No description available.

4 pp. / Leaf analysis is an excellent tool for determining the nutritional status of pecan trees.

Revised; Originally Published: 2006 / 3 pp.

Lily leaf spot, a fungal foliar disease caused by Pseudocercosporella inconspicua, leads to premature senescence of aboveground tissues in Lilium grayi. At Roan Mountain, North Carolina/Tennessee, the disease was most prevalent and most severe in seedlings and juveniles. In the two growing seasons assessed, 59 and 70% of mature plants experienced disease-induced premature senescence. Plants with disease lesions on seed capsules matured fewer capsules and had fewer seeds per capsule, and seeds had reduced viability. Disease prevalence over the growing season followed a sigmoidal pattern typical of polycyclic epidemics. Plants with low and high disease severity occurred in clusters whose locations were stable across growing seasons. Prior to the recent description of lily leaf spot, L. grayi was already considered threatened or endangered in each of the three states where it naturally occurs. Therefore, this infectious disease poses conservation and management difficulties because increases in plant density can be expected to lead to enhanced disease transmission. Lily leaf spot of L. grayi is best characterized as an annually recurring epidemic because of high prevalence rates, strong impacts on all life stages, and reductions in seed production and viability.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21824号 / 農博第2337号 / 新制||農||1067(附属図書館) / 学位論文||H31||N5196(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 大澤 晃, 教授 北山 兼弘, 教授 北島 薫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(農学) / 甲第23945号 / 農博第2494号 / 新制||農||1090(附属図書館) / 学位論文||R4||N5380(農学部図書室) / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 北島 薫, 准教授 岡田 直紀, 教授 小杉 緑子 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Flue-cured tobacco (Nicotiana tabacum) has been managed to optimize the yield of high-quality cured leaf while maintaining nicotine levels within a relatively narrow range based on the Regional Minimum Standards Program. Among the 3,000 plus alkaloids found in tobacco, nicotine accounts for greater than 90% of the total alkaloids produced in commercial tobacco varieties. Precious research has demonstrated an association with nicotine levels and cured leaf yield and quality. On March 16, 2018, the Food and Drug Administration issued a notice for proposed rulemaking to limit nicotine in combustible cigarettes to 0.3-0.5 mg nicotine per gram of tobacco (an approx. 98% reduction from current levels). Studies on achieving decreased levels of nicotine in flue-cured tobacco have been conducted since the mid-1900's and some success has been found through breeding and genetics. The FDA proposal suggested changes to standard agronomic production practices as a means of achieving their proposed nicotine levels. The primary objectives of this work are: (1) evaluate the impact of standard agronomic production practices on nicotine levels and the resulting yield and cured leaf quality and (2) quantify differences in nitrogen-use efficiency between conventional and low-nicotine flue-cured tobacco varieties. Results showed that the changes to production practices did not sufficiently lower nicotine levels to the range proposed by the FDA. The only publicly available low-nicotine variety, LA FC53, did not achieve the targeted nicotine level and the yield and cured leaf quality was severely reduced. The study of nitrogen-use efficiency quantified differences between conventional and low-nicotine flue-cured tobacco varieties. Proprietary, low-nicotine varieties developed from K 326 tended to have lower nicotine levels than LA FC53 with improved yield and cured leaf quality. Both yield and quality are associated with nitrogen-use efficiency and the nitrogen-use efficiency of the new low-nicotine lines was comparable to K 326 and better than the previously developed, low-nicotine standard variety. No evaluation of smoking characteristics of the cured tobacco from these studies was conducted and would be necessary for commercial utilization of low-nicotine flue-cured tobacco. / Master of Science / Flue-cured tobacco (Nicotiana tabacum) has been managed to optimize the yield of high-quality cured leaf while maintaining nicotine levels within a relatively narrow range based on the Regional Minimum Standards Program. Among the 3,000 plus alkaloids found in tobacco, nicotine accounts for greater than 90% of the total alkaloids produced in commercial tobacco varieties. Precious research has demonstrated an association with nicotine levels and cured leaf yield and quality. On March 16, 2018, the Food and Drug Administration issued a notice for proposed rulemaking to limit nicotine in combustible cigarettes to 0.3-0.5 mg nicotine per gram of tobacco (an approx. 98% reduction from current levels). Studies on achieving decreased levels of nicotine in flue-cured tobacco have been conducted since the mid-1900's and some success has been found through breeding and genetics. The FDA proposal suggested changes to standard agronomic production practices as a means of achieving their proposed nicotine levels. The primary objectives of this work are: (1) evaluate the impact of standard agronomic production practices on nicotine levels and the resulting yield and cured leaf quality and (2) quantify differences in nitrogen-use efficiency between conventional and low-nicotine flue-cured tobacco varieties. Results showed that the changes to production practices did not sufficiently lower nicotine levels to the range proposed by the FDA. The only publicly available low-nicotine variety, LA FC53, did not achieve the targeted nicotine level and the yield and cured leaf quality was severely reduced. The study of nitrogen-use efficiency quantified differences between conventional and low-nicotine flue-cured tobacco varieties. Proprietary, low-nicotine varieties developed from K 326 tended to have lower nicotine levels than LA FC53 with improved yield and cured leaf quality. Both yield and quality are associated with nitrogen-use efficiency and the nitrogen-use efficiency of the new low-nicotine lines was comparable to K 326 and better than the previously developed, low-nicotine standard variety. No evaluation of smoking characteristics of the cured tobacco from these studies was conducted and would be necessary for commercial utilization of low-nicotine flue-cured tobacco.

Barley leaf rust (<I>Puccinia hordei</I> G. Otth) has been the cause of numerous and often devastating disease epidemics since the beginning of agriculture. Leaf rust is one of the most important diseases that affect barley (<I>Hordeum vulgare</I> L.) throughout the world. The pathogen <I>Puccinia hordei</I> is an obligate parasite. Symptoms of barley leaf rust may range from small chlorotic flecks to large pustules containing spores. Leaf rust epidemics reduce yields and grain quality. Deployment of resistant cultivars is one of the most effective and economical means of controlling barley leaf rust. Identification and incorporation of new and effective sources of resistance are crucial to the success of barley breeding programs. Two types of resistance have been identified. They are race-specific resistance and partial resistance. A hypersensitive reaction by the host to infection of <I>P. hordei</I> isolates lacking corresponding virulence genes is indicative of race-specific resistance that is controlled by major genes. Sixteen race-specific genes (R<I>ph</I>1 to R<I>ph</I>16) have been identified. Partial resistance is generally polygenic and is often more durable that race-specific resistance. The purpose of this research is to determine the inheritance of resistance to leaf rust in the barley experimental line VA 92-42-46, to identify the gene(s) conferring resistance, identify putative resistance related markers, and to map the gene(s) to one or more barley chromosomes using molecular markers. The Virginia barley line 92-42-46 was selected for this research project because it possesses resistance to <I>P. hordei</I> race 30, which has overcome resistance conferred by R<I>ph</I>7. Crosses were made between VA 92-42-46 and Moore, a susceptible cultivar to leaf rust. Inheritance studies were performed by screening F₂ progeny and F_2:3 families against race 8 and race 30 to determine the number of leaf rust resistance genes in VA 92-42-46. Allelism tests were performed to determine gene identity. A single dominant gene at the R<I>ph</I>5 locus or a tightly linked gene confers the resistance to P. hordei in VA 92-42-46. Two populations, 'Moore' X VA 92-42-46 and 'Bowman' X 'Magnif', were used in this study for mapping molecular markers to provide comparison and confirmation of results. 'Magnif' possesses the resistance gene R<I>ph</I>5. Bulked segregant analysis was used to identify polymorphic RFLP and SSR markers that were used for mapping in each population. Linkage analysis revealed that the R<I>ph</I>5 gene maps to barley chromosome 3 (3H) above the centromeric region in the 'Moore' X VA 92-42-46 population. These findings agree with previous research that identified linkage between R<I>ph</I>5 and R<I>ph</I>7 on chromosome 3. The results obtained in this study do not support previous research that had reported the resistance gene R<I>ph</I>5 was located on barley chromosome 7 (5H). Further research should be conducted to verify the results of this study using the 'Bowman' X 'Magnif' population. The markers screened in the region above the centromere region of barley chromosome 3 were monomorphic for the 'Bowman' X 'Magnif' population except for the marker MWG561. Therefore, additional markers above the centromere of barley chromosome 3 should be screened. / Master of Science

Call number: LD2668 .T4 1949 I71 / Master of Science

No description available.