Genome-Wide Association Studies (GWAS) are widely used in the genetic dissection of complex traits. Most existing methods are based on single-marker association in genome-wide scans with population structure and polygenic background controls. To control the false positive rate, the Bonferroni correction for multiple tests is frequently adopted. This stringent correction results in the exclusion of important loci, especially for GWAS in crop genetics. To address this issue, multi-locus GWAS methodologies have been recommended, i.e., FASTmrEMMA, ISIS EM-BLASSO, mrMLM, FASTmrMLM, pLARmEB, pKWmEB and FarmCPU. In this Research Topic, our purpose is to clarify some important issues in the application of multi-locus GWAS methods. Here we discuss the following subjects: First, we discuss the advantages of new multi-locus GWAS methods over the widely-used single-locus GWAS methods in the genetic dissection of complex traits, metabolites and gene expression levels. Secondly, large experiment error in the field measurement of phenotypic values for complex traits in crop genetics results in relatively large P-values in GWAS, indicating the existence of small number of significantly associated SNPs. To solve this issue, a less stringent P-value critical value is often adopted, i.e., 0.001, 0.0001 and 1/m (m is the number of markers). Although lowering the stringency with which an association is made could identify more hits, confidence in these hits would significantly drop. In this Research Topic we propose a new threshold of significant QTN (LOD=3.0 or P-value=2.0e-4) in multi-locus GWAS to balance high power and low false positive rate. Thirdly, heritability missing in GWAS is a common phenomenon, and a series of scientists have explained the reasons why the heritability is missing. In this Research Topic, we also add one additional reason and propose the joint use of several GWAS methodologies to capture more QTNs. Thus, overall estimated heritability would be increased. Finally, we discuss how to select and use these multi-locus GWAS methods.

Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.

The Wheat Improvement, Management, and Utilization book covers some of the most recent research areas that touch on enhancement of wheat productivity. It is obvious that wheat is one of the major staple crops grown globally. This crop has widely been researched on considering that, for instance, it is afflicted by various abiotic and biotic stresses that limit its growth and productivity. Today?s goal of wheat improvement consistently is to develop varieties that are high yielding with good processing and technological qualities, well adapted and tolerant to prevailing biotic and abiotic stresses. Therefore, this is a valuable reference book on wheat improvement, agronomy, and end-use qualities, particularly for those who work in research organizations and higher academic institutions. Moreover, it provides an invaluable resource for readers interested in a quick review of trending topics in wheat.

While preparing the first edition of this textbook I attended an extension short course on writing agricultural publications. The message I remember was "select your audience and write to it. " There has never been any doubt about the audience for which this textbook was written, the introductory course in crop breeding. In addition, it has become a widely used reference for the graduate plant-breeding student and the practicing plant breeder. In its prepa ration, particular attention has been given to advances in plant-breeding theo ry and their utility in plant-breeding practice. The blend of the theoretical with the practical has set this book apart from other plant-breeding textbooks. The basic structure and the objectives of the earlier editions remain un changed. These objectives are (1) to review essential features of plant re production, Mendelian genetic principles, and related genetic developments applicable in plant-breeding practice; (2) to describe and evaluate established and new plant-breeding procedures and techniques, and (3) to discuss plant breeding objectives with emphasis on the importance of proper choice of objec tive for achieving success in variety development. Because plant-breeding activities are normally organized around specific crops, there are chapters describing breeding procedures and objectives for the major crop plants; the crops were chosen for their economic importance or diversity in breeding sys tems. These chapters provide a broad overview of the kinds of problems with which the breeder must cope.

Crops experience an assortment of environmental stresses which include abiotic viz., drought, water logging, salinity, extremes of temperature, high variability in radiation, subtle but perceptible changes in atmospheric gases and biotic viz., insects, birds, other pests, weeds, pathogens (viruses and other microbes). The ability to tolerate or adapt and overwinter by effectively countering these stresses is a very multifaceted phenomenon. In addition, the inability to do so which renders the crops susceptible is again the result of various exogenous and endogenous interactions in the ecosystem. Both biotic and abiotic stresses occur at various stages of plant development and frequently more than one stress concurrently affects the crop. Stresses result in both universal and definite effects on plant growth and development. One of the imposing tasks for the crop researchers globally is to distinguish and to diminish effects of these stress factors on the performance of crop plants, especially with respect to yield and quality of harvested products. This is of special significance in view of the impending climate change, with complex consequences for economically profitable and ecologically and environmentally sound global agriculture. The challenge at the hands of the crop scientist in such a scenario is to promote a competitive and multifunctional agriculture, leading to the production of highly nourishing, healthy and secure food and animal feed as well as raw materials for a wide variety of industrial applications. In order to successfully meet this challenge researchers have to understand the various aspects of these stresses in view of the current development from molecules to ecosystems. The book will focus on broad research areas in relation to these stresses which are in the forefront in contemporary crop stress research.