Plants cannot avoid being attacked by an almost infinite number of microorganisms and insects. Consequently, they arm themselves with molecular weapons against their attackers. Plant defense responses are the result of a complex signaling network, in which the hormones jasmonic acid (JA), salicylic acid (SA) and ethylene (ET) are the usual suspects under the magnifying glass when researchers investigate host-pest interactions. However, Green Leaf Volatiles (GLVs), C6 molecules, which are very quickly produced and/or emitted upon herbivory or pathogen infection by almost every green plant, also play an important role in plant defenses. GLVs are semiochemicals used by insects to find their food or their conspecifics. They have also been reported to be fundamental in indirect defenses and to have a direct effect on pests, but these are not the only roles of GLVs. These volatiles, being probably one of the fastest weapons exploited, are also able to directly elicit or prime plant defense responses. Moreover, GLVs, via crosstalk with phytohormones, mostly JA, can influence the outcome of the plant’s defense response against pathogens. For all these reasons GLVs should be considered as co-protagonists in the play between plants and their attackers.

/pdf/green-leaf-volatiles-a-plant-s-multifunctional-weapon-1lgzl226im.pdf

Green Leaf Volatiles: A Plant’s Multifunctional Weapon against Herbivores and Pathogens

Summary
A long-standing goal in plant research is to optimize the protective function of biochemical agents that impede pest and pathogen attack. Nearly 40 years ago, pathogen-inducible diterpenoid production was described in rice, and these compounds were shown to function as antimicrobial phytoalexins. Using rice and maize as examples, we discuss recent advances in the discovery, biosynthesis, elicitation and functional characterization of monocot terpenoid phytoalexins. The recent expansion of known terpenoid phytoalexins now includes not only the labdane-related diterpenoid superfamily but also casbane-type diterpenoids and β-macrocarpene-derived sequiterpenoids. Biochemical approaches have been used to pair pathway precursors and end products with cognate biosynthetic genes. The number of predicted terpenoid phytoalexins is expanding through advances in cereal genome annotation and terpene synthase characterization that likewise enable discoveries outside the Poaceae. At the cellular level, conclusive evidence now exists for multiple plant receptors of fungal-derived chitin elicitors, phosphorylation of membrane-associated signaling complexes, activation of mitogen-activated protein kinase, involvement of phytohormone signals, and the existence of transcription factors that mediate the expression of phytoalexin biosynthetic genes and subsequent accumulation of pathway end products. Elicited production of terpenoid phytoalexins exhibit additional biological functions, including root exudate-mediated allelopathy and insect antifeedant activity. Such findings have encouraged consideration of additional interactions that blur traditionally discrete phytoalexin classifications. The establishment of mutant collections and increasing ease of genetic transformation assists critical examination of further biological roles. Future research directions include examination of terpenoid phytoalexin precursors and end products as potential signals mediating plant physiological processes.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/tpj.12436

Biosynthesis, elicitation and roles of monocot terpenoid phytoalexins

Microorganisms colonize the surfaces of plant roots, leaves, and flowers known as the rhizosphere, phyllosphere, and anthosphere. These spheres differ largely in a number of factors that may determine the ability of microbes to establish themselves and to grow in these habitats. In this article, we focus on volatile organic compounds (VOCs) emitted by plants, and we discuss their effects on microbial colonizers, with an emphasis on bacteria. We present examples of how growth-inhibiting properties and mechanisms of VOCs such as terpenoids, benzenoid compounds, aliphatics, and sulfur containing compounds prevent bacterial colonization at different spheres, in antagonism with their role as carbon-sources that support the growth of different bacterial taxa. The notion that VOCs represent important factors that define bacterial niches is further supported by results for representatives of two bacterial genera that occupy strongly diverging niches based on scent emissions of different plant species and organs. Bacteria are known to either positively or negatively affect plant fitness and to interfere with plant-animal interactions. Thus, bacteria and other microbes may select for VOCs, enabling plants to control microbial colonizers on their surfaces, thereby promoting the growth of mutualists and preventing the establishment of detrimental microbes.

https://static.springer.com/sgw/documents/1419323/application/pdf/art%25253A10.1007%25252Fs10886-013-0325-9.pdf

Volatile Organic Compound Mediated Interactions at the Plant-Microbe Interface

Plants release a wide set of secondary metabolites including volatile organic compounds (VOCs). Many of those compounds are considered to function as defense against herbivory, pests, and pathogens. However, little knowledge exists about the role of belowground plant VOCs for attracting beneficial soil microorganisms. We developed an olfactometer system to test the attraction of soil bacteria by VOCs emitted by Carex arenaria roots. Moreover, we tested whether infection of C. arenaria with the fungal pathogen Fusarium culmorum modifies the VOCs profile and bacterial attraction. The results revealed that migration of distant bacteria in soil towards roots can be stimulated by plant VOCs. Upon fungal infection, the blend of root VOCs changed and specific bacteria with antifungal properties were attracted. Tests with various pure VOCs indicated that those compounds can diffuse over long distance but with different diffusion abilities. Overall, this work highlights the importance of plant VOCs in belowground long-distance plant–microbe interactions.

/pdf/calling-from-distance-attraction-of-soil-bacteria-by-plant-1fmp91ox81.pdf

Calling from distance: attraction of soil bacteria by plant root volatiles.

Summary 1. In their natural environment, plants are faced with a multitude of attackers, of which insect herbivores and plant pathogens are an important component. In response to these attacks, plants release volatile organic compounds (VOCs), which play an important role in the communication between plants and the associated community members, such as other herbivores, phytopathogens and the natural enemies of herbivores. 2. While numerous studies have focused on either plant–pathogen or plant–insect interactions, less is known when these two sets of interactions co-occur. Depending on the mode of attack of the pathogen (necrotroph vs. biotroph) or herbivore (chewing vs. piercing-sucking) they will activate different defence pathways in the plant in which the phytohormones salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) play key roles. As these pathways can crosstalk, a pathogen infection can interfere in a plant’s defence response to herbivory, and vice versa. 3. Infestation of a plant with organisms inducing SA signalling prior to – or simultaneously with – attack by organisms that induce the JA pathway often suppresses JA signalling. However, the impact of this signalling pathway crosstalk on VOC induction is not clear cut, as there is high variability in the effects on volatile emissions, ranging from suppression to enhanced emission. The effects of the modified volatile blends on the foraging success of carnivorous natural enemies of herbivorous insects have started to be investigated. Foraging success of natural enemies generally withstands this modification of the host-induced VOC blend, but the presence or absence of key compounds is an important determinant of the response of certain carnivores. 4. Further studies incorporating plant–insect and plant–pathogen interactions at different levels of biological integration will provide valuable insight in how plants integrate signals from different suites of attacking organisms into an adaptive defence response.

/pdf/ecological-and-phytohormonal-aspects-of-plant-volatile-3rxrza9fpo.pdf

Ecological and phytohormonal aspects of plant volatile emission in response to single and dual infestations with herbivores and phytopathogens

https://pubag.nal.usda.gov/download/50280/PDF

Fusarium infection in maize: Volatile induction of infected and neighboring uninfected plants has the potential to attract a pest cereal leaf beetle, Oulema melanopus

Gastrophysa polygoni herbivory on Rumex confertus: single leaf VOC induction and dose dependent herbivore attraction/repellence to individual compounds.

The paper presents the results of the elemental composition of the ash produced during combustion of straw and hay. Test samples of ash were characterized by alkaline pH (pH 10.2) and a substantial overall potassium content (155,7 g∙kg K), calcium (124,0 g∙kg Ca), phosphorus (15,1 g∙kg P) and magnesium (7,3 g∙kg Mg). In addition, presence of essential micronutrients for plants was found in them (Fe > Mn > Zn > Cu). A small natural content of heavy metals (Cr > Pb > Ni > Cd > Hg) in the ash is not a contraindication for the agricultural use of ash from the plant biomass.

/pdf/the-elemental-composition-of-ash-from-straw-and-hay-in-the-3thiux3u49.pdf

The elemental composition of ash from straw and hay in the context of their agricultural utilization

Economic, organizational and natural determinants of modern plant field production enforce far-reaching limitations of classical components of cultivation regime. In 2010-2012, a study was carried out at the Agricultural Production Farm in Kowroz (Kuyavian-Pomeranian voivodeship) in soil of the very well rye complex. This study aimed at determining the effect of plowing tillage, reduced tillage and minimal tillage on the grain yield and quality of winter wheat sown after winter oilseed rape, winter wheat and maize for grain. Plowing tillage involved performing: skimming, harrowing, pre-sow plowing and cultivation with a passive pre-sow unit after harvesting oilseed rape and wheat or single plowing and cultivation with a cultivation unit after maize for grain. Reduced tillage was performed using a stubble unit, grubber and pre-sow unit after oilseed rape and wheat, and a grubber and passive pre-sowing unit after maize. Minimal tillage consisted only of disking the stubble in each position. Yield components, grain yield and its quality were usually more dependent on the previous crop than on the tillage system. The highest yield of winter wheat - 5.57 Mg·ha -1 - with favorable traits of grain quality was observed in the position after winter oilseed rape, and the lowest - 4.92 Mg·ha -1 - after maize. Abandoning plowing tillage did not have a negative effect on spike density, grain yield and grain quality. Nevertheless, tillage simplification only to disking the stubble negatively affected the yield. However, in the position after winter wheat, and particularly after winter oilseed rape, this cultivation system did not have a negative effect on grain yield, grain bulk density and protein content. After harvesting maize for grain, each simplification of plowing tillage caused a reduction in winter wheat grain yield.

http://agro.icm.edu.pl/agro/element/bwmeta1.element.agro-7aa5e117-b24c-4fb9-8abe-034b5a02f208/c/12_3_2013_4.pdf

Karol Kotwica

Papers

Fusarium infection in maize: Volatile induction of infected and neighboring uninfected plants has the potential to attract a pest cereal leaf beetle, Oulema melanopus

Gastrophysa polygoni herbivory on Rumex confertus: single leaf VOC induction and dose dependent herbivore attraction/repellence to individual compounds.

The elemental composition of ash from straw and hay in the context of their agricultural utilization

Effect of tillage simplifications on yield and grain quality of winter wheat after different previous crops

Wpływ nawożenia azotem i sposobu użyźniania gleby na plonowanie pszenicy ozimej w zależności od przedplonu