between peach trees were studied and their infective potential was analysed at different times of the year. Transmission trials of the phytoplasma with potential vectors to an artificial feeding medium for insects and to healthy peach trees were conducted. Additionally, isolated phytoplasmas were genetically characterized to determine which isolates were able to infect peach trees. Results showed that the only insect species captured inside peach plots that was a carrier of the ‘Ca. Phytoplasma pyri’ phytoplasma was Cacopsylla pyri. Other insect species captured and known to be phytoplasma transmitters were present in very low numbers, and were not infected with ‘Ca. Phytoplasma pyri’ phytoplasma. A total of 1928 individuals of C. pyri were captured in the peach orchards, of which around 49% were phytoplasma carriers. All the peach trees exposed to C. pyri in 2014, and 65% in 2015, were infected by ‘Ca. Phytoplasma pyri’ 1 year after exposure, showing that this species is able to transmit the phytoplasma to peach. Molecular characterization showed that some genotypes are preferentially determined in peach. [ABSTRACT FROM AUTHOR]

An in situ localization method for Peach latent mosaic viroid (PLMVd) that is highly sensitive, has low background signal, has a short specimen processing time and is simple and inexpensive compared to other similar methods, is described. The method is based on SYBR Green reverse transcription-polymerase chain reaction (RT-PCR) amplification of pepsin, DNase I pre-treated and FAA-fixed peach leaf sections. The leaves used were derived from healthy and PLMVd infected peach plants, including a plant infected by a Peach Calico variant of the viroid. All steps of the assay, except for the signal detection, were carried out in liquid phase in 0·2 mL PCR tubes instead of on microscope slides, as usually used. Epifluorescence microscopy to detect PLMVd or rbcL (the positive control gene) amplified products revealed a bright signal in the leaf part corresponding to the palisade parenchyma, with sub-cellular localization of the signals in the chloroplasts, the organelles where PLMVd is known to replicate and accumulate. Although the method proved to be effective for the green peach PLMVd infected tissues, a yellow-green background fluorescent signal, sometimes more intense due to overexposure, was observed, presumably due to chlorophyll auto-fluorescence. In contrast, no auto-fluorescence signal was observed in the calico infected albino tissues. This is the first report of using liquid phase in situ RT-PCR for the cellular localization of a plant pathogen. [ABSTRACT FROM AUTHOR]

Field populations of Myzus persicae (Sulz.) collected from 30 sites in Yorkshire and Lancashire were tested by total esterase or bioassay techniques for resistance to organophosphorus insecticides. All the populations examined included some resistant aphids and some populations contained individuals with esterase activity characteristic of very resistant aphids. [ABSTRACT FROM AUTHOR]

Peach-potato aphids, Myzus persicae (Sulz.), collected from six potato fields in western and central Scotland in 1976 were tested for aphicide resistance biochemically and by bioassay. Most aphids were resistant to organophosphorus insecticides. At five of the sites, some aphids were both highly resistant to organophosphorus compounds and moderately resistant to pirimicarb. [ABSTRACT FROM AUTHOR]

The article discusses the first investigation on fruit rots of peaches in Greece caused by Aspergillus flavus (A. flavus). The presence of this disease on peaches suggests the need for measures to control its proliferation that may heighten toxicity to the liver and produce aflatoxins brought by the harmful strains of A. flavus. The pathogen is isolated on acidified potato dextrose agar and classified according to its morphological characteristics. Results show the resemblance of symptoms between re-isolated fungus from inoculated fruit and the rotten fruit from orchards.

This is the first report of a peach yellow leaf roll-like disease in Bolivia, and the first record of the presence of a Stolbur group phytoplasma in peach. Phytoplasmas, prokaryote plant pathogens, have been reported to cause peach yellow leaf roll and peach red leaf diseases. Older leaves had symptoms of yellowing of the leaf margin and rolling, drying and necrosis. Young leaves were tightly rolled and yellow, and proliferation of shoots was evident along branches. The greatest similarity was with papaya dieback phytoplasma from Australia, a member of the 16SrXII Stolbur group (Candidatus Phytoplasma australiense')