Antagonism to Plant Pathogens by Epichloë Fungal Endophytes—A Review

Epichloë is a genus of filamentous fungal endophytes that has co-evolved with cool-season grasses with which they form long-term, symbiotic associations. The most agriculturally important associations for pasture persistence for grazing livestock are those between asexual vertically transmitted Epichloë strains and the pasture species, perennial ryegrass, and tall fescue. The fungus confers additional traits to their host grasses including invertebrate pest deterrence and drought tolerance. Selected strains of these mutualistic endophytes have been developed into highly efficacious biocontrol products and are widely utilized within the Americas, Australia, and New Zealand for pasture persistence. Less publicized is the antagonism Epichloë endophytes display towards multiple species of saprophytic and pathogenic microbes. This opinion piece will review the current literature on antimicrobial properties exhibited by this genus of endophyte and discuss the reasons why this trait has historically remained a research curiosity rather than a trait of commercial significance

Historical Regimes of Normativity: Part 3

In this four part series, colleagues from the department discuss the reasons for the new department name as well as the definition and status of the concept

APPLE AND PEACH: A DIFFERENT ROLE FOR FRUIT TRANSPIRATION?

The environments where apple and peach originated are very different in terms of water availability and evaporative demand. This likely determined the evolution of different strategies against drought stress, with ensuing effects on the growth mechanisms of their fruit. This work compares the seasonal biophysical mechanisms of apple and peach fruit growth via an analysis of the vascular and transpiration in/outflows on ‘Gala’ apple and ‘Red Gold’ nectarine fruit. Due to their lower surface conductance, apples attain lower transpiration rates during the season, which are reflected in their lower xylem flows, as these are directly related to transpiration. By contrast, phloem flow is always comparable between the two species both in terms of daily amounts and daily patterns. It is striking that peaches exchange much more water than apples, but receive the same amount of phloem sap. This might be related to the different strategies adopted: apples unload assimilates actively and phloem-to-fruit hydrostatic pressure gradients are of relatively low importance. On the contrary, although the mechanism of phloem unloading in peach fruit is still unclear, some results suggest that it may be partly passive, at least during the cell expansion stage. As fruit turgor pressure is negatively related to transpiration rate, the high water loss of peach fruit may be the way to lower water potential and to create the hydrostatic pressure gradient needed to promote passive unloading of assimilates. Therefore, the high surface conductance and transpiration rates of peach fruit appear to have a key role for fruit growth. This feature may be the consequence of the higher water availability typical of the south-east of China, from where most of the peach genetic material derives. Similarly, the growth strategy of apple fruit, based on low surface conductance, seems related to the dry environment (Kazakhstan mountains) where the apple species originated

Aging gene pathway of microRNAs 156/157 and 172 is altered in juvenile and adult plants from in vitro propagated Prunus sp.

A. Bastías, R. Almada, P. Rojas, J.M. Donoso, P. Hinrichsen, and B. Sagredo. 2016. Aging gene pathway of microRNAs 156/157 and 172 is altered in juvenile and adult plants from in vitro propagated Prunus sp. Cien. Inv. Agr. 43(3):429-441. In vitro culture is a very popular technique to mass propagate valuable plant genotypes, including Prunus sp. cultivars. Plants that undergo tissue culture processes often change their morphology and behavior due to the "rejuvenation" caused by the plant growth regulators included in the medium. To evaluate the effects of rejuvenation by tissue culture in Prunus sp., the expression patterns of the aging gene pathway described in plant models, which include the highly conserved microRNA (miRNA or miR) 156/157 and 172 families and several of their respective target genes, were analyzed in distinct Prunus sp. genotypes at different phases of maturity, including true seedling and tissue culture micropropagated plants. In genotypes from true seedling plants, the expression of miR156 and miR157 was higher in the leaves of juvenile plants (one year old) than in those of adult plants (six year old). The opposite pattern was observed with miRNA172 expression. Our results suggest that the aging gene pathway is relatively conserved in Prunus and likely plays a key role in vegetative phase change. However, Prunus sp. plants that were rejuvenated and propagated by in vitro methods showed more erratic behavior for miR156 and miR157 and their target genes, suggesting that tissue culture alters the normal control of the aging pathway.A. Bastías, R. Almada, P. Rojas, J.M. Donoso, P. Hinrichsen y B. Sagredo. 2016. La vía génica del envejecimiento de los microARNs 156/157 and 172 es alterada en plantas juveniles y adultas de Prunus sp. que provienen de propagación in vitro. Cien. Inv. Agr. 43(3):429-441. El cultivo in vitro es una técnica muy popular para propagar en masa genotipos de plantas valiosas, incluyendo cultivares de Prunus sp. Las plantas que se someten a procesos de cultivo de tejidos a menudo cambian su morfología y comportamiento debido a la "rejuvenilización" causada por los reguladores de crecimiento de planta incluidos en el medio. Para evaluar el efecto de la rejuvenilización por cultivo de tejido en Prunus sp, los patrones de expresión de la vía génica del envejecimiento descrita en plantas modelos, la cual incluye a las familias altamente conservadas de microRNAs (miR) 156/157 y miR172 y varios de sus genes blancos respectivos, fueron analizados en diferentes genotipos de Prunus sp. en fases de madurez distintas, incluyendo tanto plantas provenientes de semilla verdadera como micropropagadas mediante cultivo de tejidos. En los genotipos de plantas que provienen de semilla verdadera, la expresión de microR156 and miR157 fue más alta en hojas de plantas juveniles que en plantas adultas. El patrón opuesto fue observado con el patrón de expresión de miR172. Nuestros resultados sugieren que la vía génica del envejecimiento es conservada en Prunus y probablemente juega una función en el cambio de fase vegetativo. Sin embargo, plantas de Prunus sp. que fueron rejuvenecidas y propagadas por métodos in vitro mostraron un comportamiento más errático para los mi156 y miR157 y sus genes blancos, sugiriendo que el cultivo de tejidos altera el control normal de la vía del envejecimiento

The transcription factor AREB1 regulates primary metabolic pathways in tomato fruits

Tomato fruit development is regulated both by the action of plant hormones and by tight genetic control. Recent studies suggest that abscisic acid (ABA) signalling may affect different aspects of fruit maturation. Previously, it was shown that SlAREB1, an ABA-regulated transcription factor involved in stress-induced responses, is expressed in seeds and in fruit tissues in tomato. Here, the role of SlAREB1 in regulating the expression of genes relevant for primary metabolic pathways and affecting the metabolic profile of the fruit was investigated using transgenic tomato lines. Metabolite profiling using gas chromatography–time of flight mass spectrometry (GC-TOF-MS) and non-targeted liquid chromatography–mass spectrometry (LC-MS) was performed on pericarp tissue from fruits harvested at three stages of fruit development. Principal component analysis of the data could distinguish the metabolite profiles of non-transgenic fruits from those that overexpress and down-regulate SlAREB1. Overexpression of SlAREB1 resulted in increased content of organic acids, hexoses, hexose-phosphates, and amino acids in immature green, mature green, and red ripe fruits, and these modifications correlated with the up-regulation of enzyme-encoding genes involved in primary carbohydrate and amino acid metabolism. A non-targeted LC-MS analysis indicated that the composition of secondary metabolites is also affected in transgenic lines. In addition, gene expression data revealed that some genes associated with fruit ripening are also up-regulated in SlAREB1-overexpressing lines compared with wild-type and antisense lines. Taken together, the results suggest that SlAREB1 participates in the regulation of the metabolic programming that takes place during fruit ripening and that may explain part of the role of ABA in fruit development in tomato

PRECISION FRUIT GROWING: HOW TO COLLECT AND INTERPRET DATA ON SEASONAL VARIATION IN APPLE ORCHARDS

Very little has been published to date on seasonal spatial variability of produc-tion in fruit crops, and most papers refer to data collected post harvest. This work analysed field information recorded within-season (fruit growth rate) and at harvest (crop load, fruit size, fruit ripening) in 2008 in two commercial apple (Malus domestica Borkh.) orchards in the Ferrara province, Italy. In high-quality apple production systems, manual refinement of chemical thinning is a must, but growers lack a methodology for assessing the efficacy of thinning treatments and to assist further management decisions, such as irrigation levels, for example. The within-season data were used to provide assistance in management decisions taken by growers and/or consultants throughout the season. The goal was to assist in improving the efficacy of management to ensure high production while maintaining as high yields as possible. The relationships between the within-season and harvest measurements were analyzed using both traditional and spatial statistical techniques. Maps of crop production/ quality parameters and fruit growth were generated by punctual kriging with a global variogram on a common grid. Within-season monitoring provided more robust estimations of the fruit load per tree than traditional methods, which underestimated fruit load, leading to more appropriate thinning. Monitoring fruit growth rates also provided good estimations of fruit size distribution at harvest and permitted better satisfaction of the target market. Useful information could be obtained by interpretation at the block (orchard) scale, however, a spatial analysis at a sub-block level appeared to offer the opportunity for differential management. The work presented is intended as a proof of concept of this methodology, the satisfactory results from which signal that it may be not far from large-scale adoption