Classical Genetics and Traditional Breeding in Cucumber (Cucumis sativus L.)

Rapid progress has been made in classical genetics and traditional breeding in cucumber for various quantitative and qualitative traits which greatly benefited the development of superior varieties suitable for open field and protected cultivation. The different breeding methods like plant introductions, hybridizations, pedigree selection, recombination breeding and marker assisted selection have been employed successfully in developing superior varieties and F1 hybrids. The development of new varieties with earliness, high-yield and resistance to diseases (powdery mildew, downy mildew and tolerant to virus) through selection of superior parental lines followed by hybridization and marker assisted introgression of desired genes was a game changer in cucumber breeding. The exploitation of gynoecious sex along with parthenocarpic traits in traditional breeding has made revolution in cucumber cultivation throughout the world which enabled the adoption of cucumber crop by farming community on large scale. Molecular markers technology could be exploited to overcome the obstacle of traditional breeding by accelerating the breeding cycle and selection of desirable traits. The high density genetic maps for various traits have been constructed in cucumber to detected quantitative traits loci (QTLs) for genetic enhancement in different market classes of cucumber. Therefore, this chapter highlighted the concepts of genetic foundations for advancement made in cucumber breeding.

Advances in Research on the Mechanism of Heterosis in Plants

Heterosis is a common biological phenomenon in nature. It substantially contributes to the biomass yield and grain yield of plants. Moreover, this phenomenon results in high economic returns in agricultural production. However, the utilization of heterosis far exceeds the level of theoretical research on this phenomenon. In this review, the recent progress in research on heterosis in plants was reviewed from the aspects of classical genetics, parental genetic distance, quantitative trait loci, transcriptomes, proteomes, epigenetics (DNA methylation, histone modification, and small RNA), and hormone regulation. A regulatory network of various heterosis-related genes under the action of different regulatory factors was summarized. This review lays a foundation for the in-depth study of the molecular and physiological aspects of this phenomenon to promote its effects on increasing the yield of agricultural production.

The Anomaly of Bacterial Genetics

This chapter reviews the research that set the stage for Joshua Lederberg’s surprising discovery of bacterial conjugation. While the foundational research of Gregor Mendel and his principles of inheritance had been effectively combined with Darwinian evolution, producing the Modern Synthesis in the mid-forties, bacteria did not fit into this grand synthesis. Most biologists believed that bacteria were too primitive to have real genes. But Delbruck, Hershey and Luria organized the Phage School, leading a novel approach to discovering the molecular biology of the gene by studying bacteriophages. Microbiologists like Tracy Sonneborn and Carl Lindegren turned to alternative microorganisms—protists, fungi, and yeast—to develop new model systems that offered advantages over the classical genetics organisms of animals and plants. The research of Edward Tatum and Jacques Monod indicated that mutations seemed to explain variation in bacteria. For many years, however, bacteriologists had known that bacteria reproduced by fission. The lack of any genetic hybridization seemed to argue against using bacteria to study basic genetic processes.

In Vivo Silencing of Genes Coding for dTip60 Chromatin Remodeling Complex Subunits Affects Polytene Chromosome Organization and Proper Development in Drosophila melanogaster

Chromatin organization is developmentally regulated by epigenetic changes mediated by histone-modifying enzymes and chromatin remodeling complexes. In Drosophila melanogaster, the Tip60 chromatin remodeling complex (dTip60) play roles in chromatin regulation, which are shared by evolutionarily-related complexes identified in animal and plants. Recently, it was found that most subunits previously assigned to the dTip60 complex are shared by two related complexes, DOM-A.C and DOM-B.C, defined by DOM-A and DOM-B isoforms, respectively. In this work, we combined classical genetics, cell biology, and reverse genetics approaches to further investigate the biological roles played during Drosophila melanogaster development by a number of subunits originally assigned to the dTip60 complex.

Gregor Mendel, Thomas Hunt Morgan en experimenten in de klassieke genetica

Gregor Mendel, Thomas Hunt Morgan and experiments in classical geneticsIn the middle of the 19th century, Gregor Mendel performed a series of crosses with pea plants to investigate how hybrids are formed. Decades later, Thomas Hunt Morgan finalized the theory of classical genetics. An important aspect of Mendel’s and Morgan’s scientific approach is that they worked in a systematic, experimental fashion. But how did these experiments proceed? What is the relation between these experiments and Mendel’s and Morgan’s explanatory theories? What was their evidential value? Using present-day insights in the nature of experimentation I will show that the answer to these questions is fascinating but not obvious. Crossings in classical genetics lacked a crucial feature of traditional experiments for causal discovery: manipulation of the purported causes. Hence they were not traditional, ‘manipulative’ experiments, but ‘selective experiments’.

Irradiation induced inversions suppress recombination between the M locus and morphological markers in Aedes aegypti

Background Aedes aegypti is the primary vector of arthropod-borne viruses and one of the most widespread and invasive mosquito species. Due to the lack of efficient specific drugs or vaccination strategies, vector population control methods, such as the sterile insect technique, are receiving renewed interest. However, availability of a reliable genetic sexing strategy is crucial, since there is almost zero tolerance for accidentally released females. Development of genetic sexing strains through classical genetics is hindered by genetic recombination that is not suppressed in males as is the case in many Diptera. Isolation of naturally-occurring or irradiation-induced inversions can enhance the genetic stability of genetic sexing strains developed through genetically linking desirable phenotypes with the male determining region. Results For the induction and isolation of inversions through irradiation, 200 male pupae of the ‘BRA’ wild type strain were irradiated at 30 Gy and 100 isomale lines were set up by crossing with homozygous ‘red-eye’ (re) mutant females. Recombination between re and the M locus and the white (w) gene (causing a recessive white eye phenotype when mutated) and the M locus was tested in 45 and 32 lines, respectively. One inversion (Inv35) reduced recombination between both re and the M locus, and wand the M locus, consistent with the presence of a rather extended inversion between the two morphological mutations, that includes the M locus. Another inversion (Inv5) reduced recombination only between w and the M locus. In search of naturally-occurring, recombination-suppressing inversions, homozygous females from the red eye and the white eye strains were crossed with seventeen and fourteen wild type strains collected worldwide, representing either recently colonized or long-established laboratory populations. Despite evidence of varying frequencies of recombination, no combination led to the elimination or substantial reduction of recombination. Conclusion Inducing inversions through irradiation is a feasible strategy to isolate recombination suppressors either on the M or the m chromosome for Aedes aegypti. Such inversions can be incorporated in genetic sexing strains developed through classical genetics to enhance their genetic stability and support SIT or other approaches that aim to population suppression through male-delivered sterility.