Levisticum officinale Koch is one of the most important plants producing essential oil. An experiment was conducted to determine the effect of drought stress on growth, total protein and essential oil content of Levisticum officinale. The experiment was conducted in a greenhouse, in a completely randomized design using 5 replications. Aridity levels of field capacity irrigation (as control), −0.6 and −1.0 MPa were applied. There was significant effect of aridity on leaf area in Levisticum officinale. The highest leaf area values were found in the lowest aridity (FC) level. The root weight and root length in the −0.6 MPa aridity level were more than that of the control aridity level, but, shoot height and shoot weight were highest in the control treatment. Total soluble protein contents under −0.6 MPa drought stress was numerically lower than that in the control treatment, but statistically there was no significant difference between protein contents in the −0.6 MPa and the control treatment. Compared to the control treatment, total soluble protein contents of Levisticum officinale were significantly decreased in the −1.0 MPa drought treatment. Essential oil content of Levisticum officinale was significantly increased in the −0.6 MPa drought treatment compared to the control. Compared to control treatment, there was a significant reduction found in essential oil content of Levisticum officinale in the −1.0 MPa aridity treatment. The results suggest that in the drought levels between −0.6 to −1.0 MPa, Levisticum officinale could be used for arid and semi-arid lands economical use.

Soybean yield differences are a combination of the genotype, environmental conditions, and management practices. Understanding how these factors interact through the analysis of the components involved in yield determination, provides a way to increase potential and actual yields in Kentucky. Two irrigated experiments were conducted to quantify differences in the mechanisms of yield determination across soybean maturity groups (MG) 2 to 5 (Chapter 1), and to quantify management options (seeding rate and choice of MG cultivar) that increase yield potential of double crop soybean systems (Chapter 2). Results showed that cultivars used different physiological strategies to achieve high yields, but these were not always consistent across the environments studied. High yields were often associated to a higher efficiency partitioning biomass to seeds that lead to a higher seed number in some cultivars, as well as associated to low seed growth rates (Chapter 1). The choice of MG cultivar had a greater impact on double-crop soybean yields than increasing seeding rates from 40 to 54 seed m-2. The higher seeding rate increased yields by 5% without an interaction with cultivar. Optimal MG choices for double-crop soybean in KY were dependent on the environment.

Master of Science / Department of Agronomy / P. V. Vara Prasad / Grain sorghum (Sorghum bicolor L. Moench) is the fourth most important cereal crop grown throughout the semi-arid regions of the world. It is a staple food crop in Africa and Asia, while it is an important feed crop in the United States (US). More recently it is increasingly becoming important as a potential bioenergy feedstock crop around the world. The state of Kansas is the largest producer of grain sorghum in the US and contributes 40% of the total production. Drought is one of the major environmental factors limiting sorghum production in the semi-arid regions of the US, Asia and Africa. It is estimated that global crop losses due to drought stress exceed $10 billion annually. In crop production, drought stress can be classified into pre- or post-flowering. Even though the world collections of sorghum contain over 35,000 accessions, the genetic base currently used in breeding programs is very small (about 3%). Thus, it is important to identify diverse breeding lines for crop improvement. The diversity (association) panel consisting of 300 sorghum lines from all over the world was assembled for trait evaluation and association mapping. In this research these lines were grouped into the five major races (Figure 1) and 10 intermediate races of sorghum. The objectives of the research are to: (i) quantify the performance of the diversity panel under field conditions in Kansas, (ii) identify critical physiological traits affected by drought at both pre- and post-flowering stages of sorghum development, (iii) identify the most sensitive stage to drought stress during the reproductive phase of sorghum development and, (iv) test the feasibility of using a chlorophyll fluorescence assay (CVA) as a tool for identifying stay-green lines in grain sorghum during early stages of crop development. Field experiments were conducted in 2006 and 2007 in two locations in Kansas (Manhattan and Hays) under rain fed and irrigated conditions for the association panel. Objectives (iii) and (iv) were achieved with controlled environment experiments conducted in the greenhouse at the agronomy department, Kansas State University in 2006 and 2007. Results showed that there was large genetic variability among and within different races in the diversity panel for growth, physiological traits and yield components. Some genotypes showed yield stability across the different environments that were investigated. Drought significantly decreased seed number and harvest index across genotypes and races. In grain sorghum the period prior to flowering (panicle initiation) was the most sensitive stage to drought stress, in terms of its effect on seed-set, during reproductive development. A cell viability assay showed that there were significant differences in the loss of cell viability between leaf sample of stay green and non-stay green genotypes when leaf samples are collected in the morning and subjected to high respiratory demand. Therefore the chlorophyll fluorescence assay has potential as a tool for stay green trait screening at early stages of growth in grain sorghum.

Made available in DSpace on 2014-06-11T19:22:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-17Bitstream added on 2014-06-13T18:48:43Z : No. of bitstreams: 1 pincelli_rp_me_botfca.pdf: 933139 bytes, checksum: dc525360fa3fad2d769f79bc71a084be (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A seca é um dos principais fatores limitantes à produtividade agrícola ao redor do mundo. Com a expansão da área de plantio da cana-de-açúcar para regiões brasileiras caracterizadas por apresentarem deficiência hídrica por longos períodos durante o ano, torna-se essencial a obtenção de germoplasma de cana-de-açúcar tolerante a esse estresse. Identificar ferramentas adequadas de seleção e características quantificáveis podem facilitar o processo de melhoramento da cultura para tolerância à seca, visto que há dificuldade em identificar características únicas que possam ser utilizadas para a seleção. O objetivo do presente trabalho foi verificar a habilidade de algumas variáveis morfofisiológicas para distinguir entre tolerantes e susceptíveis quatro cultivares comerciais de cana-de-açúcar sob dois regimes hídricos. O experimento foi conduzido em vasos contendo 22 litros de substrato, em casa de vegetação localizada na Unidade de Pesquisa e Desenvolvimento da APTA Polo Centro-Oeste, Jaú,SP. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 4x2x3 (cultivares x regimes hídricos x épocas de avaliação), com três repetições. Aos 84 dias após a emergência, as cultivares RB72454, RB855453, SP81-3250 e SP83-2847 foram submetidas aos tratamentos de teor de umidade (%): sem deficiência (-D) e com deficiência (+D) promovida por 50% do teor de umidade ideal e avaliadas durante três épocas: 0, 28 e 56 dias após o início dos tratamentos. As variáveis avaliadas foram: altura do colmo, número de folhas verdes, comprimento e largura da folha +3, área foliar, densidade estomática, massa foliar específica, estimativa do conteúdo de clorofila (via SPAD e via espectrofotômetro), máxima eficiência fotoquímica do fotossistema II (Fv/Fm), condutância estomática, conteúdo relativo de água, potencial hídrico foliar e massa... / Drought is one of major limiting factors to agricultural productivity around the world. With the expansion of planting area of sugarcane for Brazilian regions characterized by water stress for long periods during the year, it becomes essential to obtain germplasm of tolerant sugarcane. Identify appropriate tools for selection and quantifiable characteristics can facilitate the process of crop breeding for drought tolerance, since there is difficulty in identifying unique characteristics that can be used for selection. This study aimed to verify the ability of some morphological and physiological variables to distinguish between tolerant and susceptible four sugarcane commercial cultivars under two water regimes. The experiment was carried out in pots containing 22 liters of substrate, in a greenhouse located in the Unit of Research and Development of APTA, Jaú, SP. The experimental design was randomized in factorial 4x2x3 (genotypes x water regimes x evaluation times) with three replicates. At 84 days after emergence, cultivars RB72454, RB855453, SP81-3250 and SP83-2847 were exposed to humidity treatments: no stress (-D) and stress (+ D) promoted by 50% of the ideal humidity and evaluated for three times: 0, 28 and 56 days after the initiation of the treatments (DAT). The variables evaluated were: stalk height, green leaf number, length and width of leaf +3, leaf area, stomatal density, specific leaf mass, estimated chlorophyll content (via SPAD and via spectrophotometer), maximum photochemical efficiency of photosystem II (Fv/Fm), stomatal conductance, relative water content, leaf water potential and dry weight of shoots and roots. We found a higher height of stalk, number of green leaves, leaf area, stomatal density at adaxial and abaxial surfaces, higher maximal photochemical efficiency of photosystem II (Fv/Fm), estimation of chlorophyll content (SPAD index) and leaf water potential... (Complete abstract click electronic access below)

Orientador: Marcelo de Almeida Silva / Banca: Carlos Alexandre Costa Crusciol / Banca: Maria Ines Tiraboschi Ferro / Resumo: A seca é um dos principais fatores limitantes à produtividade agrícola ao redor do mundo. Com a expansão da área de plantio da cana-de-açúcar para regiões brasileiras caracterizadas por apresentarem deficiência hídrica por longos períodos durante o ano, torna-se essencial a obtenção de germoplasma de cana-de-açúcar tolerante a esse estresse. Identificar ferramentas adequadas de seleção e características quantificáveis podem facilitar o processo de melhoramento da cultura para tolerância à seca, visto que há dificuldade em identificar características únicas que possam ser utilizadas para a seleção. O objetivo do presente trabalho foi verificar a habilidade de algumas variáveis morfofisiológicas para distinguir entre tolerantes e susceptíveis quatro cultivares comerciais de cana-de-açúcar sob dois regimes hídricos. O experimento foi conduzido em vasos contendo 22 litros de substrato, em casa de vegetação localizada na Unidade de Pesquisa e Desenvolvimento da APTA Polo Centro-Oeste, Jaú,SP. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 4x2x3 (cultivares x regimes hídricos x épocas de avaliação), com três repetições. Aos 84 dias após a emergência, as cultivares RB72454, RB855453, SP81-3250 e SP83-2847 foram submetidas aos tratamentos de teor de umidade (%): sem deficiência (-D) e com deficiência (+D) promovida por 50% do teor de umidade ideal e avaliadas durante três épocas: 0, 28 e 56 dias após o início dos tratamentos. As variáveis avaliadas foram: altura do colmo, número de folhas verdes, comprimento e largura da folha +3, área foliar, densidade estomática, massa foliar específica, estimativa do conteúdo de clorofila (via SPAD e via espectrofotômetro), máxima eficiência fotoquímica do fotossistema II (Fv/Fm), condutância estomática, conteúdo relativo de água, potencial hídrico foliar e massa... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Drought is one of major limiting factors to agricultural productivity around the world. With the expansion of planting area of sugarcane for Brazilian regions characterized by water stress for long periods during the year, it becomes essential to obtain germplasm of tolerant sugarcane. Identify appropriate tools for selection and quantifiable characteristics can facilitate the process of crop breeding for drought tolerance, since there is difficulty in identifying unique characteristics that can be used for selection. This study aimed to verify the ability of some morphological and physiological variables to distinguish between tolerant and susceptible four sugarcane commercial cultivars under two water regimes. The experiment was carried out in pots containing 22 liters of substrate, in a greenhouse located in the Unit of Research and Development of APTA, Jaú, SP. The experimental design was randomized in factorial 4x2x3 (genotypes x water regimes x evaluation times) with three replicates. At 84 days after emergence, cultivars RB72454, RB855453, SP81-3250 and SP83-2847 were exposed to humidity treatments: no stress (-D) and stress (+ D) promoted by 50% of the ideal humidity and evaluated for three times: 0, 28 and 56 days after the initiation of the treatments (DAT). The variables evaluated were: stalk height, green leaf number, length and width of leaf +3, leaf area, stomatal density, specific leaf mass, estimated chlorophyll content (via SPAD and via spectrophotometer), maximum photochemical efficiency of photosystem II (Fv/Fm), stomatal conductance, relative water content, leaf water potential and dry weight of shoots and roots. We found a higher height of stalk, number of green leaves, leaf area, stomatal density at adaxial and abaxial surfaces, higher maximal photochemical efficiency of photosystem II (Fv/Fm), estimation of chlorophyll content (SPAD index) and leaf water potential... (Complete abstract click electronic access below) / Mestre

This study was part of a program to develop new genotypes of sheep (Ovis spp.) and goats (Capra spp.) which are more useful for food and fiber production. The study examined the influence of domestication on behavioral and physiological traits of ewes and lambs, the influence of a single or twin offspring on ewe and lamb behaviors, and general relationships between ewes and lambs during the lambs' first month of life. Domestication has caused the intensities of observed traits to diverge greatly from the tendencies shown by wild populations. Domestication has produced increases in measurements associated with maternal care, discovery learning, tolerance or inclination for closeness with conspecifics, length of the breeding season, fertility, birth weight, and growth rate. Behaviors associated with imitative learning have decreased with domestication. Domestication has not altered the length of estrous cycle nor length of gestation. The partly domestic groups were intermediate to the most domestic and wild groups for three traits: maternal care, birth weight, and growth rate. However, other hybridization factors apparently altered the intermediate position of the partly domestic groups for the remaining traits: learning in the young, proximity of conspecifics, and fertility. The study's findings indicated that the development of new crossbreeds is an advantageous method of improving sheep and goat productivity. Some behavioral differences between ewes and their single lambs and ewes and their twin lambs resulted from the earlier physical development of singles as compared to twins: Singles played more and spent less time close to their mothers. Mothering capacities, sibling competition, and a sibling bond caused behavioral differences between ewes and their twin young and ewes and their single young: Twins suckled more, gained less weight, spent more time close to their mothers, stood more, received less sniffing from their mothers than did singles. The ewe-lamb bond did not vary between ewes and their single lambs and ewes and their twin lambs. The high occurrence of simultaneous behaviors and the maintenance of close contact between ewes and their offspring and between twins contributed to the cohesion and organization of the flock.

The occurrence of phenotypic and genotypic diversity is the key factor in crop improvement including abiotic stress tolerance. The focal objectives of this study were to evaluate and characterize 74 tropical indica rice breeding lines for phenotypic and genotypic diversity, screening for the most devastating abiotic stresses in rice; drought and salinity at the seedling stage at morpho-physiological and molecular levels. To fulfill these objectives, five studies were conducted in pots; first two experiments aimed at assessing phenotypic and yield variability at seedling and maturity stages respectively; based on several (more than 20) root and shoot traits which exploited a wide range of variability among genotypes for measured traits. Germplasm was then screened for drought stress at two moister regimes, 50%, and 100% moisture levels, under mini-hoop structures. Nine percent of the genotypes exhibited a high tolerance to drought stress, and genotypes IR86638 and IR49830 were identified as the most and least drought tolerant respectively. Germplasm was also screened for salinity tolerance in pure sand pot-culture (a simple, efficient and alternate screening method) at three levels; high salt stress (EC 12 dSm-1), moderate salt stress (EC 6 dSm-1), and control imposed one week after emergence. Thirteen genotypes (17.57%) were identified as highly salt tolerant; genotypes FED 473 and IR85427 were highly salt tolerant and salt sensitive, respectively. Root traits were found more crucial and best descriptors in identifying both salinity and drought tolerant genotypes. Genotypes were further used in Genome-wide Association Study (GWAS) to uncover important SNPs, QTLs or genes related to salinity tolerance. A higher number of significant SNPs were discovered for root traits, indicting the importance of root traits in identifying abiotic stress tolerance in rice. The knowledge gained from this investigation could be useful in breeding for better crop establishment, yield improvement, screening for any abiotic stress tolerance.

Thesis (Ph.D. (Plant Production)) -- University of Limpopo, 2021 / Cassava (Manihot esculenta Crantz) is a widely cultivated crop in many tropical countries in Africa, Latin America, and Asia. Cassava is a staple food security crop for over one billion people worldwide. It is a multi‑purpose and well adapted to different agricultural production systems. Although cassava is adaptable to marginal soils with low fertility, and to irregular rainfall conditions, as it allows a relatively stable productivity and flexibility for harvesting process, the challenges posed by global climate change (both temperature and drought severity increasing) have caused negative impacts on this crop‘s productivity. Given the increasing demand for higher productivity to improve food security and alleviate poverty in the dry prone regions of Africa, there is a concurrent increasing demand to expand production into marginal ecologies and improve its adaptation in such ecologies. Breeding efforts have resulted in the development of high-yielding varieties, but due to late bulking and long time taken before crop is ready for harvest, the improved varieties were not easily adopted by farmers. The complex nature of yield and other productivity traits, coupled with the biology of cassava, make it more challenging to improve the crop. However, biotechnology has revolutionised breeding with the development of advanced molecular tools that have facilitated breeding-by-design approaches leading to effective manipulation of genes for complex traits. The potential and impact of the new tools are now providing a stronger basis to adopt molecular breeding to genetically improve the crop for key traits. The main objectives of the research were to: (i) Develop a mapping population and identify traits driving the physiological basis of drought tolerance in F1 cassava genotypes; (ii) Identify traits linked with early bulking in the F1 population; (iii) Identify quantitative trait loci (QTLs) for drought tolerance and early bulking in F1 cassava genotypes; and (iv) Estimate the genetic improvement for drought tolerance in the F1 population. Two genotypes (TMS98/0505 and TMS98/0581) with contrasting desirable traits such as high yield in marginal environment, good disease resistance, vigour, and flowering potentials were used in the development of the mapping population used in this study. Results indicate that there was a positive correlation between yield, yield-related traits .and morphological/physiological traits. Principal component analysis identified the scar level, height of stem with leaf, fresh root yield, dry root yield, root number and dry-matter content as traits driving drought tolerance in marginal environment. This study also identified early-bulking cassava varieties in the F1 population and traits associated with early bulking. Fresh root yield was significantly associated with morphological and productivity traits while principal component analysis identified important traits such as root weight, root number, plant biomass, fresh root yield, plant height, , and stem diameter. Composite interval mapping identified 27QTLs and 30 QTLs in the first and second year, respectively, associated with the traits phenotyped in dry savannah ecology of Nigeria, while 16 and 12 QTLs associated with early bulking at 7 MAP were identified in the first and second year. Identification of these loci will aid breeding for drought tolerance and early root bulking in cassava. There was a better performance among traits such as biomass, root number, dry-matter content, number of scars, number of leaves, and length of stem with leaf in the second population (population C) than in the first population (population B). Twenty superior genotypes were selected from population C, which will be incorporated in the breeding programmes for further evaluation and germplasm enhancement. KEY WORDS: Composite interval mapping, Fresh root yield, Manihot esculenta, morphological traits, Population C, physiological traits. / National Root Crops Research Institute (NRCRI) Umudike

L’étude des rendements en blé a mis en évidence une stagnation apparue dans les années 1990, notamment en France, et principalement lié aux stress hydrique et thermique. Dans ce contexte, améliorer la tolérance du blé européen à ces stress est de première importance. Cette étude avait pour but d’étudier le déterminisme génétique de la tolérance à ces stress chez le blé. Pour ce faire, trois populations de blé tendre du CIMMYT combinant des caractères d’adaptation à ces stress ont été cultivées en conditions irriguée, sèche et stress thermique irriguée plusieurs années. Des caractères physiologiques et agronomiques ont été mesurés sur un réseau de 15 essais. Une méthodologie de caractérisation environnementale a été développée et a permis l’identification de six scenarii de stress au sein du réseau. Une covariable environnementale représentative de chacun a été extraite. L’utilisation des modèles de régression factorielles a permis la décomposition de l’interaction génotype x environnement ainsi que la mise en évidence d’une sensibilité différentielle au stress dans le germplasm. Une recherche de QTL multi-environnementale a conduit à la détection de régions génomiques contrôlant les caractères physiologiques et agronomiques ainsi que leurs interactions avec l’environnement. De la caractérisation environnementale à la détection de QTL, cette étude a abouti au développement d’un outil pour les sélectionneurs permettant l’évaluation du potentiel des génotypes face à une gamme d’environnement, mais aussi à l’identification de régions génomiques impliquées dans le contrôle de la tolérance aux stress hydrique et thermique chez le blé tendre. Ceci pourrait améliorer la tolérance à ces stress au sein du germplasm européen. / A stagnation of wheat yield was reported in France and other countries worldwide since the 1990’s, which incriminated mainly drought and heat stress. Improving the European wheat tolerance to them is of first importance. This study aimed to investigate the genetic determinism of the tolerance to such stresses. Three CIMMYT bread wheat populations combining complementary heat and drought adaptive habits were grown in Northern Mexico under irrigated, drought and heat-irrigated treatments from 2011 to 2013. The trial network comprised 15 trials and both physiological and agronomic traits were scored. First, an environmental characterization methodology was developed and resulted in the identification of six main environmental scenarios in the network. A representative environmental covariate was extracted from each of them. Then, a factorial regression model leaded to the dissection of the genotype-by-environment interaction and highlighted differential stress sensitivity of the germplasm. Finally, a multi-environmental QTL detection resulted in the discovery of genomic regions involved in the control of both physiological and agronomic traits and the study of their sensitivity to the environment. From the environmental characterization to the QTL detection, this study resulted in the development of a tool for breeders which may enable the evaluation of the potential of any genotypes in front of a range of environment, but also the identification of genomic regions involved in the control of the tolerance to drought and heat stress in bread wheat. This may help in improving the tolerance of the European bread wheat germplasm to drought and heat stress.

Etudier un phénomène écologique requiert de le considérer dans sa globalité afin d’appréhender l’ensemble de ses causes et ses conséquences. Dans la plaine de la Crau, écosystème pseudo-steppique du sud est de la France, la fragmentation des habitats, la perte de biodiversité et les changements d’usage ont favorisé l’envahissement de fragments relictuels de steppe par Rubus ulmifolius Schott. Par une approche multiscalaire, les objectifs de cette thèse sont de mettre en évidence les facteurs responsables de cet envahissement, d’appréhender ses conséquences sur la communauté végétale et de tester d’éventuelles techniques de restauration écologique en évaluant leurs effets à l’échelle de la communauté et de la population de ronces. La présence de fortes proportions de zones irriguées et de parcelles anciennement cultivées dans la matrice paysagère proche des zones envahies correspond à des taux de recouvrements parcellaires en ronciers plus élevés. A l’échelle de la communauté végétale, les infiltrations hydriques ont également des effets importants sur la végétation steppique en permettant le développement d’une espèce herbacée compétitrice : Brachypodium phoenicoïdes (L.) Roem. & Schult. Aucun des différents régimes de perturbation (débroussaillage et/ou pâturage) testés, croisés au drainage ou non du sol ne permet de restaurer à court terme (trois années) l’intégrité de la steppe de référence. Seule une augmentation significative de la richesse et de la diversité spécifique est mesurée dans le cas d’un débroussaillage et d’un pâturage annuel des placettes. A l’échelle des ronces, les effets des différents traitements varient selon l’année, la saison ou la période de la journée considérée. Les régimes de perturbation (débroussaillage et/ou pâturage) ont cependant plus d'influence sur les traits éco-physiologiques et morphologiques de la ronce que la limitation des ressources en eau. Nos résultats soulignent ainsi la difficulté de contrôler à court terme la dynamique d’une espèce envahissante. Ils ouvrent également le débat sur les objectifs de conservation et/ou de restauration des parcelles qui peuvent alors être considérées comme des écosystèmes dégradés ou comme de « nouveaux écosystèmes » dont les potentiels patrimoniaux sont encore inconnus. / Studying an ecological phenomenon require to consider it in its entirety in order to apprehend all the causes and consequences. In the Plain of La Crau, a sub-steppic ecosystem in southeastern France, habitat fragmentation, loss of biodiversity and land-uses changes have fostered the encroachment by a species of brambles Rubus ulmifolius Schott of the original steppic patches. Using a multiscale analysis, the aims of the thesis are to highlight the main drivers, to assess the consequences on the plant community and to test restoration techniques by evaluating their effects on plant community and on bramble population. The presence of high proportions of irrigated habitats and formely fallows around invaded plots correspond to the largest cover rates of brambles. At community scale, water infiltrations have also a great impact on the steppe plant community by favoring the dynamic of an herbaceous competitor species: Brachypodium phoenicoïdes (L.) Roem. & Schult. Among the different disturbance regimes tested (scrub-clearing and / or grazing), crossed with the presence or the absence of sol draining, none could restore in the short-term (3 years), the integrity of the steppe reference. A significant increase in species richness and diversity was only measured for drained, scrub-cleared and annually grazed plots. At bramble population scale, the effects of the different treatments change depending on the year, the season and the time of the day. However, disturbance regimes (clearing and / or grazing) have more impact on eco-physiological and morphological traits of the bramble than the water resources limitation. Our results highlight the difficulty controlling short-term dynamics of an invasive species. They question the objectives of conservation and / or restoration of plots which can then be considered as degraded ecosystems or as "novel ecosystems" whose potential patrimonial values are still unknown.