The growing human population and a changing environment have raised significant concern for global food security, with the current improvement rate of several important crops inadequate to meet future demand . This slow improvement rate is attributed partly to the long generation times of crop plants. Here, we present a method called 'speed breeding', which greatly shortens generation time and accelerates breeding and research programmes. Speed breeding can be used to achieve up to 6 generations per year for spring wheat (Triticum aestivum), durum wheat (T. durum), barley (Hordeum vulgare), chickpea (Cicer arietinum) and pea (Pisum sativum), and 4 generations for canola (Brassica napus), instead of 2-3 under normal glasshouse conditions. We demonstrate that speed breeding in fully enclosed, controlled-environment growth chambers can accelerate plant development for research purposes, including phenotyping of adult plant traits, mutant studies and transformation. The use of supplemental lighting in a glasshouse environment allows rapid generation cycling through single seed descent (SSD) and potential for adaptation to larger-scale crop improvement programs. Cost saving through light-emitting diode (LED) supplemental lighting is also outlined. We envisage great potential for integrating speed breeding with other modern crop breeding technologies, including high-throughput genotyping, genome editing and genomic selection, accelerating the rate of crop improvement.

Seed development in plants involves the coordinated growth of the embryo, endosperm, and maternal tissue. Several genes have been identified that influence seed size by acting maternally, such as AUXIN RESPONSE FACTOR2, APETALA2, and DA1. However, given the lack of gain-of-function effects of these genes on seed size, it is unclear whether their activity levels are limiting in WT plants and whether they could thus be used to regulate seed size in development or evolution. Also, whether the altered seed sizes reflect local gene activity or global physiological changes is unknown. Here, we demonstrate that the cytochrome P450 KLUH (KLU) regulates seed size. KLU acts locally in developing flowers to promote seed growth, and its activity level is limiting for seed growth in WT. KLU is expressed in the inner integument of developing ovules, where it non-cell autonomously stimulates cell proliferation, thus determining the growth potential of the seed coat and seed. A KLU-induced increase in seed size leads to larger seedlings and higher relative oil content of the seeds. Genetic analyses indicate that KLU acts independently of other tested maternal factors that influence integument cell proliferation. Thus, the level of KLU-dependent growth factor signaling determines size in ovules and seeds, suggesting this pathway as a target for crop improvement.Arabidopsis ͉ clonal analysis ͉ cytochrome P450 ͉ seed growth S eed size in higher plants is an important trait with respect to ecology and agriculture (1). For example, larger seeds are less easily dispersed, but offer the germinating seedling a larger supply of nutrients, thus increasing its competitiveness during seedling establishment and tolerance to adverse environmental conditions. At the same time, limited resources in the mother plant generally cause a tradeoff between the number and size of the seeds produced (2). As for agriculture, increasing seed size has been a crucial contributor to the yield increases in crop plants during domestication (3).Seeds are formed by the coordinated growth of maternal sporophytic and zygotic tissues (4). The zygotic tissues are the result of double fertilization, with one sperm cell fertilizing the diploid central cell to yield the triploid endosperm and the other sperm cell fertilizing the haploid egg cell to give rise to the diploid embryo. These maternal gametes lie within the embryo sac that develops in the nucellus region of the ovule (5). The nucellus is surrounded by the integuments, protective organs that form the maternal component of the mature seed after fertilization, the seed coat (6).The size of seeds is known to be influenced by parent-of-origin effects, with a paternal genome excess causing seed overgrowth, whereas a maternal genome excess reduces seed size (7). In addition, recent genetic studies in the model species Arabidopsis thaliana and rice have identified a number of factors affecting seed size by acting in the maternal and/or zygotic tissues. Among the zygotically acting factors, a small cascade of genes ...

Identification of causal mutations in barley and wheat is hampered by their large genomes and suppressed recombination. To overcome these obstacles, we have developed MutChromSeq, a complexity reduction approach based on flow sorting and sequencing of mutant chromosomes, to identify induced mutations by comparison to parental chromosomes. We apply MutChromSeq to six mutants each of the barley Eceriferum-q gene and the wheat Pm2 genes. This approach unambiguously identified single candidate genes that were verified by Sanger sequencing of additional mutants. MutChromSeq enables reference-free forward genetics in barley and wheat, thus opening up their pan-genomes to functional genomics.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-016-1082-1) contains supplementary material, which is available to authorized users.