Standardisation of instrumentation in plant DNA image cytometry

DNAimage cytometry is a relatively new technique for densitometric measurement of nuclear DNAcontent, which has only rarely been used in botany and thus no methodological standards exist for this method to be applied to the measurement of plant material. In the present paper we address several problems related to standardisation of DNA image cytometry, such as stability of the measuring system, linearity of optical density measurements, correction of uneven illumination of the field of view, and uniformity of integrated optical density measurement over the entire field of view. Furthermore, image processing procedures are described for mitigation of the effects of electronic noise (image averaging) and for densitometric calibration of the measuring system. We have developed a macro for plant DNAimage cytometry, using a general image analysis software package. The described quality control procedures, adopted from international medical standards for diagnostic DNAimage cytometry, were used during software development to test performance of our measurement system. Until a specific botanical consensus is reached, we recommend that the quality control standards for instrumentation described in the present paper are considered when DNA image cytometry is used for measurement of plant genome size as well as for any other image analysis-related densitometric measurement based on light microscopy

Diagnostics of fruit trees phytoplasmas – the importance of latent infections

In the period 2000-2008 more than 1300 fruit trees from different regions of Slovenia were tested for the quarantine phytoplasmas Apple proliferation (AP), Pear decline (PD), and European stone fruit yellows (ESFY). The majority of samples were collected within systematic official surveys, which was conducted for assessing the presence of these phytoplasma in Slovenia in production and mother plant orchards. Samples were taken from trees with and without expressed symptoms. DNA was extracted from the symptomatic shoots. In addition some roots from asymptomatic trees were sampled for the evaluation of latent infections. The presence of phytoplasmas was analyzed with a nested PCR, RFLP and a real time PCR (Hren et al., 2007). AP, PD and ESFY were confirmed as being present in several areas in Slovenia where fruit trees are cultivated. AP was found not only in apple, but also in stone fruit trees such as cherry, apricot and plum (Mehle et al., 2007). By using highly sensitive diagnostic methods, such as real time PCR, some latent infections were detected and they were confirmed next year also by less sensitive methods.Keywords: Phytoplasma, AP, PD, ESFY, latent infection, fruit tree

Grapevine yellows diseases and their phytoplasma agents - Biology and detection.

Phytoplasmas were discovered almost 50 years ago and initially they were named mycoplasma-like organisms. These cell-wall lacking bacteria and members of the class Mollicutes inhabit plant phloem sieve elements and are transmitted and spread primarily by leafhoppers, plant hoppers and psyllids that feed on infected plants phloem. Phytoplasmas interact with their hosts in a strong manner, through manipulation of the morphological features of the plants, and in several cases, also of the biology of their insect vectors. Molecular genetics analyses have improved the understanding of phytoplasma taxonomy, and also enhanced the ability to identify phytoplasmas that are detected in hosts and insect vectors. In particular, it has been determined that among the plant species infected by phytoplasmas, grapevine is one of those that are most severely affected, at a worldwide level. Molecular studies have provided considerable insights into phytoplasma molecular diversity and genetic interrelationships, taxonomic ranking has been achieved by using 16S ribosomal gene classification and other phytoplasma genes as epidemiologic molecular markers. On the other hand, the inability to fulfil Koch\u2019s postulates severely restricts the understanding of the real roles of phytoplasmas in diseases and in plant\u2013insect interaction. Together with the new possibility to cultivate phytoplasmas in artificial media, molecular genetics studies are now opening new possibilities for studying the best management of these bacteria that severely threaten worldwide agriculture, and in particular viticulture

Productivity, pressure, and new perspectives: impacts of the COVID-19 pandemic on marine early-career researchers

The worldwide disruption caused by the beginning of the COVID-19 pandemic has dramatically impacted the activities of marine scientists working towards the goals of the UN Ocean Decade. As in other disciplines, marine early-career researchers (ECRs) are essential contributors to the development of novel and innovative science. Based on a survey of 322 of our peers, we show that the pandemic negatively impacted marine ECRs in ways that further exacerbate existing structural challenges such as social isolation, job insecurity, and short-term contracts, competitive funding, and work pressure. Furthermore, we find that the success and wellbeing of marine ECRs depends heavily on networking opportunities, gaining practical experience, collecting data, and producing publications, all of which were disrupted by the pandemic. Our analysis shows that those in the earliest stages of their careers feel most vulnerable to long-term career disadvantage as a result of the pandemic. This paper contributes to the empirical body of work about the impacts of the pandemic on marine science and offers recommendations on how marine ECRs should be supported to achieve the UN Ocean Decade’s goal of producing “the science we need for the ocean we want”