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  • Author or Editor: Matthew C. Martin x
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Four AM fungal isolates (Glomus sp.) were screened for effects on growth of `Volkamer' lemon (Citrus volkameriana Ten. and Pasq.) under well-watered conditions. Plants were inoculated with an isolate of AM fungi, or non-inoculated. Non-mycorrhizal plants received more phosphorus (P) fertilizer than mycorrhizal plants because mycorrhizae enhance P uptake. Mycorrhizal and non-mycorrhizal plants were grown in 8-liter containers for 3 months in a glasshouse. Plants were then harvested, and root length colonized by mycorrhizal fungi, leaf P concentration, and plant growth were determined. Root length colonized by AM fungi differed among isolates; control plants were non-mycorrhizal. Leaf P concentration was in the optimal range for all plants; however, plants colonized by Glomus mosseae Isolate 51C had higher leaf P concentration than non-mycorrhizal plants. Plants colonized by Glomus AZ112 had higher leaf P concentration than all other plants. All plants had similar canopy leaf area, shoot length, and shoot dry mass. Plants colonized with AM fungi, except Glomus mosseae Isolate 51C, had longer root length and greater root dry mass than non-mycorrhizal plants. All mycorrhizal plants had lower shoot:root dry mass and leaf area:root length ratios than non-mycorrhizal plants. Our results showed that under optimal P nutrition and well-watered conditions, AM fungal isolates differentially altered the morphology of citrus plants by stimulating root growth.

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St. augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a popular turfgrass in the southern United States as a result of its superior shade tolerance and relatively low input requirements. However, it is the least cold-tolerant of commonly used warm-season turfgrass species. ‘Raleigh’, released in 1980, has superior cold tolerance and is adapted and widely used in U.S. Department of Agriculture hardiness zones 8 to 9. More than 25 years after its release, ‘Raleigh’ is still the industry’s standard in terms of cold tolerance. However, the original foundation and breeder stock fields of the cultivar have been lost, placing the integrity of the cultivar at risk. The objectives of this study were to investigate whether current ‘Raleigh’ production fields across the southern United States are true to the original source. In this study, 15 amplified fragment length polymorphism (AFLP) primer combinations were used to assess levels of genetic variability among three original stocks of ‘Raleigh’ and 46 samples obtained from sod farms and universities in six states. Genetic similarities among the original stocks were Sij = 1, whereas similarities between this group and all other samples ranged from 0.24 to 1.0. Results based on cluster analysis, principal coordinate analysis, and analysis of molecular variance (AMOVA) revealed separation between original stocks of ‘Raleigh’ and some commercial samples. Results from this study offer further evidence that molecular markers provide a useful and powerful technique for identity preservation of clonally propagated cultivars and the detection of genetic variants in sod production fields and turfgrass breeding programs.

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