			Home About us Contact

Yield Reduction (yield + reduction)

Distribution by Scientific Domains

Life Sciences	37%
Earth and Environmental Science	31%
Engineering	25%

Kinds of Yield Reduction

significant yield reduction

Selected Abstracts

Assessment of the water,salinity crop production function of wheat using experimental data of the Golestan province, Iran,

IRRIGATION AND DRAINAGE, Issue 4 2009
A. R. Kiani
stress hydrique; stress de salinité; fonctions de production; blé Abstract Optimisation of agricultural water management in arid and semi-arid regions requires the availability of water,salinity crop production functions. A two-year experiment was conducted in the northern Golestan province of Iran to assess the water,salinity production function of wheat. The treatments in the experiment consisted of four levels of irrigation water, i.e. 50 (W1), 75 (W2), 100 (W3) and 125 (W4) % of crop water requirement, and four levels of water salinity, respectively 1.5 (S1), 8.5 (S2), 11.5 (S3) and 14.2 (S4) dS,m,1. The plots were arranged in a randomised complete block design with three replications and water quantity as main plot treatment and water quality as subplot treatment. The data were analysed using linear, quadratic, Cobb,Douglas and transcendental functions, complemented with an economic analysis. The results indicate that for the given climate,soil conditions, transcendental functions best predict wheat yield under both water and salinity stress conditions. Yield reduction caused by a unit increase of matric potential is found to be larger than that caused by a unit increase of osmotic potential. The marginal rate of technical substitution indicates that each one of the two factors studied, namely soil salinity and water supply, can be substituted with the other in a wide range in order to achieve equal amount of yield. Copyright © 2008 John Wiley & Sons, Ltd. L'optimisation de la gestion de l'eau agricole dans les zones arides et semi-arides nécessite de savoir la relation entre l'apport d'eau selon sa salinité et la production végétale. Une expérience de deux ans a été menée dans le nord de la province du Golestan en Iran pour évaluer la fonction de production de l'eau saline sur le blé. Les traitements expérimentaux consistaient en quatre niveaux d'apports d'eau soit 50% (W1), 75% (W2), 100% (W3) et 125% (W4) des besoins en eau des cultures, et quatre niveaux de salinité de l'eau, respectivement 1.5 (S1), 8.5 (S2), 11.5 (S3) et 14.2 (S4) dS,m,1. Les parcelles ont été disposées dans un bloc de Fisher randomisé avec trois répétitions avec la quantité de l'eau comme variable principale et la qualité de l'eau comme variable secondaire. Les données ont été analysées en utilisant les fonctions linéaires, quadratiques, Cobb,Douglas et transcendantes, complétées par une analyse économique. Les résultats indiquent que, pour un climat et un état du sol donnés, les fonctions transcendantes donnent les meilleures prédictions du rendement de blé en condition de salinité et de stress hydrique. La baisse de rendement causée par une augmentation d'une unité de potentiel hydrique est plus importante que celle causée par l'augmentation d'une unité de potentiel osmotique. Le taux marginal de substitution technique indique que chacun des deux facteurs étudiés, à savoir la salinité des sols et l'apport d'eau, peuvent être largement substitués l'un à l'autre pour viser rendement identique. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Impact of Water Stress on Maize Grown Off-Season in a Subtropical Environment

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2007
C. M. T. Soler
Abstract During the last decade, the production of off-season maize has increased in several regions of Brazil. Growing maize during this season, with sowing from January through April, imposes several climatic risks that can impact crop yield. This is mainly caused by the high variability of precipitation and the probability of frost during the reproduction phases. High production risks are also partially due to the use of cultivars that are not adapted to the local environmental conditions. The goal of this study was to evaluate crop growth and development and associated yield, yield components and water use efficiency (WUE) for maize hybrids with different maturity ratings grown off-season in a subtropical environment under both rainfed and irrigated conditions. Three experiments were conducted in 2001 and 2002 in Piracicaba, state of São Paulo, Brazil with four hybrids of different maturity duration, AG9010 (very short season), DAS CO32 and Exceler (short season) and DKB 333B (normal season). Leaf area index (LAI), plant height and dry matter were measured approximately every 18 days. Under rainfed conditions, the soil water content in the deeper layers was reduced, suggesting that the extension of the roots into these layers was a response to soil water limitations. On average, WUE varied from 1.45 kg m,3 under rainfed conditions to 1.69 kg m,3 under irrigated conditions during 2001. The average yield varied from 4209 kg ha,1 for the hybrids grown under rainfed conditions to 5594 kg ha,1 under irrigated conditions during 2001. Yield reductions under rainfed conditions were affected by the genotype. For the hybrid DKB 333B with a normal maturity, yield was reduced by 25.6 % while the short maturity hybrid Exceler was the least impacted by soil water limitations with a yield reduction of only 8.4 %. To decrease the risk of yield loss, the application of supplemental irrigation should be considered by local farmers, provided that this practice is not restricted by either economic considerations or the availability of sufficient water resources. [source]

Drainage and salinity assessment in the Huinong Canal Irrigation District, Ningxia, China,

IRRIGATION AND DRAINAGE, Issue 2 2005
Peter Hollanders
irrigation; drainage; salinisation; développement durable Abstract In the Huinong Canal Irrigation District, Ningxia, China, annually almost half of the amount of irrigation water, which is supplied from the Yellow River, is drained back to the river through an open drainage system. Waterlogging and salinization occur in parts of the irrigated area and part of the water drains to the surrounding desert. While 85,90% of inflow to the area is irrigation water there are good possibilities for water saving. To analyse water movement at field level and resulting drainage needs, from autumn 1998 until spring 2001 observations were made in two experimental areas: Pingluo and Huinong. The data were used for the calibration and validation of three computer models: SWAP, MODFLOW and DUFLOW. Different scenarios of water and salt behaviour in the unsaturated and saturated zone were simulated, as well as the flow through one of the main drains. The effects of various irrigation amounts and groundwater tables on crop growth, percolation and drainage needs were analysed. The present average irrigation water application during the growing season is 630,mm. On average 15% of the supplied water (665 million m3,yr,1) remains in the area. This is mainly irrigation water that was not used by the crops and did not reach the drainage system. It was found that an irrigation level of 75% of the present practice with a groundwater table of 1.0,m below the surface during the growing season gave the best results. Under such a practice the soil salinity will fluctuate around 3,3.5,dS,m,1, resulting in a good growth of wheat and a yield reduction for maize of about 20%. When adequate amounts of irrigation water are supplied in combination with local drainage improvements, the areas with middle and low-yielding crops can be reduced, as well as the area of wasteland. Copyright © 2005 John Wiley & Sons, Ltd. Annuellement presque la moitié de la quantité d'eau d'irrigation dans le district d'irrigation du canal Huinong, Ningxia, Chine, alimenté par la Rivière Jaune, est retournée à la rivière par un système de drainage à ciel ouvert. Des cas de saturation d'eau et de salinisation surgissent dans certaines parties de la zone irriguée et une partie de l'eau suinte vers le désert environnant. Comme 85,90% de l'entrée de l'eau dans la zone est de l'eau d'irrigation il y a de bonnes possibilités pour économiser de l'eau. Pour analyser la circulation de l'eau au niveau du champ et la nécessité de drainage des observations ont été effectuées pendant la période d'automne 1998 jusqu'au printemps 2001 dans deux zones expérimentales, Pingluo et Huinong. Les données rassemblées ont servi pour le calibrage et la validation de trois modèles informatiques: SWAP, MODFLOW et DUFLOW. Ces modèles ont été employés pour simuler plusieurs scénarios de comportement de l'eau et du sel dans la zone non saturée et dans la zone saturée tout comme l'écoulement par un des tuyaux d'écoulement principaux: le cinquième tuyau d'écoulement. L'effet de l'apport de différentes quantités d'eau d'irrigation, de différents niveaux de la nappe phréatique sur la croissance des cultures, la percolation et la nécessité de drainage a été analysé. L'actuel apport d'eau d'irrigation est de 630,mm en moyenne pendant la saison de croissance. Quinze pour cent en moyenne de l'eau fournie (665 millions m3/année) reste dans la zone, principalement de l'eau d'irrigation qui n'a pas servi aux cultures et qui n'a pas atteint le système de drainage. Un niveau d'irrigation représentant 75% des valeurs actuelles et une surface de la nappe phréatique de 1.0,m sous la surface donnent les meilleurs résultats pendant la saison de croissance. De tels apports entretiennent une salinisation du sol qui fluctuera entre environ 3 et 3.5,dS,m,1, donnant un bon résultat de la croissance du blé et une diminution du rendement pour le maïs d'environ 20%. Lorsque l'alimentation par des quantités adéquates d'eau d'irrigation sera assurée en combinaison avec des améliorations du drainage local, la zone donnant des récoltes moyennes et basses peut être réduite ainsi que les zones incultes. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Optimization of water management in the RUT Irrigation District, Colombia,

IRRIGATION AND DRAINAGE, Issue 1 2004
Herman Depeweg
canaux d'irrigation; régulation de canaux; simulation des écoulements en canal Abstract The RUT Irrigation District is a flat polder area with an infrastructure for irrigation, drainage and flood protection. Water is pumped out for drainage, mainly during the wet season and is pumped in for irrigation during the two growing seasons. The RUT Irrigation District is one of the 16 districts that were transferred by the Colombian government to a water users' association. During this process the farmers agreed to take over the management and to give up governmental subsidies. It appeared that the farmers grossly underestimated the future energy costs and nowadays they complain about high costs for operation and maintenance of the pumping stations. In addition, the service provided is not adequate and the condition of the pumps is declining. The supplementary irrigation is based on the rainfall deficit, but a distinct criterion to supply water according to daily rainfall and cropping calendar does not exist. Hence, it is possible that more water than required is supplied to the area, affecting not only the pumping costs for irrigation but also for drainage. The present situation has been evaluated with a water balance at scheme level and an analysis of the measured groundwater fluctuations. Consecutively, a water balance at field level with an unsaturated groundwater flow model has been simulated to determine the irrigation requirements, yield reduction and drain flow based on a 20-year analysis. The water balance at field level and the one-, two- and three-day rainfall with a return period of 5 years resulted in design drain flows. Finally, these flows were used in hydrodynamic simulations to analyse the pumping requirements for optimal drainage. The simulations also indicated the inundated areas to be expected for different rainfall intensities and frequencies. Copyright © 2004 John Wiley & Sons, Ltd. Le district de RUT possède un système d'irrigation et de drainage avec une protection contre les inondations. L'eau est non seulement pompée pour assurer le drainage du polder durant la saison humide, mais aussi pour alimenter le système d'irrigation durant les deux saisons agricoles. Le district de RUT est l'un des seize districts transférés par le gouvernement colombien à une association d'usagers de l'eau. Durant ce transfert, les exploitants agricoles ont accepté de prendre en charge la gestion et d'abandonner les aides gouvernementales. Il est apparu alors que les exploitants agricoles se plaignent des couts élevés pour l'opération et la maintenance des stations de pompages. De plus, le service fourni n'est pas adéquat et les pompes se détériorent. L'irrigation de complément est fonction des précipitations, mais il n'existe pas de critère précis pour la fourniture d'eau en fonction de précipitations quotidiennes ou du calendr des récoltes. Il est ier possible qu'une quantité d'eau supérieure à celle requise soit apportée au système, affectant non seulement les exigences de pompage pour l'irrigation mais aussi pour le drainage. L'évaluation de la situation actuelle est basée sur un bilan hydrique à l'échelle de système et sur une analyse des fluctuations des eaux souterraines. Par la suite, un bilan hydrique a l'échelle de la campagne délivré par le model WASIM a été utilisé pour déterminer les exigences d'irrigation, la réduction des récoltes et le débit dans le drain basé sur une simulation de 20 ans. Enfin, le drain principal fut simulé avec DUFLOW pour analyser les caractéristiques du pompage pour le drainage utilisant le débit de drainage fourni par un bilan hydrique pour des durées deun, deux et trois jours de pluie fréquence de quinquennale. La simulation a aussi permis d'identifier les étendues des inondations pour différentes intensités et fréquences de pluie. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Evaluation of Common Bean for Drought Tolerance in Juana Diaz, Puerto Rico

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 5 2009
T. G. Porch
Abstract Drought tolerance is an increasingly important trait in common bean (Phaseolus vulgaris L.) due to the reduction in water resources, a shift in production areas and increasing input costs. The objective of this study was to evaluate 29 genotypes for drought tolerance under drought stress (DS) and reduced stress treatments in Juana Diaz, Puerto Rico. The use of DS and reduced stress treatments facilitated the identification of drought tolerant germplasm that also had good yield potential under more optimal conditions. Based on the results of seed yield under DS and reduced stress conditions, and DS indices, including the geometric mean (GM), stress tolerance index (STI) and percent yield reduction (YR), genotypes were identified with greater yield potential under the tested environment. Based on average GM over the 2 years, the superior common bean genotypes identified were SEA 5, G 21212, A 686, SEN 21 and SER 21. These genotypes performed well in both years and under both treatment conditions and thus may serve as parents for DS improvement and genetic analysis. [source]

Drip Irrigation Frequency: The Effects and Their Interaction with Nitrogen Fertilization on Sandy Soil Water Distribution, Maize Yield and Water Use Efficiency Under Egyptian Conditions

JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2008
S. E. El-Hendawy
Abstract Irrigation frequency is one of the most important factors in drip irrigation scheduling that affects the soil water regime, the water and fertilization use efficiency and the crop yield, although the same quantity of water is applied. Therefore, field experiments were conducted for 2 years in the summer season of 2005 and 2006 on sandy soils to investigate the effects of irrigation frequency and their interaction with nitrogen fertilization on water distribution, grain yield, yield components and water use efficiency (WUE) of two white grain maize hybrids (Zea mays L.). The experiment was conducted by using a randomized complete block split-split plot design, with four irrigation frequencies (once every 2, 3, 4 and 5 days), two nitrogen levels (190 and 380 kg N ha,1), and two maize hybrids (three-way cross 310 and single cross 10) as the main-plot, split-plot, and split-split plot treatments respectively. The results indicate that drip irrigation frequency did affect soil water content and retained soil water, depending on soil depth. Grain yield with the application of 190 kg N ha,1 was not statistically different from that at 380 kg N ha,1 at the irrigation frequency once every 5 days. However, the application of 190 kg N ha,1 resulted in a significant yield reduction of 25 %, 18 % and 9 % in 2005 and 20 %, 13 % and 6 % in 2006 compared with 380 kg N ha,1 at the irrigation frequencies once every 2, 3 and 4 days respectively. The response function between yield components and irrigation frequency treatments was quadratic in both growing seasons except for 100-grain weight, where the function was linear. WUE increased with increasing irrigation frequency and nitrogen levels, and reached the maximum values at once every 2 and 3 days and at 380 kg N ha,1. In order to improve the WUE and grain yield for drip-irrigated maize in sandy soils, it is recommended that irrigation frequency should be once every 2 or 3 days at the investigated nitrogen levels of 380 kg N ha,1 regardless of maize varieties. However, further optimization with a reduced nitrogen application rate should be aimed at and will have to be investigated. [source]

Impact of Water Stress on Maize Grown Off-Season in a Subtropical Environment

Suppression of generation and replication of acyclovir-resistant herpes simplex virus by a sensitive virus

JOURNAL OF MEDICAL VIROLOGY, Issue 1 2004
Tomoko Okuda
Abstract The role of acyclovir-sensitive herpes simplex virus (HSV) was analyzed in the process of its replacement by a resistant virus in vitro and in vivo in the aspect of acyclovir therapy. The mode of replacement of acyclovir-sensitive HSV with acyclovir-resistant HSV was examined by the passages of acyclovir-sensitive wild type HSV in Vero cells under acyclovir-treatment. The development of resistance was monitored more adequately by counting the number of acyclovir-resistant viruses in 10,000 plaque forming units than by the conventional susceptibility assay. The resistance increased with the proportion of thymidine kinase-deficient (TK,) viruses, when the susceptibilities of acyclovir-treated HSV population to 5,-iodo-2,deoxyuridine and phosphonoacetic acid were examined. The increased resistance was due to the increased proportion of acyclovir-resistant virus but not intermediately resistant virus. Infection with mixtures of TK, and acyclovir-sensitive strains rendered TK, sensitive to acyclovir, and virus yields were reduced to the levels of acyclovir-sensitive virus in Vero cells. Their yield reduction depended on the proportion of acyclovir-sensitive viruses and induction of TK activity. This reduction in virus yields of the mixture of TK, and acyclovir-sensitive strains was confirmed by acyclovir treatment in the skin of mice with cutaneous infection. Acyclovir treatment combined with superinfection of acyclovir-sensitive virus delayed the development of herpetic skin lesions due to acyclovir-resistant virus and reduced virus yields in the infected skin. Acyclovir-sensitive virus plays an important role in suppressing the generation and replication of acyclovir-resistant virus during acyclovir therapy. J. Med. Virol. 72:112,120, 2004. © 2004 Wiley-Liss, Inc. [source]

Cultivation of medicinal isabgol (Plantago ovata) in alkali soils in semiarid regions of Northern India

LAND DEGRADATION AND DEVELOPMENT, Issue 3 2006
J. C. Dagar
Abstract There is growing global demand for medicinal drugs including isabgol (Plantago ovata). With increasing demand of food for an ever-increasing population in India, it is not possible to bring arable lands under cultivation for aromatic and medicinal plants. Salt-affected lands (both saline and alkali) occupy about 8·6 million ha. Due to poor physical properties and excessive exchangeable Na+, most of these lands do not support good vegetation cover. The marginal and salt-affected lands could be successfully utilized for the cultivation of aromatic and medicinal plants. We achieved almost complete germination of isabgol seeds using up to 5000,ppm salt-solution. Grain yield (including husk) was 1·47 to 1·58,t,ha,1 at pH 9·2 showing no significant yield reduction as compared to normal soil. At pH 9·6 the grain yield was 1·03 to 1·12,t,ha,1. At higher pH there was significant reduction in yield. Sowing in good moisture (at field capacity) of soil was found best, but to save time sowing at shallow depth in dry soil, followed by irrigation was also suitable as compared to broadcasting seeds. The chlorophyll content was greater 70 days after sowing compared to younger stages (50 days after sowing). The total chlorophyll and plant biomass were lower from crops grown by broadcasting methods of sowing as compared to two other methods of sowing. The leaf area index (LAI) was higher for the broadcasting method of sowing as compared to the other two methods. Na+ absorption increased and K+ and K+/Na+ ratio decreased with increase in pH. Results reported in this paper clearly indicate that isabgol can successfully be grown on moderately alkali soils up to pH 9·6 without the application of any amendment. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Quantitative trait loci and epistatic interactions in barley conferring resistance to net type net blotch (Pyrenophora teres f. teres) isolates

PLANT BREEDING, Issue 4 2010
S. Gupta
With 2 figures and 5 tables Abstract Net type net blotch (NTNB) is an important barley disease in Australia and elsewhere, with significant yield reduction. This trait is important in selection along with other traits of quality and agronomic value. Two-hundred doubled-haploid lines were generated through anther culture from a cross between ,Pompadour' and ,Stirling'. Quantitative trait loci (QTL) were identified against five isolates of Pyrenophora teres f. teres, which represent virulences across Australia. QTL were mapped on chromosomes 3H and 6H using simple sequence repeat (SSR) markers. The resistance locus on 6H was detected with all isolates while the 3H locus was detected with two isolates. The 6H QTL from ,Pompadour' contributed resistance to isolates 97NB1, 95NB100 and NB81, whereas 6H QTL from ,Stirling' contributed resistance to isolates NB50 and NB52B. The 3H QTL from ,Pompadour' contributed resistance to NB50 and NB52B. Significant epistatic interactions were detected between QTL on 3H and 6H. These resistance QTL are a useful resource and identifying closely linked SSR markers with allelic combinations will facilitate in marker-assisted selection to develop NTNB resistant breeding lines. [source]

Pyramiding of genes conferring resistance to Tomato yellow leaf curl virus from different wild tomato species

PLANT BREEDING, Issue 6 2008
F. Vidavski
Abstract Tomato (Solanum lycopersicum) production in tropical and subtropical regions of the world is limited by the endemic presence of Tomato yellow leaf curl virus (TYLCV). Breeding programmes aimed at producing TYLCV-resistant tomato cultivars have utilized resistance sources derived from wild tomato species. So far, all reported breeding programmes have introgressed TYLCV resistance from a single wild tomato source. Here, we tested the hypothesis that pyramiding resistances from different wild tomato species might improve the degree of resistance of the domesticated tomato to TYLCV. We have crossed TYLCV-resistant lines that originated from different wild tomato progenitors, Solanum chilense, Solanum peruvianum, Solanum pimpinellifolium, and Solanum habrochaites. The various parental resistant lines and the F1 hybrids were inoculated in the greenhouse using viruliferous whiteflies. Control, non-inoculated plants of the same lines and hybrids were exposed to non-viruliferous whiteflies. Following inoculation, the plants were scored for disease symptom severity, and transplanted to the field. Resistance was assayed by comparing yield of inoculated plants to those of the control non-inoculated plants of the same variety. Results showed that the F1 hybrids between the resistant lines and the susceptible line suffered major yield reduction because of infection, but all hybrids were more resistant than the susceptible parent. All F1 hybrids resulting from a cross between two resistant parents, showed a relatively high level of resistance, which in most cases was similar to that displayed by the more resistant parent. In some cases, the hybrids displayed better levels of resistance than both parents, but the differences were not statistically significant. The F1 hybrid between a line with resistance from S. habrochaites and a line with resistance from S. peruvianum (HAB and 72-PER), exhibited the lowest yield loss and the mildest level of symptoms. Although the resistance level of this F1 hybrid was not statistically different from the level of resistance displayed by the 72-PER parent itself, it was statistically better than the level of resistance displayed by the F1 hybrids between 72-PER and any other resistant or susceptible line. [source]

Soil water content and yield variability in vineyards of Mediterranean northeastern Spain affected by mechanization and climate variability

HYDROLOGICAL PROCESSES, Issue 11 2006
M. C. Ramos
Abstract The objective of this paper was to analyse the combined influence of the Mediterranean climate variability (particularly the irregular rainfall distribution throughout the year) and the land transformations carried out in vineyards of northeastern Spain on soil water content evolution and its influence on grape production. The study was carried out in a commercial vineyard located in the Anoia,Alt Penedès region (Barcelona province, northeastern Spain), which was prepared for mechanization with important land transformations. Two plots were selected for the study: one with low degree of transformation of the soil profile, representing a non-disturbed situation, and the second one in which more than 3 m were cut in the upper part of the plot and filled in the lower part, representing the disturbed situation. Soil water content was evaluated at three positions along the slope in each plot and at three depths (0,20, 20,40, 40,60 cm) during the period 1999,2001, years with different rainfall characteristics, including extreme events and long dry periods. Rainfall was recorded in the experimental field using a pluviometer linked to a data-logger. Runoff rates and yield were evaluated at the same positions. For the same annual rainfall, the season of the year in which rainfall is recorded and its intensity are critical for water availability for crops. Soil water content varies within the plot and is related to the soil characteristics existing at the different positions of the landscape. The differences in soil depth created by soil movements in the field mechanization give rise to significant yield reductions (up to 50%) between deeper and shallow areas. In addition, for the same annual rainfall, water availability for crops depends on its distribution over the year, particularly in soils with low water-storage capacity. The yield was strongly affected in years with dry or very dry winters. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Progress in Wheat Resistance to Spot Blotch in Bangladesh

JOURNAL OF PHYTOPATHOLOGY, Issue 1 2006
A. B. Siddique
Abstract Spot blotch, caused by Cochliobolus sativus, is considered one of the most destructive diseases of wheat (Triticum aestivum) in the warm areas of South Asia. Over the past 20 years, wheat breeding efforts in the region have improved spot blotch resistance in susceptible commercial cultivars. This study assessed resistance and spot blotch-induced yield losses in newly released wheat cultivars developed in Bangladesh since the release of the landmark wheat variety ,Kanchan'. Replicated field studies were conducted during the 2003 and 2004 wheat seasons at two sites: a farmer's field and a research station in a warm region of Bangladesh where spot blotch has been a serious problem. Spot blotch affected 60% of the crop and caused yield losses of from 2% to 22%. Disease severity and disease-induced grain yield reductions were less in wheat genotypes developed since 1983, with a corresponding trend towards higher yield in newly developed varieties. The level of resistance to spot blotch in the new cultivars and advanced breeding lines represents considerable progress in breeding for resistance over the past two decades. [source]

Grain mineral concentrations and yield of wheat grown under organic and conventional management

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2004
MH Ryan
Abstract On the low-P soils in southeastern Australia, organic crops differ from conventional ones primarily in the use of relatively insoluble, as opposed to soluble, P fertilisers and in the non-use of herbicides. As organic management, particularly elimination of soluble fertilisers, is often claimed to enhance grain mineral concentrations, we examined grain from wheat on paired organic and conventional farms in two sets of experiments: (1) four pairs of commercial crops (1991,1993); and (2) fertiliser experiments on one farm pair where nil fertiliser was compared with 40 kg ha,1 of P as either relatively insoluble reactive phosphate rock or more soluble superphosphate (1991 and 1992). All wheat was grown following a 2,6 year legume-based pasture phase. Both conventional management and the superphosphate treatment greatly increased yields but reduced colonisation by mycorrhizal fungi. While only minor variations occurred in grain N, K, Mg, Ca, S and Fe concentrations, conventional grain had lower Zn and Cu but higher Mn and P than organic grain. These differences were ascribed to: soluble P fertilisers increasing P uptake but reducing mycorrhizal colonisation and thereby reducing Zn uptake and enhancing Mn uptake; dilution of Cu in heavier crops; and past lime applications on the organic farm decreasing Mn availability. These variations in grain minerals had nutritional implications primarily favouring the organic grain; however, organic management and, specifically, elimination of soluble fertilisers did not induce dramatic increases in grain mineral concentrations. In addition, organic management was coupled with yield reductions of 17,84 per cent due to P limitation and weeds. The impact of large regional variations in the characteristics of organic and conventional systems on the general applicability of the results from this study and other similar studies is discussed. Copyright © 2004 Society of Chemical Industry [source]

Growth, productivity, and competitiveness of introgressed weedy Brassica rapa hybrids selected for the presence of Bt cry1Ac and gfp transgenes

MOLECULAR ECOLOGY, Issue 10 2005
MATTHEW D. HALFHILL
Abstract Concerns exist that transgenic crop × weed hybrid populations will be more vigorous and competitive with crops compared with the parental weed species. Hydroponic, glasshouse, and field experiments were performed to evaluate the effects of introgression of Bacillus thuringiensis (Bt) cry1Ac and green fluorescent protein (GFP) transgenes on hybrid productivity and competitiveness in four experimental Brassica rapa × transgenic Brassica napus hybrid generations (F1, BC1F1, BC2F1 and BC2F2). The average vegetative growth and nitrogen (N) use efficiency of transgenic hybrid generations grown under high N hydroponic conditions were lower than that of the weed parent (Brassica rapa, AA, 2n = 20), but similar to the transgenic crop parent, oilseed rape (Brassica napus, AACC, 2n = 38). No generational differences were detected under low N conditions. In two noncompetitive glasshouse experiments, both transgenic and nontransgenic BC2F2 hybrids had on average less vegetative growth and seed production than B. rapa. In two high intraspecific competition field experiments with varied herbivore pressure, BC2F2 hybrids produced less vegetative dry weight than B. rapa. The competitive ability of transgenic and nontransgenic BC2F2 hybrids against a neighbouring crop species were quantified in competition experiments that assayed wheat (Triticum aestivum) yield reductions under agronomic field conditions. The hybrids were the least competitive with wheat compared with parental Brassica competitors, although differences between transgenic and nontransgenic hybrids varied with location. Hybridization, with or without transgene introgression, resulted in less productive and competitive populations. [source]

Moniliophthora perniciosa, the causal agent of witches' broom disease of cacao: what's new from this old foe?

MOLECULAR PLANT PATHOLOGY, Issue 5 2008
LYNDEL W. MEINHARDT
SUMMARY Moniliophthora perniciosa (=Crinipellis perniciosa) causes one of the three main fungal diseases of Theobroma cacao (cacao), the source of chocolate. This pathogen causes Witches' broom disease (WBD) and has brought about severe economic losses in all of the cacao-growing regions to which it has spread with yield reductions that range from 50 to 90%. Cacao production in South America reflects the severity of this pathogen, as the yields in most of the infected regions have not returned to pre-outbreak levels, even with the introduction of resistant varieties. In this review we give a brief historical account and summarize the current state of knowledge focusing on developments in the areas of systematics, fungal physiology, biochemistry, genomics and gene expression in an attempt to highlight this disease. Moniliophthora perniciosa is a hemibiotrophic fungus with two distinct growth phases. The ability to culture a biotrophic-like phase in vitro along with new findings derived from the nearly complete genome and expression studies clearly show that these different fungal growth phases function under distinct metabolic parameters. These new findings have greatly improved our understanding of this fungal/host interaction and we may be at the crossroads of understanding how hemibiotrophic fungal plant pathogens cause disease in other crops. Historical summary of WBD:, The first WDB symptoms appear to have been described in the diaries of Alexandre Rodrigues Ferreira (described as lagartão; meaning big lizard) from his observations of cacao trees in 1785 and 1787 in Amazonia, which is consistent with the generally accepted idea that M. perniciosa, like its main host T. cacao, evolved in this region. The disease subsequently arrived in Surinam in 1895. WBD moved rapidly, spreading to Guyana in 1906, Ecuador in 1918, Trinidad in 1928, Colombia in 1929 and Grenada in 1948. In each case, cacao production was catastrophically affected with yield reductions of 50,90%. After the arrival of M. perniciosa in Bahia in 1989, Brazil went from being the world's 3rd largest producer of cacao (347 000 tonnes in 1988,1990; c. 15% of the total world production at that time) to a net importer (141 000 tonnes in 1998,2000). Fortunately for chocolate lovers, other regions of the world such as West Africa and South East Asia have not yet been affected by this disease and have expanded production to meet growing world demand (predicted to reach 3 700 000 tonnes by 2010). Classification:,Moniliophthora perniciosa (Stahel) Aime & Phillips-Mora: super-kingdom Eukaryota; kingdom Fungi; phylum Basidiomycota; subphylum Agaricomycotina; class Agaricomycetes; subclass Agaricomycetidae; order Agaricales; family Marasmiaceae; genus Moniliophthora. Useful websites:,http://www.lge.ibi.unicamp.br/vassoura/, http://nt.ars-grin.gov/taxadescriptions/keys/TrichodermaIndex.cfm, http://www.worldcocoafoundation.org/info-center/research-updates.asp, http://www.ars.usda.gov/ba/psi/spcl [source]