Parâmetros fisiológicos e produtivos de trigo afetados pela remoção de perfilhos e pela desfolha

The objective of this work was to evaluate the photosynthetic parameters, yield potential, and response to defoliation of wheat (Triticum aestivum) plants subjected to tiller removal. Two experiments were conducted under greenhouse conditions. In the first, the two following cultivars were evaluated for complete tiller removal: TBIO Audaz and BRS 394, with a high and low tillering capacity, respectively. In the second, only 'TBIO Audaz' was subjected to detillering and defoliation at post-anthesis. Tiller removal increased the yield potential of the main stem of both tested cultivars and the CO2 assimilation potential of the flag leaf, which was possibly a strategy to meet the demands for an increased sink strength, as evidenced by the response curves to irradiance and leaf internal CO2 concentration. The partial defoliation of 'TBIO Audaz' increased daily CO2 assimilation, both in intact and detillered plants. Detillered plants show a higher photosynthetic and yield potential of the main stem, but also a greater sensitivity to defoliation in the post-anthesis period.O objetivo deste trabalho foi avaliar os parâmetros fotossintéticos, o potencial produtivo e as respostas à desfolha de plantas de trigo (Triticum aestivum) submetidas à remoção de perfilhos. Dois experimentos foram conduzidos em cultivo protegido. No primeiro, as duas seguintes cultivares foram avaliadas quanto à remoção total de perfilhos: TBIO Audaz e BRS 394, com alto e baixo potencial de perfilhamento, respectivamente. No segundo, apenas 'TBIO Audaz' foi submetida à remoção de perfilhos e à desfolha no período de pós-antese. A remoção dos perfilhos aumentou o potencial produtivo do colmo principal das duas cultivares testadas e a assimilação de CO2 da folha bandeira, que, possivelmente, foi uma estratégia para suprir a maior demanda de drenos, como evidenciado pelas curvas de resposta à irradiância e à concentração foliar interna de CO2. A desfolha parcial de 'TBIO Audaz' aumentou a assimilação diária de CO2, tanto em plantas intactas quanto nas com perfilhos removidos. As plantas submetidas à remoção de perfilhos apresentam maior potencial fotossintético e produtivo do colmo principal, mas, também, maior sensibilidade à desfolha no período de pós-antese

Floret development and grain setting differences between modern durum wheats under contrasting nitrogen availability

Wheat yield depends on the number of grains per square metre, which in turn is related to the number of fertile florets at anthesis. The dynamics of floret generation/degeneration were studied in contrasting conditions of nitrogen (N) and water availability of modern, well-adapted, durum wheats in order to understand further the bases for grain number determination. Experiments were carried out during the 2008-2009 and 2009-2010 growing seasons at Lleida (NE Spain). The first experiment involved four cultivars (Claudio, Donduro, Simeto, and Vitron) and two contrasting N availabilities (50 kgN ha(-1) and 250 kgN ha(-1); N50 and N250) while experiment 2 included the two cultivars most contrasting in grain setting responsiveness to N in experiment 1, and two levels of N (N50 and N250), under irrigated (IR) and rainfed (RF) conditions. In addition, a detillering treatment was imposed on both cultivars under the IR+N250 condition. The number of fertile florets at anthesis was increased by ~30% in response to N fertilization (averaging across treatments and spikelet positions). The effect of N and water availability was evident on floret developmental rates from the third floret primordium onwards, as these florets in the central spikelets of all genotypes reached the stage of a fertile floret in N250 while in N50 they did not. In this study, clear differences were found between the cultivars in their responsiveness to N by producing more fertile florets at anthesis (through accelerating developmental rates of floret primordia), by increasing the likelihood of particular grains to be set, or by both traits.We thank the team of the crop physiology laboratory of the UdL for technical assistance. Funding was provided by the Spanish Ministry of Science and Innovation through project AGL2009- 11964. AF held a FPU, AP2006-03719, scholarship from the Spanish Ministry of Education

Assessment of Yield Loss in Rice due to Yellow Stem Borer, Scirpophaga incertulas, Using Simulation Models

The yield loss simulation (YLS) and the MACROS LIQ.CSM models were used to simulate the effect of stem borer damage at a detillering rate of 5, 15, 30, 60% at vegetative, panicle initiation and grain filing stages, on yield of rice cultivar’s Ratna. This stem borer damage during vegetative and panicle initiation stages was not simulated appropriately by both the models. Relatively MACROS simulated pest effects better than YLS at this stage. The predicted reduction in yield due to detillering at grain filling stage varied from 10.93-62.5 and 2.59-57.2% with the YLS and MACROS models, respectively in comparison to observed reduction of 4.8-56.1%. The simulated and observed pest effects on crop yield during grain filling stage were found to be comparable

Aspectos morfofisiológicos do trigo submetido à remoção de perfilhos e desfolha

TCC (graduação)- Universidade Federal de Santa Catarina. Campus Curitibanos. Agronomia.O perfilhamento é uma característica importante de plantas de trigo e é controlada por fatores genéticos e ambientais. Em condições desfavoráveis para o crescimento e desenvolvimento, ocorre a competição entre os perfilhos por assimilados. Além disso, as plantas de trigo são muito sensíveis a estresses ambientais, elevadas temperaturas e déficit hídrico, em situações extremas, podem causar a desfolha. O objetivo do presente estudo foi avaliar se a retirada manual de perfilhos e a desfolha promovem alterações entre as relações fisiológicas e produtivas da cultura do trigo. O experimento foi conduzido em cultivo protegido, na Universidade Federal de Santa Catarina, Campus de Curitibanos. O delineamento experimental utilizado, foi o de blocos ao acaso com 4 repetições, em esquema fatorial 2 x 3. O primeiro fator foi constituído pela remoção (unicolmo) ou não de todos os perfilhos emitidos de cada planta. O segundo fator composto por: (i) controle (sem desfolha); (ii) retirada de todas as folhas; e (iii) retirada de todas as folhas exceto a folha bandeira. A cultivar utilizada no ensaio foi a BRS 394. A remoção dos perfilhos foi realizada de forma manual no tratamento unicolmo, na antese as plantas foram submetidas a desfolha, sendo que a folha bandeira do tratamento desfolha total foi coletada para avaliações de tamanho de folha, densidade de estômatos e tamanho de células guarda. Ainda na antese foram realizadas determinações das trocas gasosas da folha bandeira das plantas. No final do ciclo da cultura foram avaliados os parâmetros biométricos e os componentes de produção, determinando-se a altura de plantas, diâmetro do colmo principal (basal e apical), número de espiguetas férteis e inférteis, comprimento da ráquis, número e massa de grãos. Os dados foram submetidos à análise de variância e quando significativas as médias foram comparadas por meio do teste t de Student (p<0,05). Foi observado que com a remoção dos perfilhos e consequentemente à ausência de competição por fotoassimilados, plantas unicolmos apresentaram aumento das estruturas morfológicas como diâmetro do colmo e comprimento da folha bandeira. Ainda houve incremento de potencial produtivo da espiga do colmo principal. Plantas submetidas a desfolha parcial apresentaram maior potencial produtivo, em função da maior força de dreno da espiga que estimulou o aumento do potencial fotossintético da folha bandeira. Plantas submetidas à remoção dos perfilhos são mais susceptíveis à desfolha total no período pós antese.Tillering is an important characteristic for wheat crop and is controlled by genetic and environmental factors. Under unfavorable growth and development conditions, tillers will compete for assimilates. In addition, wheat plants are very sensitive to environmental stresses, high temperatures and water deficit, which in extreme conditions can cause defoliation. The aim of this study was to evaluate if tillers removal and defoliation promote changes between physiological and productive characteristics of wheat. The experiment was carried out under controlled conditions at Universidade Federal de Santa Catarina, Curitibanos campus. The experimental design was a randomized blocks with 4 repetitions in a factorial 2 x 3. The first factor was composed by full detillering (single stem) or no detillering in each plant. The second factor was composed by: (i) control (no defoliation); (ii) all leaves removed; (iii) all leaves removed, but the flag leaf. Cultivar BRS 394 was used in the experiment. Tiller removal was manually performed in the full detillering treatment, in anthesis plants were subjected to defoliation, with the flag leaf from the total defoliation treatment collected for evaluation on size, stomatal density and size of guard cells. In the anthesis were also determined gaseous exchange on the flag leaf. At the end of crop cycle, biometric and productivity parameters were evaluated for plant height, diameter of main stem (basal and apical), number of fertile and unfertile spikelets, rachis length, number and weight of grains. The results were submitted to analysis of variance and when significant, compared by t test of Student (p<0.05). With the full detillering and hence to the absence of competitions for photoassimilates, the single stem plants resulted in increased morphological structures, such as stem diameter and length of flag leaf. In addition, there was increase in the production potential of the main stem ear. Plants under partial defoliation resulted in higher production potential, due to higher ear drain strength, stimulating the photosynthetic potential of the flag leaf. Plants under detillering are more susceptible to total defoliation in the post-anthesis period

Evaluation of a tiller inhibition (tin) gene in wheat

Reduced tillering cereals have been proposed as being advantageous under terminal drought conditions through their presumed reduction in leaf area and increased partitioning of assimilate towards fertile stems. The reduced leaf area should reduce preanthesis transpiration and conserve soil water for grain filling while the partitioning of a greater proportion of biomass into fertile stems should subsequently result in more efficient partitioning of assimilate towards grain. The tiller inhibition (tin) gene reduces the number of tillers produced by spring wheat plants and this study was undertaken to assess the agronomic potential of this gene in addition to investigating the physiological changes associated with it on a plant and crop basis. The inhibition of tiller bud growth by the tin gene and the phenomenon known as "stunting" are linked and the latter appears to be an extreme manifestation of the former whereby the development of the mainstem apex is retarded. High light intensity, long photoperiod and low minimum temperatures are required to induce stunting, while high C02 induces associated traits such as reduced leaf length. The accumulation of biomass did not appear to be significantly affected by the presence of the tin gene. The reduction in tiller number was compensated for by more assimilate being partitioned into those tillers that were produced. The presence of the tin gene resulted in higher harvest index values, indicating more efficient partitioning of biomass into grain, as well as larger spikes with more kernels spike-1 at low densities. However, as spike densities of the tin lines approached 450 spike m-2, the differences in the characteristics associated with the tin gene disappeared. Leaf area index was not reduced by the presence of the tin gene as plants were able to produce longer and wider leaves. Using epidermal cells as an example, the increase in leaf length was due primarily to an increase in the number, rather than the length, of the leaf cells. The maximum rate of cellular division was also increased by the presence of the tin gene. Yield was not significantly altered by the presence of the tin gene under most conditions where it was tested. There were however significant changes in the composition of yield with kernel weight increased by 5 to 6% for the spring lines containing the tin gene relative to the near-isogenic pairs, and although the number of kernels spike-1 was often greater for the tin lines, kernels m-2 was reduced due to lower spike densities. The application of nitrogen increased spike densities in the tin lines, but not to similar densities as those produced by the freely tillering near-isogenic pairs. Water extraction was the same for the lines with and without the tin gene under field conditions, except at one site at maturity where the tin lines extracted more than their near-isogenic pairs. Root length density appeared to be unaffected by the tin gene. The intrinsic benefits of the tin gene appeared to be higher harvest index values, shorter stems and higher kernel weights as these traits were exhibited in the tin lines when plants were grown to achieve the same spike densities as their near-isogenic pairs. Most other traits such as increased number of spikelets spike-1, increased number of kernels spike-1 and increased stem length density appear to be contingent on spike densities being lower for the tin lines. Stem water soluble carbohydrates were also as high or higher for the tin lines under field conditions when spike densities were low, although when grown to achieve the same spike density the levels were the same or lower in the tin lines than their near-isogenic pairs

Leaf area Index and yield of upland rice. II. Manifestation through yield components

A relação entre o índice de área foliar (IAF e a produtividade, manifesta através dos componentes, foi estudada na cultivar de arroz de sequeiro IAC 47, em dois experimentos de campo, com distintas épocas de plantio. As chuvas foram abundantes e bem distribuídas durante o período reprodutivo da 1ª época, enquanto escassas para a 2ª, ocasionando deficiência hídrica. Variação no IAF foi obtida através de cinco níveis de desfolhamento (0, 25, 50, 75 e 100%) praticados no estágio de diferenciação das espiguetas, a partir de IAF em torno de 6,5 e 5,5 para a 1 e 25 épocas, respectivamente. Foi testado um tratamento adicional na 2ª época, em que 50% de desfolhamento foi obtido pela eliminação de perfilhos. A análise de covariância indicou que o efeito do IAF se deu através do número de espiguetas na 1ª época, e da fertilidade de espiguetas, na 2ª. A comparação do tratamento adicional com o padrão para 50% de desfolhamento, indicou que o número de perfilhos pode ser aumentado sem decréscimo da resistência à seca, desde que a área foliar por perfilho seja reduzida.- The relationship between leaf area index (LAI) and yield, through its components, was studied in the upland rice cultivar, IAC 47, in two field experiments with different planting dates. Rains were abundant and well distributed during the reproductive stage of the first experiment (EXP I), whereas were scarce for the second one (EXP II), resulting in water stress to the plants. In order to achieve variation in LAI, five defoliation levels (O, 25, 50, 75 and 100%) were performed at the stage of spikelet differentiation. Before cutting, LAI was 6,5 for EXP I, and 5,5 for EXP II. An additional treatment was tested in EXP II, in which 50% of the leaf area was removed through detillering. Covariance analysis showed that LAI effect on yield was exerted through spikelet number in EXP I, and through spikelet fertility in EXP II. Comparison of the detillering treatment with the standard 50% defoliation showed that the number of tillers can be increased without decrease in drought resistance if leaf area per tiller is reduce