Interploid St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] hybrids recovered by embryo rescue
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St. Augustinegrass is one of the most important warm season turfgrasses in the southern United States because of its shade tolerance. Most cultivars are diploids (2n=2x=18) and are susceptible to various diseases and insects. Polyploid cultivars in the species have some resistance to pests, but most lack cold tolerance. In this study, eight polyploid genotypes were crossed with six diploid cultivars to transfer pest resistance to the diploids. Because interploid crosses often result in aborted seed, it was necessary to use in vitro techniques. Using embryo rescue, 268 plants were recovered from 2,463 emasculated and pollinated florets (10.88% crossability). Because of the heterogeneous nature of the species, these purported hybrids could not be verified by phenotype. DNA markers were used for hybrid identification. A subset of 25 plants from crosses between the aneuploid cultivar Floratam (2n=4x=32) and five diploid cultivars were analyzed using 144 expressed sequence tags-simple sequence repeats (EST-SSRs) developed from buffelgrass cDNA sequence data. Chi-square tests for paternal-specific markers revealed that all analyzed progeny were true F1 hybrids and none originated from self-fertilization or unintended outcrossing. In addition to identifying DNA polymorphism, the EST-SSRs revealed that genetic variation exists among all analyzed cultivars and is not partitioned between ploidy levels. The findings demonstrate that these embryo rescue techniques will enable the entire spectrum of St. Augustinegrass genetic variation to be better used through the recovery of interploid hybrids. © The Society for In Vitro Biology 2009.
author list (cited authors)
Genovesi, A. D., Jessup, R. W., Engelke, M. C., & Burson, B. L.