Plant Immunology Lecture 1

Contents Principles of techniques in Plant Immunology Agro eco systems and microbes Application of immunology Antigens, antibodies Monoclonal antisera Polyclonal antisera Phage displade recombinant antibodies Basic Immuno-detection techniques Preciptation and agglutination reactions Immuno diffusion tests Immuno electrophoresis Immuno electron microscopy Immuno capture reverse transcription technique Immuno capillary zone electrophoresis

Structure and constituents of healthy plants Components of Plant cells Organization of tissues of plant body Plant stress interaction Plant abiotic stress interaction Plant biotic stress interaction Plant Bacterial pathogen attraction Plant Fungal pathogen attraction Plant viruses pathogen attraction Approaches for plant health management Improvement of host plant resistance through genetic manipulation Induction of disease resistance Production of disease free plants

Assessment of food safety Mycotoxins and food safety Detection of mycotoxins Management of micotoxins Detection of fungicides Detection of pesticides Recommended books: Immunology in Plant Health and Its Impact on Food Safety by P. Narayanasamy. CRC Press.

Agro-ecosystems and Microbes

Ecosystem An ecosystem can be defined as a functional system of complementary relations between living organisms and their environment. The most basic components of ecosystems are biotic and abiotic factors. The assemblages of individuals, communities, and physical environments. Ex. Ponds, lakes, forests etc. Ecosystems are ultimate unit for study in ecology Life systems: subdivision of ecosystems

Basic components of ecosystems

Agroecosystem Agriculture + ecosystem =Agroecosystem Any ecosystem largely created and maintained to satisfy a human want or need is called an agroecosystem Agroecological research is the idea that, by understanding ecological relationships and processes, agroecosystems can be manipulated to improve production and to produce more sustainably, with fewer negative environmental or social impacts and fewer external inputs.

Difference between manipulated Agroecology and Natural Ecology Six ways difference : Maintenance at an early succession state Monoculture Crops generally planted in rows Simplification of biodiversity Plough which exposes soil to erosion Use of genetically modified organisms and artificially selected crops

Semi-domesticated ecosystems that fall on a gradient between ecosystems that have experienced minimal human impact, and those under maximum human control. E.g.- Integrated pest management aims to control problematic pests through introduction of other species, not application of pesticides or herbicides to kill that pest. Method of intercropping. Elimination of unsustainable practices such as increasingly intensified pesticide use.

Sustainable agroecosystems Maintain their natural resource base. Rely on minimum artificial inputs from outside the farm system. Manage pests and diseases through internal regulating mechanisms Recover from the disturbances caused by cultivation and harvest

Role of microbes in agroecosystems Agricultural lands are more complex and diverse ecosystems. Most of this biodiversity is hidden in the soil, with up to 107 prokaryotes per gram of soil and at least 105 bacterial species and agroecosystems also host insects, weeds, birds and rodents, leading to complex interactions and trophic networks.

Managing interactions between and within the different trophic levels may enhance agroecosystem functions and increase crop productivity and improve pest control and sustainability. For example, interactions between belowground soil organisms and aboveground plant communities influence ecosystem processes and properties with consequences for the provision of the related services.

The direct management of biotic interactions to promote plant growth and the enhancement of services that ecosystems provide naturally, such as pest control, underlies the ecological intensification of cropping systems. Given its potential as an alternative to chemical intensification, interest in ecological intensification has been growing, both in ecological and agronomic research

Ecological intensification The process of increasing crop production to satisfy future food demand while meeting acceptable standards of environmental quality. It is based on management of ecosystem processes rather than fossil fuel inputs by (i) integrating biological and ecological processes into food production processes (ii) minimizing the use of non-renewable inputs

FIGURE 2 | Possible means (blue frames) and objectives (red frames) of ecological intensification.

Aims of ecological intensification To promote beneficial biological interactions to limit the massive use of chemical inputs such as pesticides and fertilizers. To reduce the environmental impact.

Pesticide use A conventional approach for decreasing pesticide use is based on antagonistic interactions between pests and their natural enemies. One of the successes of such biological control in crops was the release of the parasitoïd Encarsia formosa against the greenhouse whitefly Trialeurodes vaporariorum in the 1970s as a substitute for pesticides to which the whitefly had evolved to be resistant.

Disease control In soils, interactions between the pathogens and the indigenous soil microorganisms are responsible for reducing the severity of the disease by inhibiting the growth or activity of the pathogen. The potential for biocontrol of diseases by using interactions such as amensalism (e.g., antibiosis), competition and parasitism between fungal or bacterial strains and plant pathogens has been widely studied in microbial ecology

Positive interactions such as facilitation and mutualism can also help to reduce fertilizer inputs and increase primary production. In an intercropped agroecosystem, the exudation of phosphorous-mobilizing compounds or other mechanisms for increasing phosphate availability by one species can facilitate phosphorous uptake by the other species.

Saprophytic microorganisms thriving in the rhizosphere also increase soil resource availability by cycling nutrients, which is beneficial for the plants. Plant growth promoting rhizobacteria(PGPR), which are commonly applied in developing countries where the use of mineral fertilizer is limited by costs, can also trigger growth by synthesizing volatiles mimicking plant hormones.

Managing plant-microbe interactions is of interest not only for optimizing nutrient cycling but also for reducing consequences such as leaching and greenhouse gas emissions. It has recently been demonstrated that compounds inhibiting the microbial oxidation of ammonium into nitrate released by plant roots resulted in reduced field emissions of N2O. Selection for such traits may lead to a new generation of crop cultivars that limit microbial emissions of greenhouse gases.

Applications of immunology It has applications in both medicine and agriculture. Immunological techniques are highly specific sensitive simple rapid cost effective and can be automated for large scale applications. Immunoassays have largely replaced conventional methods that are time consuming and expensive.

Immunoassays provide a reliable and sensitive methods for assessment of levels of resistance of crop cultivars and also wild relatives which are source of disease resistant genes Production of disease free seeds and plant propagative materials e.g tubers corms are possible because of immunological methods Food safety can be easily assessed by immunological assays