Genotypic and Phenotypic Evaluation of Off-Type Grasses in Hybrid Bermudagrass [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy] Putting Greens using Genotyping-by-Sequencing and Morphological Characterization

Many bermudagrass cultivars established for putting greens can be genetically unstable and lead to the occurrence of undesirable off-type grasses that vary in phenotype. The objective of this research was to genetically and phenotypically differentiate off-type grasses and hybrid cultivars

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Isolates of <i>Discula destructiva</i> and <i>Discula</i> species used in this study.

<p>Isolates of <i>Discula destructiva</i> and <i>Discula</i> species used in this study.</p

Cross-amplification of seventeen microsatellite loci from <i>Discula destructiva</i> across <i>Discula</i> spp. and <i>Juglanconis</i> species.

<p>Cross-amplification of seventeen microsatellite loci from <i>Discula destructiva</i> across <i>Discula</i> spp. and <i>Juglanconis</i> species.</p

Confirmation of independent introductions of an exotic plant pathogen of <i>Cornus</i> species, <i>Discula destructiva</i>, on the east and west coasts of North America

<div><p><i>Cornus florida</i> (flowering dogwood) and <i>C</i>. <i>nuttallii</i> (Pacific dogwood) are North American native tree species that belong to the big-bracted group of dogwoods. <i>Cornus</i> species are highly valued for their ornamental characteristics, and have fruits that contain high fat content for animals. Also, they are an important understory tree in natural forests. Dogwood anthracnose, caused by <i>Discula destructiva</i>, was observed in the late 1970s on the east and west coasts of the United States and by 1991 had quickly spread throughout most of the native ranges of <i>C</i>. <i>florida</i> and <i>C</i>. <i>nuttalli</i>. We investigated the genetic diversity and population structure of 93 <i>D</i>. <i>destructiva</i> isolates using 47 microsatellite loci developed from the sequenced genome of the type strain of <i>D</i>. <i>destructiva</i>. Clone-corrected data indicated low genetic diversity and the presence of four genetic clusters that corresponded to two major geographic areas, the eastern United States and the Pacific Northwest, and to the two collection time periods when the isolates were collected (pre- and post-1993). Linkage disequilibrium was present in five out of six subpopulations, suggesting that the fungus only reproduced asexually. Evidence of population bottlenecks was indicated across four identified genetic clusters, and was probably the result of the limited number of founding individuals on both coasts. These results support the hypothesis that <i>D</i>. <i>destructiva</i> is an exotic pathogen with independent introductions on the east and west coasts of North America. We also tested the cross-amplification of these microsatellite primers to other <i>Discula</i> species. Genomic DNA from 17 isolates of four other <i>Discula</i> species and two isolates of <i>Juglanconis</i> species (formerly <i>Melanconis</i> species) were amplified by 17 of 47 primer pairs. These primers may be useful for investigating the genetic diversity and population structure of these <i>Discula</i> species.</p></div

Analysis of molecular variance (AMOVA) for <i>Discula destructiva</i> isolates across 47 microsatellite loci and six subpopulations.

<p>Five analyses were conducted—the first included all subpopulations as one hierarchical group (i), the second was based on two time periods—before and after 1993 [ii], the third one was partitioned based on two geographic regions—eastern and western United States (iii), the fourth one was based on three hosts of <i>D</i>. <i>destructiva</i>, <i>C</i>. <i>florida</i>, <i>C</i>. <i>nuttallii</i>, <i>and C</i>. <i>kousa</i> (iv), and the last one was based on 4 clusters identified by program STRUCTURE (v).</p

Forty-seven microsatellite loci used to assess genetic diversity of <i>Discula destructiva</i> isolates and cross-amplification to other <i>Discula</i> species.

<p>Forty-seven microsatellite loci used to assess genetic diversity of <i>Discula destructiva</i> isolates and cross-amplification to other <i>Discula</i> species.</p

Bottleneck determination by sign tests for <i>Discula destructiva</i> isolates using 47 microsatellite loci and grouped by the four genetic clusters identified by STRUCTURE.

<p>Bottleneck determination by sign tests for <i>Discula destructiva</i> isolates using 47 microsatellite loci and grouped by the four genetic clusters identified by STRUCTURE.</p

Principle coordinates analysis (PCoA) observed among <i>Discula destructiva</i> isolates from three geographic regions and two time periods using 47 microsatellite loci.

<p>The first two axes explain 83.51% of the observed variation.</p