|Mck. Bird, Robert|
Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2007
Publication Date: 6/10/2007
Citation: Mano, Y., Omori, F., Takamizo, T., Kindiger, B.K., Mck. Bird, R., Loaisiga, C.H., Takahashi, H. 2007. Qtl mapping of root aerenchyma formation in seedlings of a maize x rare teosinte, Zea nicaraguenis cross. Plant and Soil. 295:103-113. Interpretive Summary: Flooding conditions during periods of high rainfall typically result in reduced plant growth and reduced production in most cereal grain and grass forage species. The presence of small channels of open cells called aerenchyma cells in the root systems of some grass species has been observed to confer tolerance to long and short term flooding conditions. In addition, the ability to develop aerenchyma cells prior to flooding conditions is considered advantageous since this allows a plant to more effectively and efficiently respond to a long or short term flooded condition. Rice is one example of a grass species that possesses abundant aerenchyma cells and is well known for its tolerance to flooding. Though the potential advantages of possessing aerenchyma cells in plant root systems during periods of flooding are well known, few studies have been undertaken to assess the degree and inducement of aerenchyma cell formation in species that do not possess this characteristic; or the potential transfer of this trait from one species into another. Zea nicaraguensis teosinte is a rare and distant relative of corn that has been previously identified to possess aerenchyma cells in flooding and non-flooding conditions. The presence of this trait in a relative of corn suggests a potential for the mapping of genes regulating this trait in Zea nicaraguensis and the transfer of these genes into cultivated corn. In this study, hybrids between Zea nicaraguensis and a maize line that could not form aerenchyma cells were generated and analyzed with DNA markers to identify the chromosome location of genes conferring the aerenchyma trait. Results of the analysis identified four genes: two on chromosome 1, one on chromosome 5, and one on chromosome 8 that are involved in aerenchyma cell formation during non-flooding conditions. These data can be used by corn breeders to transfer the aerenchyma forming genes from this rare teosinte to corn with the ultimate goal of developing flooding tolerant corn hybrids. Since many grasses exhibit similarities in genome structure and gene locations, these data are also applicable toward the potential development of flooding tolerant cultivars of wheat, oat, sorghum and a variety of forage grasses. This information will be of value to corn breeders interested in developing superior maize hybrids having tolerance to short or long periods of flooding.
Technical Abstract: Aerenchyma cell formation in plant root systems is considered to be among one of the most important physiological root characteristics affecting flooding tolerance in species possessing such structures. In some species, aerenchyma cell development is an induced response, occurring shortly following exposure to flooding conditions. In other instances, aerenchyma cell development is a naturally occurring, non-flooding induced component of a species physiology. Rather than develop aerenchyma following flooding, the presence of aerenchyma cells prior to flooding conditions may allow the plant to more rapidly and efficiently respond to flooding conditions when they occur. A rare ancestor of Zea mays, Zea nicaraguensis has been identified to exhibit clear aerenchyma cell structure in the cortex of adventitious roots during non-flooding conditions. In this study, QTL regulating aerenchyma formation in roots, during non-flooding conditions, were identified in a segregating maize-teosinte F2 hybrid population. Composite interval mapping revealed four QTL associated to aerenchyma development on chromosomes 1, 5 and 8 of Z. nicaraguensis. Two of these QTL were assigned to two distinct regions of chromosome 1. These results make it possible to utilize Zea SSR markers, in a marker-assisted-selection approach to transfer the genes coding-regulating aerenchyma cell formation into maize inbred lines. Eventually, these aerenchyma possessing maize inbred lines can be used to develop flooding tolerant maize hybrids. This research is of value to maize breeders and geneticists involved in developing superior cultivars of maize.