M.Sc. (Botany) / Please refer to full text to view abstract

Investigations of three low-water requiring landscape species produced the following results: (1) Although Calliandra californica flowered under photoperiods from 12 to 16 hours, plants produced more elongation under 16 hour days. Plants grew taller and developed greener foliage under irradiances of 600 μmol·m⁻²·s⁻¹. Branching was not stimulated by foliar sprays of BA, PBA, or BA + GA₄₊₇. (2) Caesalpinia pulcherrima increased biomass under 16 hour days, but were stunted and chlorotic under irradiances of 1950 μmol·m⁻²·s⁻¹. Internodal lengths were restricted with drenches of 3.75 mg · pot-1 uniconazole, and plants sprayed with 500 mg·liter⁻¹ PBA developed more axillary branching without negative elongating effects. (3) Justicia specigera gained more height under 12 hour days, and produced greener foliage, more elongation, and faster flowering under irradiances of 600 μmol·m⁻²·s⁻¹. Plants showed restricted internodal elongation and fewer flowers when drenched with 5.0 mg·pot⁻¹ uniconazole, and developed more axillary branching with no detrimental elongation effects when sprayed with 100 mg·liter⁻¹ BA + GA₄₊₇.

Both salinity and drought stresses induce osmotic stress. Thus, cross-tolerance responses and mechanisms may occur in plants. The overall objectives of this study were to determine morphological and physiological responses and mechanisms of turfgrasses and woody species under salinity and drought stress conditions, and determine the relationship between drought and salinity tolerance ability in those species. Five turfgrass entries, ‘Gazelle’ and ‘Matador’ tall fescue (TF), ‘Midnight’ Kentucky bluegrass (KBG), PI368233 (Tolerant KBG), and PI372742 (Susceptible KBG), and three woody species, bigtooth maple (xeric-non saline), bigleaf maple (mesicnon saline) and Eucalyptus (mesic-saline) were compared. For the drought study, water was withheld in Chapter 2 while the dry down treatment was based on daily evapotranspiration (ET) in Chapters 5 and 6. For the salinity study, NaCl and CaCl2 in turfgrasses at electrical conductivity (EC) of 1, 6, 12, 18, and 30 dS m-1 (Chapter 3) and woody species at EC of 1, 3, 6, 9, and 12 dS m-1 (Chapter 4). Susceptible KBG was sensitive to s

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20752号 / 理博第4328号 / 新制||理||1622(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)教授 石田 厚, 教授 工藤 洋, 教授 田村 実 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The Corral de Piedra community is located in Chiquimula, Guatemala. The main agricultural activities are corn and bean production, small-scale gardens, and small animal production, such as poultry and pigs. The crop areas are predominantly located on lands with slopes between 12 and 55%, presenting low fertility conditions and poor moisture retention capabilities. In addition, local crop varieties have low productivity potentials and the winter season is characterized by poorly distributed and erratic periods of rain. The Benson Institute introduced a technology transfer model to increase and diversify agricultural production, while preserving current natural resources. An integral part of this model included educating the community on nutrition and health topics. The school was considered to be the most appropriate place to introduce training and education in agriculture among students and community leaders, thus contributing to community development.

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Peanut (Arachis hypogaea L.) is second major legume crop grown after soybean in the United States, and its productivity is often limited by drought stress. Drought negatively impacts the yield and quality of peanut. Drought stress in peanut causes an annual loss of approximately $520 million in the United States. Improving peanut yield under water deficit conditions is crucial for peanut growers to maintain their profitability in the market. To achieve this, it is essential to either breed or adopt already available drought tolerant cultivars that can produce higher yield under water deficit conditions. Therefore, the objectives of this research were to (1) evaluate five commercially available virginia and runner type peanut cultivars for pod yield stability using multilocation trials by studying G x E interaction across 13 environments including year, location, and irrigation regime. Linn and Binns, AMMI, Shukla, Wricke's, Finlay and Wilkinson stability models were used to determine pod yield stability. Bailey and Sullivan showed higher stability and adaptability across all stability indices whereas Wynne and TUFRunner presented high mean productivity with lesser stability across environments reflecting specific adaptation to just a few environments. Bailey and Sullivan are recommended for sustainable production across the growing region of Virginia and Carolinas. The second objective (2) was identification of drought tolerance related quantitative trait loci (QTL) and genetic markers to facilitate the development of drought tolerant cultivars. Three diverse recombinant inbred line (RIL) populations, derived from crossing lines N05006 x N04074FCT (Pop-1), line N05006 x Phillips, an old virginia-type cultivar (Pop-2), and lines N08086olJCT x PI 585005 (Pop-3) were phenotyped for the Normalized Difference Vegetation Index (NDVI), Canopy Temperature Depression (CTD), SPAD-meter relative chlorophyll content of the leaves (SPAD) and wilting for QTL mapping. Mapping identified 27 minor QTL on eight chromosomes for all physiological characteristics, i.e NDVI, CTD, SPAD and wilting, with logarithmic of odds values ranging from 2.5 to 38.5 and the phenotypic variance explained by these traits from 1.04 to 11.46 %. There were 4 loci on chromosome 2 associated with NDVI in Pop-1 and Pop-3, explaining 1.8 to 10.38% of the phenotypic variation. These genomic regions may be important resources in peanut breeding programs to improve drought tolerance. Further research is needed to increase the marker density in order to fine map the identified QTL and validate markers linked with these regions. / Doctor of Philosophy / Peanut is a multi million-dollar industry in the United States, but water limitations have a detrimental impact on yield, quality, and grower income. Drought along with aflatoxin contamination are two major challenges faced by U.S peanut industry. Annual losses to peanut caused by drought are around $520 million in the United States. Irrigation can alleviate water shortage in drought prone regions, but around 65% of peanut production in U.S is under rainfed condition, meaning that only rainfall can satisfy peanut crop water requirements. The most feasible and economical solution to peanut growers under these circumstances is to adopt drought tolerant varieties. In this research, our goal was to facilitate breeding drought tolerant cultivars through identification of molecular markers associated with drought tolerance and to identify already available drought tolerant peanut cultivars that could be a game changer for the producers. Therefore, the objectives of my research were to (1) evaluate in multiple environments five commercially available virginia and runner type peanut cultivars for pod yield stability and grade factors. In this study, we considered 13 environments, including 4 years, 4 locations, and 2 water regime. Statistical tools including Linn and Binns, AMMI, Shukla, Wricke's, and Finlay and Wilkinson were used to determine pod yield stability. These stability indices showed that Bailey and Sullivan are more stable and adaptable across different locations in terms of yield, whereas Wynne and TUFRunner presented high mean yield with lesser stability showing specific adaptation to only few environments. Based on stability analysis, Bailey and Sullivan are recommended for sustainable production across different growing region of Virginia and Carolinas. The second objective (2) was to identify drought tolerance related genomic regions using three mapping populations. Phenotyping and genotyping of three diverse recombinant inbred line (RIL) populations, derived from crossing lines N05006 x N04074FCT (Pop-1), lines N05006 x Phillips, an old virginia-type cultivar (Pop-2), and lines N08086olJCT x PI 585005 (Pop-3) were done to find quantitative trait loci (QTL) for drought related traits. These population were phenotyped for the Normalized Difference Vegetation Index (NDVI), Canopy Temperature Depression (CTD), SPAD-meter relative chlorophyll content of the leaves (SPAD) and wilting for QTL mapping. These surrogate traits are related to trait of interest for drought tolerance. NDVI is effective in predicting biomass and yield. Similarly, CTD is associated with transpiration efficiency and carbon dioxide assimilation. Mapping identified 27 minor QTL on eight chromosomes for all physiological characteristics, i.e NDVI, CTD, SPAD and wilting with logarithmic of odds values range from 2.5 to 38.5 and the phenotypic variance explained by these traits ranging from 1.04 to 11.46 %. There were 4 loci on chromosome 2 associated with NDVI in Pop-1 and Pop-3, explaining 1.8 to 10.38% of the phenotypic variation. These genomic regions may be important resources in peanut breeding programs to improve drought tolerance. Further research is needed to increase the marker density in order to fine map the identified QTL and validate markers linked with these regions.

Northern red oak (Quercus rubra L.), a major commercial tree species native to North America, is an introduced tree species in Europe and is currently the most common non-native deciduous tree species in its introduced range. Although the species is widespread in the introduced range, there is a lack of knowledge on growth and climate sensitivity, especially at the provenance level. The aim of this thesis is to conduct a detailed evaluation of provenances from North America and the introduced range with respect to growth and retrospective climate sensitivity in order to identify suitable provenances for adaptive forest management in the face of more frequent extreme events in the future. The emphasis is on the differentiation between a sample of provenances, originating from Canada and the United States respectively, and from introduced stands in Germany, planted on three sites of a provenance trial in 1991 along an environmental gradient. The provenance comparison enables to address the question from which region of the natural distribution a potential seed transfer should originate in order to increase productivity and improve climate adaptation. In this context, the evaluation of adaptive strategies and phenotypic variation was pursued, focusing on the site-specific provenance response to extreme events, such as droughts and late frosts. A specific goal was to examine provenance-specific safety-efficiency trade-offs in resistance to these extreme events and absolute growth, as well as resistance and vessel size, to identify differences in adaptive strategies as response to drought and late frost. The growth analyses showed a significant increase in the performance of introduced provenances compared to those of North America, particularly at the two sites with high water availability. On the continental site, the differences in performance between provenance were less pronounced, with those from Canada in particular showing comparable growth to German provenances. Due to the strong growth differentiation, the quantification of provenance × environment interactions enabled the classification of generalists, i.e. provenances with an environment-independent growth, and specialists, i.e. provenances with an environment-dependent growth, in order to identify site-specific superior provenances. The examinations revealed most introduced provenances as good performing generalists or specialists on sites with higher water availability, whereas provenances from North America were classified as poor performing generalists, except for a Canadian provenance which showed comparable growth patterns at the continental site. The study of climate-growth relationships detected summer drought and spring temperatures as main climatic constraints for the red oak provenances. Here, provenances differed in their climate sensitivity, revealing site-specific climatic dependencies based on the prevailing environmental conditions. In contrast to tree-ring width, the study of climate variables on wood anatomical traits detected two main physiological essential periods that are decisive for wood formation. On the one hand, the climatic conditions in the previous year play a key role in the storage of reserves needed for growth in spring. On the other hand, the temperature and moisture conditions in late winter and spring determine the onset of wood formation and consequently the length of the growing season. In general, the intra-specific variation in wood anatomical traits was high, showing a high phenotypic plasticity at all sites and consequently the trait expression was mainly determined by the site-specific environmental conditions. The response in tree-ring width to extreme drought and late frost showed a high variation within sites with distinct rank changes of provenances between drought years. Further, a trade off between growth and resistance to extreme events could not be proved. On the contrary, high growth was coupled with a high frost hardiness, whereas drought hardiness showed no significant trend. Consistent with these results, no trade-off between resistance to extreme events and vessel size could be demonstrated, suggesting that the commonly reported but controversially discussed relationship between wide vessels and higher resistance to embolism does not apply to the red oak provenances studied. The findings of this thesis contribute to a broader understanding of the climate adaptation of red oak provenances for future perspectives in the introduced range. While the effect of studied summer droughts on the growth response was negligible in terms of the overall growth rates, late frost events may significantly impact red oaks. Since late frost events are suggested to increase in frequency and severity, cold adaptation is suggested to be one of the most important traits considerable for future adaptive forest management. Further, the site-specific adjustment in vessel traits to extreme climatic effects indicates a high phenotypic plasticity, which can be used to improve provenance recommendations. For this reason, provenances from introduced stands provide the best choice for forest management, whereas provenances from Canada are suggested to be promising for a continental climate, representing partly the predicted future climate. In contrast, provenances originating from the southern part of the natural distribution should not be considered in recommendations.:Acknowledgments Summary Kurzfassung List of Tables List of Figures Abbreviations 1 Introduction 1.1 Alternative tree species to mitigate climate impact 1.2 Northern red oak 1.3 Climate adaptability 1.4 Assessment of climate adaptability 1.5 General research objectives 1.6 Thesis outline 1.7 Study design and research approach 1.8 Author contributions 2 Provenances from introduced stands of Northern Red Oak (Quercus rubra L.) outperform those from the natural distribution Appendix A 3 Growth behavior of Northern Red Oak (Quercus rubra L.) in two provenance trials in Germany 4 High risk, high gain? Trade-offs between growth and resistance to extreme events differ in Northern Red Oak (Quercus rubra L.) Appendix B 5 Variation in vessel traits of Northern Red Oak (Quercus rubra L.) provenances revealed high phenotypic plasticity to prevailing environmental conditions Appendix C 6 Synthesis 6.1 Provenance differentiation 6.1.1 Local adaptation 6.1.2 Origin of introduced stands 6.1.3 Epigenetic effects during seed development 6.2 Provenance response to climate 6.2.1 Spatial and temporal variations in growth response 6.2.2 Intra-specific variation to climate 6.2.3 Response to drought and frost 6.3 Provenance choice in the face of climate change 6.3.1 The presence of provenance × environment interactions 6.3.2 Comprehensive evaluation of provenances 6.4 Concluding remarks and outlook References

<p dir="ltr">Sorghum [Sorghum bicolor (L) Moench], a crop grown in arid and semi-arid environments, can be enhanced with the stay-green trait to improve post-flowering drought tolerance. Previous studies on stay-green sorghum hybrids have noted a positive association between stay-green and grain yield in low potential environments but did not assess the combining ability or heterotic responses of individual genotypes. In this study, stay-green seed parents developed at Purdue University were crossed with three elite pollinators, and their combining ability and heterotic responses were assessed in multiple locations which represented both stress and non-stress environments. Results showed greater variation in general and specific combining ability estimates in stress environments compared to non-stress environments, with a higher proportion of additive genetic variance compared to non-additive variance in both types of environments. Levels of heterosis for grain yield, 1000 seed weight, and plant height varied across locations and between R-lines. Several experimental hybrids derived from the stay-green inbred lines outyielded commercial hybrid checks in the Ethiopian environments while showing good hybrid seed production potential, with high seed parent yield and good nicking.</p>