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Due to increasingly limited water resources, diminishing farmland acreage, and potentially negative effects of climate change, an urgent need exists to improve agricultural productivity to feed the ever-growing population. Plants interact with microorganisms at all trophic levels, adapting growth, developmental, and defense responses within a complicated network of community members. Endophytic fungi have been widely reported for their ability to aid in the defense of their host plants. Currently, many reports focus on the application of endophytic fungi with the capability to produce valuable bioactive molecules, while others focus on endophytic fungi as biocontrol agents. Plant responses upon endophytic fungi colonization are also good for the immune system of the plant. In this paper, the possible mechanisms between endophytic fungi and their hosts were reviewed. During long-term evolution, plants have acquired numerous beneficial strategies in response to endophytic fungi colonization. The interaction of endophytic fungi with plants modulates the relationship between plants and both biotic and abiotic stresses. It has previously been reported that this endophytic relationship confers additional defensive mechanisms on the modulation of the plant immune system, as the result of the manipulation of direct antimicrobial metabolites such as alkaloids to indirect phytohormones, jasmonic acid, or salicylic acid. Furthermore, plants have evolved to cope with combinations of stresses and experiments are required to address specific questions related to these multiple stresses. This review summarizes our current understanding of the intrinsic mechanism to better utilize these benefits for plant growth and disease resistance. It contributes new ideas to increase plant fitness and crop productivity.

Background Grapevine trunk diseases (GTDs) are a disease complex that pose a serious challenge to vineyard productivity worldwide. Their increasing occurrence, coupled with the absence of effective treatments, turns their incidence one of the biggest obstacles to viticulture. A deeper understanding of grapevine defence mechanisms is essential to develop new strategies for a sustainable disease management. Results This study explored the transcriptome profiling of GTDs symptomatic and asymptomatic plants of ‘Trincadeira’ (a slightly susceptible or tolerant cultivar to GTDs) and ‘Alicante Bouschet’ (a highly susceptible susceptible or susceptible cultivar to GTDs), under natural field conditions. RNA-seq yielded 1 598 differentially expressed genes (DEGs) when comparing cultivars, and 64 DEGs associated with symptomatology, regardless of the cultivar. Transport was revealed as the main biological process involved, predominantly activated in ‘Alicante Bouschet’, indicating a possible link between these genes and disease progression. Conversely, the relative tolerance of ‘Trincadeira’ to this disease complex might be supported by the activation of secondary and hormonal metabolism and the differential expression of a set of defence-related genes, which may act as key factors to limit GTDs infection. An important role of the peroxidase gene PER42 in the inhibition of GTDs symptoms was highlighted in this study. Conclusions Our results provide novel insights into grapevine resistance mechanisms to GTDs and highlight candidate genes for improving disease tolerance. To the best of our knowledge, this is the first transcriptomic study of naturally infected grapevines with multiple trunk pathogens under natural field conditions. By modulating the activation or inhibition of key plant response regulators, it may be possible to enhance resistance, offering sustainable and effective strategies for successful management of GTDs. Clinical trial number Not applicable.

Plants need to deal with antagonists, such as herbivores, while maintaining interactions with mutualists, such as pollinators that help plants to maximize their reproductive output. Although many plant species have inducible defences to save metabolic costs of defence in the absence of herbivores, plant responses induced by herbivore attack can have ecological costs. For example, herbivore‐induced responses can affect flower traits and alter interactions with flower visitors. Such plant‐mediated interactions between herbivores and flower visitors can affect plant reproductive output. Current knowledge on the generality and specificity of plant‐mediated herbivore–flower–visitor interactions and its consequences for plant fitness is limited. In this study, we investigated whether a broad range of herbivores feeding on the annual plant Brassica nigra affect interactions with flower visitors, whether the direction of interactions is predicted by the feeding modes (chewing and sap‐feeding) and sites (above‐ and belowground) of the herbivores, and whether it results in fitness consequences for the plant. Our results show that attack of B. nigra by a range of different herbivores influenced plant interactions with mutualist pollinators and an antagonist florivore, the pollen beetle Meligethes aeneus. Pollinator community composition was affected by herbivory, whereas overall pollinator attraction was maintained. Pollinator community composition of uninfested plants differed from that of chewing and root herbivore‐infested plants. Main responders in the pollinator communities to changes induced by herbivory were syrphid flies, bumblebees, and solitary bees. Although the preference of pollen beetle adults was not affected by herbivory, beetle larvae performed best on plants infested with the nematode Heterodera schachtii. The changes in pollinator community composition and syrphid fly visitation can explain the observed increase in seed set of root herbivore‐infested plants. Interactions of flowering B. nigra plants with mutualist and antagonist insects are well integrated and conflicting interactions do not reduce reproductive output. Our results suggest some degree of specificity in herbivore–flower–visitor interactions with consequences for plant fitness. Specificity of plant responses were determined at the species level as well as the herbivore functional group level, and differed depending on the flower visitor. Because plant reproduction was affected by indirect plant‐mediated interactions, these can potentially result in selection on plant strategies to optimize growth, defence and reproduction. A plain language summary is available for this article. Plain Language Summary

1. Genetic variation in individual species can have important ecological consequences, and sometimes, these interactions are mediated through another species. For example, genetic variation in an herbivore could alter plant responses that then influence other plant-associated arthropods. However, few systems have experimentally tested the ecological consequences of genetic variation as mediated through other species, especially within the same trophic community context. 2. I studied how evolution of feeding preference in the willow leaf beetle (Plagiodera versicolora), which occurs under selection in a herbivore community context, feeds back to an arthropod community through plant-mediated indirect interactions. Previous studies show beetle populations locally adapt distinct preferences ranging from the gourmet-type, which feeds exclusively on new leaves of willows, to the no-preference (no-pref) type, which displays non-preferential feeding on leaves of different ages. 3. I conducted field experiments at two sites that mimicked evolutionary changes in the feeding preference of the leaf beetle. I manipulated the composition of leaf beetle feeding types for 6 days in spring and then investigated subsequent development of arthropod communities. I found that initial herbivory by a higher proportion of gourmet-type beetles led to lower subsequent abundance of conspecific beetle larvae. In contrast, a higher proportion of gourmet-type beetles resulted in higher abundance of aphids. Aphid-tending ants also increased with the increasing abundance of aphids. As a result, species diversity of arthropod communities decreased with the proportion of gourmet-type beetles in the initial beetle treatment. 4. Community assembly dynamics were significantly influenced by interactive effects between the initial beetle treatment and subsequent colonizer species identities. Thus, beetle genetic variation had long-lasting effects through a temporal chain of indirect interactions likely mediated through induced plant responses and the abundance of aphids. 5. Synthesis. Evolutionary changes in feeding traits within an herbivore species had profound but predictable impact on local arthropod communities. Because the feeding evolution of herbivores nearly always occurs in a community context, plant-mediated feedback loops between the evolution and ecological community of arthropods may be widespread in nature.

Salinity is one of the major threats faced by the modern agriculture today. It causes multidimensional effects on plants. These effects depend upon the plant growth stage, intensity, and duration of the stress. All these lead to stunted growth and reduced yield, ultimately inducing economic loss to the farming community in particular and to the country in general. The soil conditions of agricultural land are deteriorating at an alarming rate. Plants assess the stress conditions, transmit the specific stress signals, and then initiate the response against that stress. A more complete understanding of plant response mechanisms and their practical incorporation in crop improvement is an essential step towards achieving the goal of sustainable agricultural development. Literature survey shows that investigations of plant stresses response mechanism are the focus area of research for plant scientists. Although these efforts lead to reveal different plant response mechanisms against salt stress, yet many questions still need to be answered to get a clear picture of plant strategy to cope with salt stress. Moreover, these studies have indicated the presence of a complicated network of different integrated pathways. In order to work in a progressive way, a review of current knowledge is critical. Therefore, this review aims to provide an overview of our understanding of plant response to salt stress and to indicate some important yet unexplored dynamics to improve our knowledge that could ultimately lead towards crop improvement.

Most high-yielding rice cultivars developed for irrigated conditions, including the widely grown lowland variety IR64, are highly susceptible to drought stress. This limits their adoption in rainfed rice environments where there is a risk of water shortage during the growing season. Mapping studies using lowland-by-upland rice populations have provided limited information about the genetic basis of variation in yield under drought. One approach to simultaneously improve and understand rice drought tolerance is to generate backcross populations, select superior lines in managed stress environments, and then evaluate which features of the selected lines differ from the recurrent parent. This approach was been taken with IR64, using a range of tolerant and susceptible cultivars as donor parents. Yields of the selected lines measured across 13 widely contracting water environments were generally greater than IR64, but genotype-by-environment effects were large. Traits expected to vary between IR64 and selected lines are plant height, because many donors were not semi-dwarf types, and maturity, because selection in a terminal stress environment is expected to favour earliness. In these experiments it was found that some lines that performed better under upland drought were indeed taller than IR64, but that shorter lines with good yield under drought could also be identified. In trials where drought stress developed in previously flooded (lowland) fields, height was not associated with performance. There was little change in maturity with selection. Other notable differences between IR64 and the selected backcross lines were in their responses to applied ABA and ethylene in greenhouse experiments at the vegetative stage and in leaf rolling observed under chronic upland stress in the field. These observations are consistent with the hypothesis that adaptive responses to drought can effectively allow for improved performance across a broad range of water environments. The results indicate that the yield of IR64 under drought can be significantly improved by backcrossing with selection under stress. In target environments where drought is infrequent but significant in certain years, improved IR64 with greater drought tolerance would be a valuable option for farmers.

Herbivore‐induced defences in plants are considered a strategy to manage multiple interactions while saving resources. The optimal defence theory (ODT) is one of the most prominent theoretical frameworks to explain the defence allocation patterns within plants. It was recently shown that the ODT generally applies to constitutive glucosinolate (GSL) allocation in shoot and root organs. Previous studies showed that both root and shoot herbivore feeding may alter defence allocation over plant organs. For shoots, the effect depends on where the herbivores feed. It is as yet unknown whether similar principles apply to root‐herbivore‐induced GSLs. To analyse the effects of root localized herbivore feeding on GSL allocation, we conducted a pot experiment using Anomala cuprea grubs and four Brassicaceae; Brassica rapa, B. nigra, B. oleracea and Sinapis alba. Individuals of these four plant species were grown in dedicated mesocosms. The grubs were confined either to the bottom soil, the middle section or the topsoil. Plants grown in the same set‐ups but without root herbivores served as controls. Glucosinolate levels of the leaf lamina, petiole and stem as well as of the taproot, lateral roots and fine roots were measured after 8 days of herbivory. Plant biomass reduction due to herbivory was the largest when herbivores were confined to the topsoil. In the three Brassica species, taproot GSL levels increased upon herbivory independent of where the root herbivores were feeding. Glucosinolate levels in fine roots and shoots, on the other hand, hardly responded to root herbivory. Indole GSLs, which are more effective to pathogens than to herbivores, were more strongly induced than aliphatic and aromatic GSLs, especially in the taproots. Sinapis alba did not show remarkable increments in any GSL level upon herbivory. These results show that locally and systemically induced defences in roots are consistent with the ODT: The taproot which is the most vulnerable and valuable to plant performance shows the highest increase in defence induction. The induced GSL profiles suggest that the response may not only target herbivores, but may also help to prevent secondary infection by microbial pathogens. A plain language summary is available for this article. Plain Language Summary

1. A large proportion of the world's land surface is extensively managed for livestock production. In areas where livestock systems are becoming more intensive, a major challenge is to predict those plant species likely to decline, persist or increase as a result of agricultural intensification. 2. Most analyses develop inferences for frequent or abundant species, or rely on intensive studies of single species. A promising approach is to identify plant traits related to disturbance to enable inference to be made about changes in plant community composition. We used a Bayesian hierarchical model to analyse the response to agricultural intensification of 494 plant species of pastures and woodlands in southern Australia, and to identify how simple species' traits (life form, growth form and species origin) influence those responses. 3. The probability of occurrence of most species declined along the two intensification gradients, grazing intensity and soil phosphorous concentration, although the occurrence of a greater proportion of species was negatively correlated with soil phosphorous. Responses could be broadly predicted from both plant origin and plant traits, in particular growth form. 4. Native perennial geophytes, ferns and shrubs were most negatively affected by both gradients, while exotic annual grasses and forbs were more tolerant. Along the phosphorous gradient, 24 of the 30 most negatively affected plant species were native geophytes. Mean within-group responses masked considerable within- and between-species variation, particularly for the exotic species group which included species that responded both negatively and positively to intensification. 5. Synthesis and applications. The hierarchical model described here provides a powerful method for estimating individual plant responses and identifying how species' traits influence those responses. Plant species native to southern Australia are sensitive to grazing and phosphorous apparently due to a shared evolutionary history of low grazing intensity and low phosphorous soils. Invading exotic plants have faced strongly contrasting ecological filters, leading to a greater diversity of responses. Where grazing systems have been most intense, a small suite of exotics dominate. Maintaining native and functional plant diversity will necessitate limits being placed on intensive livestock management systems.

Background Being sessile organisms, plants are often exposed to a wide array of abiotic and biotic stresses. Abiotic stress conditions include drought, heat, cold and salinity, whereas biotic stress arises mainly from bacteria, fungi, viruses, nematodes and insects. To adapt to such adverse situations, plants have evolved well-developed mechanisms that help to perceive the stress signal and enable optimal growth response. Phytohormones play critical roles in helping the plants to adapt to adverse environmental conditions. The elaborate hormone signaling networks and their ability to crosstalk make them ideal candidates for mediating defense responses. Results Recent research findings have helped to clarify the elaborate signaling networks and the sophisticated crosstalk occurring among the different hormone signaling pathways. In this review, we summarize the roles of the major plant hormones in regulating abiotic and biotic stress responses with special focus on the significance of crosstalk between different hormones in generating a sophisticated and efficient stress response. We divided the discussion into the roles of ABA, salicylic acid, jasmonates and ethylene separately at the start of the review. Subsequently, we have discussed the crosstalk among them, followed by crosstalk with growth promoting hormones (gibberellins, auxins and cytokinins). These have been illustrated with examples drawn from selected abiotic and biotic stress responses. The discussion on seed dormancy and germination serves to illustrate the fine balance that can be enforced by the two key hormones ABA and GA in regulating plant responses to environmental signals. Conclusions The intricate web of crosstalk among the often redundant multitudes of signaling intermediates is just beginning to be understood. Future research employing genome-scale systems biology approaches to solve problems of such magnitude will undoubtedly lead to a better understanding of plant development. Therefore, discovering additional crosstalk mechanisms among various hormones in coordinating growth under stress will be an important theme in the field of abiotic stress research. Such efforts will help to reveal important points of genetic control that can be useful to engineer stress tolerant crops.