Breeding Approaches for Biotic Stress Resistance in Vegetables

In vegetables the factors for biotic stress are pests, diseases and nematodes. The damages induced by these factors reflect highly on production, productivity and quality. Although application of pesticides/fungicides and nematicides has managed these stresses, excessive use of unsafe chemicals results in environmental pollution and leave residues in vegetables which are above threshold levels and also promote the development of new races/biotypes of pests and pathogens. Therefore vegetable improvement works concentrate on high yielding varieties with multiple resistance to these biotic stresses. For such studies, the knowledge on the genetic basis of resistance and plant-pest/pathogen interactions is necessary which will in turn improve the efficiency of the breeding programmes by introducing resistant genes and result in high-yielding genetically resistant cultivars. For the development of resistant varieties and pre-breed lines, information on sources of resistance is prerequisite and serve as a backbone in the breeding programme. Further, gene action responsible for the inheritance of characters helps in the choice of suitable breeding methods for the improvement of the crop. Work has been done by using the various breeding methods and resistant varieties have been bred and they offer the cheapest means of pest/disease/nematode control. Resistant varieties obviate the use of chemicals, thus reduce environmental pollution and facilitate safe food for human consumption.

Plant Breeding and Microbiome

In this review, references to the use of microorganisms in the process of plant domestication, genetic improvement, and production of traditional and improved varieties have been identified. The domestication process may have had an adverse impact on the composition and functions of the associated microbiota and the microbiota associated with plants influences multiple regulatory processes of plants that together define their phenotype. According to scientific evidence, to increase agricultural production and the sustainability of production systems, future research should develop breeding methods that optimize the symbiosis between plants and microorganisms, to produce new plant phenotypes that result in the production of enough food to meet the needs of the human population.

Association Mapping for Improving Fiber Quality in Upland Cottons

Improved fiber yield is considered a constant goal of upland cotton (Gossypium hirsutum) breeding worldwide, but the understanding of the genetic basis controlling yield-related traits remains limited. Dissecting the genetic architecture of complex traits is an ongoing challenge for geneticists. Two complementary approaches for genetic mapping, linkage mapping and association mapping have led to successful dissection of complex traits in many crop species. Both of these methods detect quantitative trait loci (QTL) by identifying marker–trait associations, and the only fundamental difference between them is that between mapping populations, which directly determine mapping resolution and power. Nowadays, the availability of genomic tools and resources is leading to a new revolution of plant breeding, as they facilitate the study of the genotype and its relationship with the phenotype, in particular for complex traits. Next Generation Sequencing (NGS) technologies are allowing the mass sequencing of genomes and transcriptomes, which is producing a vast array of genomic information with the development of high-throughput genotyping, phenotyping will be a major challenge for genetic mapping studies. We believe that high-quality phenotyping and appropriate experimental design coupled with new statistical models will accelerate progress in dissecting the genetic architecture of complex traits.

Breeding for Drought Resistance

Drought is the most severe abiotic stresses in many parts of the world and is one of the major problems in present-day climatic scenario. Drought tolerant varieties are with high demand which seems to be a great challenging task to plant breeders however difficulties are combined by the difficulty of crop yield on the genetic and physiological bases. Drought resistance may be defined as the mechanism(s) causing minimum loss of the yield in a drought environment relative to the maximum yield in a constant-free of optimal environment for the crop. Several researchers explained the plant reaction to drought through drought escape, dehydration avoidance, and/or dehydration tolerance mechanisms. Drought stress decreases size of the leaves, stem extension and root proliferation inside the soil, it also disturbs plant water relations and reduces water-use efficiency ultimately reduces the yielding ability of the plant so, breeding for Drought resistance is a good approach, following different breeding strategies and approaches to develop a drought resistant variety combining both conventional and molecular approaches. Considering the parameters like root morphology studies, proline estimation, leaf rolling etc., Selection based on a comprehensive approach of testing might be more effective in breeding better drought-tolerant cultivars.

Breeding Mechanisms for High Temperature Tolerance in Crop Plants

Increase in global warming poses a severe threat on agricultural production thereby affecting food security. A drastic reduction in yield at elevated temperature is a resultant of several agro-morphological, physiological and biochemical modifications in plants. Heat tolerance is a complex mechanism under polygenic inheritance. Development of tolerant genotypes suited to heat extremes will be more advantageous to tropical and sub tropical regimes. A clear understanding on heat tolerance mechanism is needed for bringing trait based improvement in a crop species. Heat tolerance is often correlated with undesirable traits which limits the economic yield. In addition, high environmental interactions coupled with poor phenotyping techniques limit the progress of breeding programme. Recent advances in molecular technique led to precise introgression of thermo-tolerant genes into elite genetic background which has been reviewed briefly in this chapter.

Breeding Strategy for Improvement of Omega-3 Fatty Acid through Conventional Breeding, Genetic Mapping, and Genomics in Soybean

Plant-derived omega (ω)-3 polyunsaturated fatty acid is an essential fatty acid in human and animal diets and is a precursor of eicosapentaenoic acid and docosahexaenoic acid, which exists as α-linolenic acid (ALA, ω-3) in plant oil. Several epidemiological studies have revealed the health benefits of regular consumption of ω-3 fatty acid-containing diets. Soybean [Glycine max (L.) Merr.] is one of the major oil crops in the world and has around 8% ALA (ω-3) in seed oil. Soybean-derived ω-3 can be potential alternative sources of ω-3 fatty acids for populations living in countries with high risks of inadequate ω-3 intake. Therefore, increasing ω-3 concentration became an important goal in soybean breeding. Conversely, higher content of ω-3 fatty acids makes seed oil rancid, necessitating chemical hydrogenation, which generates trans fats. Since trans fats have been associated with the heart and other diseases, demand for soybeans with reduced ALA content is growing. In this book chapter, we described the importance of ω-3 fatty acid and consumption of diets with balanced ω-6/ω-3 ratio and discussed breeding and biotechnological means (and integrated approaches) for altering the ω-3 fatty acid content to avoid the need for chemical hydrogenation as well as to improve the ω-6/ω-3 ratio.