Progress in understanding Pseudocercospora banana pathogens and the development of resistant Musa germplasm

Article purchased; Published online: 9 Feb 2018Banana and plantain (Musa spp.) are important food crops in tropical and subtropical regions of the world where they generate millions of dollars annually to both subsistence farmers and exporters. Since 1902, Pseudocercospora banana pathogens, Pseudocercospora fijiensis, P. musae and P. eumusae, have emerged as major production constraints to banana and plantain. Despite concerted efforts to counter these pathogens, they have continued to negatively impact banana yield. In this review, the economic importance, distribution and the interactions between Pseudocercospora banana pathogens and Musa species are discussed. Interactions are further scrutinized in the light of an emerging climate change scenario and efforts towards the development of resistant banana germplasm are discussed. Finally, some of the opportunities and gaps in knowledge that could be exploited to further understanding of this ubiquitous pathosystem are highlighted

Performance and long-term stability of the barley hordothionin gene in multiple transgenic apple lines

Introduction of sustainable scab resistance in elite apple cultivars is of high importance for apple cultivation when aiming at reducing the use of chemical crop protectants. Genetic modification (GM) allows the rapid introduction of resistance genes directly into high quality apple cultivars. Resistance genes can be derived from apple itself but genetic modification also opens up the possibility to use other, non-host resistance genes. A prerequisite for application is the long-term performance and stability of the gene annex trait in the field. For this study, we produced and selected a series of transgenic apple lines of two cultivars, i.e. ‘Elstar’ and ‘Gala’ in which the barley hordothionin gene (hth) was introduced. After multiplication, the GM hth-lines, non-GM susceptible and resistant controls and GM non-hth controls were planted in a random block design in a field trial in 40 replicates. Scab resistance was monitored after artificial inoculation (first year) and after natural infection (subsequent years). After the trial period, the level of expression of the hth gene was checked by quantitative RT-PCR. Four of the six GM hth apple lines proved to be significantly less susceptible to apple scab and this trait was found to be stable for the entire 4-year period. Hth expression at the mRNA level was also stable

Study of the role of antimicrobial glucosinolate-derived isothiocyanates in resistance of arabidopsis to microbial pathogens.

Crude aqueous extracts from Arabidopsis leaves were subjected to chromatographic separations, after which the different fractions were monitored for antimicrobial activity using the fungus Neurospora crassa as a test organism. Two major fractions were obtained that appeared to have the same abundance in leaves from untreated plants versus leaves from plants challenge inoculated with the fungus Alternaria brassicicola. One of both major antimicrobial fractions was purified to homogeneity and identified by 1H nuclear magnetic resonance, gas chromatography/electron impact mass spectrometry, and gas chromatography/chemical ionization mass spectrometry as 4-methylsulphinylbutyl isothiocyanate (ITC). This compound has previously been described as a product of myrosinase-mediated breakdown of glucoraphanin, the predominant glucosinolate in Arabidopsis leaves. 4-Methylsulphinylbutyl ITC was found to be inhibitory to a wide range of fungi and bacteria, producing 50% growth inhibition in vitro at concentrations of 28 microM for the most sensitive organism tested (Pseudomonas syringae). A previously identified glucosinolate biosynthesis mutant, gsm1-1, was found to be largely deficient in either of the two major antimicrobial compounds, including 4-methylsulphinylbutyl ITC. The resistance of gsm1-1 was compared with that of wild-type plants after challenge with the fungi A. brassicicola, Plectosphaerella cucumerina, Botrytis cinerea, Fusarium oxysporum, or Peronospora parasitica, or the bacteria Erwinia carotovora or P. syringae. Of the tested pathogens, only F. oxysporum was found to be significantly more aggressive on gsm1-1 than on wild-type plants. Taken together, our data suggest that glucosinolate-derived antimicrobial ITCs can play a role in the protection of Arabidopsis against particular pathogens

Resistance against Botrytis cinerea in smooth leaf pruning wounds of tomato does not depend on major disease signalling pathways

In high-tech, heated tomato glasshouses, stem infections caused by Botrytiscinerea usually end up girdling the stem, resulting in plant death and consequently high economic losses. Such infections originate primarily from wounds created during leaf pruning, a common cultural practice in which it is intended to remove leaves completely, resulting in smooth stem wounds. However, hasty leaf pruning often results in numerous petiole stubs accidentally left behind. In this study analysis of disease incidences clearly proved that pruning leaves flush to the stem resulted in absolute resistance of the stem wounds, whereas petiole stubs displayed a high level of susceptibility to B.cinerea. Postponing inoculation of wounds after pruning indicated that development of nearly complete resistance occurs within 48h after deleafing. Monitoring of the wound wetness period showed that drying of the wound surface is not the cause of the decreased susceptibility, contrary to what was commonly believed. Tomato mutants deficient in disease signalling showed altered phenotypes for susceptibility to B.cinerea, indicating that defences against this pathogen in petiole stubs depend on ethylene signalling. Additionally, the decreased susceptibility of mutants deficient in the biosynthesis of jasmonates and abscisic acid suggest an antagonistic effect of these signal molecules. On the other hand, resistance of smooth stem wounds could not be altered by disruption of salicylic acid, ethylene, jasmonate or abscisic acid signalling. This indicates that this remarkable absolute resistance to B.cinerea does not depend on the major disease signalling pathways

Digital microfluidics for time-resolved cytotoxicity studies on single non-adherent yeast cells

Single cell analysis (SCA) has gained increased popularity for elucidating cellular heterogeneity at genomic, proteomic and cellular levels. Flow cytometry is considered as one of the most widely used techniques to characterize single cell responses; however, its inability to analyse cells with spatio-temporal resolution poses a major drawback. Here, we introduce a digital microfluidic (DMF) platform as a useful tool for conducting studies on isolated yeast cells in a high-throughput fashion. The reported system exhibits (i) a microwell array for trapping single non-adherent cells by shuttling a cell-containing droplet over the array, and allows (ii) implementation of high-throughput cytotoxicity assays with enhanced spatio-temporal resolution. The system was tested for five different concentrations of the antifungal drug Amphotericin B, and the cell responses were monitored over time by time lapse fluorescence microscopy. The DMF platform was validated by bulk experiments, which mimicked the DMF experimental design. A correlation analysis revealed that the results obtained on the DMF platform are not significantly different from those obtained in bulk; hence, the DMF platform can be used as a tool to perform SCA on non-adherent cells, with spatio-temporal resolution. In addition, no external forces, other than the physical forces generated by moving the droplet, were used to capture single cells, thereby avoiding cell damage. As such, the information on cellular behaviour during treatment could be obtained for every single cell over time making this platform noteworthy in the field of SCA.crosscheck: This document is CrossCheck deposited related_data: Supplementary Information copyright_licence: The Royal Society of Chemistry has an exclusive publication licence for this journal copyright_licence: The accepted version of this article will be made freely available after a 12 month embargo period history: Received 15 December 2014; Accepted 10 February 2015; Accepted Manuscript published 12 February 2015; Advance Article published 24 February 2015; Version of Record published 31 March 2015status: publishe