The status of global food security, i.e., the balance between the growing food demand of the world population and global agricultural output, combined with discrepancies between supply and demand at the regional, national, and local scales (Smil 2000; UN Department of Economic and Social Affairs 2011; Ingram 2011), is alarming. This imbalance is not new (Dyson 1999) but has dramatically worsened during the recent decades, culminating recently in the 2008 food crisis. It is important to note that in mid-2011, food prices were back to their heights of the middle of the 2008 crisis (FAO 2011). Plant protection in general and the protection of crops against plant diseases in particular, have an obvious role to play in meeting the growing demand for food quality and quantity (Strange and Scott 2005). Roughly, direct yield losses caused by pathogens, animals, and weeds, are altogether responsible for losses ranging between 20 and 40 % of global agricultural productivity (Teng and Krupa 1980; Teng 1987; Oerke et al. 1994; Oerke 2006). Crop losses due to pests and pathogens are direct, as well as indirect; they have a number of facets, some with short-, and others with long-term consequences (Zadoks 1967). The phrase “losses between 20 and 40 %” therefore inadequately reflects the true costs of crop losses to consumers, public health, societies, environments, economic fabrics and farmers. The components of food security include food availability (production, import, reserves), physical and economic access to food, and food utilisation (e.g., nutritive value, safety), as has been recently reviewed by Ingram (2011). Although crop losses caused by plant disease directly affect the first of these components, they also affect others (e.g., the food utilisation component) directly or indirectly through the fabrics of trade, policies and societies (Zadoks 2008). Most of the agricultural research conducted in the 20th century focused on increasing crop productivity as the world population and its food needs grew (Evans 1998; Smil 2000; Nellemann et al. 2009). Plant protection then primarily focused on protecting crops from yield losses due to biological and non-biological causes. The problem remains as challenging today as in the 20th century, with additional complexity generated by the reduced room for manoeuvre available environmentally, economically, and socially (FAO 2011; Brown 2011). This results from shrinking natural resources that are available to agriculture: these include water, agricultural land, arable soil, biodiversity, the availability of non-renewable energy, human labour, fertilizers (Smil 2000), and the deployment of some key inputs, such as high quality seeds and planting material (Evans 1998). In addition to yield losses caused by diseases, these new elements of complexity also include post harvest quality losses and the possible accumulation of toxins during and after the S. Savary (*) : J.-N. Aubertot INRA, UMR1248 AGIR, 24 Chemin de Borde Rouge, Auzeville, CS52627, 31326 Castanet-Tolosan Cedex, France e-mail: Serge.Savary@toulouse.inra.fr

Crop losses due to diseases and their implications for global food production losses and food security

A number of different types of induced resistance have been defined based on differences in signalling pathways and spectra of effectiveness, including systemic acquired resistance and induced systemic resistance. Such resistance can be induced in plants by application of a variety of biotic and abiotic agents. The resulting resistance tends to be broad-spectrum and can be long-lasting, but is rarely complete, with most inducing agents reducing disease by between 20 and 85%. Since induced resistance is a host response, its expression under field conditions is likely to be influenced by a number of factors, including the environment, genotype, crop nutrition and the extent to which plants are already induced. Although research in this area has increased over the last few years, our understanding of the impact of these influences on the expression of induced resistance is still poor. There have also been a number of studies in recent years aimed at understanding of how best to use induced resistance in practical crop protection. However, such studies are relatively rare and further research geared towards incorporating induced resistance into disease management programmes, if appropriate, is required.

Controlling crop diseases using induced resistance: challenges for the future

The importance of sustainable agriculture can be understood as an ecosystem approach toward the integrated agricultural management practices. It is capable of enhancing soil and environmental quality with conserving natural resources. Therefore, in recent years, it has become a component of the modern agricultural practices. However, at the same time, yield loss of field crops due to diseases is causing bottlenecks toward the sustainable agricultural production systems worldwide. The conventional method for disease management has caused degradation of environment, land resources, and water bodies, developed pesticide resistance in pathogens, and contaminated the food with toxins. These have evolved crave for the alternative disease management practices, which are economic, eco-friendly, and sustainable approach for farmers. To be precise, rate of development of diseases can be reduced by an adequate and balanced mineral nutrition in crops. The plant nutrients determine its resistance or susceptibility to disease, its histological or morphological structure or properties, and the ability of pathogens to survive on the host. The disease symptoms frequently reflect the altered nutritional status of the plant, and many factors that influence this response are not well understood. This article summarizes some of the most recent developments regarding the effect of macronutrients (e.g., N, P, K), secondary nutrients (e.g., Ca, Mg), and micronutrients (e.g., B, Mn, Zn, Fe, Cu, and Si) on disease resistance/tolerance and susceptibility and their use in sustainable agriculture.

Role of Nutrients in Controlling the Plant Diseases in Sustainable Agriculture

IPM Strategies and Their Dilemmas Including an Introduction to www. eurowheat.org

Findings on climate change influence on plant pathogens are often inconsistent and context dependent. Knowledge of pathogens affecting agricultural crops and natural plant communities remains fragmented along disciplinary lines. By broadening the perspective beyond agriculture, this review integrates cross-disciplinary knowledge to show that at scales relevant to climate change, accelerated evolution and changing geographic distribution will be the main implications for pathogens. New races may evolve rapidly under elevated temperature and CO2 , as evolutionary forces act on massive pathogen populations boosted by a combination of increased fecundity and infection cycles under favourable microclimate within enlarged canopy. Changing geographic distribution will bring together diverse lineages/genotypes that do not share common ecological niche, potentially increasing pathogen diversity. However, the uncertainty of model predictions and a lack of synthesis of fragmented knowledge remain as major deficiencies in knowledge. The review contends that the failure to consider scale and human intervention through new technology are major sources of uncertainty. Recognizing that improved biophysical models alone will not reduce uncertainty, it proposes a generic framework to increase focus and outlines ways to integrate biophysical elements and technology change with human intervention scenarios to minimize uncertainty. To synthesize knowledge of pathogen biology and life history, the review borrows the concept of 'fitness' from population biology as a comprehensive measure of pathogen strengths and vulnerabilities, and explores the implications of pathogen mode of nutrition to fitness and its interactions with plants suffering chronic abiotic stress under climate change. Current and future disease management options can then be judged for their ability to impair pathogenic and saprophytic fitness. The review pinpoints improving confidence in model prediction by minimizing uncertainty, developing management strategies to reduce overall pathogen fitness, and finding new sources of data to trawl for climate signatures on pathogens as important challenges for future research.

Migrate or evolve: options for plant pathogens under climate change.

Potassium phosphite combined with reduced doses of fungicides provides efficient protection against potato late blight in large-scale field trials

Impact of temperature and precipitation on yield and plant diseases of winter wheat in southern Sweden 1983–2007

The economics of fungicide use in winter wheat in southern Sweden

We have investigated to what degree induced resistance with β-aminobutyric acid (BABA) can protect potato from late blight infection under Swedish field conditions and if synergistic interactions occur if BABA is applied in combination with a commonly used fungicide, Shirlan. In greenhouse experiments we also investigated the durability of BABA induced resistance, the dose-response relationships in susceptible (Bintje) and partially resistant (Ovatio, Suberb) cultivars and effects of combined applications of BABA and fungicides. We found a clear effect of BABA on P. infestans infection of greenhouse grown potato plants. The lesion sizes were reduced by on average 40–50% compared to untreated control. However, this effect lasted for only 4–5 days after BABA treatment and then the efficacy was lower. When BABA was given in combination with the fungicides it appeared to have an additive effect both in greenhouse and field experiments. Higher concentrations of BABA gave a stronger protective effect. The partially resistant cultivars Ovatio and Superb reacted to lower concentrations of BABA where no effect was found in susceptible Bintje. According to our field data, 20–25% reduction of the fungicide dose in combination with BABA gave on average the same result on late blight development as full dose Shirlan alone; while reduced dose of Shirlan alone sometimes resulted in less effective protection. Our results indicate that induced resistance could be used in practice in combinations with fungicides in order to reduce the amount of toxic compounds under north European conditions.

/pdf/induced-resistance-in-potato-to-phytphthora-infestans-3qbwi7zrhs.pdf

Lars Wiik

Papers

Potassium phosphite combined with reduced doses of fungicides provides efficient protection against potato late blight in large-scale field trials

Impact of temperature and precipitation on yield and plant diseases of winter wheat in southern Sweden 1983–2007

The economics of fungicide use in winter wheat in southern Sweden

Induced resistance in potato to Phytphthora infestans—effects of BABA in greenhouse and field tests with different potato varieties

Yield and disease control in winter wheat in southern Sweden during 1977-2005.