ARS | Publication request: Frequency of androgenesis in Poa arachnifera hybridizations

Submitted to: Grassland Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 11, 2009
Publication Date: November 16, 2009
Citation: Kindiger, B.K., Wipff, J. 2009. Frequency of androgenesis in Poa arachnifera hybridizations. Grassland Science. 55(4):200-205.

Interpretive Summary: Bluegrass represents a major grass species commonly utilized for both forage and turf. However, many bluegrass species exhibit a novel mode of reproduction where their offspring are genetically identical to the seed parent. This novel form of reproduction is known as apomixis. The apomictic nature of bluegrass forces breeding within the species to be time consuming and a labor intensive endeavor. The presented research has identified a novel method of utilizing a sexual reproducing native species, Texas bluegrass, as the female parent to facilitate the derivation of genetically diverse offspring from both apomictic and non-apomictic bluegrass species. The examination of 2041 hybrids, using Texas bluegrass as the seed parent; and, Kentucky bluegrass, Sandberg bluegrass and Argentine bluegrass as pollen parents resulted in 31 individuals that did not possess a Texas bluegrass genome and supported only the genomes of Kentucky, Sandberg or Argentine bluegrass. Associated molecular analysis of these special individuals, when compared to the true hybrid class, confirmed the unique genetic constitution of these materials. This special class of hybrids occurred at a frequency of 1.5%, regardless of which bluegrass species was utilized as the pollen parent. Though low in occurrence, the identification of these special hybrids is rapid and efficient and offers a new approach for developing new and diverse Poa breeding resources or cultivars.

Technical Abstract: Androgenic dihaploids represent a unique germplasm resource that have historically been utilized for cytoplasmic transfer, the generation of inbred lines and polyploidy genome manipulations. Due to the apomictic nature of many Poa species, breeding improvements can be slow and difficult; therefore, an alternative breeding approach that can capitalize on sampling the genetic diversity of near obligate Poa would be advantageous. This study investigates the frequency and use of androgenic derived dihaploids generated from a series of Poa arachnifera (Texas bluegrass) x P. secunda (Big bluegrass), P. pratensis (Kentucky bluegrass) and P. ligularis (Argentine bluegrass) interspecific hybrids. The examination of 2041 F1 hybrids from three interspecific hybridizations confirmed the generation of 31 dihaploid individuals. In addition, the Apo1 locus that has been indicated to be associated to apomixis in P. pratensis and P. secunda was readily transferred through the pollen and identified by PCR markers. All the generated dihaploids possess a Texas bluegrass cytoplasm, rather than the cytoplasm of the respective parental line. Though infrequent, the generation of androgenic derived dihaploids generated through interspecific hybridization offers a non-traditional breeding approach for the sampling of genetic variation of Poa species and the development of new breeding resources.