Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/11/2005
Publication Date: 6/10/2005
Citation: Mano, Y., Muraki, M., Fujimori, M., Takamizo, T., Kindiger, B.K. 2005. Identification of QTL's controlling adventitious root formation during flooding conditions in Teosinte (Zea mays ssp. huehuetenangensis) seedlings. Euphytica. 142:33-42. Interpretive Summary: During the spring, when precipitation can be overly abundant, heavy economic losses can be inflicted on corn crops that are sown in low areas. Excessive rainfall that results in flooding can cause serious injury to a corn crop depending on its stage of development, particularly at the seedling stage. During flooding, the major stress applied to corn seedlings is the lack of oxygen that is required for proper functioning of the root system. If flooding occurs at the seedling stage, plants generally die within five to six days of submersion. Previous research in Z. mays ssp. huehuetenangensis, a form of teosinte that is a close relative of maize, has indicated that the formation of adventitious roots during periods of flooding is one mechanism whereby this species circumvents the lethal effects of flooding. Evaluations of several corn x Z. mays ssp. huehuetenangensis hybrids, utilizing an array of well placed molecular markers, has identified that chromosomes 4 and 8 of Z. mays ssp. huehuetenangensis possess genes that are responsible for adventitious root formation. The expression of this trait in the hybrids as well as the identification of molecular markers associated to the trait suggest that adventitious root formation and/or flooding tolerance can be transferred to maize through a marker-assisted-selection breeding program. The results of this study will be valuable to maize breeders and geneticists interested in transferring a degree of flooding tolerance to selected maize lines and corn hybrids.
Technical Abstract: The generation of adventitious roots at the soil surface is an important plant adaptation mechanism for coping with periods of soil flooding. Quantitative trait loci controlling adventitious root formation under flooding conditions were identified in a 94 F2 individual population by crossing Zea mays L. (maize) x Z. mays ssp. huehuetenangensis (teosinte). A base-map was constructed using 66 SSR and 42 AFLP markers, covering a total of 1,378 cM throughout all ten maize chromosomes. The hybrids capacity for developing adventitious roots was determined by evaluating the degree of root formation at the soil surface following a two week flooding period. Interval mapping and composite interval mapping analyses revealed that the QTL for adventitious root formation is located on chromosome 8. Utilizing a selective genotyping strategy on a second 186 F2 population, derived from the same cross combination, 32 AFLP primer combinations identified QTL's for adventitious root formation regions on chromosomes 4 and 8 of the Z. mays ssp. huehuetenangensis parent. The identification of two loci controlling adventitious root formation indicate that a program of marker-assisted-selection can be used to selectively transfer flooding tolerance from Z. mays ssp. huehuetenangensis to selected maize lines.