Estimation of Mycotoxin Multiple Contamination in Mexican Hybrid Seed Maize by HPLC-MS/MS

In Mexico, the presence of mycotoxins in chemical treated seed maize by sowing is not well known, despite the need to improve the quality and corn safe for human consumption. It collected twenty-five genotypes maize samples from Morelos State in the spring of 2013, all of them treated with synthetic colors (pink, green, yellow), fungicides and insecticides. Two samples (synthetic seed and hybrid commercial) were selected for analysis of twenty-two mycotoxins by LC-MS/MS and AFB1 determination by liquid chromatography and fluorescence detection (HPLC-FLD). The results of the 25 samples showed the presence of Aflatoxin B1 in 25% of samples in a ranged concentration between 2 to 6 μg&middotkg-1, and average of 4.1-1 μg&middotkg, which were within the allowed limits by national and international legislation. Twenty-two mycotoxins were found in levels ranging between 791.7 and 891.2 μg&middotkg. The content average in both samples was for total aflatoxins (AFB1, AFB2, AFG1, AG2) of 16.95 μg&middotkg, with G aflatoxins the most prevalence. Twelve trichothecenes (Nivalenol, Neosolanol, Fusarenone X, DAS, HT-2, FB1, FB2, FB3, T-2, Zearalenone, ZEA2, ZEA3) were in a level of 292.7 μg&middotkg-1, Enniantine 8.6 μg&middotkg-1, Sterigmatocystin 6.5 μg&middotkg-1, Roquefortine C, 2.9 μg&middotkg-1. Ochratoxin 8.8 μg&middotkg-1 and Mycophenolic acid at 535 μg&middotkg-1 were the highest content. The synthetic color present in seeds analyzed inhibited a good purification in the extracted mycotoxin by optimizing the step in HPLC-MS/MS quantification system. The information generated in this study would be useful in breeding programs in order to improve the sanitary quality and also to investigate the final contamination of agricultural products with multiple mycotoxin contamination.

Early Morphological and Physiological Events Occurring During Germination of Maize Seeds

The early morphological and physiological events occurring during maize （Zea mays cv. Nongda 108） seed imbibition and germination were studied. Water uptake of seeds exhibited a triphasic pattern with a marked increase during the initial phase of imbibition, and then a slow increase, followed by a second substantial increase. Imbibition time for 10 and 50% of seed germination was about 26 and 46 h at 30℃, respectively. The relative conductivity of maize seeds dramatically decreased during the initial phase of imbibition, followed by a substantial increase. Respiratory rate of seeds gradually increased with imbibition. Length of root cap cells decreased during the initial phase and then increased; those of meristematic zone cells increased during the initial phase and then decreased; and those of elongation zone cells and of the whole elongation zone of the radicle gradually increased during germination. The contents of soluble sugars and starch in embryos gradually decreased as the activities of α- and β-amylase strikingly increased with imbibition. In the meantime, protein contents of embryos gradually decreased and free amino acid content increased. The activities of aminopeptidase and endopeptidase increased until 12 h of imbibition and then decreased. It is concluded that germination of maize seeds is mainly completed by extension of cells in the elongation zone of the radicle, and that mobilization of stored reserves in the embryo during the initial phase of imbibition is also an early event during seed germination.

The regulatory network behind maize seed germination: Effects of temperature, water, phytohormones, and nutrients

Seed germination is the process by which an organism grows from a seed. It requires suitable conditions and environmental factors. Maize is one of the most important crops worldwide. Germination influences both final maize yield and quality. Seed germination is regulated by a complex gene network. It is also influenced by endogenous(phytohormones and nutrients) and exogenous(temperature and water)inputs, involving molecular networks only partly identified to date. This review describes current understanding of the influence of temperature, water, phytohormones, and nutrients in regulating maize seed germination, and indicates knowledge gaps that should be addressed.

Farmers' seed choice behaviors under asymmetrical information: Evidence from maize farming in China

the financial support of the National Social Science Foundation of China （14ZDA038）;the National Natural Science Foundation of China （71222302;71373255;71573133）;the Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences （2012RC102）

Effect of Different Plant Growth Promoting Rhizobacteria on Maize Seed Germination and Seedling Development

Our study aimed at assessing the effects of 3 Plants Growth Promoting Rhizobacteria (PGPR) either singly or in combination on maize growth under laboratory and greenhouse conditions. Seeds were inoculated with single and combined solution of 108 CFU/ml of Rhizobacteria. Seeds were not inoculated for the control variant. The highest germination percentage was obtained with the combination of Pseudomonas fluorescens and Pseudomonas putida. This combination also recorded the best vigor index, plants circumferences number of leaves and the leaf area. The maximal heights of plants were observed with seeds treated with Azospirillum lipoferum with an increase of 37.32%. The highest rates of underground dry matter were recorded with A. lipoferum, with an increase of more than 56% comparative to control, while the combination P. fluorescens and P. putida increased the aerial dry matter of 59.11%. Finally, the highest value of the aerial biomass was obtained with the plants treated with the combination of P. fluorescens and P. putida and the highest underground biomass was obtained with plants treated only with A. lipoferum. These results suggest that specific combinations of PGPR can be considered as efficient alternative biofertilizers to promote maize seed germination, biomass and crop yield.

The effects of grain texture and phenotypic traits on the thin-layer drying rate in maize(Zea mays L.) inbred lines

To explore the relation of maize grain texture and phenotypic traits with grain thin-layer drying rate,we observed the ultra-structure of maize grain,and tested three traits about the maize grain texture and four phenotypic traits.The vitreous part percentage was different（P〈0.05） among different maize inbred lines.There was a significant relationship between the drying rate with grain texture and phenotypic traits.Main factors that influenced the drying rate were different during different drying stages.New results observed that empirical constants（k and N） in drying equation were different for seed of the 30 inbred lines of maize.The k of simplified diffusion equation and N of page equation were significantly influenced by both grain texture and phenotypic traits.These results could be used as guideline parameters for drying maize seeds having different grain characteristics during different drying stages.

Molecular mechanisms controlling seed set in cereal crop species under stress and non-stress conditions

Maximizing seed yield is the ultimate breeding goal in important cereal crop species. Seed set is a key developmental stage in the process of seed formation, which determines grain number, seed mass, and realized yield potential, and can be severely affected by abiotic and biotic stresses. However, seed set can also be substantially reduced by genetic factors even under optimal fertilization conditions. The underlying molecular genetic mechanisms are still obscure. In this review, we elucidate the process of seed set of cereal crop species in detail, including development of floral structures, formation of viable gametes, double fertilization, seed development, and abortion. We discuss how genetic and non-genetic factors affect seed set in different development stages. Finally, we will propose novel strategies to study genetic mechanisms controlling seed set and exploit genetic resources to improve seed set in cereal crop species.

Analysis of the metering performance for typical shape maize seeds using DEM

The irregular shape,varying internal compositions,and uneven distributions of maize seeds can degrade the metering performance of maize seeders.This study investigates the effect of irregular maize on the performance of a high-filling-rate seed metering device using DEM.The results show that the seed population in the seed box formed large and small cycles of seed transport due to the disturbances caused by the three wheels.The increasing angular speed of the three wheels reduced the rate of seed filling in the seed filling regions by gravity and disturbances.In addition,an analysis of the repose angle formed by the dropped seed indicated that the angular speed of the taking seed wheel has a certain effect.The large angular speed reduced the coefficient of variation of the seed drop location.The repose angle of the horse tooth seed was greater than those of the other.Meanwhile,the irregular maize seed can also reduce the coefficient of variation of the seed drop location.A comparison between the simulation and experiment results indicates the number of metering seed were basically the same.

Measurement and analysis of restitution coefficient between maize seed and soil based on high-speed photography

The restitution coefficient is an important elementary physical parameter related to the research and development of agricultural machinery.The kinematic model of maize seed in the falling and impacting processes was developed to measure the restitution coefficient between maize seed and soil.A test bench for measuring the restitution coefficient was designed and built referred to the theory of mirror reflection.The velocities for impacting maize seed were measured and analyzed in a three-dimensional space via high-speed photography,and then restitution coefficients of in different impact conditions were obtained.On this basis,this study took flat dent seed and round seed as samples.Single factor tests were conducted to analyze the influences of these factors on the restitution coefficient.The impact angle,falling height,soil compaction,soil moisture,maize moisture content and different parts of seed were selected as test factors.The corresponding regression equations were obtained by analysis.The results showed that,as the impact angle was bigger than 25°,the restitution coefficient increased with the increase of impact angle.The restitution coefficient had a linear decreasing trend with the increase of falling height.As the soil compaction strength was 200-350 kPa,the restitution coefficient increased with the increase of soil compaction.As the soil compaction strength was larger than 350 kPa,the changing trend of the restitution coefficient was relatively stable.As the soil moisture content was 13.5%-18%,the restitution coefficient decreased with the increase of soil moisture.As the soil moisture content was 18%,the restitution coefficient was the minimum.As the maize moisture content was 11%-16%,the restitution coefficient decreased with the increase of maize moisture content.The rotational motion always occurred in falling process of flat dent seed and round seed.The probabilities of crown part and lateral part of maize seed impacting with soil were the highest,and the restitution coefficient between crown part and soil was higher than that of other parts in the same condition.

Defective Kernel 39 encodes a PPR protein required for seed development in maize

RNA editing is a posttranscriptional process that is important in mitochondria and plastids of higher plants. All RNA editing-specific trans-factors reported so far belong to PLS-class of pentatricopeptide repeat(PPR)proteins. Here, we report the map-based cloning and molecular characterization of a defective kernel mutant dek39 in maize. Loss of Dek39 function leads to delayed embryogenesis and endosperm development, reduced kernel size, and seedling lethality. Dek39 encodes an E subclass PPR protein that targets to both mitochondria and chloroplasts, and is involved in RNA editing in mitochondrial NADH dehydrogenase3(nad3) at nad3-247 and nad3-275. C-to-U editing of nad3-275 is not conserved and even lost in Arabidopsis, consistent with the idea that no close DEK39 homologs are present in Arabidopsis. However, the amino acids generated by editing nad3-247 and nad3-275 are highly conserved in many other plant species, and the reductions of editing at these two sites decrease the activity of mitochondria NADH dehydrogenase complex I,indicating that the alteration of amino acid sequence is necessary for Nad3 function. Our results indicate that Dek39 encodes an E sub-class PPR protein that is involved in RNA editing of multiple sites and is necessary for seed development of maize.

Effects of irrigation water salinity on soil salt content distribution,soil physical properties and water use efficiency of maize for seed production in arid Northwest China

In order to explore the use of groundwater resources,field experiments were conducted for three consecutive years during 2012-2014 in the Shiyang River basin of Northwest China.Irrigation was conducted using four different water salinity levels that were arranged in a split plot design.These four water salinity levels were s0,s3,s6 and s9(0.71,3,6 and 9 g/L,respectively).The soil salt content,soil bulk density,soil porosity,saturated hydraulic conductivity,plant height,leaf area index and yield of maize for seed production were measured for studying the effects of saline water irrigation on soil salt content distribution,soil physical properties and water use efficiency.It was observed that higher salinity level of irrigation water and long duration of saline water irrigation resulted in more salt accumulation.Compared to initial values,the soil salt accumulation in 0-100 cm soil layer after three years of experiments for s0,s3,s6 and s9 was 0.189 mg/cm3,0.654 mg/cm3,0.717 mg/cm3 and 1.135 mg/cm3,respectively.Both greater salt levels in the irrigation water and frequent saline water irrigation led to greater soil bulk density,but poorer soil porosity and less saturated hydraulic conductivity.The saturated hydraulic conductivity decreased with increase in soil bulk density,but increased with improvement in soil porosity.It was noted that the maize height,leaf area index and maize yield gradually decreased with increase in water salinity.The maize yield decreased over 25%and the water use efficiency also gradually declined when irrigated with water containing 6 g/L and 9 g/L salinity levels.However,maize yield following saline water irrigation with 3 g/L decreased less than 20%and the decline in water use efficiency was not significant during the three-year experiment period.The results demonstrate that irrigation with saline water at the level of 6 g/L and 9 g/L in the study area is not suitable,while saline water irrigation with 3 g/L would be acceptable for a short duration together with salt leaching through spring irrigation before sowing.

Effects of irrigation and nitrogen management on hybrid maize seed production in north-west China

Scientific irrigation and nitrogen management is important for agricultural production in arid areas. To quantify the effect of water and nitrogen management on yield components, biomass partitioning and harvest index(HI) of maize for seed production with plastic filmmulching, field experiments including different irrigation and N treatments were conducted in arid north-west China in 2013 and 2014. The results indicated that kernel number per plant(KN) was signi ficantly affected by irrigation and N treatments. However, 100-kernel weight was relatively stable. Reducing irrigation quantity signi ficantly increased stem partitioning index(PI_(stem)) and leaf partitioning index(PIl_(eaf)), and decreased ear partitioning index(PI_(ear)) at harvest, but lowering Nrate(from 500 to 100 kg N$hm^(–2))did not signi ficantly reduce PI_(stem), PI leaf, andPIl_(eaf) at harvest. HI was signi ficantly reduced by reducing irrigation quantity, but not by reducing Nrate. Linear relationships were found between KN, PI_(stem), PI leaf,PIl_(eaf) at harvest and HI and evapotranspiration(ET).

Remote monitoring system for maize seeding parameters based on Android and wireless communication

Most traditional maize seeding parameter monitoring devices use wired data transmission.The problems include wiring troubles,short transmission distances.And human-computer interaction display terminals are unique and usually customized rather than universal.A remote monitoring system for maize seeding parameters based on Android and wireless communication was developed in this study.The system used a single-chip microcomputer as the main controller and an infrared photoelectric sensor to capture seed information.The Android terminal application was used to set and display the seeder’s seed parameter information and monitor it.The Air202 communication module enabled remote data transmission,while the Global Positioning System(GPS)monitored the speed of the planter.By establishing a message queue telemetry transmission(MQTT)cloud served as a data freight station,data reception,storage and forwarding can be performed.Seeding parameters can generate Excel spreadsheets in real-time for easy data processing and storage.In order to verify the reliability of the system,the seeding parameter monitoring comparison test and the multi-terminal remote monitoring test were designed.The results of the seeding parameter monitoring comparison test showed that the monitoring system of this study had higher monitoring accuracy.The maximum average relative error of seeding parameter monitoring was 0.4%,which had high monitoring accuracy.The multi-terminal remote monitoring test showed that the monitoring system of this research can adapt many types of Android terminals,realize the wireless connection,and realize remote synchronous monitoring at different distances.This study provides a reference for intelligent remote monitoring and intelligent agriculture on unmanned farms.

A positioning method for maize seed laser-cutting slice using linear discriminant analysis based on isometric distance measurement

It is necessary that vision system should aid laser-cutting manipulator to position the specified part of each maize seed for getting the slice breeding genotype analysis with high throughput.Each of trivial maize seeds should be recognized and positioned in a certain posture.Correlation area ratio(CAR)is defined as the metric of pixel attribute.A large template of round mask is adopted for seed morphological detection to measure the CAR values.We get the feature points extracted from the seed image through the isometric mapping operation.Iterative processes of linear discriminant analysis search the morphological data space to learn non-linear transformations to the space where data are linearly separable.Linear discriminant analysis utilizes the data directional distribution to position the major axis and distinguish different parts of maize seed.The labeling partition operation is applied for picking out the scattered pieces to be finely clustered.Without denoising process,the feature region could be recognized with accuracies by the synthetical methods.Extensive experiments on a large amount of seeds demonstrate the effectiveness of proposed methods.

A comparison of the toxicity of landfill leachate exposure at the seed soaking and germination stages on Zea mays L.(maize)

To compare the toxicity of landfill leachate exposure at the early stages of seed soaking and germination on maize,a field experiment was conducted to evaluate the physiological aspects of growth,yield and potential clastogenicity of root-tip cells. The maizes were treated with leachate at levels of 2%,10%,20%,30% or 50%（V/V）. First,the change of physiological indexes,including chlorophyll（Chl）,Malondialdehyde（MDA）and Reactive oxygen species（ROS）levels,combined with yield all showed that soaking with leachate,but not germination,generated a greater ecological risk on maize. After a soaking treatment of maize with 50% leachate,the Chl,MDA and ROS levels during a vigorous growth period were 47.3%,149.8% and 309.7%,respectively,of the control,whereas the yield decreased to 68.6% of the control. In addition,our results demonstrated that the leachate at lower levels could promote growth. This is mainly embodied in that the yield of maize treated with 10%leachate at the soaking stage increased to 116.0% of the control. Moreover,the cytological analysis experiment also demonstrated that the ecological risk of leachate still exists in both cases. Furthermore,the gray relational analysis showed that the ear row number and tassel branch number were the major factors affecting the yield of maize treated with 50%leachate at the stages of soaking and germination,respectively. In general,these results are helpful in understanding the phytotoxicity of leachate,which provides additional reference data for risk assessment and management of leachate.