Physiological variation among native and exotic winter annual plants associated with microbiotic crusts in the Mojave Desert

An experiment was established in 1992 in eastern Ontario, Canada to determine the effects of crop rotation (continuous maize, soybean-maize and alfalfa-maize) and nitrogen (N) amendment [0, 100 and 200 kg N ha^–1 of fertilizer (NH₄NO₃), and 50 and 100 Mg ha^–1 (wet wt.) each of stockpiled and rotted dairy manure] on maize production and soil properties. From 1997 to 1999, an additional study was added to the experiment to investigate treatment effects on the susceptibility of maize hybrids to gibberella ear rot. A moderately resistant and a susceptible hybrid were planted in each plot and inoculated with a macroconidial suspension of Fusarium graminearum by both the silk channel injection and the kernel-wound techniques. At harvest, ears were rated for the severity of disease symptoms and harvested kernels were analyzed for the mycotoxin deoxynivalenol (DON). The greatest number of significant N effects were found in the continuous maize treatments and with the susceptible hybrid. Most N amendments decreased both disease severity and DON accumulation in the susceptible hybrid. The most consistent effect was a decrease in disease severity with 100 kg N ha^–1 fertilizer and an increase in disease severity with the higher rate of 200 kg N ha^–1. This study is the first to report on the effects of soil N amendments on gibberella ear rot susceptibility.     

Feasibility of 3D UV-C treatment to reduce fungal growth and mycotoxin loads on maize and wheat kernels

Fungal disease of grain crops is a concern for the agricultural industry, resulting in economic losses. Aside from severe yield losses, mycotoxigenic fungi such as Penicillium and Fusarium can produce harmful mycotoxins, including deoxynivalenol (DON), zearalenone (ZEN), and ochratoxin A (OTA). This proof-of-concept study explored the feasibility and effects of ultraviolet (UV) C light at 253.7 nm to reduce fungal and mycotoxin loads on model surfaces as well as on maize and wheat kernels using benchtop 2D and 3D illumination strategies. Reduction of Penicillium verrucosum (98.6%) and Fusarium graminearum (88.8%) on agar was achieved using a UV-C dose of 100 mJ cm^?2. Naturally occurring fungal growth resembling P. verrucosum on maize was reduced by 79% after exposure to 5000 mJ cm^?2. Similarly, fungal growth resembling F. graminearum on maize was reduced by 60% with 1000 mJ cm^?2. On wheat, significant reduction of fungal growth was not observed. Maximal reduction of DON (97.3%), ZEN (75.4%), and OTA (91.2%) on filter paper was obtained using 15,000 mJ cm^?2. The overall reduction of DON (30%; 14%), ZEN (52%; 42%), and OTA (17%; 6%) on maize and wheat, respectively, was lower than on filter paper. Moisture and crude protein content as well as percent germination of maize kernels were not affected by UV-C treatment up to 5000 mJ cm^?2. This study has shown that 3D UV-C treatment is a feasible option for reducing Fusarium and Penicillium growth on maize kernels and, at higher doses, decreasing ZEN by ~?50%.     

Long-Term Miscanthus Yields Influenced by Location,Genotype, Row Distance,Fertilization and Harvest Season

Long-term yield studies in perennial crops like miscanthus are important to determine mean annual energy yield and the farmer’s economy. In two Danish field trials, annual yield of two miscanthus genotypes was followed over a 20-year period. The trials were established in 1993 on loamy sand in Foulum and on coarse sand in Jyndevad. Effects of genotype, row distance and fertilization were investigated. In both trials, yield development over time was characterized by an increase during the first years, optimum yields after 7–8 years and a decrease to a lower level which remained relatively constant from year 11 to 20. Spring harvest reduced the yield by 34–42 % compared to autumn harvest. In Foulum annual fertilization with 75 kg ha^?1 N increased the yield of the genotype Goliath (Miscanthus sinensis) by 26 %. Additional N fertilization only increased the yield of Goliath little, and the genotype Giganteus (Miscanthus?×?giganteus) did not respond to fertilization at all. The highest mean yield in Foulum for the period 1997–2012 was obtained with the shortest row distance (～18,000 rather than ～12,000 plants ha^?1) and harvested in late autumn, namely 13.1 and 12.0 Mg ha^?1 DM annually for Giganteus and Goliath, respectively. In Jyndevad, where only Goliath was studied, the highest yield during 1995–2001 was obtained by short row distance, autumn harvest and annual fertilization with 75 kg ha^?1 N, with yield increasing up to 116 % in response to fertilization. A mean yield of 14.4 Mg ha^?1 DM was achieved over the period 1995–2012.     

Cumulation of mycotoxins in maize cobs infected with<Emphasis Type="Italic">Fusarium gramihearum</Emphasis>

Maize cobs withFusarium ear rot were collected at 1986 season and five infected byFusarium graminearum were analyzed for presence of triohothecenes and zearalenone. Collected material was subsampled forFusarium damaged kernels and corresponding axial stems and healthy looking kernels. All investigated cobs contained deoxynivalenol (DON) (range 18.0–131.5 mg/kg) and zearalenone (ZEA) (range 0.38–2.17 mg/kg), in four cobs 15-acetyl-deoxynivalenol (15-AcDON) (range 5.2–6.2 mg/kg) was present and two cobs besides three all metabolites contained 3-acetyl-deoxynivalenol (3-AcD0N) (range 0.5–0.8 mg/kg).The average of individual toxins amount in axial stems: in mg/kg was equal to: DON — 110.36, ZEA — 4.57, 15-AcD0N — 16.66, and 3-AcD0N — 1.32.Fusarium damaged kernels contained in average the following amount (mg/kg) of: DON 77.00, ZEA 0.98, 15-AcD0N 3.78 and 3-AcD0N 0.06. Healthy looking kernels contained DON 1.96 mg/kg and ZEA 0.07 mg/kg only. Cooccurrence of 3-AcDON and 15-AcDON in two samples was an interesting finding. The amount of DON in total cob was highly correlated (r = 0.94) with percentage ofFusarium damaged kernels in given ear.     

Distribution of trichothecene mycotoxins in maize ears infected withF. graminearum andF. crookwellense

Maize ears naturally infected withF. graminearum (6 samples) andF. crookwellense (6 samples) were collected in 1990 and 1991. All samples exhibited symptoms of severe ear rot with high percentage ofFusarium damaged kernels. Thousand kernels weight ranged 108.5 – 235.0g and was significantly lower than in control, not infested kernels (330g). All ears were contaminated withFusarium toxins but DON and NIV were the most frequently analyzed metabolites. Distribution of trichothecene mycotoxins in different parts of ear as well as toxicity of extracts toArtemia salina is reported in this paper.     

Characterisation of<Emphasis Type="Italic">fusarium graminearum</Emphasis> and<Emphasis Type="Italic">F. culmorum</Emphasis> isolates by mycotoxin production and aggressiveness to wheat

A total of 27Fusarium culmorum isolates from Germany and 41F. graminearum isolates from Kenya were investigated for aggressiveness and mycotoxin production on wheat ears. In addition, ergosterol content of the kernels from ears inoculated withF. graminearum was determined and theF. culmorum isolates were tested for mycotoxin productionin vitro. For both pathogens, isolates markedly differed in aggressiveness. 59% and 37% of theF. culmorum isolates produced NIV and DON, respectively,in vivo andin vitro. The DON-producing isolates also produced 3-acDONin vitro. The more aggressive isolates produced mainly DON while the less aggressive isolates produced mainly NIV. 12% and 85% of theF. graminearum isolates produced NIV and DON, respectively. The highly aggressive isolates produced higher amounts of DON, aggressiveness being highly correlated to DON content in the kernels. NIV-producing isolates were less aggressive. Ergosterol content of kernels was moderately correlated to aggressiveness but highly correlated to DON content. Disease severity was associated with kernel weight reduction.     

Reprogrammed endophytic microbial community in maize stalk induced by Trichoderma asperellum biocontrol agent against Fusarium diseases and mycotoxin accumulation

Maize stalk rot and ear rot, caused by Fusarium graminearum and Fusarium verticillioides, respectively, are major diseases that threaten the sustainable production of maize. In this study, an artificial inoculation assay demonstrated that the control efficacy of maize stalk rot and ear rot by Trichoderma asperellum granules were 49.83 % and 39.63 %, respectively. By high-throughput sequencing of maize plants, a total of 76 196 ITS1 sequences and 887 226 V3V4 16S rRNA sequences were analyzed and were grouped into 2934 fungal and 24 248 bacterial operational taxonomic units (OTUs), respectively. It revealed a significantly higher endophytic microbial abundance in the stem tissue of plants grown in T. asperellum-treated soil than in those grown in the control, with the largest increase observed in the basal stem section. In addition, the endophytic microbial diversity and corresponding control effects all gradually decreased from the basal to apical parts of the stem in plants grown in Trichoderma-treated soil, indicating that Trichoderma stimulated a more significant effect on the defense system in the basal section of the stalk than in the apical parts of plants. Furthermore, the accumulation of deoxynivalenol (DON) and fumonisin B1 (FB1) decreased in the stem and ear of maize grown in T. asperellum-treated soil.     

Biomass Yield and Nutrient Removal Rates of Perennial Grasses under Nitrogen Fertilization

Perennial grasses may provide a renewable source of biomass for energy production. Biomass yield, nutrient concentrations, and nutrient removal rates of switchgrass (Panicum virgatum L.), giant miscanthus (Miscanthus x giganteus), giant reed (Arundo donax L.), weeping lovegrass [Eragrostis curvula (Shrad.) Nees], kleingrass (Panicum coloratum L.), and Johnsongrass (Sorghum halepense (L.) Pers.) were evaluated at four N fertilizer rates (0, 56, 112, or 168?kg?N?ha^?1) on a Minco fine sandy loam soil in southern Oklahoma. Species were established in 2008 and harvested for biomass in winter of 2009 and 2010. Biomass yield (dry matter basis) did not show a strong relationship with N fertilizer rate (p?=?0.08), but was affected by year and species interactions (p?<?0.01). Weeping lovegrass and kleingrass produced 29.0 and 16.0?Mg?ha^?1 in 2009, but only 13.0?Mg?ha^?1 and 9.8?Mg?ha^?1 in 2010, respectively. Biomass yields of giant reed, switchgrass, and Johnsongrass averaged 23.3, 17.8, and 6.0?Mg?ha^?1, respectively. Giant miscanthus established poorly, producing only 4.7?Mg?ha^?1. Across years, giant reed had the highest biomass yield, 33.2?Mg?ha^?1 at 168?kg?N?ha^?1, and the highest nutrient concentrations and removal rates (162 to 228?kg?N?ha^?1, 23 to 25?kg?P?ha^?1, and 121 to 149?kg?K?ha^?1) among the grasses. Although giant reed demonstrated tremendous biomass production, its higher nutrient removal rates indicate a potential for increased fertilization requirements over time. Switchgrass had consistently high biomass yields and relatively low nutrient removal rates (40 to 75?kg?N?ha^?1, 5 to 12?kg?P?ha^?1, and 44 to 110?kg?K?ha^?1) across years, demonstrating its merits as a low-input bioenergy crop.     

Deoxynivalenol and 3-acetyldeoxynivalenol and Fusarium species in winter triticale

Fusarium species infecting heads of Triticale and mycotoxins presence in infected kernels and chaff were studied during two seasons. The most important species observed on infected heads were in 1986F. avenaceum (39%),F. nivale (21%),F. culmorum (20%),F. graminearum (14%), and others (6%). In 1987 after long and snowy winterF. nivale dominated (64%), followed byF. avenaceum (24%),F. culmorum (6%), andF. graminearum (5%). The mycotoxins deoxynivalenol (DON) and 3-acetyl DON were present in all 11 subsamples of kernels from heads infected byF. culmorum and/orF. Graminearum (1.6–16.4 mg and 0.7–2.4mg/kg, respectively). Chaff from the same subsamples contained 9.9–33.2mg/kg of DON and 5.2–16.0mg/kg of 3-AcDON. Kernels with visibleFusarium-damage contained 2.4–31.2 mg/kg of DON and 1.2–6.0 mg/kg of 3-AcDON. Remaining part of kernels without symptoms of visibleFusarium-damage contained only DON in an amount of 0.9–5.9 mg/kg.     

Deoxynivalenol accumulation and other scab symptoms in six romanian wheat genotypes inoculated withFusarium graminearum

At anthesis, under field conditions at Fundulea, each of 6 Romanian winter wheat genotypes was inoculated with 3Fusarium graminearum isolates used individually.Fusarium head blight (FHB) was assessed according to the following traits: relative weight of spikes (RWS), percentage of Fusarium damaged kernels (FDK), relative weight of kernels per head (RWKH), area under the disease progress curve (AUDPC) and deoxynivalenol (DON) content in total sample of kernels. Correlations between these traits and parameters revealed important differences between examined wheat genotypes in: DON accumulation, progress of FHB development, yield reduction, and models of host — pathogen interactions in theTriticum - Fusarium pathosystem. Significant correlations between different attributes of FHB were found forFusarium isolate 1 which is a moderate producer of DON (0.89 μg g^-1). Weight of spike was significantly correlated with weight of kernels per spike (r = 0.93**) and with percentage of damaged kernels (r = - 0.87**), while FDK was highly correlated with RWKH (r = - 0.85*) and with DON content (r = 0.82*). Area under the disease progress curve was also found to be significantly correlated with DON content (r = 0.86*).     

Reduced Contamination by the Fusarium Mycotoxin Zearalenone in Maize Kernels through Genetic Modification with a Detoxification Gene

Maize is subject to ear rot caused by toxigenic Aspergillus and Fusarium species, resulting in contamination with aflatoxins, fumonisins, trichothecenes, and zearalenone (ZEN). The trichothecene group and ZEN mycotoxins are produced by the cereal pathogen Fusarium graminearum. A transgenic detoxification system for the elimination of ZEN was previously developed using an egfp::zhd101 gene (gfzhd101), encoding an enhanced green fluorescent protein fused to a ZEN-degrading enzyme. In this study, we produced a transgenic maize line expressing an intact copy of gfzhd101 and examined the feasibility of transgene-mediated detoxification in the kernels. ZEN-degrading activity has been detected in transgenic kernels during seed maturation (for a period of 6 weeks after pollination). The level of detoxification activity was unaltered after an additional storage period of 16 weeks at 6°C. When the seeds were artificially contaminated by immersion in a ZEN solution for 48 h at 28°C, the total amount of the mycotoxin in the transgenic seeds was uniformly reduced to less than 1/10 of that in the wild type. The ZEN in the transgenic maize kernels was also efficiently decontaminated under conditions of lower water activity (a_w) and temperature; e.g., 16.9 μg of ZEN was removed per gram of seed within 48 h at an a_w of 0.90 at 20°C. F. graminearum infection assays demonstrated an absence of ZEN in the transgenic maize seeds, while the mycotoxin accumulated in wild-type kernels under the same conditions. Transgene-mediated detoxification may offer simple solutions to the problems of mycotoxin contamination in maize.     

Effect of Potassium and Nitrogen Fertilizer on Switchgrass Productivity and Nutrient Removal Rates under Two Harvest Systems on a Low Potassium Soil

Biomass demand for energy will lead to utilization of marginal, low fertility soil. Application of fertilizer to such soil may increase switchgrass (Panicum virgatum L.) biomass production. In this three-way factorial field experiment, biomass yield response to potassium (K) fertilizer (0 and 68 kg?K?ha^?1) on nitrogen (N)-sufficient and N-deficient switchgrass (0 and 135 kg?N?ha^?1) was evaluated under two harvest systems. Harvest system included harvesting once per year after frost (December) and twice per year in summer (July) at boot stage and subsequent regrowth after frost. Under the one-cut system, there was no response to N or K only (13.4 Mg?ha^?1) compared to no fertilizer (12.4 Mg?ha^?1). Switchgrass receiving both N and K (14.6 Mg?ha^?1) produced 18 % greater dry matter (DM) yield compared to no fertilizer check. Under the two-cut harvest system, N only (16.0 Mg?ha^?1) or K only (14.1 Mg?ha^?1) fertilizer produced similar DM to no fertilizer (15.1 Mg?ha^?1). Switchgrass receiving both N and K in the two-cut system (19.2 Mg?ha^?1) produced the greatest (P?<?0.05) DM yield, which was 32 % greater than switchgrass receiving both N and K in the one-cut system. Nutrient removal (biomass?×?nutrient concentration) was greatest in plots receiving both N and K, and the two-cut system had greater nutrient removal than the one-cut system. Based on these results, harvesting only once during winter months reduces nutrient removal in harvested biomass and requires less inorganic fertilizer for sustained yields from year to year compared to two-cut system.     

Proteomic profiling of two maize inbreds during early gibberella ear rot infection

Fusarium graminearum is the causal agent of gibberella ear rot in maize ears, resulting in yield losses due to mouldy and mycotoxin‐contaminated grain. This study represents a global proteomic approach to document the early infection by F. graminearum of two maize inbreds, B73 and CO441, which differ in disease susceptibility. Mock‐ and F. graminearum‐treated developing kernels were sampled 48 h post‐inoculation over three field seasons. Infected B73 kernels consistently contained higher concentrations of the mycotoxin deoxynivalenol than the kernels of the more tolerant inbred CO441. A total of 2067 maize proteins were identified in the iTRAQ analysis of extracted kernel proteins at a 99% confidence level. A subset of 878 proteins was identified in at least two biological replicates and exhibited statistically significantly altered expression between treatments and/or the two inbred lines of which 96 proteins exhibited changes in abundance >1.5‐fold in at least one of the treatments. Many proteins associated with the defense response were more abundant after infection, including PR‐10 (PR, pathogenesis‐related), chitinases, xylanase inhibitors, proteinase inhibitors, and a class III peroxidase. Kernels of the tolerant inbred CO441 contained higher levels of these defense‐related proteins than B73 kernels even after mock treatment, suggesting that these proteins may provide a basal defense against Fusarium infection in CO441.     

Maize Yield Response to Water Supply and Fertilizer Input in a Semi-Arid Environment of Northeast China

Maize grain yield varies highly with water availability as well as with fertilization and relevant agricultural management practices. With a 311-A optimized saturation design, field experiments were conducted between 2006 and 2009 to examine the yield response of spring maize (Zhengdan 958, Zea mays L) to irrigation (I), nitrogen fertilization (total nitrogen, urea-46% nitrogen,) and phosphorus fertilization (P₂O₅, calcium superphosphate-13% P₂O₅) in a semi-arid area environment of Northeast China. According to our estimated yield function, the results showed that N is the dominant factor in determining maize grain yield followed by I, while P plays a relatively minor role. The strength of interaction effects among I, N and P on maize grain yield follows the sequence N+I >P+I>N+P. Individually, the interaction effects of N+I and N+P on maize grain yield are positive, whereas that of P+I is negative. To achieve maximum grain yield (10506.0 kg·ha⁻¹) for spring maize in the study area, the optimum application rates of I, N and P are 930.4 m³·ha⁻¹, 304.9 kg·ha⁻¹ and 133.2 kg·ha⁻¹ respectively that leads to a possible economic profit (EP) of 10548.4 CNY·ha⁻¹ (CNY, Chinese Yuan). Alternately, to obtain the best EP (10827.3 CNY·ha⁻¹), the optimum application rates of I, N and P are 682.4 m³·ha⁻¹, 241.0 kg·ha⁻¹ and 111.7 kg·ha⁻¹ respectively that produces a potential grain yield of 10289.5 kg·ha⁻¹.     

Impacts of changing climate and agronomic factors on fusarium ear blight of wheat in the UK

Climate change will have direct impacts on fusarium ear blight (FEB) in wheat crops, since weather factors greatly affect epidemics, the relative proportions of species of ear blight pathogens responsible and the production of deoxynivalenol (DON) toxin by two Fusarium species, F. graminearum and F. culmorum. Many established weather-based prediction models do not accurately predict FEB severity in the UK. One weather-based model developed with UK data suggests a slight increase in FEB severity as a direct effect of climate change. However, severity of the disease is likely to increase further due to indirect effects of climate change, such as increased cropping of grain maize, since maize debris is a potent source of inoculum of F. graminearum. To guide strategies for adaptation to climate change, further research on forecasting, management options to reduce mycotoxin production, and breeding for resistant varieties is a high priority for the UK. Adaptation strategies must also consider factors such as tillage regime, wheat cultivar (flowering time and disease resistance) and fungicide use, which also influence the severity of FEB and related toxin production.     

Identification of lipopeptide antibiotics of a <Emphasis Type="Italic">Bacillus subtilis</Emphasis> isolate and their control of <Emphasis Type="Italic">Fusarium graminearum</Emphasis> diseases in maize and wheat

Substances produced by Bacillus subtilis D1/2, a bacterium isolated from cultivated soil, were found to inhibit Fusarium graminearum. The antifungal activity of the bacterium was attributable to major extracellular lipopeptides isolated and identified as fengycins. Their synthesis was enhanced by casamino acids added to the culture medium. The unpurified cell-free spent medium elicited hemolysis with increasing concentration. Its application to field-cultivated maize and chamber-grown wheat suppressed gibberella ear rot and Fusarium head blight, respectively, when the plants were inoculated with F. graminearum macroconidia. The treatment of maize ears consistently arrested ear-rot development, while the treatment of wheat spikes retarded the progress of Fusarium head blight. Although the deoxynivalenol and ergosterol contents of treated maize kernels were halved, they remained high because of the experimental requirement to inoculate with a high number (1.5 × 10⁴) of macroconidia. As a potential antifungal agent for controlling Fusarium diseases, B. subtilis D1/2 can be further developed as a useful component of integrated pest management. Handling Editor: Reijo Karjalainen.     

Fusarium species complex and mycotoxins in grain maize from maize hybrid trials and from grower's fields

Aims: To quantify and to compare the occurrence of Fusarium species in maize kernels and stalk pieces, to analyse mycotoxins in kernels and maize crop residues, to evaluate two approaches to obtain kernel samples and to compare two methods for mycotoxin analyses. Methods and Results: The occurrence of Fusarium species in maize kernels and stalk pieces from a three‐year maize hybrid trial and 12 kernel samples from grower’s fields was assessed. Nine to 16 different Fusarium species were detected in maize kernels and stalks. In kernels, F. graminearum, F. verticillioides and F. proliferatum were the most prevalent species whereas in stalks, they were F. equiseti, F. proliferatum and F. verticillioides. In 2006, 68% of the kernel samples exceeded the recommended limit for pig feed for deoxynivalenol (DON) and 42% for zearalenone (ZON), respectively. Similarly, 75% of the samples from grower’s fields exceeded the limits for DON and 50% for ZON. In maize crop residues, toxin concentrations ranged from 2·6 to 15·3 mg kg^?1 for DON and from 0·7 to 7·4 mg kg^?1 for ZON. Both approaches to obtain maize kernel samples were valid, and a strong correlation between mycotoxin analysis using ELISA and LC‐MS/MS was found. Conclusions: The contamination of maize kernels, stalk pieces and remaining crop residues with various mycotoxins could pose a risk not only to animal health but also to the environment. With the hand‐picked sample, the entire Fusarium complex can be estimated, whereas combine harvested samples are more representative for the mycotoxin contents in harvested goods. Significance and Impact of the Study: This is the first multi‐year study investigating mycotoxin contamination in maize kernels as well as in crop residues. The results indicate a high need to identify cropping factors influencing the infection of maize by Fusarium species to establish recommendations for growers.     

Integrated use of plant residues,phosphorus and beneficial microbes improve hybrid maize productivity in semiarid climates

Phosphorus unavailability and lack of organic matter in calcareous soils under semiarid climates are the major reasons for low crop productivity. A field experiment was conducted at The Agronomy Research Farm of The University of Agriculture Peshawar (semiarid climate), during summer 2015. The objective of the research was to investigate the effect of plant residues, organic and inorganic phosphorus management on improving yield and yield components of hybrid maize (CS-200) with (+) and without (?) phosphate solubilizing bacteria. The experiment was laid out in randomized complete block design with split plot arrangement, using three replications. A combination of plant residues and phosphorus sources were used as mainplot factor, and phosphate solubilizing bacteria were used as a subplot factor. The results revealed that plant residues, phosphorus sources and phosphate solubilizing bacteria significantly affected all parameters under study except number of plants at harvest. Application of legume residues (Faba bean) increased ear length (22.9 cm), grains row^?1 (46) and ear^?1 (419), 1000 grains weight (365 g), grain yield (6175 kg ha^?1) and shelling percentage (83) as compared to paper mulberry and garlic residues. Phosphorus application at the higher rate of 120 kg ha^?1 from inorganic source (single super phosphate) was superior in terms of higher ear length (24.4 cm), number of grains row^?1 (48) and ear^?1 (455), 1000 grains weight (380 g), grain yield (6558 kg ha^?1), harvest index (42.7%) and shelling percentage (83%) than the lower rate of phosphorus (60 kg P ha^?1). Inoculation of maize seeds with beneficial microbes (phosphate solubilizing bacteria) significantly increased ear length (22.9 cm), number of grains row^?1 (45) and ear^?1 (413), 1000 grains weight (364 g), grain yield (6237 kg ha^?1), harvest index (41.8%) and shelling percentage (82) than without seed inoculation. On the basis of our results from this study, we concluded that application of faba bean residues, 120 kg P ha^?1 as single super phosphate along with seed inoculation with phosphate solubilizing bacteria could improve yield and yield components of hybrid maize under semiarid climates.     

Drought-tolerant endophytic actinobacteria promote growth of wheat (Triticum aestivum) under water stress conditions

Drought tolerant endophytic actinobacteria Streptomyces coelicolor DE07, S. olivaceus DE10 and Streptomyces geysiriensis DE27 were isolated from cultivated plants of arid and drought affected regions of Rajasthan, India. These isolates exhibited plant growth promotion traits and intrinsic water stress tolerance from ?0.05 to ?0.73 MPa. Maximum auxin production was observed in majority of actinobacterial cultures in the logarithmic to stationary phase of growth. Significant enhancement of wheat seedling vigour was recorded by the inoculation of these endophytic actinobacteria. S. olivaceus DE10 recorded maximum accumulation of indole 3-acetic acid (84.34?μg?mg^?1 protein). Culture and cell-free extract of the endophytes was applied on to wheat seeds to assess the effect on growth in water-stressed soil. Maximum yield was recorded with the inoculation of S. olivaceus DE10 culture (492.77?kg?ha^?1) and cell-free extract (262.31?kg?ha^?1). Co-inoculation of S. olivaceus DE10?+?S. geysiriensis DE27 recorded highest yield of 550.09?kg?ha^?1 while their cell-free extract yielded 524.92?kg?ha^?1. Overall, wheat seeds treated with cultures showed better plant growth and yield in comparison to control. Direct coating of cultures on seeds yielded better performance than cell-free extract coated on seeds and co-inoculation of cultures or cell-free extract proved better than single culture inoculations. Production of phytohormones, plant growth promotion traits combined with water stress tolerance potential in these endophytic actinobacteria played a cumulative synergistic role that supported enhanced plant growth promotion of wheat in the stressed soil.     

Responses of maize grain yield to changes in acid soil characteristics after soil amendments

An experiment was conducted from 1997 to 2000 on an acid soil in Cameroon to assess the effectiveness of cultivating acid tolerant maize (Zea mays L.) cultivar and the use of organic and inorganic fertilizers as options for the management of soil acidity. The factors investigated were: phosphorus (0 and 60 kg ha^?1), dolomitic lime (0 and 2 t ha^?1), organic manure (no manure, 4 t ha^?1 poultry manure, and 4 t ha^?1 of leaves of Senna spectabilis), and maize cultivars (ATP-SR-Y – an acid soil-tolerant, and Tuxpeño sequia – an acid susceptible). On acid soil, maize grain yield of ATP-SR-Y was 61% higher than the grain yield of Tuxpeño sequia. Continuous maize cultivation on acid soil further increased soil acidity, which was manifested by a decrease in pH (0.23 unit), exchangeable Ca (31%) and Mg (36%) and by an increase in exchangeable Al (20%). Yearly application of 60 kg ha^?1 of P for 3 years increased soil acidity through increases in exchangeable Al (8%) and H (16%) and a decrease in exchangeable Ca (30%), Mg (11%) and pH (0.07 unit). Lime application increased grain yield of the tolerant (82%) and susceptible (208%) cultivars. The grain yield increases were associated with a mean decrease of 43% in exchangeable Al, and 51% in H, a mean increase of 0.27 unit in pH, 5% in CEC, 154% in exchangeable Ca, and 481% in Mg contents of the soil. Poultry manure was more efficient than leaves of Senna producing 38% higher grain yield. This yield was associated with increases in pH, Ca, Mg and P, and a decrease in Al. The highest mean grain yields were obtained with lime added to poultry manure (4.70 t ha^?1) or leaves of Senna (4.72 t ha^?1). Grain yield increase was more related to the decrease in exchangeable Al (r = ?0.86 to ?0.95, P<0.01) and increase in Ca (r = 0.78–0.94, P<0.01), than to pH (r = ?0.57 (non-significant) to ?0.58 (P<0.05)). Exchangeable Al was the main factor determining pH (r = ?0.88 to ?0.92, P<0.01). The yield advantage of the acid tolerant cultivar was evident even after correcting for soil acidity. Acid soil-tolerant cultivars are capable of bringing unproductive acid soils into cultivation on the short run. The integration of soil amendments together with acid soil-tolerant cultivar offers a sustainable and comprehensive strategy for the management of acid soils in the tropics.