Improved lodging resistance has contributed significantly to the dramatic increase in cereal yields observed in many countries during recent decades. Several advances in understanding lodging have been made since the last major review of lodging in 1973. These include: (1) a more thorough quantification of the effects of lodging on grain yield and quality, (2) collaborative studies by biologists and engineers have elucidated the mechanisms of stem and anchorage failure and the way in which cereal shoots interact with the wind and rain, (3) the development of models of the lodging process and (4) explanations for how crop husbandry decisions affect lodging. This review collates the new understanding of lodging and attempts to set out cultural and genetic-based approaches for the continued reduction of lodging risk in high-yielding cereals. The review demonstrates that the prospects for continuing to reduce lodging risk through the selection of shorter genotypes may be limited because there appears to be a minimum crop height that is compatible with high yields. There does appear to be significant scope for increasing lodging resistance by strengthening the stem and the anchorage system by exploiting the wide genetic variation in these plant characters and through crop management decisions.

Understanding and Reducing Lodging in Cereals

Oats are a low input cereal widely grown across the world as both a grain and forage crop. Significant areas of production are in Northern Europe and North America and also in China and Australia. Although a traditional crop in many countries, in the last 50 years there has been a significant shift in oat production as a consequence of changing agricultural production and competition from other cereal crops. Oats are of significant economic importance for human consumption, for livestock feed and increasingly as a source of high value compounds with industrial applications as a consequence of the many unique properties of the oat grain. Traditional use in human diets in many countries has been boosted by the recent recognition of oats as a health food. This is attributed to the presence of β-glucan, the major endospermic cell wall polysaccharide. As a result, there has been an increase in the use of oats and a broadening of oat based products. Increasing knowledge of the composition of the oat grain and its value for the various end-users is leading to new opportunities for the crop. While the value of oats as a break crop in cereal based rotations is widely recognised, maintaining the profitability of the crop whilst meeting the needs of end users is essential for future production. Opportunities exist for plant breeders and agronomists to introduce new oat varieties with tailored agronomic approaches to address this challenge and to ensure the sustainability of oats for the future.

Crops that feed the world 9. Oats- a cereal crop for human and livestock feed with industrial applications

This chapter attempts to summarize the main findings about the dwarfing genes in different plant species with emphasis on their breeding and genetics aspects Most of the examples presented are on the use of dwarfing genes in cereal breeding because of their importance for agriculture The biochemical basis of the dwarf phenotype is discussed and examples of GA-sensitive, GA-insensitive, and phytochrome mutants presented Although several dwarfing genes have been identified and studied in different species, only a few have had wide application for plant improvement The most universally accepted dwarfing genes have been the Rht1 and Rht2 of wheat and the sd1 of rice The positive pleiotropic effect of these genes on other plant traits, especially on yield and yield components, is one of the reasons for the success of these genes Breeding challenges to transfer these and other dwarfing genes to different genetic backgrounds are discussed and their impact in variety development presented Several dwarfing genes have been associated to molecular markers and their orthologous relationships identified through mapping Cloning of some of the GA-insensitive genes has been recently achieved and opened the possibility of transferring these genes to a range of other crop species

Dwarfing genes in plant improvement

The ability to identify, study, create and utilize genetic variation are arguably fundamental aspects in the development of human beings. Traditional, or forward, genetics has its roots in man’s first attempts at the domestication of plants and animals. Novel and preferred traits such as the lack of seed shattering were selected from large populations and maintained for future propagation, leading to the first cultivars. The discovery of DNA as the heritable material thousands of years later enabled the development of reverse genetics whereby targeted lesions in the genome are recovered to test and utilize functional variation in genes. A major contributor to both forward and reverse genetics was the discovery in the early twentieth century that mutations can be induced in genomes at frequencies in several orders of magnitude higher than typically observable in nature. The ability to produce novel variation has fueled the development of thousands of new crop cultivars. Examples exist of increased disease resistance, higher yields, tolerance to abiotic stresses such as drought and salinity and improved nutritional quality. In an era where global food security is threatened by climate change and variation and growing populations, use of induced mutations is an important method in the breeder’s toolbox. This review describes the use of induced mutations for forward and reverse genetics in plants, with a focus on crops. Different mutagens and random versus targeted approaches are described. Additionally, newly emerging methods and technologies are discussed that promise to advance basic and applied plant sciences.

Forward and Reverse Genetics in Crop Breeding

The use of oat (Avena saliva L.) dwarfing genes in breeding programs to improve lodging resistance has been limited, mainly because of decreases in yield and grain quality in many environments. The objectives of this study were to evaluate the effects of the dominant Dw6, Dw7, and Dw8 dwarfing genes on plant height components and the gibberellic acid (GA) response of the dwarf lines. Plant height components including internode length, panicle length, and panicle exertion were measured in plants of three nondwarf and nine dwarf lines grown in the field at St. Paul in 1992 and 1993. Five experiments were performed in growth chambers to assay the response of nondwarf and dwarf oat genotypes to exogenous GA applied at the seedling stage. The Dw6 gene in line OT207 caused a 34 to 37% reduction in plant height due to the reduction in the length of the three uppermost internodes but not internode number. The 46% reduction in height caused by the Dw7 gene in line NC2469-3 resulted from decreases in both internode number and elongation. The Dw8 gene present in derivatives of seven Japanese lines shortened all internodes but did not affect internode number, reducing plant height by about 50%. The dwarf lines that carry these dwarfing loci are responsive to exogenously added GA 3 , GA 1 and GA 20 , and thus the mutations appear not to involve disruptions of the conversion of GA 20 to GA 1 . The results indicate that different strategies may be needed to adjust for the different plant height component effects of each of the three dwarfing genes for their use in oat cultivar development.

R. I. H. McKenzie

Papers

Agronomic, Genetic, and Cytologic Evaluation of a Vigorous New Semidwarf Oat1