Circumventing Apomixis in Poa Cultivar Development

Authors: Kindiger, Bryan; WIPFF, JOSEPH - WEST COAST RSRCH CENTER

Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/5/2008
Publication Date: 1/6/2009
Citation: Kindiger, B.K., Wipff, J.P. 2009. Circumventing Apomixis in Poa Cultivar Development. Plant and Animal Genome Conference Proceedings. 18-20.

Interpretive Summary: Improvement and breeding of bluegrass is extremely difficult and time consuming due to its non-sexual reproductive nature, termed apomixis. In this form of reproduction, seed are generally produced that are exact genetic copies of the maternal parent. Since this limits the generation of variation in offspring, identifying new and useful variation through a traditional, bluegrass breeding program is highly inefficient. This research has identified a new breeding method where the paternal or pollen parent is utilized in crosses with Texas bluegrass, a sexual reproducing bluegrass species, to generate variation from elite, apomictic bluegrass cultivars. Utilizing Texas bluegrass as the female parent in crosses with apomictic bluegrass cultivars of Big bluegrass and Kentucky bluegrass, several non-hybrids were generated. These non-hybrids, called androgenic dihaploids, lack the Texas bluegrass genome and retain only the Big bluegrass or Kentucky bluegrass genomes. When using this approach, elite apomictic bluegrass cultivars provide new variation for selection and subsequent cultivar development. Molecular marker analysis and visual examination of these non-hybrid individuals confirmed their genetic composition. The frequency of these, non-hybrid, androgenic dihaploids occurred at a level near 1.5%. Though low in occurrence, this approach offers a new and rapid method for development of new and elite cultivars of apomictic bluegrass.

Technical Abstract: Poa represents one of the world’s most highly regarded cool-season grasses for both turf and forage. The genus is highly variable, with approximately 500 species worldwide, several being indigenous to the United States. Cultivar uniformity is a rigorous component of Poa cultivar registration that requires the expression of high levels of apomictic reproduction. However, high levels of apomixis greatly restrict breeding improvements. If apomixis expression is reduced or removed during the breeding process, it is a difficult and time-consuming trait to regain. Due to the highly apomictic nature of many bluegrass cultivars, breeding improvement with or within these germplasm resources are slow and difficult. Alternative approaches that can capitalize on sampling the genetic diversity of elite and near obligate Poa germplasm resources 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) and P. pratensis (Kentucky bluegrass)interspecific hybrids. Screening of the putative androgenic dihaploids with Poa SSR and SCAR markers confirmed the generation of paternal dihaploids; and, screening with the Poa derived Apo1 molecular marker suggests that the apomixis locus is transmitted through the pollen. Though low in occurrence, the generation of androgenic dihaploids is easily confirmed using SSR markers or phenotypic examination and offers a new approach for cultivar development with apomictic Poa.