Comportamento de cultivares de arroz de terras altas em função do preparo do solo e irrigação por aspersão, em latossolo vermelho de cerrado

Pós-graduação em Agronomia - FEIS

Mecanismos de distribuição do fertilizante e adubação nitrogenada em cobertura no arroz de terras altas em plantio direto

Pós-graduação em Agronomia (Energia na Agricultura) - FCA

Anatomia floral de espécies de Cyperaceae (Poales)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Leaf gas exchange and yield of three upland rice cultivars

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Developmental Morphology of a Dimorphic Grass Inflorescence: The Brazilian Bamboo Eremitis (Poaceae)

Premise of research.The highly specialized grass inflorescence varies with respect to phyllotaxis, with the reproductive meristem forming primary lateral branches that are either spirally arranged or distichous. The Brazilian bamboo Eremitis is highly unusual in that it has a dimorphic inflorescence, typically composed of an apical gynecandrous whorl of both male and female spikelets and basal whorls of male spikelets. Although not closely related to them, Eremitis shares some structural similarities with some early-divergent grasses.Methodology.We use SEM and LM to describe the development of the reproductive structures of Eremitis to clarify our understanding of the highly specialized grass inflorescence and flower.Pivotal results.Developmental studies show that the inflorescence of Eremitis is actually partially whorled and partially distichous. The apical whorl is abortive. The female spikelet is not terminal on the axis, in contrast with the majority of grasses. All the male spikelets are distichously attached to the inflorescence axis and separated into groups. There is a hollow style with two vascular bundles.Conclusions.The strong morphological similarities between Eremitis and some early-divergent grasses are here supplemented by several anatomical similarities, perhaps due to a shared pollination syndrome.

Aplicação de thidiazuron na cultura do arroz de terras altas irrigado por aspersão na região de Selvíria-MS

Pós-graduação em Agronomia - FEIS

A multiparental cross population for mapping QTL for relevant agronomic traits in durum wheat (Triticum durum Desf.)

Multiparental cross designs for mapping quantitative trait loci (QTL) in crops are efficient alternatives to conventional biparental experimental populations because they exploit a broader genetic basis and higher mapping resolution. We describe the development and deployment of a multiparental recombinant inbred line (RIL) population in durum wheat (Triticum durum Desf.) obtained by crossing four elite cultivars characterized by different traits of agronomic value. A linkage map spanning 2,663 cM and including 7,594 single nucleotide polymorphisms (SNPs) was produced by genotyping 338 RILs with a wheat-dedicated 90k SNP chip. A cluster file was developed for correct allele calling in the framework of the tetraploid durum wheat genome. Based on phenotypic data collected over four field experiments, a multi-trait quantitative trait loci (QTL) analysis was carried out for 18 traits of agronomic relevance (including yield, yield-components, morpho-physiological and seed quality traits). Across environments, a total of 63 QTL were identified and characterized in terms of the four founder haplotypes. We mapped two QTL for grain yield across environments and 23 QTL for grain yield components. A novel major QTL for number of grain per spikelet/ear was mapped on chr 2A and shown to control up to 39% of phenotypic variance in this cross. Functionally different QTL alleles, in terms of direction and size of genetic effect, were distributed among the four parents. Based on the occurrence of QTL-clusters, we characterized the breeding values (in terms of effects on yield) of most of QTL for heading and maturity as well as yield component and quality QTL. This multiparental RIL population provides the wheat community with a highly informative QTL mapping resource enabling the dissection of the genetic architecture of multiple agronomic relevant traits in durum wheat.

Long-Day Up-Regulation of a GAMYB Gene during Lolium temulentum Inflorescence Formation

Long-day exposure of the grass Lolium temulentum may regulate flowering via changes in gibberellin (GA) levels. Therefore, we have examined both GA levels and expression of a MYB transcription factor that is specific to the GA signal transduction pathway in monocots. This MYB gene from L. temulentum shows over 90% nucleotide identity with the barley and rice GAMYB genes, and, like them, gibberellic acid (GA3) up-regulates its expression in the seed. Furthermore, cDNAs of both the barley and L. temulentum GAMYB show the same simple patterns of hybridization with digests of L. temulentum genomic DNA. Compared with vegetative shoot apices of L. temulentum, the in situ mRNA expression of LtGAMYB does not change during the earliest steps of “floral” initiation at the apex. However, by 100 h (the double-ridge stage of flowering) its expression increased substantially and was highest in the terminal and lateral spikelet sites. Thereafter, expression declined overall but then increased within stamen primordia. Prior to increased LtGAMYB expression, long-day exposure sufficient to induce flowering led to increased (5- to 20-fold) levels of GA1 and GA4 in the leaf. Thus, increases first in GA level in the leaf followed by increased expression of LtGAMYB in the apex suggest important signaling and/or response roles in flowering.

Developmental and Hormonal Regulation of Genes Coding for Proline-Rich Proteins in Female Inflorescences and Kernels of Maize1

The pattern of expression of two genes coding for proteins rich in proline, HyPRP (hybrid proline-rich protein) and HRGP (hydroxyproline-rich glycoprotein), has been studied in maize (Zea mays) embryos by RNA analysis and in situ hybridization. mRNA accumulation is high during the first 20 d after pollination, and disappears in the maturation stages of embryogenesis. The two genes are also expressed during the development of the pistillate spikelet and during the first stages of embryo development in adjacent but different tissues. HyPRP mRNA accumulates mainly in the scutellum and HRGP mRNA mainly in the embryo axis and the suspensor. The two genes appear to be under the control of different regulatory pathways during embryogenesis. We show that HyPRP is repressed by abscisic acid and stress treatments, with the exception of cold treatment. In contrast, HRGP is affected positively by specific stress treatments.

Germination response of Phalaris paradoxa L. seed to different light qualities

The influence of different light regimes on the germination of Australian and English populations of Phalaris paradoxa L. (awned canary-grass) seed was investigated to determine the impact of changing tillage practices on weed infestation. Seeds of all biotypes were highly viable, but differed in levels of innate dormancy (26-99%). In one experiment seed from a single Australian biotype, either enclosed in the spikelet glumes or having the spikelet glumes removed, were exposed to nine light treatments. Germination was stimulated by red and white light, but was inhibited by far-red light. Time to 50%, germination was less for seed enclosed in the spikelet glumes than for naked caryopses, although the final percentage of seed germinating when still enclosed in the spikelet glumes was significantly lower than for naked caryopses. In another experiment, six Australian and English biotypes with varying dormancy characteristics were exposed to eight light treatments. Red light did not stimulate germination in the deeply dormant biotype, however stimulated all other biotypes. Germination in darkness was below 20% in all biotypes except for one where germination was 51%. To overcome dormancy seeds were imbibed and placed in darkness at 16degreesC for either 7 or 14 days prior to exposure to red or white light for a single 15-min period. Dormancy in all biotypes was overcome indicating that a period of burial may decrease the dormancy level and increase seed sensitivity to light. This increased light sensitivity suggests that exposure to light during tillage may stimulate germination in P. paradoxa seed.

Genotypic variation for cold tolerance during reproductive development in rice: Screening with cold air and cold water

Rice (Oryza sativa L.) plants are susceptible to low temperature during the young microspore stage, which occurs 10-12 days before heading. Low temperature at this time increases spikelet sterility which can cause massive yield loss. Increasing the cold tolerance of cultivars can reduce yield variability in temperate rice-growing environments. Two experiments were conducted in cold air screenings and two were conducted in cold water screenings to examine genotypic variation for cold tolerance, explore flowering traits related to spikelet sterility, and investigate whether the results reflect the level of cold tolerance determined previously in the field. Cold air screenings imposed day/night temperatures of 27 degrees C/13 degrees C, 25 degrees C/15 degrees C and 32 degrees C/25 degrees C following particle initiation until 50% heading, while cold water screenings maintained a relatively constant 19 degrees C. The variation in the commencement of low air temperature treatment did not have an effect on the level of spikelet sterility, indicating that exposure to low temperature during the young microspore stage was more important than the duration of exposure. Spikelet sterility of common cultivars showed a significant correlation between cold air and cold water screenings (r(2) = 0.63, p < 0.01), cold air and field screenings (r(2) = 0.52, p < 0.01) and cold water and field screenings (r(2) = 0.53, p < 0.01), indicating that cold air and cold water can be used for screening genotypes for low temperature tolerance. HSC55, M 103 and Jyoudeki were identified as cold tolerant and Doongara, Sasanishiki and Nipponbare as susceptible cultivars. There was a significant negative relationship between spikelet sterility and both the number of engorged pollen grains per anther and anther area only after imposing cold air and cold water treatment hence, it was concluded that these flowering traits were facultative in nature. In addition, cultivars originating from Australia and California were inefficient at producing filled grain with similar sized anthers containing a similar number of engorged pollen grains as cultivars from other origins. One suggested reason for this poor conversion to filled grain of cultivars from Australia and California may be associated with their small stigma area, particularly when exposed to low temperature conditions. (c) 2006 Elsevier B.V. All rights reserved.

Minimising cold damage during reproductive development among temperate rice genotypes. II. Genotypic variation and flowering traits related to cold tolerance screening

Low temperature during microspore development increases spikelet sterility and reduces grain yield in rice (Oryza sativa L.). The objectives of this study were to determine genotypic variation in spikelet sterility in the field in response to low-temperature and then to examine the use of physio-morphological traits at flowering to screen for cold tolerance. Multiple-sown field experiments were conducted over 4 consecutive years in the rice-growing region of Australia to increase the likelihood of encountering low-temperature during microspore development. More than 50 cultivars of various origins were evaluated, with 7 cultivars common to all 4 years. The average minimum temperature for 9 days during microspore development was used as a covariate in the analysis to compare cultivars at a similar temperature. The low-temperature conditions in Year 4 identified cold-tolerant cultivars such as Hayayuki and HSC55 and susceptible cultivars such as Sasanishiki and Doongara. After low temperature conditions, spikelet sterility was negatively correlated with the number of engorged pollen grains, anther length, anther area, anther width, and stigma area. The number of engorged pollen grains and anther length were found to be facultative traits as their relationships with spikelet sterility were identified only after cold water exposure and did not exist under non-stressed conditions.