Detection and Quantification of Leveillula taurica Growth in Pepper Leaves
Zheng, Z. ; Nonomura, T. ; Bóka, K. ; Matsuda, Y. ; Visser, R.G.F. ; Toyoda, H. ; Kiss, L. ; Bai, Y. - \ 2013
Phytopathology 103 (2013)6. - ISSN 0031-949X - p. 623 - 632.
internal transcribed spacer - powdery-mildew - genus leveillula - capsicum-annuum - resistance - pcr - infections - sequences - fungi - dna
Leveillula taurica is an obligate fungal pathogen that causes powdery mildew disease on a broad range of plants, including important crops such as pepper, tomato, eggplant, onion, cotton, and so on. The early stage of this disease is difficult to diagnose and the disease can easily spread unobserved; for example, in pepper and tomato production fields and greenhouses. The objective of this study was to develop a detection and quantification method of L. taurica biomass in pepper leaves with special regard to the early stages of infection. We monitored the development of the disease to time the infection process on the leaf surface as well as inside the pepper leaves. The initial and final steps of the infection taking place on the leaf surface were consecutively observed using a dissecting microscope and a scanning electron microscope. The development of the intercellular mycelium in the mesophyll was followed by light and transmission electron microscopy. A pair of L. taurica-specific primers was designed based on the internal transcribed spacer sequence of L. taurica and used in real-time polymerase chain reaction (PCR) assay to quantify the fungal DNA during infection. The specificity of this assay was confirmed by testing the primer pair with DNA from host plants and also from another powdery mildew species, Oidium neolycopersici, infecting tomato. A standard curve was obtained for absolute quantification of L. taurica biomass. In addition, we tested a relative quantification method by using a plant gene as reference and the obtained results were compared with the visual disease index scoring. The real-time PCR assay for L. taurica provides a valuable tool for detection and quantification of this pathogen in breeding activities as well in plant-microbe interaction studies.
Towards genomic selection in apple (Malus x domestica Borkh.) breeding programmes: Prospects, challenges and strategies
Kumar, S. ; Bink, M.C.A.M. ; Volz, R.K. ; Bus, V.G.M. ; Chagne, D. - \ 2012
Tree Genetics and Genomes 8 (2012)1. - ISSN 1614-2942 - p. 1 - 14.
marker-assisted selection - mildew-resistance gene - linear unbiased prediction - quantitative trait loci - fire blight resistance - fruit-quality traits - linkage group 3 - powdery-mildew - venturia-inaequalis - molecular markers
The apple genome sequence and the availability of high-throughput genotyping technologies have initiated a new era where SNP markers are abundant across the whole genome. Genomic selection (GS) is a statistical approach that utilizes all available genome-wide markers simultaneously to estimate breeding values or total genetic values. For breeding programmes, GS is a promising alternative to the traditional marker-assisted selection for manipulating complex polygenic traits often controlled by many small-effect genes. Various factors, such as genetic architecture of selection traits, population size and structure, genetic evaluation systems, density of SNP markers and extent of linkage disequilibrium, have been shown to be the key drivers of the accuracy of GS. In this paper, we provide an overview of the status of these aspects in current apple-breeding programmes. Strategies for GS for fruit quality and disease resistance are discussed, and an update on an empirical genomic selection study in a New Zealand apple-breeding programme is provided, along with a foresight of expected accuracy from such selection.