Umesh Goutam

Recent trends and perspectives of molecular markers against fungal diseases in wheat

Wheat accounts for 19% of the total production of major cereal crops in the world. In view of ever increasing population and demand for global food production, there is an imperative need of 40–60% increase in wheat production to meet the requirement of developing world in coming 40 years. However, both biotic and abiotic stresses are major hurdles for attaining the goal. Among the most important diseases in wheat, fungal diseases pose serious threat for widening the gap between actual and attainable yield. Fungal disease management, mainly, depends on the pathogen detection, genetic and pathological variability in population, development of resistant cultivars and deployment of effective resistant genes in different epidemiological regions. Wheat protection and breeding of resistant cultivars using conventional methods are time-consuming, intricate and slow processes. Molecular markers offer an excellent alternative in development of improved disease resistant cultivars that would lead to increase in crop yield. They are employed for tagging the important disease resistance genes and provide valuable assistance in increasing selection efficiency for valuable traits via marker assisted selection (MAS). Plant breeding strategies with known molecular markers for resistance and functional genomics enable a breeder for developing resistant cultivars of wheat against different fungal diseases.

Allelic variations of functional markers for polyphenol oxidase (PPO) genes in Indian bread wheat (Triticum aestivum L.) cultivars.

Polyphenol oxidase (PPO) activity causes undesirable browning and discolouration of products manufactured from bread wheat (Triticum aestivumL.) during processing or storage. PPO is a copper-containing metalloprotein which catalyses hydroxylation of o-monophenols to o-diphenols and oxidation of o-diphenols to o-quinones. Auto-oxidation and polymerization of quinones with amino acid group of cellular proteins results in dark and brown discolouration of products made from bread wheat grains (Anderson and Morris 2001). The darkening phenomena of such products may reduce the quality of products and thus affect consumer acceptance. Flour protein content has a negative association with flour PPO activity (Park et al. 1997) presumably because of reactivity of phenolic side groups (Demeke et al. 2001). In wheat, PPO genes belong to a multi-gene family and are classified into two clusters: kernel and nonkernel, based on gene expression sites (Anderson et al. 2006; Jukanti et al. 2006). Recently, Massa et al. (2007) reported 21 distinct PPO sequences in kernel-type genes in wheat and wild relatives. Many studies have implied that PPO activity is mainly conditioned by the genes located on homoeologous group 2 chromosomes in wheat and wild relatives (Demeke et al. 2001; Watanabe et al. 2004, 2006; Sun et al. 2005; He et al. 2007, 2009; Raman et al. 2007). The high activity PPO alleles on chromosomes 2AL and 2DL are most thoroughly studied and were first reported by Wrigley and McIntosh (1975). A relatively low PPO activity was also found to be associated with chromosomes 2B, 3D and 6B (Demeke et al. 2001; Fuerst et al. 2008). Functional Sequence tagged site (STS) markers for PPO genes on chromosomes 2A and 2D have been developed, based on DNA sequences in GenBank (Sun et al. 2005; He et al. 2007;

Recent Approaches for Late Blight Disease Management of Potato Caused by Phytophthora infestans

Potato (Solanum tuberosum) is the fourth most produced noncereal crop worldwide. Among various biotic stresses, late blight caused by Phytophthora infestans is the most devastating disease. It affects both potato foliage in the field and tuber in the storage which can absolutely destroy a crop, producing a 100% crop loss. The occurrence and rigorousness of late blight caused by Phytophthora can be reduced by adopting effective and durable control methods. The use of conventional control methods (cultural practices and fungicides) was limited due to their inefficiency and non-biodegradable nature. Control of the disease has been achieved up to a great extent through the use of fungicides, but their extensive application is harmful for the environment. Therefore, there is an urgent need to find alternative eco-friendly crop protection methods. The use of microorganisms as biological control agents owing to their different modes of actions (i.e. antagonistic effects or induction of plant defence mechanisms) has proved to be a potential approach. Another economical and eco-friendly remedial measure for plant diseases being adopted involves the use of nanoparticles against plant pathogens. Providing genetic resistance against pests and diseases is another crop protection approach. Multiple resistance (R) genes have been introduced in potato varieties to provide durable resistance to late blight. Genetic modification using cisgenes is preferable as it is a feasible and highly efficient approach with low risks and high societal acceptability. Accumulation of new virulent P. infestans strains decreases the effectiveness of R-genes. Therefore, the loss of function in susceptible gene via gene silencing is the emerging approach which helps in exploring plant-pathogen interactions and provides potential strategies for disease control. RNA silencing without altering the plant genome overcomes the risk associated with transgenic plants.

Fungal Disease Management in Chickpea: Current Status and Future Prospects

Chickpea (Cicer arietinum L.) is one of the most important leguminous crops grown predominantly in tropical and temperate areas. The beneficial effects of chickpea on soil health and human health are well recognized. The area under chickpea production in India is 9.6 million ha with an average production of 8.8 million tons. Yield of chickpea is largely affected by exposure to both abiotic and biotic stresses. It has been observed that insects and diseases cause around 50–100% yield loss in chickpea in temperate regions. Among various diseases caused by a variety of pathogens, fungal diseases have shown to have devastating effects on the chickpea yield. Among various fungal diseases, the diseases caused by Fusarium oxysporum (fusarium wilt) and Ascochyta rabiei (Ascochyta blight) are the most common root and foliar diseases, respectively, causing severe loss to crop yield. Identification of pathogen, variation in genome and pathology, development of disease-resistant varieties, and organizing the resistant genes in different regions play an important role in fungal disease management. Implication of conventional methods is both time-consuming and slow process. Development of new genomic tools and resources aid the employment of genomics selection in improvement of chickpea. This will provide greater insight to the breeding program to work with high precision and accuracy to develop resistant chickpea cultivars.

Milestones achieved in response to drought stress through reverse genetic approaches

Drought stress is the most important abiotic stress that constrains crop production and reduces yield drastically. The germplasm of most of the cultivated crops possesses numerous unknown drought stress tolerant genes. Moreover, there are many reports suggesting that the wild species of most of the modern cultivars have abiotic stress tolerant genes. Due to climate change and population booms, food security has become a global issue. To develop drought tolerant crop varieties knowledge of various genes involved in drought stress is required. Different reverse genetic approaches such as virus-induced gene silencing (VIGS), clustered regularly interspace short palindromic repeat (CRISPR), targeting induced local lesions in genomes (TILLING) and expressed sequence tags (ESTs) have been used extensively to study the functionality of different genes involved in response to drought stress. In this review, we described the contributions of different techniques of functional genomics in the study of drought tolerant genes.

Genetic Engineering of Poplar: Current Achievements and Future Goals

Global biomass demand for industrial applications is ever increasing especially in biofuels and pulp industries. Poplar is likely to have great biological advantages over the other forest trees which include small genome size, large number of species, rapid juvenile growth, ease of clonal propagation, easy recovery of genetic transformants, and available genome draft. Wide and sustainable farming of rapidly growing trees such as poplars may supplement to attain the requirement of renewable resources. This chapter covers the progress in both basic and applied studies in poplar genetic tailoring. Certain advices are given for future direction of the research in poplar genetic tailoring so as to achieve the needs of environmental cleansing system and the timber industries. Emerging new thoughts for designing wood improvement approaches are discussed.

Changing Trends in Microalgal Energy Production- Review of Conventional and Emerging Approaches

The depletion of fossil fuel for energy production is one of the major problems being faced worldwide. As an alternative to fossil fuels, first and second generation biofuel was developed from corn, grains and lignocellulosic agricultural residues. These generations are inefficient in achieving the desired rate of biofuel production, climate change mitigation and economic growth. Therefore, third generation biofuel specifically derived from microalgae have proved to be a promising unconventional energy source. Microalgae are microscopic organisms that grow in salt or fresh water and have been used for producing metabolites, cosmetics and for energy production. The conventional approaches used for biofuel production include pyrolysis, gasification, direct combustion and thermomechanical liquefaction. The search for biological and eco-friendly approaches led to the emergence of Microbial Fuel Cell (MFC), which provide a new solution to energy crisis. Integration of photosynthetic organisms such as microalgae into MFC resulted in a new approach i.e. Microbial Solar Cell, which can convert solar energy into electrical energy via photosynthesis. Microbial solar cells have broad range application in wastewater treatment, biodiesel processing and intermediate metabolite production.