Graduate Thesis Or Dissertation
 

Selection for Persistence in Red Clover through Improved Tolerance to Northern Anthracnose [NA; Kabatiella caulivora (Kirch.) Karak.] and Drought

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3n204546z

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  • Twenty-three red clover cultivars and accessions were grown in Boyd, KY, and Philomath, OR to evaluate their tolerance of northern anthracnose [NA; Kabatiella caulivora (Kirch.) Karak.] and drought, dry matter (DM) production, and their agro-morphological characteristics. The key research questions of this study were the influence of NA on yield of red clover, and the influence of drought stress on shoot and root dry matter production of red clover. Previous red clover NA disease and drought tolerance studies have primarily studied the mechanism of tolerance in a few cultivars, rather than evaluating many cultivars and accessions for recurrent phenotypical selection. In the second chapter of the thesis, we evaluated 23 entries for their yield and their tolerance of NA. Small plots were harvested for forage dry matter in 2018 and 2019. Tolerance of NA was evaluated using a drone photograph visual evaluation technique with a scale of 1 to 9, with 1 being necrotic (susceptible) and 9 being no visible symptoms. Significant differences (P<0.001) were observed among the entries for yield and disease severity. Cultivar ‘Evolve’ had the highest dry matter, approximately 23% and 14% more than the check cultivar ‘Kenland’ in 2018 and 2019. ‘Kenland’ had the highest tolerance to NA, with an average value of 7.8 while ‘Vesna’ had the lowest tolerance with an average value of 2.8. In the third chapter of the thesis, genotypes were evaluated for root weight, shoot weight, combined root and shoot weight, root to shoot ratio, and shoot weight after recovery from soil moisture stress. We tested cultivars and accessions in two-cycles of selection; (1) field selection based on plant mortality, and (2) a pot experiment under a rainout shelter, selecting the six-best field-performing cultivars. Highly significant (P<0.01) two-way interactions were observed on development stage by cultivar for root weight. Significant differences were also observed for shoot weight (P<0.05), root weight (P<0.001), total biomass (P<0.001), root weight to shoot ratio (P<0.001), and shoot weight after recovery (P<0.01). Development stage and stress level affected most of the traits. Seed from the first selection cycle will be further evaluated for yield, disease tolerance, and drought tolerance to develop improved cultivars.
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  • Pending Publication
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  • 2020-04-10 to 2021-05-11

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