Graduate Thesis Or Dissertation
 

Environmental and genetic factors affecting seed set in Dactylis glomerata L.

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/v405sd539

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  • Field, growth chamber, and greenhouse studies were carried out to evaluate factors that cause low seed set in Dactylis Glomerata L. The variety, 'Latar', and the parental clones of the variety, 'Pennlate', were studied in detail. Floral anatomy investigations indicated that 98 percent of Dactylis flowers opened at Corvallis in 1968 and that non-necrotic ovaries were present in 96.5 percent of the florets. The variety, 'Latar', and clone 'R' from 'Pennlate' which showed more necrotic ovaries at flowering time than the other types examined were also lower in seed set. Abnormal stigmatic bending was found to be associated with low seed set clonal types; reduced stigmatic area was found to be partially responsible for low seed set in these clones. Clonal types set slightly more seed at 82 F than at 72 F in a growth chamber. Plants maintained at 20 atmospheres of moisture stress at flowering time set significantly less seed than plants maintained at 12.5 atmospheres of stress. Greenhouse studies indicated that Dactylis seed set was significantly reduced by moisture stress during the flowering period but not by moisture stress shortly after heading or during the five day period after flowering. Forty-one 'Latar' plants from field grown material had a chromosome count of 2n = 28 which indicated that this low seed set variety did not contain a large number of aneuploid plants. Evidence for genetic irregularity was found in other aspects of the research. Examination of microsporocytes in clone 'R' revealed that ten percent of the metaphase cells showed lagging chromosomes, chromosome fragments, and bridges. A significant correlation between normal pollen and seed set was found in 616 heads from 43 commercial varieties grown at Corvallis in 1969. Genetic instability may have been responsible for both pollen and ovule abortion. Plants with a normal pollen rating of 91 percent or over had seed set six percent greater than the population mean. Significant differences were found in seed set between clonal types which indicated that some clones were more fertile than others. Significant year-to-year differences in seed set were found within clones; genetic environmental interactions were apparently responsible for these fertility differences. This research indicated that some Dactylis varieties grown for seed in Oregon were low in seed set and procedures were worked out for identifying the infertility in varieties. Screening clonal materials in polycross nurseries to remove infertile types was suggested as a way of increasing seed set in commercial varieties.
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