The benefits of mycorrhizal inoculation on growth, yield and nutrition of plants are well documented. However, mycorrhiza use in pepper and sweet pepper crops (Capsicum spp.) is still rarely exploited compared to other crops of economic importance. The current paper reviews the main aspects of the association between arbuscular mycorrhizal (AM) fungi and plants of pepper and sweet pepper. It includes topics about the effects of AM fungi on nutrition, growth and yield in Capsicum spp., paying particular attention to AM fungi–pathogen interactions, responses to some environmental stresses, as well as biochemical and physiological aspects of AM fungi–plant interaction in Capsicum annuum L.

Cultivar depreciation – the gradual decline in relative advantage of a cultivated variety over time – accentuates the vulnerability of resource-poor farmers to production risks. The current paper addresses constraints in combating cultivar depreciation of wheat in India. National level data on quoted demand for breeder seeds and breeder seed production indicated a slowdown in the rate of cultivar turnover of wheat, with average varietal age increasing from 9 years in 1997 to 12 years in 2009. Analysis of cultivar adoption patterns among farmer households of Haryana State also indicates that farmers prefer cultivars that were released a decade ago over the recent ones. Cultivar turnover rates are found to be particularly low among marginal farmers. While the structure of India's wheat breeding and seed delivery systems might be the primary cause of slow cultivar turnover, a number of social and economic factors at the micro-level are also responsible. Many of the constraints to technology adoption and wheat productivity growth, identified during the Green Revolution era, persist even today.

Rice production in the Mekong Delta, Vietnam is threatened by future water scarcity caused by changing rainfall patterns and increasing irrigation costs. To improve resilience of the triple rice farming system to future climate-related stresses, profitability needs to be increased through water use efficiency, fertilizer management and planting methods.

During four cropping seasons in 2011–13, alternate wetting and drying (AWD) irrigation was applied in the triple rice production area within An Giang Province, Vietnam. An issue with the application of AWD is the prevalence of acid sulphate soils in the Mekong Delta. Three types of irrigation management were tested; continuously flooded (CF) where the water in the paddy was maintained at 5 cm; AWD where the water level was allowed to fall to 15 cm below the ground surface, at which point the field was irrigated until the water level was at 1 cm above the ground surface (designated −15 cm); AWD where the water level was allowed to fall to 30 cm below the ground surface before irrigation until the water level was at 1 cm above the ground surface (designated −30 cm). Two further experiments were also undertaken which examined the planting method (transplant v. direct sowing) and phosphorus rate on rice yield. There was no effect on yield caused by P fertilizer rate and irrigation management in any year, and there was no significant effect on soil pH or salinity caused by irrigation management. Overall net profitability was greatest for the AWD treatments because of the reduction in pumping and labour costs in the dry season. Transplanted rice improved yields, but the labour cost reduced overall profitability. The study shows that AWD (−15 cm) can be safely applied in acid sulphate soil areas within the triple rice areas of An Giang Mekong Delta and saved at least 0·27 of total irrigated water quantity used during three of the six cropping seasons. The increased profitability of the AWD rice production system will help to improve the resilience of triple rice cropping systems to future water scarcity.

Perennial ryegrass (Lolium perenne L.) cultivars are out-breeding populations of differing phenotypes, potentially allowing for directional selection to occur after sowing. To investigate this, the morphology of individual space plants (i.e. isolated plants sown at 0·75 m row spaces) grown from tillers extracted from single-cultivar swards subjected to frequent cutting (FC) or infrequent cutting (IC) for 5 years (aged accessions) were compared with plants grown from seed (seed accessions). The study examined 12 cultivars, creating 36 ‘accessions’ of 80 plants in each. These plants were examined for 23 morphological measurements to test for and classify directional selection in perennial ryegrass swards. A high degree of separation was achieved between the 12 seed accessions, validating the discriminating power of the experiment. Changes in morphological expression of plants taken from swards indicated selection in favour of particular morphological ideotypes. This directional selection was identified in 10 of the accessions subjected to FC and eight subjected to IC management. Emergence natural height (plant undisturbed height at inflorescence emergence) and plant volume (emergence width × emergence natural height) were the characters modified most between seed and aged accessions. The magnitude of these morphological changes varied between cultivars. Glencar had the greatest number of morphological characters exhibiting directional selection under frequent cutting, whereas Greengold had the greatest number exhibiting directional selection under infrequent cutting. The plants grown from aged swards were also smaller than the seed accessions in all characters, raising the possibility that they may also be less productive. The present study showed that sward management can cause and influence directional selection of plants from within the morphological range of expression within perennial ryegrass cultivars.

Safety evaluation of a genetically modified crop entails assessing its equivalence to conventional crops under multi-site randomized block field designs. Despite mounting petitions for regulatory approval, there lack a scientifically sound and powerful statistical method for establishing equivalence. The current paper develops and validates two procedures for testing a recently identified class of equivalence uniquely suited to crop safety. One procedure employs the modified large sample (MLS) method; the other is based on generalized pivotal quantities (GPQs). Because both methods were originally created under balanced designs, common issues associated with incomplete and unbalanced field designs were addressed by first identifying unfulfilled theoretical assumptions and then replacing them with user-friendly approximations. Simulation indicated that the MLS procedure could be very conservative in many occasions irrespective of the balance of the design; the GPQ procedure was mildly liberal with its type I error rate near the nominal level when the design is balanced. Additional pros and cons of these two procedures are also discussed. Their utility is demonstrated in a case study using summary statistics derived from a real-world dataset.

Breeding for resistance to Striga hermonthica Del. (Benth) and tolerance to drought has been a major strategy to improve maize (Zea mays L.) production and productivity in West and Central Africa during the last three decades. The three decades consisted of three breeding periods or eras based on the germplasm and methodologies used; that is, 1988–2000, 2001–06 and 2007–11. A total of 50 early maturing cultivars, combining Striga resistance with drought tolerance were developed, including 15, 16 and 19 cultivars for the three periods, respectively. Although the cultivars were not selected intentionally for low-nitrogen (N) tolerance, it was hypothesized that tolerance to low-N had been significantly improved while selecting for drought tolerance and Striga resistance. This hypothesis was tested by evaluating the 50 cultivars in 2010 and 2011 in Nigeria at Mokwa and Ile-Ife under both low-N (30 kg N/ha) and high-N (90 kg N/ha) levels. Under low-N conditions, grain yield improved from 2280 kg/ha during the first period to 2610 kg/ha during the third period, an increase of 165 kg/ha per period with r2 of 0·99. Under high-N, yield increased from 3200 to 3650 kg/ha, an increase of 225 kg/ha and r2 of 0·93. Relative gain per period was 30 kg/ha for the two N rates with r2 values of 0·99 and 0·94 respectively. Grain yield performance of the 50 cultivars under low-N conditions adequately predicted their performance under high-N. Selection for Striga resistance and drought tolerance in early maturing maize populations enhanced low-N tolerance in the maize cultivars derived from the populations. The improvement was higher in later than earlier breeding periods.

Eleven widely used crop simulation models (APSIM, CERES, CROPSYST, COUP, DAISY, EPIC, FASSET, HERMES, MONICA, STICS and WOFOST) were tested using spring barley (Hordeum vulgare L.) data set under varying nitrogen (N) fertilizer rates from three experimental years in the boreal climate of Jokioinen, Finland. This is the largest standardized crop model inter-comparison under different levels of N supply to date. The models were calibrated using data from 2002 and 2008, of which 2008 included six N rates ranging from 0 to 150 kg N/ha. Calibration data consisted of weather, soil, phenology, leaf area index (LAI) and yield observations. The models were then tested against new data for 2009 and their performance was assessed and compared with both the two calibration years and the test year. For the calibration period, root mean square error between measurements and simulated grain dry matter yields ranged from 170 to 870 kg/ha. During the test year 2009, most models failed to accurately reproduce the observed low yield without N fertilizer as well as the steep yield response to N applications. The multi-model predictions were closer to observations than most single-model predictions, but multi-model mean could not correct systematic errors in model simulations. Variation in soil N mineralization and LAI development due to differences in weather not captured by the models most likely was the main reason for their unsatisfactory performance. This suggests the need for model improvement in soil N mineralization as a function of soil temperature and moisture. Furthermore, specific weather event impacts such as low temperatures after emergence in 2009, tending to enhance tillering, and a high precipitation event just before harvest in 2008, causing possible yield penalties, were not captured by any of the models compared in the current study.

Weed infestation is a major yield-reducing factor that also decreases crop water productivity. Yet weeds are often neglected in crop productivity simulation studies, because existing empirical equations and mechanistic models are not widely applicable or have a high demand for input data and calibration. For that reason, AquaCrop, a widely applicable crop water productivity model, was expanded with a weed management module which requires only two easily obtainable input variables: (i) relative leaf cover of weeds, and (ii) weed-induced increase of total canopy cover. Using these inputs, AquaCrop directly simulates soil water content, crop canopy development and production as it is observed in weed-infested fields. Despite this simple approach, AquaCrop performed well to simulate soil water content in the root zone (relative root-mean-square error (RRMSE) of 5–13%), canopy cover (RRMSE of 15–22%), dry above-ground crop biomass during the season (RRMSE of 21–39%) and at maturity (RRMSE of 5–6%) and yield (RRMSE of 11–25%) of barley and wheat grown under different weed infestation levels and environments. The current study illustrates that the AquaCrop model can be used to assess the effect of weed infestation on crop growth and production, using a simple approach that is applicable to diverse environmental and agronomic conditions, even in data-scarce regions.

Forage sorghum is an important component of the fodder supply chain in the arid and semi-arid regions of the world because of its high productivity, ability to utilize water efficiently and adaptability to a wide range of climatic conditions. Identification of high-yielding stable genotypes (G) across environments (E) is challenging because of the complex G × E interactions (GEI). In the present study, the performance of 16 forage sorghum genotypes over seven locations across the rainy seasons of 2010 and 2011 was investigated using GGE biplot analysis. Analysis of variance revealed the existence of significant GEI for fodder yield and all eight associated phenotypic traits. Location accounted for a higher proportion of the variation (0·72–0·91), while genotype contributed only 0·06–0·21 of total variation in different traits. Genotype-by-location interactions contributed 0·02–0·13 of total variation. Promising genotypes for fodder yield and each of the associated traits could be identified effectively using a graphical biplot approach. The majority of test locations were highly correlated. A ‘Which-won-where’ study partitioned the test locations into two mega-environments (MEs): ME1 was represented by five locations with COFS 29 as the best genotype, while ME2 had two locations with S 541 as the best genotype. The existence of two MEs suggested a need for location-specific breeding. Genotype-by-trait biplots indicated that improvement for forage yield could be achieved through indirect selection for plant height, leaf number and early vigour.

A study was performed in controlled conditions to reproduce cold and warm spring regimes in the east Po valley, northern Italy with a temperate subcontinental climate, to evaluate whether and to what extent spring weather regimes favour the attack of Rhizoctonia solani or Colletotrichum coccodes on potato, in view of predicted climate change. The main experiment, preceded by a controlled chamber set of tests to quantify response to temperatures of R. solani anastomosis group (AG)-3 and C. coccodes strains, showed that limit temperatures (minimum, maximum and optimum of colony radial growth) of R. solani AG-3 are 6 °C lower than those of C. coccodes. Then, a trial to reproduce early growth stages of potato was performed in phytotrons with sprouts of cvar Hermes to simulate cold and warm spring regimes with two different relative soil moisture contents. That simulation was carried out on native non-sterilized soil samples which were co-inoculated artificially with R. solani AG-3 and C. coccodes. Species-abundance findings of fungal root colonization in potato roots and molecular quantification (quantitative polymerase chain reaction) of C. coccodes and R. solani AG-3 inoculum growth in soil showed that: (i) C. coccodes is more competitive than R. solani AG-3 in colonizing potato root both in warm and cold spring regimes; (ii) R. solani AG-3 infected potato roots only in the coldest spring regimes regardless of soil moisture content; (iii) soil temperature is the greatest factor that influences root colonization of C. coccodes and R. solani as well as that of soil inhabiting fungi including some potential antagonists; (iv) R. solani AG-3 and C. coccodes seem to greatly increase in soil under the relative driest and warmest spring weather regimes expected according to the mean scenarios of climate changing in northern Italy; (v) binucleate Rhizoctonia AG-A, a common non-pathogenic fungus indigenous to agricultural soil of that area, appears to be antagonistic towards root fungal pathogens of potato.

The extent and severity of wheat take-all (caused by Gaeumannomyces graminis var. tritici (Ggt)) can vary considerably between growing seasons. The current study aimed to identify climatic factors associated with differing concentrations of Ggt DNA in soil and take-all disease at different stages of a sequence of wheat crops. Pre-sowing soil Ggt DNA concentrations and subsequent take-all disease in consecutive wheat crop sequences were compared across six seasons in 90 commercial cropping fields in Canterbury and Southland, New Zealand, between 2003 and 2009. Disease progress was assessed in additional fields in 2004/05 and 2005/06. While a general pattern in inoculum and disease fluctuations was evident, there were exceptions among wheat crop sequences that commenced in different years, especially for first wheat crops. In three consecutive growing seasons, there was very low inoculum increase in the first wheat crop, while increases in first wheat crops during the following three seasons was much greater. Low spring–summer rainfall was associated with low build-up of inoculum in first wheat crops. The inoculum derived from the first wheat then determined the amount of primary inoculum for the subsequent second wheat, thereby influencing the severity of take-all in that crop. Differing combinations of weather conditions during one wheat crop in a sequence and the conditions experienced by the next crop provided explanations of the severity of take-all at grain fill and the resulting post-harvest soil Ggt DNA concentrations in second wheat crops. Examples of contrasting combinations were: (a) a moderate take-all epidemic and high post-harvest inoculum that followed high rainfall during grain fill, despite low pre-sowing soil Ggt DNA concentrations; (b) severe take-all and moderate to high inoculum build-up following high pre-sowing soil Ggt DNA concentrations and non-limiting rainfall; and (c) low spring and early summer rainfall slowing epidemic development in second wheat crops, even where there were high pre-sowing soil Ggt DNA concentrations. The importance of the environmental conditions experienced during a particular growing season was also illustrated by differences between growing seasons in take-all progress in fields in the same take-all risk categories based on pre-sowing soil Ggt DNA concentrations.

Palm oil comprises mainly triacylglycerols (TAG) that account for about 0·95 of its composition. Lipolysis of TAG releases free fatty acids that are then oxidized, impairing oil quality. Lower endogenous lipase activity is therefore desirable for better quality oil. Identifying genotypes for this should allow production of oils with improved shelf-life. A novel non-radioactive cold-activation titration assay was used to assay for lipase activity in 49 randomly selected Elaeis guineensis palms using the novel method as well as the traditional radioactive method. The results confirmed significant correlation between the radioactive and novel non-radioactive methods. A total of 148 E. guineensis palms originating from Angola, Cameroon, Guinea Conarky, Nigeria, Senagal, Sierra Leone, Tanzania and Zaire were then screened for lipase activity using the novel non-radioactive method. The analysis revealed genotypes with significantly different lipase activities, indicating that the activity is genotype-dependent. Quantitative polymerase chain reaction indicated similarity in pattern between gene expression and lipase activity determined by the novel assay. Several low and high lipase genotypes were identified. The findings pave the way for selection and breeding for low lipase genotypes. They are also relevant to genetic marker development for oil quality. Evidence is presented for the presence of at least two different lipases that determine oil quality in the oil palm mesocarp.

The cropping systems of the Eastern Gangetic Plains of Bangladesh, India and Nepal are based on rice. There is a scope to intensify such systems through diversification with lentil, the most popular food legume. Two strategies were evaluated to fit lentil into the short fallow between successive monsoonal (i.e., T. aman) and pre-monsoonal (aus) or irrigated rice (boro) crop. These were early-flowering sole-cropped lentil and relay-sown lentil into rice. Firstly, 18 early-flowering lentil lines at three contrasting sowing dates were tested over two seasons on a research station at Ishurdi in Bangladesh. Secondly, relay sowing was evaluated at the same location with six early-flowering lines and two control cultivars in two seasons. It was also assessed on ten farms in Western Bangladesh, comparing relay with sole cropping over 3 years. Flowering in the early-flowering lentil lines was consistently 9–17 days earlier, than the control cultivars, but they did not achieve an economic yield (<1·0 t/ha). Relay sowing with an existing cultivar produced an economic yield of lentil, which was comparable or higher than sole-cropped lentil in all situations. The relay-sown lentil matured in sufficient time to allow the land to be prepared for the succeeding rain-fed rice crop. It was concluded that the substitution of relay-sown lentil for fallow in the monsoonal rice–fallow–rain-fed rice cropping pattern is a useful option to intensify and diversify cropping in the Eastern Gangetic Plain.

Delineating site-specific management zones within fields can be helpful in addressing spatial variability effects for adopting precision farming practices. A 3-year (2008/09 to 2010/11) field study was conducted at the Postgraduate Agricultural Research Station, University of Agriculture, Faisalabad, Pakistan, to identify the most important soil and landscape attributes influencing wheat grain yield, which can be used for delineating management zones. A total of 48 soil samples were collected from the top 300 mm of soil in 8-ha experimental field divided into regular grids of 24 × 67 m prior to sowing wheat. Soil and landscape attributes such as elevation, % of sand, silt and clay by volume, soil electrical conductivity (EC), pH, soil nitrogen (N) and soil phosphorus (P) were included in the analysis. Artificial neural network (ANN) analysis showed that % sand, % clay, elevation, soil N and soil EC were important variables for delineating management zones. Different management zone schemes ranging from three to six were developed and evaluated based on performance indicators using Management Zone Analyst (MZA V0·1) software. The fuzziness performance index (FPI) and normalized classification entropy NCE indices showed minimum values for a four management zone scheme, indicating its appropriateness for the experimental field. The coefficient of variation values of soil and landscape attributes decreased for each management zone within the four management zone scheme compared to the entire field, which showed improved homogeneity. The evaluation of the four management zone scheme using normalized wheat grain yield data showed distinct means for each management zone, verifying spatial variability effects and the need for its management. The results indicated that the approach based on ANN and MZA software analysis can be helpful in delineating management zones within the field, to promote precision farming practices effectively.

The aim of the current research was to analyse the effect of four water irrigation treatments (1·20, 1·00, 0·80 and 0·60 of the crop water requirement) on the relationships among leaf area index (LAI), radiation use efficiency (RUE) and green canopy cover in a potato crop (Solanum tuberosum L.) cv. Agria. The crop was established in a commercial plot irrigated with a centre pivot system in Southeast Spain during the 2011 and 2012 seasons. In both seasons, the highest light absorption efficiency values occurred at the LAI value of 3 that corresponded to maximum ground cover. With regard to the irrigation treatment, a significant linear response was indicated for RUE. The results indicate that the 1·00 irrigation treatment produced the best result, improving water resources management without reducing crop yield.

Yield responses of a grain amaranth accession to different irrigation strategies were evaluated in Naples, Italy. Field experiments were carried out to evaluate the quantitative and qualitative response of amaranth under combined abiotic stresses (salinity and drought) in a Mediterranean environment of South Italy affected by problems due to groundwater salinization from seawater intrusion.

A comparison was made in 2009 and 2010 between a fully irrigated treatment (1·00), with the restitution of all of the water necessary to replenish to field capacity the soil layer explored by roots (0·00–0·36 m), and two treatments with restitution of 0·50 and 0·25 of the water volume used for the fully irrigated treatment. The three levels of irrigation volume were combined with two levels of salinity, either fresh or salt water, with electrical conductivity (EC) of the irrigation water of 0·64 and 22 dS/m respectively, in a factorial experiment thus harbouring six treatments in a randomized complete block design. The results showed good adaptation of amaranth to drought. It was possible to obtain high yields even if groundwater with infiltrated seawater was used for irrigation (50% yield reduction when the EC of soil saturated paste extract (ECe) was 13·97 dS/m). A reduction of 50% in the volume of irrigation did not cause a significant reduction in yield, whether using fresh or saline water, compared to the treatment fully irrigated with fresh water. The chemical composition of amaranth seeds, however, was significantly affected by the treatments. Starch and ash content decreased with increasing drought while protein content was increased by both salt and drought.

In view of the increased presence of salinity and drought stress in the Mediterranean area and the scarce information on amaranth response to salt and water stress, the aim of the present work is evaluation of the quantitative and qualitative response of amaranth grown in a Mediterranean environment of South Italy under combined drought and salinity stress.

Land use and management, together with soil properties, determine soil organic carbon (SOC) concentration and its stabilization mechanisms. Four soils (0–30 cm depth) were studied in a semi-arid region with different uses and management regimes: two soils with olive cultivation, both under a non-tillage regime and one with a cover crop (OCC) and the other without (ONT); a fluvial terrace soil (FT) with cereal–sunflower–fallow rotation; and an unaltered soil under natural vegetation (oak trees; OT). The OT soil had a higher SOC concentration than the agricultural soils (OCC, ONT and FT), followed by the FT soil without significant differences. The olive grove soils had a lower SOC concentration but the two types of management differed significantly, with higher concentrations due to the cover crop. Hydrofluoric acid (HF)-soluble, hydrochloric acid (HCl)-resistant, and non-oxidizable (sodium peroxodisulphate; Na2S2O8) SOC fractions were determined at different depths (0–5, 5–10, 10–20 and 20–30 cm). The relative HCl-resistant and non-oxidizable SOC fractions increased with depth, whereas the relative HF-soluble SOC fraction varied slightly among the four soils considered. Differences in the SOC-stabilization mechanism were found according to the chemical SOC fractionation. In the FT and OT soils, where HF-soluble SOC and soil respiration rates were higher, the intense biological activity rapidly degraded the plant debris, being partially fixed and stabilized by the fine mineral-soil fraction as the principal stabilization mechanism of SOC. The olive grove soils had lower biological activity but higher SOC resistance to oxidation with Na2S2O8, thus suggesting that chemical recalcitrance of soil organic matter was a relevant stabilization mechanism in these soils.

Biased assessment of tillage impacts on soil organic carbon (SOC) sequestration are often associated with a lack of information on the initial level of SOC stocks. The present study reported the changes in SOC concentrations and stocks following 10-year different tillage practices relative to the initial SOC levels. The tillage trial included no tillage (NT), ridge tillage (RT) and mouldboard plough (MP) on a Black soil (Hapludolls) in Northeast China. Results showed that tillage, soil depth and time significantly affected SOC concentration and SOC stock. Tillage and crop residue retention had great impacts on the SOC concentrations in the top 0·1 m layer. Compared with MP and NT, RT resulted in higher SOC concentration and SOC stock in the plough layer (0–0·2 m), which became more obvious with time. The soil under NT and RT had higher stratification ratios (SR) of SOC (SR, the ratio of SOC concentration in 0–0·05 m to that in 0·1–0·2 m) than under MP. Significant positive and nearly identical linear relationships between the SR of SOC and the duration of tillage practices occurred for both NT and RT soils; the increased SR in NT resulted from both SOC increase in surface and SOC decrease in subsurface soils, but in RT, the increased SR was only from a substantial SOC increase in surface soil. Accordingly, the present study highlights that RT was more helpful than NT in carbon sequestration for the studied Black soil in Northeast China.