So far in this course we have dealt entirely with the evolution of characters that are controlled by simple Mendelian inheritance at a single locus. There are notes on the course website about gametic disequilibrium and how allele frequencies change at two loci simultaneously, but we didn’t discuss them. In every example we’ve considered we’ve imagined that we could understand something about evolution by examining the evolution of a single gene. That’s the domain of classical population genetics. For the next few weeks we’re going to be exploring a field that’s actually older than classical population genetics, although the approach we’ll be taking to it involves the use of population genetic machinery. If you know a little about the history of evolutionary biology, you may know that after the rediscovery of Mendel’s work in 1900 there was a heated debate between the “biometricians” (e.g., Galton and Pearson) and the “Mendelians” (e.g., de Vries, Correns, Bateson, and Morgan). Biometricians asserted that the really important variation in evolution didn’t follow Mendelian rules. Height, weight, skin color, and similar traits seemed to

Human biochemical genetics

https://cyberleninka.org/article/n/1302921.pdf

Plant biostimulants: Definition, concept, main categories and regulation

Regulation of photosynthesis of C3 plants in response to progressive drought: stomatal conductance as a reference parameter.

Agronomic approaches for improving the micronutrient density in edible portions of field crops

Chitosan is a biopolymer obtained from chitin, one of the most abundant and renewable materials on Earth Chitin is a primary component of cell walls in fungi, the exoskeletons of arthropods such as crustaceans, eg, crabs, lobsters and shrimps, and insects, the radulae of molluscs, cephalopod beaks, and the scales of fish and lissamphibians The discovery of chitin in 1811 is attributed to Henri Braconnot while the history of chitosan dates back to 1859 with the work of Charles Rouget The name of chitosan was, however, introduced in 1894 by Felix Hoppe-Seyler Chitosan has attracted major scientific and industrial interests from the late 1970s due to its particular macromolecular structure, biocompatibility, biodegradability and other intrinsic functional properties Chitosan and derivatives have practical applications in the food industry, agriculture, pharmacy, medicine, cosmetology, textile and paper industries, and in chemistry In recent years, chitosan has also received much attention in dentistry, ophthalmology, biomedicine and bioimaging, hygiene and personal care, veterinary medicine, packaging industry, agrochemistry, aquaculture, functional textiles and cosmetotextiles, catalysis, chromatography, beverage industry, photography, wastewater treatment and sludge dewatering, and biotechnology Nutraceuticals and cosmeceuticals are actually growing markets, and therapeutic and biomedical products should be the next markets in the development of chitosan Chitosan is also the object of numerous fundamental studies In this review, we highlight a selection of works on chitosan applications published over the past two decades

https://hal.archives-ouvertes.fr/hal-02402948/document

Applications of chitosan in food, pharmaceuticals, medicine, cosmetics, agriculture, textiles, pulp and paper, biotechnology, and environmental chemistry

Chitosan is a natural biopolymer modified from chitins which act as a potential biostimulant and elicitor in agriculture. It is non-toxic, biodegradable and biocompatible which favors potentially broad application. It enhances the physiological response and mitigates the adverse effect of abiotic stresses through stress transduction pathway via secondary messenger(s). Chitosan treatment stimulates photosynthetic rate, stomatal closure through ABA synthesis; enhances antioxidant enzymes via nitric oxide and hydrogen peroxide signaling pathways, and induces production of organic acids, sugars, amino acids and other metabolites which are required for the osmotic adjustment, stress signaling, and energy metabolism under stresses. It is also known to form complexes with heavy metals and used as tool for phytoremediation and bioremediation of soil. Besides, this is used as antitranspirant compound through foliar application in many plants thus reducing water use and ensures protection from other negative effects. Based on such beneficial properties, chitosan is utilized in sustainable agricultural practices owing to changing climates. Our review gathers the recent information on chitosan centered upon the abiotic stress responses which could be useful in future crop improvement programs.

/pdf/application-of-chitosan-on-plant-responses-with-special-4tlam8ubkf.pdf

Application of chitosan on plant responses with special reference to abiotic stress

Biopolymer “Chitosan” has received much interest for potential wide application in agriculture due to its excellent biocompatibility, biodegradability and bioactivity. This naturally occurring molecule with interesting physiological potential has been getting more attention in recent years. Chitosan enhanced the efficacy of plants to reduce the deleterious effect of unfavorable conditions as well as on plant growth. Chitosan affects various physiological responses like plant immunity, defense mechanisms involving various enzymes such as, phenylalanine ammonium lyase, polyphenol oxidase, tyrosine ammonia lyase and antioxidant enzymes viz., activities superoxide dismutase, catalase and peroxide against adverse conditions. Recent studies have shown that chitosan induces mechanisms in plants against various biotic (fungi, bacteria, and insects) and abiotic (salinity, drought, heavy metal and cold) stresses and helps in formation of barriers that enhances plant's productivity. This paper takes a closer look at the physiological responses of chitosan molecule.

Chitosan as a promising natural compound to enhance potential physiological responses in plant: a review

Crop plant evolution either natural or human-directed, is primarily based on existing genetic diversity in the population. Diversity can be described as the degree of differentiation between or within species. Existing intraand inter-specific differences are at the base of all crop improvement programmes. If all the individuals within the species would have been similar, then possibly there could not have been any scope for improvement in plant performances for different traits. Since the beginning of systematic plant breeding, natural variability and divergence between crops have been extensively identified and used in improvement of crop species. However, with the progress of time, natural variability got depleted due to (i) lopsided breeding practices focusing on improvement of only few traits (like yield and its component traits), (ii) frequent use of few selected genotypes as parents in varietal development programme and (iii) introduction of few outstanding lines to many countries thereby leading to increased genetic similarity between modern crop cultivars. Reduced genetic variability and diversity among crop plant species has raised serious concern among agricultural workers. With reduced genetic diversity, further improvement in crop varieties will be an arduous task. Breaking yield barriers will become difficult and plant breeders will be unable to meet the requirements arising out of ever-increasing demand on account of exploding population. Genetic diversity becomes more important in context of climatic change and associated unforeseen events as it may serve as the reservoir of many novel traits conferring tolerance to different biotic and abiotic stresses. Genetic diversity is the underlying cause of many important agriculturally important phenomena like heterosis and transgressive segregation. Diverse lines are needed for defect correction of commercial varieties and development of novel varieties. Hence, identification of diverse lines (if available), creation of diversity (if not available or limited) and its subsequent utilization are the major goals of any crop improvement programmes. In this context, knowledge on all aspects of genetic diversity viz., factors affecting genetic diversity, different methods of diversity analysis, their measurement and the softwares for carrying statistical analysis becomes imperative in order to utilize them prudently. Many reviews have been written focusing on vital issues like changes in genetic diversity under plant breeding,1 genetic vulnerability of modern crop cultivars,2 conservation and utilization of genetic resources3,4 assessment of genetic diversity using molecular markers5 and measurement of genetic diversity using statistical tools.6–8 In the present review, an attempt is being made for comprehensive compilation of overall concepts in the area of genetic diversity, which could be of immense significance for extending knowledge and meaningful research.

/pdf/assessment-of-genetic-diversity-in-crop-plants-an-overview-v06xo1hxs4.pdf

Assessment of genetic diversity in crop plants - an overview

The rising ambient temperature by plant cells is crucial for the timely activation of various molecular defences before the appearance of heat damage. The heat-threshold level varies considerably at different developmental stages. With a view to survive under heat stress, mechanisms of regulation at the molecular level enable plants to prosper. Traditional breeding contributed for improving heat tolerance meagrely. The genetic transformation approach needs to be accelerated that can mitigate harmful effects by developing improved thermotolerance of crop plants. In this background, a thorough understanding of physiological responses of plants to high temperature, mechanisms of heat tolerance and possible strategies is vital. Temperature changes are sensed through cellular responses due to signal transduction into the cell. A key ingredient for plants temperature sensing ability is a specialized histone protein, dubbed H2A.Z that wraps DNA into a more tightly packed structure. Further, metabolic reactions and internal conductance to CO 2 decrease Rubisco activation, inhibition of Rubisco activase and subsequently slowing down net photosynthesis (Pn). Importance of internal conductance to CO 2 , heat inducible transcription factor for heat shock response (HSR) involve different HSR genes. The mechanisms, which are regulated at the molecular level, facilitate plants to thrive under heat stress. Exogenous applications of protectants such as osmoprotectants, phytohormones, signaling molecules, trace elements etc. have shown beneficial effects on plants growing under high temperature, due to the growth promoting and antioxidant activities of these compounds. There is acute necessity of crop biotechnology research for evolving genetically modified (GM) crops for a high CO 2 world at this juncture. So, attaining thermotolerance is a lively process to escape damages caused by heat stress.

https://medcraveonline.com/APAR/APAR-01-00012.pdf

Heat stress responses and thermotolerance

Chitosan and its oligosaccharides have received much interest for potential application in agriculture biomedicine and biotechnology due to their biocompatibility biodegradability and bioactivity Synthetic bactericide treatment has been the main method for controlling diseases there is a growing international concern over the indiscriminate use of synthetic compounds on crops because of the possible harmful effects on human health and the emergence of pathogen resistance to bactericides Thus there is a worldwide trend to explore new alternatives in order to reduce the use of synthetic chemical agents This review focuses on the biological activities of chitosan and its oligosaccharides based on the latest research results Among the novel families of biological macromolecules whose relevance is increased in research are chitosan and chitooligosaccharides COS Both become a promising alternative treatment due to its antimicrobial activity They have a wide scope of application in the food pharmaceutical agricultural industries COS are known to have eliciting activities leading to a variety of defence responses in plants in response to microbial infections to reduce the negative impact of diseases on yield and quality of crops This review reiterates the properties and uses of chitosan and its oligosaccharides and focuses on their applications on plant bacterial infections

/pdf/a-future-perspective-in-crop-protection-chitosan-and-its-xw8iov2yto.pdf

A. Hemantaranjan

Papers

Application of chitosan on plant responses with special reference to abiotic stress

Chitosan as a promising natural compound to enhance potential physiological responses in plant: a review

Assessment of genetic diversity in crop plants - an overview

Heat stress responses and thermotolerance

A future perspective in crop protection chitosan and its oligosaccharides