In this chapter we review the transgenic approaches in improving N and K use efficiency in plants. It is thus important to verify in which way the term PPB is being used in specific publications. In countries that experience harsh winters such as Iceland, Germany and further east in Europe, plant breeders are involved in breeding for tolerance to frost, continuous snow-cover, frost-drought (desiccation from wind and solar radiation under frost) and high moisture levels in soil in winter. 1995. Genetic modification of plants is achieved by adding a specific gene or genes to a plant, or by knocking down a gene with RNAi, to produce a desirable phenotype. CBF1, c-repeat binding factor-1; CGMMV, cucumber green mottle mosaic virus; CMV, cucumber mosaic virus; DHN10, gene encoding a Solanum sogarandium dehydrin with 10 kDa; NOA1, nitric oxide associated 1; PAC, phytoene synthase-2a carotene desaturase; pDefH9, Antirrhinum majus deficiens homologue 9 promoter; PRSV W, papaya ringspot virus type W; RCC2, a rice chitinase cDNA; SOD, superoxide dismutase; WMV, watermelon mosaic virus; WSMoV, watermelon silver mottle virus; ZYMV, zucchini yellow mosaic virus. Another limitation of viral vectors is that the virus is not usually passed on to the progeny, so every plant has to be inoculated.  Plant tissue culturing can produce haploid or double haploid plant lines and generations. PPB is enhanced by farmers knowledge of the quality required and evaluation of target environment which affects the effectiveness of PPB. Agrobacterium-mediated, particle bombardment, and infiltration techniques have been commonly used for the introduction of foreign genes into organisms. Plant breeding programs can be divided into two groups including classical and modern plant breeding. Breeding programs are aimed at improving and increasing traits such as quality, flavor, yield, tolerance of abiotic and biotic stresses, and storage period. Such concerns are not new to plant breeding. Plant Breeding and Genomics eXtension Community of Practice, Infography about the History of Plant Breeding, Glossary of plant breeding terminology by the Open Plant Breeding Foundation, National Association of Plant Breeders (NAPB), The Global Partnership Initiative for Plant Breeding Capacity Building – GIPB, FAO/IAEA Programme Mutant Variety Database, FDA Statement of Policy – Foods Derived from New Plant Varieties, List of organic gardening and farming topics, https://en.wikipedia.org/w/index.php?title=Plant_breeding&oldid=987419696, Articles with dead external links from May 2020, Articles with permanently dead external links, Articles needing additional references from August 2018, All articles needing additional references, Articles needing additional references from December 2011, Wikipedia articles needing clarification from October 2013, Articles needing additional references from March 2017, Articles with unsourced statements from October 2020, Wikipedia articles needing clarification from October 2020, Wikipedia articles needing clarification from March 2017, Articles with unsourced statements from January 2019, Creative Commons Attribution-ShareAlike License, Longer storage period for the harvested crop, Early maturity (as a mechanism for avoidance of particular stresses), Abiotic stress tolerance (i.e. Previously, scientists formed very simple genetic maps using conventional techniques. The classical plant breeder may also make use of a number of in vitro techniques such as protoplast fusion, embryo rescue or mutagenesis (see below) to generate diversity and produce hybrid plants that would not exist in nature. Furthermore, two different homozygous plants created in that way can be used to produce a generation of F1 hybrid plants which have the advantages of heterozygosity and a greater range of possible traits. Figure 17.1.  It has been used to improve the quality of nutrition in products for humans and animals. Plant breeders strive to create a specific outcome of plants and potentially new plant varieties.. For example, the cereal triticale is a wheat and rye hybrid. Insect resistance is achieved through incorporation of a gene from Bacillus thuringiensis (Bt) that encodes a protein that is toxic to some insects. Selective breeding has played a vital role in crop and animal improvement since Antediluvian times. Traits that breeders have tried to incorporate into crop plants include: Successful commercial plant breeding concerns were founded from the late 19th century. Biotechnology assisted participatory plant breeding: Complement or contradiction? Plant breeding exploits biodiversity. The doubled haploid will be homozygous for the desired traits. Plant breeders of all kinds—full-time professionals, farmer-breeders, and dedicated amateurs—add to the stock of genetically diverse organisms by continually producing new and genetically diverse plant varieties with new, ecologically diverse adaptations. In the early 20th century, plant breeders realized that Mendel's findings on the non-random nature of inheritance could be applied to seedling populations produced through deliberate pollinations to predict the frequencies of different types. There have been instances where plants bred using classical techniques have been unsuitable for human consumption, for example the poison solanine was unintentionally increased to unacceptable levels in certain varieties of potato through plant breeding.  This process removes most of the genetic contribution of the mildew resistant parent. For example, mass selection for sucrose concentration in the beet root began in 1786 and was continued until 1830. If for genetic modification genes of the species or of a crossable plant are used under control of their native promoter, then they are called cisgenic plants. Pollinators may be excluded through the use of pollination bags. It is now time to evenly assess the studies related to the benefits and possible dangers of genetic engineering in comparison with other crop development techniques (Gepts, 2002). Because the markers and the genes are close in position on the same chromosome, they tend to stay together as each generation of plant is produced.  Most notably, organic farmers have fewer inputs available than conventional growers to control their production environments. Crops need to be able to mature in multiple environments to allow worldwide access, which involves solving problems including drought tolerance. It is possible to consider the three elements of the plant breeding processes (noted above as: to produce genetic variation, to select, and to stabilize and multiply for commercial use) in order to understand modern plant breeding. Conventional breeding, the slow rate of development of new crop varieties, and the curb of fertility barriers that prevented the hybridization of the same or closely associated species, have all significantly contributed to the development of high-yielding crop cultivars.