Frost can be detrimental to canola (Brassica napus L.) production. Depending on the severity, the entire field can be killed. Having frost tolerance in canola would benefit growers by allowing them to plant early, utilize early season moisture, and avoid high heat during flowering. However, frost tolerance in canola has not been well studied. A protocol was developed that determined 14 day old seedlings should be acclimated at 4°C for 7 days before being exposed to overnight frost (-4°C) in a small freezing chamber. However, when a larger chamber was used for freezing, the protocol was optimized to -8°C instead. A greenhouse study was conducted on a diverse collection of 231 genotypes and genome-wide association scan (GWAS) was conducted to identify potential genes that were related to frost tolerance or abiotic stress tolerance. Thirty-eight significant single nucleotide polymorphism (SNP) markers were selected based on 10,000 bootstraps and 0.1 percent tail of the empirical distribution. The markers were located on chromosomes A01, A02, A03, A04, A07, A08, A09, A10, C03, C05, C06, C07, and C09. Stepwise regression highlighted a QTL located on chromosomes A02. Another GWAS was done on 147 canola germplasm lines phenotyped under natural conditions. Thirty-eight significant SNPs identified from this study were located on chromosomes A05, A07, A09, C01, C02, C03, C04, C05, C06, C07, and C09. Stepwise regression identified a QTL located on chromosome C04. A protocol was developed to measure the freezing induced electrolyte leakage from leaves of rapeseed/canola. A total of 157 germplasm lines were evaluated for freezing induced (-12°C for 2 h) electrolyte leakage. Thirty-six significant SNPs located on chromosomes A01, A02, A03, A04, A05, A06, A07, A08, A09, A10, C01, C02, C04, C05, C06, C07, and C09 were identified. Stepwise regression identified 10 QTL located on chromosomes A01, A02, A04, A06, A07, C02, C05, C07, C09, and one that could not be assigned. All GWAS studies identified potential genes of interest that were related to frost tolerance, abiotic stress, and transcription factors. / Northern Canola Growers Association

Call number: LD2668 .T4 1956 G46 / Master of Science

Call number: LD2668 .T4 1961 V39

No description available.

In 1984 and 1985 visual differences in frost damage were observed among 40 jojoba clones growing in a field in Tucson, Arizona. More detailed data were collected on the clone with the least damage (Clone-1) and the one with the most damage (Clone-2). On 10-ten terminal branch samples, Clone-1 showed an average of 12% leaf damage compared to 35% for Clone-2. Leaf freezing under controlled conditions on a monthly schedule showed that leaves of Clone-1 consistently froze at a lower temperature than Clone-2. Also, a second exotherm occurred in 50% of the samples for Clone-1 whereas a second exotherm occurred in only 15% of the samples of Clone-2. Soil moisture content and plant water potential were measured biweekly. Neither seemed to relate to the differences in freezing tolerance of the two clones. Total nonstructural carbohydrates (TNC), total soluble sugars, sucrose and proline were determined monthly. Accumulation patterns of TNC were similar for the two clones, however, Clone-1 generally accumulated more soluble sugars, sucrose and proline which might have contributed to its freezing tolerance. Growth measurements were recorded monthly to determine whether differences occurred between the two clones. Growth of both clones peaked in the spring, showed minor peaks in summer and ceased in winter. Under greenhouse conditions, pot grown cuttings from Clone-1 and Clone-2 were given zero, six or 12 gm of Osmocote fertilizer and watered at 35 or 70% field capacity to determine the effect of irrigation and fertilization on leaf freezing point. Fertilization significantly increased leaf concentrations of N and P and produced more growth. In the greenhouse study, no differences were found in leaf freezing point due to clones, irrigation or fertilization treatment. Leaves of Clone-1 froze at a higher temperature compared to field grown plants.

No description available.

The non-native Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) has been grown to a limited extent in the southern part of Sweden since the early 1900s. A more extensive use has probably been curtailed by its known susceptibility to damage by frost, pine weevil and other pests. Limited access to vital seedlings of suitable provenances has also restricted its more widespread growth. The need for valuable species that will grow well through ongoing climate change has increased the interest for Douglas fir in Sweden. This thesis addresses a number of important questions relating to the planting of Douglas fir in Sweden: seedling storability, freezing tolerance, timing of bud burst, frost damage and seedling response to site preparation. Seven Douglas fir provenances originating from British Columbia, Canada were used in the experiments and where applicable, compared with a local provenance of Norway spruce (Picea abies (L.) Karst.). The early bud burst of interior Douglas fir provenances, observed both in greenhouse tests and in the field, results in a high risk of damage by late spring frost. This type of damage does not seem, however, to be fatal and does not obviously retard the early growth of seedlings. The difference in growth between coastal and interior provenances was insignificant, but survival was greater for interior than for coastal provenances. All the provenances of Douglas fir studied showed a later development of freezing tolerance of shoots and roots in the autumn than Norway spruce, with the coastal provenances developing such tolerance even later than interior provenances. This could be a contributory cause for the severe damage by winter desiccation observed on seedlings of coastal origin. A thorough site preparation proved to be an effective way to increase survival and root growth. Interior provenances of Douglas fir became ready for storage earlier in autumn than coastal provenances. When freezing tolerance of shoots had increased sufficiently, Douglas fir seedlings could safely be kept in frozen storage using the same procedures used for Norway spruce. The results emphasise the need to gain further knowledge about how the remaining obstacles to establishment of Douglas fir could be reduced with different silviculture methods.

Thesis (M.S.) University of Delaware, 2006. / Principal faculty advisor: Frederick E. Nelson, Dept. of Geography. Includes bibliographical references.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

No description available.