Use of morphological, molecular markers and cytology to differentiate between closely related Gaura coccinea, G. drummondii for breeding purposes

Abstract

Collection of wild species is critical to increase crop germplasm gene pools. Gaura coccinea has been identified as an important source of cold tolerance (winter hardiness) for hybridization with non-cold tolerant G. lindheimeri. Identification of species in the wild is often complicated by diagnostic, morphological characteristics that may not be present at the time of collection. G. drummondii, however, can be misidentified as G. coccinea even when using some diagnostic and quantitative traits. Therefore, additional methods of distinguishing between the species are needed. Fifteen populations of both G. coccinea and G. drummondii collected for potential breeding purposes in Texas, California, and Minnesota were used to identify species-specific molecular markers and morphological characteristics. A dendrogram based on randomly amplified polymorphic DNA (RAPD) markers separated the genotypes into two groups, G. coccinea and G. drummondii. One unique RAPD marker was identified in all G. drummondii genotypes, but absent in G. coccinea. Dendrograms based on morphological data separated genotypes into three distinct groups: G. coccinea, G. drummondii, and G. sp. (393-1). Petal/sepal lengths and leaf width were smaller in G. coccinea, while fruit/stipe lengths were smaller in both G. coccinea and genotype 393-1. Cytological analysis of G. coccinea confirmed that most populations were tetraploid (2n = 4x = 28) with one hexaploid (2n = 6x = 42) genotype from Texas (1000-1). G. drummondii were primarily tetraploid (2n = 4x = 28). Occasional triploids were found. These markers, along with screening for cold tolerance, will allow for accurate identification of G. coccinea genotypes for hybridization with G. lindheimeri.