Economic returns from fungicide application to control foliar fungal diseases in winter wheat

Fungicides are commonly applied to control foliar fungal diseases of winter wheat in the central Great Plains of the United States and often are routinely recommended. However, economic benefits from fungicide application in winter wheat have rarely been quantified in this region. A total of eight field experiments were conducted in 2006 and 2007 in Nebraska, USA to quantify yield increases from fungicide applications to control foliar fungal diseases in winter wheat. Experiments were conducted at the same four locations (Mead, Clay Center, North Platte and Sidney) in both years. The fungicides used were azoxystrobin + propiconazole, pyraclostrobin, propiconazole, azoxystrobin and trifloxystrobin + propiconazole applied at varying rates and growth stages. Average wheat prices were calculated from data provided by the United States Department of Agriculture (USDA) Agricultural Marketing Service. Average fungicide and fungicide application costs were obtained through surveys of local retailers, chemical manufacturers and commercial applicators. These prices and costs were used to calculate net returns from fungicide treatments. The probability of a positive net return was 0.60, 1.00 and 0.80 in 2006 (dry, low disease severity), 2007 (wet, moderate to high disease severity) and both years combined, respectively. Net returns ranged from $−101 ha⁻¹ to $172 ha⁻¹ in 2006 and from $60 ha⁻¹ to $294 ha⁻¹ in 2007. Net returns were at least two times the total cost ($2 return on $1 investment) in 4 out of 60 or 6.7% of treatments in 2006 and 51 out of 60 or 85% of treatments in 2007. In 2006, the best net returns occurred at Mead and Clay Center and resulted from the treatments 1) azoxystrobin + propiconazole applied at Zadoks growth stage (GS) 31 (first node detectable) at a rate of 0.58 l ha⁻¹ and 2) azoxystrobin + propiconazole applied at GS 31 at a rate of 0.58 l ha⁻¹ and again at GS 37 (flag leaf just visible) at the same rate. In 2007, the treatments that resulted in the best net returns were 1) azoxystrobin + propiconazole applied at GS 39 (ligule/collar of flag leaf just visible) at a rate of 1.02 l ha⁻¹, 2) pyraclostrobin applied at GS 39 at a rate of 0.66 l ha⁻¹, 3) propiconazole applied at GS 39 at a rate of 0.29 l ha⁻¹, and 4) trifloxystrobin + propiconazole applied at GS 39 at a rate of 0.73 l ha⁻¹. For the same fungicide applied at the same rate at GS 31 and GS 39 in 2007 (wet, moderate to high disease severity), the GS 39 application generally resulted in a higher net return than the GS 31 application. Averaged across treatments and locations, net returns were $6 ha⁻¹ and $183 ha⁻¹ in 2006 and 2007, respectively. The results from this study indicate that foliar fungicide application to winter wheat can be profitable in years with moderate to high disease severity; however, net loss can result if fungicides are applied in years with low disease severity.     

Interaction between cultivar and crop management effects on winter wheat diseases, lodging, and yield

The breeding of winter wheat (Triticum aestivum L.) for resistance to major fungal diseases has been a priority over the last 15 years in France. During this period, integrated low-input strategies have been developed for winter wheat, to cope with falling grain prices and growing environmental concerns. We investigated the interactions between genotype and management for disease and lodging intensities, and analysed their effects on yield within an integrated crop management (CM) context.

A multi-environment experimental network (13 locations, studied in three seasons, between 1999–2000 and 2001–2002) comprising several combinations of cultivars and CM systems was carried out. Four rule-based CM plans were defined, with a decrease in input level from CM1 (a high-input CM plan designed to maximise the yield of a given cultivar) to CM4 (a low-input system with no fungicide protection, no plant growth regulator applications, a sowing density 40% lower than for CM1, and 90 kg ha⁻¹ less N fertiliser than for CM1). Cultivars were clustered into three groups (cultivar type (CT) CT1–CT3), according to their scores for resistance to diseases, for the analysis of yield, whereas the resistance cultivar rating (CR) for each disease and for lodging was considered for the analysis of disease and lodging intensities.

For all diseases, CM had a significant effect (P<0.0001), with disease intensity increasing from CM1 to CM4, whereas CR had a negative effect (P<0.005). An interaction between CR and CM was also detected for all diseases (P<0.005) except eyespot. Lodging intensity decreased significantly from CM1 to CM4 (P<0.0001), and significant increases in lodging resistance score (P<0.0001) were not associated with a genotype by management interaction.

Lastly, yield was significantly affected by CM (P<0.0001), CT (P<0.0003), and CM by CT interaction (P=0.0023). Cultivar ranking differed as a function of CM for yield, demonstrating that breeding programs focusing on cultivar evaluation in high-input environments do not result in the selection of cultivars suited to low-input environments.     

Clover cover crops under-sown in winter wheat increase yield of subsequent spring barley—Effect of N dose and companion grass

Four two-year field trials, arranged in randomised split-plots, were carried out in southern Sweden with the aim of determining whether reduced N fertiliser dose in winter wheat production with spring under-sown clover cover crops, with or without perennial ryegrass in the seed mixture, would increase the clover biomass and hence the benefits of the cover crops in terms of the effect on the wheat crop, on a subsequent barley crop and on the risk of N leaching. Four doses of nitrogen (0, 60, 120 or 180 kg N ha⁻¹) constituted the main plots and six cover crop treatments the sub-plots. The cover crop treatments were red clover (Trifolium pratense L.), white clover (Trifolium repens L.) and perennial ryegrass (Lolium perenne L.) in pure stands and in mixtures. The winter wheat (Triticum aestivum L.) was harvested in August and the cover crops were ploughed under in November. The risk of N leaching was assessed in November by measuring the content of mineral N in the soil profile (0–30, 30–90 cm). In the following year, the residual effects of the cover crops were investigated in spring barley (Hordeum distichon L.) without additional N. Under-sowing of cover crops did not influence wheat yield, while reduced N fertiliser dose decreased yield and increased the clover content of the cover crops. When N was applied, the mixed cover crops were as effective in depleting soil mineral nitrogen as a pure ryegrass cover crop, while pure clover was less efficient. The clover content at wheat harvest as well as the amount of N incorporated with the cover crops had a positive correlation with barley yield. Spring barley in the unfertilised treatments yielded, on average, 1.9–2.4 Mg DM ha⁻¹ more in treatments with clover cover crops than in the treatment without cover crops. However, this positive effect decreased as the N dose to the preceding wheat crop increased, particularly when the clover was mixed with grass.     

Connection between primary Fusarium inoculum on gramineous weeds, crop residues and soil samples and the final population on wheat ears in Flanders, Belgium

Fusarium head blight (FHB) is a devastating wheat disease and is influenced by weather conditions and agronomic factors. Since FHB is a mostly monocyclic disease, the quantity of primary inoculum is a key factor influencing its incidence. To investigate the connection between the primary Fusarium inoculum and the final population on wheat ears, naturally occurring populations of Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Fusarium poae and Microdochium nivale were studied at eight locations in Flanders, Belgium during the growing seasons of 2008-2009 and 2009-2010. To determine the composition of the primary inoculums in November, weeds, wheat and maize residues as well as soil samples were examined. At the end of the growing season, in July, the population on wheat ears was determined. In both growing seasons, the population was characterized by a large complexity and a differential composition at each location and for each type of sample. Nevertheless, some clear correspondences were observed: F. culmorum was a predominant species in crop residues and in soil samples in November, while the population on wheat ears in July consisted mainly of F. graminearum and F. poae, with only a lower frequency of F. culmorum, indicating that soil is not an important source of primary inoculum. The presence of M. nivale was restricted to weeds, crop residues and soil samples in November, and was nearly absent in July at the majority of locations. Finally, our results also indicate that the Fusarium population in July is more complex than the population at the beginning of the season in November. The information of the primary inoculum and the composition of the FHB population at the end of the growing season is important to predict FHB incidence and to implement control strategies for FHB.     

Effects of genetic improvements on grain yield and agronomic traits of winter wheat in the Yangtze River Basin of China

Wheat is an important food crop worldwide. Genetic improvements have contributed much to wheat production since the 1960s. Verifying the evolution of agronomic traits and the physiological basis of grain yield will facilitate breeders and agronomists in developing new wheat cultivars, with the aim of stable and high yields. Thirty-five wheat cultivars, bred or widely planted in the Yangtze River Basin from 1950 to 2005, were grown in field experiments under three N rates (0, 112.5, and 225 kg N ha⁻¹) from 2006 to 2009 in Nanjing, China. Wheat grain yield, kernels per spike, 1000-kernel weight (TKW), and harvest index (HI) increased linearly with cultivar development from the 1950s to the 2000s, whereas spikes per unit land decreased significantly with cultivar development during the same period, and stabilized with further genetic improvements in cultivars. Grain yield, kernels per spike, and TKW differed with N rate and with cultivar. Grain yield, spikes per unit land, and kernels per spike increased significantly with increasing N fertilizer, but TKW and HI decreased. Cultivar height decreased with cultivar development from the 1950s to the 1980s, and remained relatively stable in subsequent cultivars. The proportion of the length of the top internode to total plant height increased with cultivar development from the 1950s to the 1980s and thereafter fell, while the length of the basal internode (BI) maintained a shortening trend. Leaf area per culm, leaf area index (LAI), net photosynthetic rate (Pn), and photosynthetic activity duration (PAD) of the flag leaf increased with cultivar development. Leaf area, LAI, and Pn increased significantly with increasing N fertilizer, while PAD did not. Single spike yield increased linearly with genetic development in cultivars, and these increases mainly resulted from increasing kernel number and weight, which were closely related to source size and cultivar. Grain yield was positively correlated to leaf area, LAI, Pn_Max, PAD, and single spike yield; single spike yield was positively correlated to leaf area, LAI, Pn_Max, and PAD, suggesting that grain yield improvements were mainly associated with improvements in the source (leaf area, LAI, Pn, PAD, etc.) and sink (single spike yield). Sink-source ratios increased with genetic development of cultivars, suggesting that productivity per leaf improved and that sink-source relationships have reached close to optimum in the Yangtze River Basin. Furthermore, breeding for high yield should be related to improvement in kernels per spike and TKW per unit land and increased sink-source ratios with a feasible LAI, and N fertilizer management should be considered during breeding for higher yields.     

The effect of tillage practice,input level and environment on the grain yield of winter wheat in the Czech Republic

The response of winter wheat grain yield to four variants of treatment (two input levels, combined with either conventional or reduced tillage) was tested over six seasons at three locations. These experiments with 10 and 12 winter wheat varieties were analysed within three experimental series. The environmental (location and season) effects on grain yield were large in all combinations of input level and tillage type, and the varieties responded differentially to both season and location. However, there was no varietal response either to the tillage system used, or to the level of nitrogen (and other inputs) supplied. The high input reduced tillage system (surface stubble-ploughing to a depth of 8–10 cm) resulted in all series in significantly higher grain yields than the equivalent conventional tillage system. The reduced tillage system combined with high input level delivered a yield advantage for all of the wheat varieties tested.     

Improving sink regulation,and searching for promising traits associated with hybrids,as a key avenue to increase yield potential of the rice crop in the tropics

Yield advantage of hybrid rice in the tropics has been reported recently as the result of higher biomass accumulation and better biomass partitioning over the whole crop growth. Considering that increasing biomass accumulation is the main target for higher yield potential in sub-tropical and temperate conditions, it is relevant to investigate in a wide range of growing conditions in the tropics if improved biomass partitioning plays a significant and consistent role in higher yield of hybrids. The growth pattern of two high-yielding and popular hybrid (H1) and inbred (I1) of the same maturity group was compared under six contrasted growing conditions to evaluate traits related to sink regulation. Grain yield of H1 was consistently higher than that of I1 by 16–32% with respect to the situation. Higher partitioning coefficients of the hybrid to key organs were confirmed over the whole crop growth for this set of environments whereas crop growth rates of hybrid were not consistently higher than that of inbreds. Sink strength index, as a way to express sink regulation at maturity more efficiently than harvest index, was higher with hybrids in five out of six environments. In search for promising traits related to sink regulation, higher specific leaf area of hybrids at very early stage was associated with higher leaf area, and earlier cessation of tiller production with hybrids coincided with higher partitioning of biomass to early culm growth: yet, maximum tiller number ranged from 548 to 962 tiller m⁻² with H1 and from 629 to 1427 tiller m⁻² with I1 while culm dry weight at 55 days after sowing ranged from 65 to 81 g m⁻² with H1 and from 46 to 53 g m⁻² with I1. This analysis strongly reinforced the pertinence of improving sink regulation for increasing yield potential in the tropics.     

Sustainability of winter wheat production on sandy-loamy Cambisol in the Czech Republic: Results from a long-term fertilizer and crop rotation experiment

Although Cambisols are the predominant soil type in Central Europe, especially in less favoured mountain areas, the long-term sustainability of winter wheat production on such soils has not been examined. In this paper, the yield of winter wheat over 50 years of farmyard manure, N, P and K fertilizer application (12 treatments altogether) was analysed in the Lukavec Crop Rotation Experiment (LCRE), which was established in 1955 in a potato-growing area (mean annual precipitation and temperature 686 mm and 6.8 °C, respectively).     

Variability and regulation of the number of ovules, seeds and pods according to assimilate availability in winter oilseed rape (Brassica napus L.)

The number of pods per plant and the number of seeds per pod are the most variable yield components in winter oilseed rape (WOSR). Both the number of ovules per pod and the potential for the ovule to develop into a mature seed may depend on pod position in the plant architecture and time of appearance. The complex developmental pattern of WOSR makes it difficult to analyse. The objectives of this study were to investigate the variability of the following yield components (a) ovules/pod, (b) seeds/pod, and (c) pods/axis in relation to two explanatory variables. These two variables include (1) flower and inflorescence position and (2) time of pod appearance, linked to the effect of assimilate availability.Field experiments were conducted with the variety Mendel. Different trophic states were created by clipping the main stem or ramifications. The number and position of flowers that bloomed within the inflorescence were recorded based on observations every two to three days throughout the flowering season.On the control plants, for the main stem we observed that the number of ovules per pod decreased for a few ranks and then tended to increase and again to decrease at the end. On ramification R1 and R4, the number of ovules increased at first, and then remained constant with the pod rank. Furthermore, the number of ovules per pod remained constant along the inflorescence on the other ramifications and increased with ramifications from top to bottom. The number of seeds per pod did not vary with the pod rank at the basal positions on inflorescences and decreased afterwards along the inflorescence. The clipping of the main stem or ramifications increased the number of ovules per pod, seeds per pod and pods per axis. The number of ovules and seeds per pod did not vary with the time of pod appearance for the pods located at normalised rank 0.01-0.1. However, the number of ovules and seeds per pod can be impacted by the time of pod appearance on the plant scale. Thus, our results indicate that the amount of available assimilates was the primary determinant of pod and seed production during the flowering period. The distribution of resources was significantly affected by both the positions of pods within an inflorescence and the position of inflorescences within a plant.     

Optimal numbers of environments to assess slopes of joint regression for grain yield,grain protein yield and grain protein concentration under nitrogen constraint in winter wheat

Plant breeders are interested in rationally reducing the number of testing environments for breeding new genotypes adapted to diverse conditions. One way to characterize the adaptation of a genotype is to use the joint regression model. Our objectives were to estimate the stability for grain yield (GY), grain protein yield (GPY) and grain protein content (GPC) of a set of wheat genotypes grown under varying nitrogen conditions and then to determine optimal numbers of environments for assessing the slopes of joint regression.     

Yield development of winter wheat over 50 years of FYM,N, P and K fertilizer application on black earth soil in the Czech Republic

The black earths of Central Europe are an important soils for crop production but sustainability of crop production on such soils has not been examined. In the present paper, yield of winter wheat over 50 years of FYM, N, P and K fertilizer application (12 treatments altogether) was analyzed in the Ivanovice Crop Rotation Experiment (ICRE), established in 1955 on a degraded black earth soil (chernozem).     

Responses of glutamine synthetase activity and gene expression to nitrogen levels in winter wheat cultivars with different grain protein content

Glutamine synthetase (GS) plays a central role in plant nitrogen (N) metabolism, which improves crops grain protein content. A pot experiment in field condition was carried out to evaluate GS expression and activity, and grain protein content in high (Wanmai16) and low grain protein (Loumai24) wheat cultivars under two N levels (0.05 and 0.15 g N kg⁻¹ soil). High nitrogen (HN) resulted in significant increases in GS1 and GS2 expression at 10 days after anthesis (DAA), and higher GS activity during the entire grain filling stage. HN also significantly increased yield, grain protein content and protein fraction (except for glutenin of Luomai24) in two wheat cultivars, which indicated that it increased grain yield and protein content by improving nitrogen metabolism. Wanmai16 showed higher grain protein content, gliadin and glutenin content, and had higher expression level of GS2 both in flag leaves and grains at early grain filling stage. However, Luomai24 had greater yield and higher expression level of GS1. The difference expression of GS2 and GS1 genes indicates they had various contributions to the accumulation of protein and starch in wheat grains, respectively. The results suggest that GS2 would be serving as a potential breeding target for improving wheat quality.     

Influence of the cultivar,environment and management on the grain yield and bread-making quality in winter wheat

The genotype, environment and their interaction play an important role in the grain yielding and grain quality attributes. The main aim of this study was to determine the contributions of the genotype, environment and their interaction to the variation in bread-making traits. The data that were used for the analyses performed in this study were obtained from 3 locations in Poland from post-registration multi-environment trials with winter wheat in 2009 and 2010. The experimental factors were the cultivar (7 cultivars) and the crop management level (low input and high input). In the multi-environment trials, 17 traits were investigated that characterize grain, flour and dough quality. Most of the traits were affected much more strongly by environmental factors (i.e., year and location) than by genotype. The variance components revealed an especially strong effect of the year on the baking score, loaf volume and water absorption, as well a strong effect of the location on dough development and protein content. The obtained results demonstrate that the grain quality as measured by the parameters based on the protein content and quality may be substantially improved by crop management practices, especially by N fertilization level.     

Real-time quantitative PCR based method for the quantification of fungal biomass to discriminate quantitative resistance in barley and wheat genotypes to fusarium head blight

Fusarium head blight (FHB) caused by Fusarium graminearum is one of the devastating diseases of small grain crops, including barley and wheat. Breeding for resistance is one of the best and ecofriendly strategies to manage the FHB. However, the existing methods used for screening genotypes, both under field and greenhouse conditions, often resulted in high experimental error, leading to inconsistent ranking of genotypes over years. In the postgenomic era, precise assessment of resistance is crucial to identify candidate genes. Here, we report a pathogen inoculation procedure and a real-time quantitative polymerase chain reaction (qPCR) based protocol for the quantification and discrimination of quantitative resistance among barley and wheat genotypes to FHB. Using Fusarium specific primer pair Tri6_10, for the trichothecene biosynthetic cluster (Tri6) gene, we successfully quantified the relative fungal biomass in both spikelets and rachis. A qPCR of spikelets and rachis collected on 6 dpi, from inoculated three alternate spikelet regions, discriminated resistance with less experimental error than those based on the proportion of spikelets diseased (PSD) at 9 dpi. This method can be applied for medium to high-throughput barley and wheat breeding programmes to discriminate quantitative resistance among genotypes against FHB.