The genetic interactions among 9 soybean [<i>Glycine max</i> (L.) Merr.] cultivars and 6 strains of soybean mosaic virus (SMV) were investigated. The objectives were to identify genes and/or alleles conditioning resistant and necrotic reactions to SMV and to determine the genetic relationships among resistance genes from cultivars exhibiting differential responses to the SMV strains. Seven SMV-resistant (R) cultivars (‘PI 486355’, ‘Suweon 97’, ‘PI 96983’, ‘Ogden’, ‘York’, ‘Marshall’, and ‘Kwanggyo’) were crossed in all combinations among each other and with susceptible (S) cultivars ‘Essex’ and ‘Lee 68’. F₂ populations and F₂-derived F₃ lines were inoculated in field with the SMV type strain Gl and in the greenhouse with the virulent strains G4, G5, G6, G7, and G7A. All F₂ populations from R x S and necrotic (N) x S crosses having PI 96983, Ogden, York, Marshall, and Kwanggyo as either resistant or necrotic parents segregated 3R:1S and 3N:1S, respectively. F₂-derived F₃ progenies from R x S crosses exhibited an F₂ genotypic ratio of 1 homogeneous R : 2 segregating (3R:1S) : l homogeneous S. The results indicate that each of these five resistant parents has a single, dominant or partially dominant gene conditioning the resistant and necrotic reactions to SMV. No segregation for SMV reaction was evident in F₂ and F₃ generations from R x R, N x N, and S x S crosses among the five differential cultivars, indicating that the resistance genes in the five cultivars are alleles at a common locus. The alleles in PI 96983 and Ogden were previously labeled <i>Rsy</i> and <i>rsy^t</i>, respectively. Gene symbols, <i>Rsy^y</i>, <i>Rsy^m</i>, and <i>Rsy^k</i> are proposed for the resistance genes in York, Marshall, and Kwanggyo, respectively. It is also proposed that the gene symbol <i>rsy^t</i> be changed to <i>Rsy^t</i> to more accurately reflect its genetic relationship to the susceptible allele. The R x S crosses with PI 486355 and Suweon 97 as resistant parents segregated 15R:1S in the F₂ and 7 (all R) : 4 (3R:1S) : 4 (15R:1S) : 1 (all S) in the F₃, indicating that each has two independent genes for resistance to SMV. The F₂ plants of PI 486355 x Suweon 97 showed no segregation for SMV reaction, suggesting that they have at least one gene in common. The crosses among all 7 resistant parents produced no susceptible segregates when inoculated with strain G1. It is concluded that the 7 resistant cultivars each have a gene or allele at the <i>Rsy</i> locus. Data from the experiments furnished conclusive evidence that the necrotic reaction in segregating populations is highly associated with plants that are heterozygous for the resistance gene. / Ph. D.

Video acquired using a camera mounted on a mini Unmanned Air Vehicle (mUAV) may be very helpful in Wilderness Search and Rescue and many other applications but is commonly plagued with limited spatial and temporal field of views, distractive jittery motions, disorienting rotations, and noisy and distorted images. These problems collectively make it very difficult for human viewers to identify objects of interest as well as infer correct orientations throughout the video. In order to expand the temporal and spatial field of view, stabilize, and better orient users of noisy and distorted mUAV video, a method is proposed of estimating in software and in real time the relative motions of each frame to the next by tracking a small subset of features within each frame to the next. Using these relative motions, a local Euclidean mosaic of the video can be created and a curve can be fit to the video's accumulative motion path to stabilize the presentations of both the video and the local Euclidean mosaic. The increase in users' abilities to perform common search-and-rescue tasks of identifying objects of interest throughout the stabilized and locally mosaiced mUAV video is then evaluated. Finally, a discussion of remaining limitations is presented along with some possibilities for future work.

Call number: LD2668 .T4 1986 S76 / Master of Science / Plant Pathology

Call number: LD2668 .T4 1978 N94 / Master of Science

Call number: LD2668 .T4 1979 M62 / Master of Science

Call number: LD2668 .T4 1965 A22 / Master of Science

Call number: LD2668 .T4 1966 P122 / Master of Science

Polyphagy is a very common trait among insects. In this study, we focus on a generalist bark-beetle predator, Thanasimus formicarius (L.) (Coleoptera, Cleridae), which feeds on many scolytids in spruce, pine and broad-leaf stands. It is known to respond to the pheromones of many scolytids, among which the most harmful spruce bark beetle in Europe, Ips typographus (L.). The adults attack scolytid adults and oviposit on attacked trees where their larvae feed upon immature stages of the prey. However, a bottom-up process limits Thanasimus formicarius’ impact on spruce bark beetles, because in most cases the bark of spruce is too thin for sheltering pupal niches and mature larvae have to leave the trees. On pine however, pupation is quite successful and reproductive success is high. The present work estimates the advantages (complementary prey during gaps among the phenology of pine bark beetles or due to the population fluctuations of most scolytids) and constraints (landing on unsuitable host trees for the predator’s reproduction) for T. formicarius to have a wide range of prey. Passive barrier-trappings showed that the presence and abundance of scolytid species vary strongly from year to year. So, polyphagy in T. formicarius appears as a response to fluctuating prey supplies. This way of foraging may lead T. formicarius towards stands not always favourable for its development (for example, spruces). At the tree level, funnels and pitfall-traps caught high numbers of third-instar T. formicarius larvae walking on the bark surface of standing spruces infested by Ips typographus (respectively 365 and 70 L3s). After feeding into the whole infested part of the trunk, these larvae are obliged to migrate outside of the galleries to favourable pupation site (e.g. the base of the trees where the bark is thicker), or even to leave the trees and search for an acceptable pupation substrate in the litter. At the landscape level, different trapping experiments showed a correlation between catches of T. formicarius and the proportion of pines around each trap. Consequently, in a metapopulation landscape pattern, pines would act as “sources” of predators, whilst spruces are “sinks”. Indeed, Thanasimus formicarius are trapped in higher numbers in mixed stands comprising pines. This observation is also corroborated in a four-year trapping experiment in the North-East of France, following the storms of December 1999. The predator/prey ratios (T. formicarius/I. typographus) were higher in stands comprising pines than in stands without pines. The first step of a method to estimate Ips typographus infestation trends thanks to the predator/prey ratios was also developed.

Survey of crops of common bean (Phaseolus vulgaris L.) in Sonora, Mexico revealed the presence of two isometric viruses and one flexuous rod virus on the basis of host reaction, particle morphology, serology and physico-chemical properties. The isometric viruses were identified as Bean Southern Mosaic Virus (BSMV) and Cowpea Chlorotic Mottle Virus (CCMV); the flexuous rod virus was identified as Bean Common Mosaic Virus (BCMV). Using bean cultivar differentials, two strains of the potyvirus BCMV were identified, NY-15 and a previously undescribed strain designated YV-1. Host range, serological tests, and RNA electrophoresis indicated that the Sonoran BSMV cultures are similar to BSMV-strain A. Serology and RNA-electrophoresis indicated that the Sonoran CCMV isolates are identical to CCMV-strain A. BSMV and CCMV were always isolated as a mixture from seed lots and from field collected bean tissue. BCMV occurred alone or in mixed infections with BSMV and CCMV. BCMV was seed transmitted with an average efficiency of 58 percent. The BSMV-CCMV mixture was transmitted with an efficiency of 6 percent. BSMV and CCMV were seed transmitted together, but separate transmission of BSMV or CCMV was not detected. Commercial seed lots from two major bean growing regions of Sonora (Hermosillo Coast, Sonora River) were contaminated with the BSMV-CCMV mixture but not with BCMV. The average contamination level was 13 percent. Two common weeds present in Sonoran agricultural areas were found to be potential alternate hosts of CCMV. Both Sisymbrium irio L. and Melilotus indica L. were infected systemically, although the infection in M. indica was latent. Potential losses due to Sonoran bean viruses were measured in greenhouse experiments with the cultivar Pinto 111. BCMV strains caused a 29.4 to 60.1% reduction, whereas BSMV-CCMV mixtures induced a 22.5 to 74.6% yield reduction. A synergism occurred between the BSMV-CCMV mixture and BCMV resulting in more severe symptoms and a yield reduction of 92.7%. Synergistic effects were also observed between BSMV and CCMV. Actual yield reduction resulted from impaired flower production and, consequently, reduced pod production. Significant effects on plant tissue production, flower fertilization and seed quality were not observed. Cowpea chlorotic mottle virus infected mung bean (Vigna radiata (L.) Wilczek) a previously unreported host. Infection of mung bean by BSMV was only possible when CCMV was present in the inoculum. Both BSMV and CCMV could be isolated from symptomatic plants infected with the BSMV-CCMV mixture, however, symptoms on mung bean were unchanged from infection by CCMV alone.

No description available.