Rice is the staple food for nearly one half of the ever growing world's population. Phosphorus (P) deficiency commonly constrains crop productivity on a large area of arable land worldwide. P fertilizer is a finite resource and an expensive input, so it must be used efficiently. The main objective of this study was to investigate plant and soil P interaction in P deficient conditions and understand plant mechanisms that could enhance P uptake efficiency throughout two main research approaches: Firstly, investigating plant and soil microbes' interaction that promotes plant growth in Plimited conditions. Secondly, evaluating the P uptake efficiency of a number of rice genotypes in a high throughput screening systems in order to understand genotypic variations in P uptake mechanisms. The genotypes used were genotyped for the allelic variation in the Pup1 locus and the effect of this QTL on the plant growth was also investigated. In an experiment investigating the influence of soil microbes on rice growth in P deficient conditions, an experimental system where pots were filled with a mix of 95% low P Insch subsoil and 5% Insch topsoil, where the subsoil was sterilized by autoclaving and the top soil was either sterilized or live. Non-autoclaved (live) topsoil caused a significant increase in shoot dry weight (SDW) for IAC 25 compared to autoclaved soil while the opposite was true for Azucena suggesting that the presence of soil microbes is needed for IAC 25 to access soil-bound P under P-limiting condition while for Azucena it is not. Most importantly, a very strong cultivar x treatment interactions on almost all growth parameters and elements in the shoot except for Mn were found. In a dose experiment investigating whether there is a general toxic effect for autoclaving Insch topsoil being used in this study on the growth of IAC 25, a strong positive correlations of plant growth parameters with the percentage of sterile topsoil vi levels were observed indicating that the autoclaved topsoil was not toxic. The influence of soil wash (distilled water added to the soil then extracted) and different types of soil as sources of inocula on the plant growth of rice cultivars were also studied. Soil wash inoculation did not affected plant growth but soil inocula increased the biomass of all rice cultivars (Azucena, IAC 25 and Lemont) tested suggesting that if it is microbes that are important they must be remaining in the soil and are not transferable by washing. Two autoclaved soils did not behave similarly in terms of affecting plant growth of rice cultivars (Azucena and IAC 25). Moreover, the live treatment of a new soil stimulated the growth of both cultivars and the cultivar x treatment interaction that was found in earlier experiment was lost with the use of this new soil. The implication is that the cultivar by autoclave treatment interaction is soil specific. The fluctuating results between the experiments indicate that it is unlikely that such studies can be extended into plant genetics. So, the second approach of the study focused on examining simpler plant/soil P interaction in P limiting conditions. A 25/75% subsoil/sand mix was determined as a P deficient and used to screen 30 rice genotypes in two experiments: the first when watered with Yoshida's nutrient solution (YNS) either with (YNS+P) or without P (YNS-P) to assess whether rice genotypes differ in extracting P added in liquid form while the second was designed to test if shallow and deep-rooted genotypes differ in extracting P present in soil by using rock phosphate in three treatments: when rock P was absent or embedded either in a shallow 10 cm layer or distributed homogenously in soil mix. For both experiments, P treatment x genotype interaction was significant on SDW. On average, YNS-P treatment significantly reduced the SDW for genotypes compared to that of plants grown in YNS+P treatment while the addition of rock phosphate greatly stimulated plant growth where SDW of plants grown in homogenous P and shallow P significantly outgrew vii those in zero P treatment. In both experiments, rice from the aus subgroup grown in -P treatment accumulated significantly more SDW than indica and japonica genotypes. In -P treatment, the genotypes that accumulated higher SDW relative to the others were Black Gora, Rayada, Kasalath, Azucena, IAC 25, Dom Sufid, Aux1Wild type, FR 13A and especially Sadu Cho. In the rock phosphate experiment, both P treatment and genotype affected RDW and root/shoot ratio significantly. Most importantly, two root angle traits (the mean root direction and the weighted average of the unsigned root angles) measured in rhizotrons were correlated with the relative SDW in shallow P (SDW in shallow P/SDW in zero P) slightly stronger than with relative SDW in homogenous P (SDW in homogenous P/SDW in zero P) indicating that the relationship between plant growth and root distribution with depth was altered by the distribution of rock phosphate in soil. In both experiments, the presence of Kasalath alleles in the Pup1 QTL significantly increased SDW of the genotypes. However, some genotypes, especially Dom Sufid and Sadu Cho performed well in these experiments despite lacking the Pup1 allele suggesting that Pup1 QTL is not the only determinant for tolerance to P deficiency. The system appears to be suitable for high throughput screens of rice genotypes.

Graduation date: 1993

No description available.

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (M.S.)--Mississippi State University. Department of Plant and Soil Sciences. / Title from title screen. Includes bibliographical references.

Made available in DSpace on 2016-12-08T16:44:52Z (GMT). No. of bitstreams: 1 PGPV06MA008.pdf: 598779 bytes, checksum: 554505b1ffde03f58a3b2e9e4f7cf845 (MD5) Previous issue date: 2006-02-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The water management has great importance to the pre-germinated paddy rice production system. The irrigation water contributes to soil tillage, helps to control weeds, insects and diseases, and increases nutrient availability. The water drainage at tillering is a common management practice among rice growers in Santa Catarina. Rice producers state that irrigation suppression at tillering enhances plant sustainability, preventing lodging and favoring water removal before harvesting the crop. Conversely, this water management strategy may create some problems, such as enhancement in the incidence of weeds and diseases, stimulation of nitrogen losses by denitrification and reduction of grain yield due to water deficit. This work was conducted aiming to determine the effect of water removal at tillering on plant root morphology system, physical and chemical soil attributes, grain yield and kernel quality of rice cultivars. A green house and a field experiment were conducted in Lages and Pouso Redondo, respectively. Four water management systems at tillering were tested on each trial: continuous irrigation during tillering, water removal at V6 and water return at 7, 14 and 21 days after soil drainage. Two cultivars were evaluated for each irrigation system: Epagri 106 (early cycle) and Epagri 109 (late cycle). The experiments were installed on 09/24/2004 in Lages, and 10/16/2004 in Pouso Redondo. The experimental area was flooded 30 days before sowing rice at both experimental sites. The soil was fertilized with 20 kg of P2O5, 40 kg of K2O and 100 kg of N ha-1 in each experiment. A completely randomized design was used in the green house experiment. A randomized block design with split-plots was employed in the field, where the irrigation systems were tested in the main plots and the cultivars in the split-plots. The plant height, total number of leaves per plant, number of green and senesced leaves, root length, volume, radium and area, as well as root and shoot dry mass were assessed in the green house experiment. In the field experiment, soil samples were collected at 7, 14 and 20 days after drainage to determine mineral N. Evaluations of soil resistance to penetration were carried out at soil drainage, 7, 14 and 20 days after water removal. Soil density, micro porosity, macro porosity and total porosity were assessed 7 days after water removal and at harvesting. Grain yield, yield components and grain quality parameters were determined after harvesting. In both experiments, data were analyzed by the Variance Analysis. Means were compared by the Duncan s Test at the 5% error probability level. Results from the green house experiment showed that the root and shoot dry mass were not affected by the irrigation management system and were higher for the early cultivar Epagri 106. Soil drainage for 21 days increased leaf senescence, decreasing the number of green leaves at harvesting, in relation to the treatment with continuous irrigation. The late cultivar Epagri 109 presented higher number of tillers and leaves than the early cultivar Epagri 106. The root length, area and volume were reduced with the increase in drainage period. In the field, water removal at tillering had a small effect on the amount of mineral N (NH4 + and NO3-) 7, 14 and 20 days after drainage. The water management system did not affect soil resistance penetration at the 0-10 cm layer from drainage to water return. The water removal at tillering enhanced soil density at harvesting of cultivar Epagri 106. Grain yield and kernel quality were not affected by the water management system at tillering. There were no significant differences between grain yields of both cultivars. Epagri 109 presented higher values of panicle length, weight of 1,000 grains, percentage of empty grains and percentage of full length grains than Epagri 106. Results from the green house experiment indicate that long drainage periods at tillering hasten leaf senescence and restrict rice root growth, regardless of cultivar cycle. Such physiological restrictions did not decrease grain yield in the field possibly due to the high amount of rainfall during the 20 days where water management systems were tested / O manejo da água é de grande importância para cultura do arroz irrigado no sistema pré-germinado. A água contribui para o preparo do solo, controle de plantas daninhas, pragas e doenças e eleva a disponibilidade de nutrientes. A retirada de água no perfilhamento é uma prática comum entre os produtores do Estado de Santa Catarina. Estes afirmam que a supressão da irrigação no perfilhamento melhora a sustentação das plantas, evitando o acamamento e facilitando a drenagem antes da colheita. Por outro lado, esta prática pode ocasionar alguns problemas, tais como maior incidência de brusone e de plantas daninhas, perdas de nitrogênio por desnitrificação e redução na produtividade devido à falta de água. Este trabalho foi conduzido objetivando determinar o efeito da retirada de água no perfilhamento sobre a morfologia do sistema radicular da planta, características físico-químicas do solo, rendimento de grãos e parâmetros de engenho de cultivares de arroz. Foram conduzidos dois experimentos, um em casa de vegetação, em Lages e outro a campo, no município de Pouso Redondo. Em cada ensaio foram testados quatro sistemas de manejo da água durante o perfilhamento: irrigação contínua, retirada da água no estádio V6 e retorno 7 dias após, 14 dias após e 21 dias após a drenagem. Para cada sistema de manejo de água foram avaliadas duas cultivares, uma de ciclo precoce, EPAGRI-106, e outra de ciclo tardio, EPAGRI-109. O ensaio em casa de vegetação foi implantado no dia 24/09/2004 e o ensaio a campo no dia 16/10/2004, sendo que a inundação inicial ocorreu 30 dias antes da semeadura para os dois ensaios. A adubação foi equivalente a 20 kg de P2O5 ha-1, 40 kg K2O ha-1 e 100 kg de N ha-1 para os dois ensaios. O delineamento experimental do experimento em casa de vegetação foi completamente casualizado. No experimento de campo utilizou-se o delineamento experimental de blocos ao acaso com parcelas subdivididas, sendo que na parcela principal foram testados os sistemas de manejo da irrigação e nas sub-parcelas as cultivares de arroz. No experimento conduzido em casa de vegetação determinou-se a estatura e o número de perfilhos por planta, o número de folhas totais, verdes e senescidas, o comprimento, a área, o volume e o raio das raízes, bem como a quantidade de massa seca alocada à parte aérea e ao sistema radicular. No experimento a campo determinou-se a quantidade de N mineral no solo aos 7, 14 e 20 dias após a drenagem e a resistência do solo à penetração no momento da drenagem, aos 7, 14 e 20 dias após a drenagem. Coletou-se também amostras indeformadas de solo para determinação da densidade, microporosidade, macroporosidade e porosidade total aos 7 dias após a drenagem e no momento da colheita. Após a colheita, determinou-se o rendimento de grãos, os componentes do rendimento e parâmetros de engenho. Os dados obtidos nos dois ensaios foram submetidos à análise de variância. Quando alcançada significância estatística, as médias foram comparadas pelo teste de Duncan, ao nível de 5% de probabilidade de erro. As matérias seca de parte aérea, de raiz e total não foram afetadas pelo sistema de manejo da irrigação, sendo maior na cultivar de ciclo precoce Epagri 106. A drenagem do solo por 21 dias acelerou a senescência foliar e diminuiu o numero de folhas verdes na colheita, em relação ao tratamento com irrigação contínua. A cultivar Epagri 109 apresentou maior número de folhas totais e de perfilhos do que a cultivar Epagri 106, na média dos quatro sistemas de manejo da água. O comprimento, a área e o volume radicular foram reduzidos quadraticamente com o aumento no período de drenagem. No experimento de campo, a retirada da água no perfilhamento teve pequeno efeito sobre a quantidade de nitrogênio mineral (NO3 - e NH4 +) determinada aos 7, 14, 20 dias após a drenagem. O sistema de manejo da irrigação não interferiu significativamente sobre a resistência do solo à penetração na camada de 0-10cm da drenagem até o retorno da irrigação. A retirada de água no perfilhamento aumentou a densidade do solo no momento da colheita da cultivar Epagri 106. O rendimento de grãos e os componentes do rendimento não foram afetados pelo sistema de manejo da irrigação no perfilhamento. Não houve diferença significativa no rendimento de grãos entre cultivares. A cultivar Epagri 109 apresentou maior comprimento de panícula, percentagem de grãos chochos, massa de 1000 grãos, porcentagem de impurezas e rendimento de engenho do que a Epagri 106. Os resultados do trabalho feito em casa de vegetação demonstram que períodos prolongados de drenagem aceleram a senescência foliar e restringem o desenvolvimento do sistema radicular da cultura do arroz, independente do ciclo da cultivar. Estas restrições não reduziram o rendimento de grãos a campo, possivelmente devido ao índice pluviométrico registrado durante os 20 dias de aplicação dos sistemas de manejo da irrigação