Revised; Originally Published: 2002 / 6 pp.

No description available.

The genus Antirrhinum (commonly known as snapdragons) contains more than twentyfive recognised species. The genus has been divided into three morphological subsections: Antirrhinum, Streptosepalum and Kickxiella (Rothmaler, 1956). One of the major characteristics distinguishing the three subsections is flower colour. Most species in subsection Antirrhinum have dark pink or yellow flowers, Kickxiella species are white or pale pink and Streptosepalum species have yellow or pale pink flowers. All Antirrhinum species can be crossed to produce fertile hybrids which allow the genes that underlie their differences to be identified. I used quantitative trait locus (QTL) analysis on hybrids of A. majus (dark magenta flowers) and A. charidemi (pale-pink flowers) to map genomic regions underlying differences in flower colour. This identified two major-effect loci, in Linkage Group 3 (LG3) and LG7, that explained most of the differences between these species. I used near-isogenic lines (NILs) to further test involvement of two candidate genes - Rosea (Ros) in LG3, which encodes a regulator of the anthocyanin biosynthesis pathway (ABP) and Incolorata (Inc) in LG7 which encodes a rate-limiting enzyme of the ABP. In both cases, the A. majus allele increased pigmentation. Sequence differences between Ros alleles of A. majus, A. charidemi and A. molle (a Kickxiella species with white flowers) suggest that A. molle carries a ros loss-of-function mutation and that a transposon insertion in the ROS promoter might contribute to differences in expression between A. majus and A. charidemi. Ros genotypes were found to be strongly correlated with pigmentation in the corolla tube in A. majus x A. charidemi hybrids, and to a lesser extent with corolla lobe pigmentation, although NILs suggested that ROS did not correspond to the major-effect QTL indentified in LG3. I also mapped a minor-effect QTL for tube pigmentation to a region of LG4 containing the ABP structural gene Candica. Analysis of NILs revealed that Inc was not the second major-effect QTL mapped to LG7, although sequence differences were detected between Inc alleles of A. majus and A. charidemi. I was further able to narrow down the region containing the second LG7 major-effect QTL to an interval of 11 cM, between two molecular markers, which could be used to determine the likely QTL genotypes of segregating NILs. Surprisingly, several ABP genes, particularly Nivea, Inc and Pallida, were expressed at higher levels in pale flowers that were homozygous for the A. chardemi QTL allele than in their dark flowered siblings that carried an A. majus allele. This suggests that ABP genes might be up-regulated in pale flowers as part of a negative feedback mechanism. Two potential roles of the LG7 QTL are considered 1) its requirement for anthocyanin modification or transport to the vacuole, so that a build-up of cytosolic anthocyanins or their break-down products in pale flowers increases structural gene expression but cannot compensate for the overall reduction in anthocyanin, or 2) a role in promoting production of flavonols at the expense of anthocyanins.

The cultivation of chrysanthemums originated in China more than 2000 years ago. Today this flower is regarded as one of the most popular cut flowers in the world. It is, therefore, important to ensure that high quality flowers are produced consistently for the local and export markets. Chrysanthemum morifolium cv. ‘Sunny Reagan’ flowers were grown in a greenhouse sprayed with an electro-activated sodium bicarbonate solution (anolyte) in an attempt to improve productivity and postharvest quality. A non-activated sodium bicarbonate solution was also used to determine the overall effect of sodium bicarbonate on chrysanthemum plants. Sodium bicarbonate acts to enrich the environment of the plant with CO₂ thereby increasing its photosynthetic activity. Anolyte showed a positive preharvest effect on the chrysanthemum plant by increasing the leaf size and overall quality. On the other hand, sodium bicarbonate produced low quality plants with fewer flowers than the control. These plants also exhibited necrotic leaf edges, which is a sign of salt stress. Anolyte-treated plants exhibited no significant increase in postharvest longevity. Anolyte treated plants showed an increase in leaf cell size and density and a decrease in the size of intercellular air spaces, indicating an improved ability for photosynthesis, whereas, treatment with sodium bicarbonate resulted in thinner leaves with a smaller midrib and a less developed vascular system when compared to the control. The chloroplasts in anolyte-treated plants exhibited an increase in starch grains, also an indication of enhanced photosynthesis. Anolyte-treated plants also showed an increase in chlorophyll concentration and an improved CO₂ uptake. It is clear from this study that anolyte stimulated photosynthesis in chrysanthemum plants, thus resulting in longer stems with more and larger flowers and leaves. / Prof. C.S. Whitehead

No description available.

Seed dispersal is a crucial ecological and evolutionary process that allows plants to colonize sites and expand their ranges, while also reducing inbreeding depression and facilitating the spread of adaptive genetic variation. However, our fundamental understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. In recent years, genetic marker methods have furthered our understanding of colonization and range expansion due to seed dispersal. Most investigations focus on regional scales of dispersal, due to low levels of variation in the chloroplast genome (cpDNA), which can serve as an indirect measure of seed dispersal. Here, I employ a whole-genome assay of cpDNA variation in Plagiobothrys nothofulvus to resolve variation due to patterns of seed dispersal within a 400x400 meter section of the Whetstone Savanna Preserve in Central Point, OR, USA. Whetstone is characterized by a mosaic of habitat types, including vernal pools, hummocks of dry prairie, and large Ceanothus cuneatus bushes, as well as a network of vole runways. Plagiobothrys nothofulvus grows in dense patches on hummocks within this prairie. I found evidence of limited seed dispersal in P. nothofulvus, indicated by strong genetic structure over distances of less than 100 meters. There was little evidence that geographic distance predicts genetic distance; environmental features have a stronger influence on dispersal. Habitat preference was the strongest predictor of genetic variation in P. nothofulvus, indicating that it may be a habitat specialist in this prairie. Flower density also accounted for a significant portion of dispersal, which may be a consequence of the annual life history of P. nothofulvus resulting in seasonal turnover and lack of competition with adult plants. Least-cost-path analysis indicated that seeds are secondarily dispersed by small mammals along vole runways. Overall, I found significant evidence that landscape features influence dispersal, even at a very fine spatial scale.

3 pp. / This publication contains guidelines for identifying and managing pests and diseases of Roses.

5 pp. / Revision of AZ1306: Troubleshooting Problems with Roses in the Low Desert / This publication contains guidelines for identifying and managing pests and diseases of Roses.

Recently, it was hypothesized that pollinator selectivity for large inflorescences has led to the evolution of monocarpic reproduction in agaves. To test this hypothesis, fruit set and stalk length data were collected for six species of paniculate agaves and two species of spicate agaves. Regression results, for all of the paniculate species and for one species of the spicate agaves, showed no significant correlation between fruit set and stalk length. These results do not support the pollinator selectivity hypothesis. The validity of the assumptions was then examined, utilizing the results from hand pollination, pruning, and tie down experiments. These results imply that factors other than pollinator availability might be important in determining fruit set in agaves. In an effort to determine the relative importance of resource and pollinator limitation to fruit set in Agave chrysantha, three treatments were applied to entire plants: (1) natural pollination, (2) natural and hand pollination, and (3) hand pollination. When fruits were collected, there were no significant differences between percent fruit set for the three treatments, implying that fruit set is not limited by the availability of pollinators. When additional plants were pruned to reduce the total number of flowers by approximately one-half, thereby doubling the amount of resources available to each flower, the percent fruit set was twice that for control plants, implying that percent fruit set is energy limited. It is common for plants that exhibit resource limited fruit set to have relatively low fruit-to-flower ratios. This is surprising, since it appears that the resources expended for production of these "excess flowers" could be allocated to fruit maturation and thereby increase fruit production. Four hypotheses explaining the fruit set in Agave mckelveyana are tested. Results from pruning, bagging, and hand pollination experiments indicate that the apparently "excess flowers" do not contribute to fruit production (female fitness). Additional data on nectar production imply that these flowers act primarily as pollen donors and contribute only to male fitness. The importance of pollen donation (male fitness) in determining fruit set is examined for hermaphroditic, monecious, and dioecious plants.

No description available.