Near infrared reflectance spectroscopy (NIRS) to predict biological parameters of maize silage: effects of particle comminution, oven drying temperature and the presence of residual moisture

Maize silage nutritive quality is routinely determined by near infrared reflectance spectroscopy (NIRS). However, little is known about the impact of sample preparation on the accuracy of the calibration to predict biological traits. A sample population of 48 maize silages representing a wide range of physiological maturities was used in a study to determine the impact of different sample preparation procedures (i.e., drying regimes; the presence or absence of residual moisture; the degree of particle comminution) on resultant NIR prediction statistics. All silages were scanned using a total of 12 combinations of sample pre-treatments. Each sample preparation combination was subjected to three multivariate regression techniques to give a total of 36 predictions per biological trait. Increased sample preparations procedure, relative to scanning the unprocessed whole plant (WP) material, always resulted in a numerical minimisation of model statistics. However, the ability of each of the treatments to significantly minimise the model statistics differed. Particle comminution was the most important factor, oven-drying regime was intermediate, and residual moisture presence was the least important. Models to predict various biological parameters of maize silage will be improved if material is subjected to a high degree of particle comminution (i.e., having been passed through a 1 mm screen) and developed on plant material previously dried at 60 °C. The extra effort in terms of time and cost required to remove sample residual moisture cannot be justified.     

农杆菌介导玉米遗传转化体系的研究进展

玉米(Zea maysL.)是世界上三大主要粮食作物之一,至今其遗传转化仍比较困难,目前报道有多种成功的方法,其中农杆菌(Agrobactierium tumefaciens)介导法是当前玉米遗传转化的主要方法。本文综述了农杆菌介导的玉米遗传转化研究的发展历史、存在问题和影响因素等,并对未来发展趋势进行展望。     

海拔对甘肃河西走廊玉米生育期的影响

为了研究海拔高度对玉米生育期的影响,1999年和2004年在甘肃省河西走廊的张掖市安排了4个试点的田间试验,海拔高度分别是1506.5、1706.5、2000.0和2231.5m.结果表明,608、酒单3号和中单2号3个不同熟期类型的玉米品种在同日播种条件下,随着海拔的升高成熟期延迟,海拔与品种的生育期之间呈极显著正相关,海拔每升高100m,生育期延长5～6d.海拔与播种至拔节天数之间也表现正相关,海拔与株高之间为负相关.     

Cinnamic acid induced changes in reactive oxygen species scavenging enzymes and protein profile in maize (Zea mays L.) plants grown under salt stress

Plant growth and development are greatly affected due to changes in environmental conditions and become a serious challenge to scientific people. Therefore, present study was conducted to determine the role of secondary metabolites on the growth and development of maize under abiotic stress conditions. Cinnamic acid (CA) is one of the basic phenylpropanoid with antioxidant activity, produced by plants in response to stressful conditions. Response of maize seeds to the presoaking treatment with 0.5 mM CA was studied under different concentrations of NaCl stress. Exogenous CA increased growth characteristics in saline and non-saline conditions, while effects of CA were more significant under saline conditions in comparison to non-saline conditions in maize plants. CA also reduced oxidative damage through the induction of ROS scavenging enzymes such as supperoxide dismutase (SOD) (EC 1.15.1.1), peroxidase (POD) (EC 1.11.1.7), while the activity of enzyme catalase (CAT) (EC 1.11.1.6) was decreased. The content of malondialdehyde (MDA) was reduced significantly in maize leaf under CA treatment. Changes in protein banding patterns in the maize leaves showed a wide variation in response to NaCl-stress, while in the presence of CA salt-induced expression of polypeptides was reduced significantly. Present study clearly reports the alleviative effects of CA in response to salinity stress on growth, metabolic activity and changes in protein profile of 21 days old maize plants.     

Comprehensive genotyping of the USA national maize inbred seed bank

Background

Genotyping by sequencing, a new low-cost, high-throughput sequencing technology was used to genotype 2,815 maize inbred accessions, preserved mostly at the National Plant Germplasm System in the USA. The collection includes inbred lines from breeding programs all over the world.

Results

The method produced 681,257 single-nucleotide polymorphism (SNP) markers distributed across the entire genome, with the ability to detect rare alleles at high confidence levels. More than half of the SNPs in the collection are rare. Although most rare alleles have been incorporated into public temperate breeding programs, only a modest amount of the available diversity is present in the commercial germplasm. Analysis of genetic distances shows population stratification, including a small number of large clusters centered on key lines. Nevertheless, an average fixation index of 0.06 indicates moderate differentiation between the three major maize subpopulations. Linkage disequilibrium (LD) decays very rapidly, but the extent of LD is highly dependent on the particular group of germplasm and region of the genome. The utility of these data for performing genome-wide association studies was tested with two simply inherited traits and one complex trait. We identified trait associations at SNPs very close to known candidate genes for kernel color, sweet corn, and flowering time; however, results suggest that more SNPs are needed to better explore the genetic architecture of complex traits.

Conclusions

The genotypic information described here allows this publicly available panel to be exploited by researchers facing the challenges of sustainable agriculture through better knowledge of the nature of genetic diversity.     

Exogenous carnitine application augments transport of fatty acids into mitochondria and stimulates mitochondrial respiration in maize seedlings grown under normal and cold conditions

This study aimed to investigate whether exogenous application of carnitine stimulates transportation of fatty acids into mitochondria, which is an important part of fatty acid trafficking in cells, and mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions. Cold stress led to significant increases in lipase activity, which is responsible for the breakdown of triacylglycerols, and carnitine acyltransferase (carnitine acyltransferase I and II) activities, which are responsible for the transport of activated long-chain fatty acids into mitochondria. While exogenous application of carnitine has a similar promoting effect with cold stress on lipase activity, it resulted in further increases in the activity of carnitine acyltransferases compared to cold stress. The highest activity levels for these enzymes were recorded in the seedlings treated with cold plus carnitine. In addition, these increases were correlated with positive increases in the contents of free- and long-chain acylcarnitines (decanoyl-l-carnitine, lauroyl-l-carnitine, myristoyl-l-carnitine, and stearoyl-l-carnitine), and with decreases in the total lipid content. The highest values for free- and long-chain acylcarnitines and the lowest value for total lipid content were recorded in the seedlings treated with cold plus carnitine. On the other hand, carnitine with and without cold stress significantly upregulated the expression level of citrate synthase, which is responsible for catalysing the first reaction of the citric acid cycle, and cytochrome oxidase, which is the membrane-bound terminal enzyme in the electron transfer chain, as well as lipase. All these results revealed that on the one hand, carnitine enhanced transport of fatty acids into mitochondria by increasing the activities of lipase and carnitine acyltransferases, and, on the other hand, stimulated mitochondrial respiration in the leaves of maize seedlings grown under normal and cold conditions.     

玉米幼苗抗氧化酶活性、脯氨酸含量变化及与其耐寒性的关系

研究了黄C（耐寒型）和Mo17（低温敏感型）两种耐寒性不同的玉米自交系幼苗在低温逆境（5 ℃,3 d）下,根、中胚轴和胚芽鞘3个部位过氧化氢酶（CAT）、过氧化物酶（POD）活性和脯氨酸（Pro）含量变化及与其耐寒性的关系.结果表明,低温期间,黄C的中胚轴、胚芽鞘相对生长率显著高于Mo17;黄C的根、中胚轴、胚芽鞘3个部位的CAT、POD活性和Pro含量变化率（其中,中胚轴分别为39.02%、-31.35%和86.86%）均高于Mo17（中胚轴变化率分别为1.86%、-48.67%和12.01%）;黄C 3个部位的质膜透性（中胚轴为22.05%）均低于Mo17（中胚轴为29.11%）.逐步回归分析表明黄C低温期间积累的干物质主要与Pro含量有关,而Mo17主要与POD活性有关,玉米幼苗中胚轴对低温反应最敏感,中胚轴Pro含量变化率与玉米耐寒性关系最密切.     

Biochemical Origin and Refractory Properties of Humic Acid Extracted from the Maize Plant

Humic acids (HA) contribute to soil fertility because of their chemical, physical, and biological properties. The origin of HAs in soils has puzzled scientists for decades, and what HAs are and what their origin is remain unclear. The isolation of HAs in plants, which have characteristics close to soil HAs, suggests the probable origin of soil-HA is the preservation of plant tissue, indicating biochemical origin. In this paper HA from maize plant at different stages of maturity is isolated, from which it was found that the evolution of this fraction depends on and is derived from cell wall formation. Evidence was also found that HA was above all composed of lignin and cutin residues, and was characterized by low surface area. After 8 months of incubation in both mineral-artificial and natural soils, humic acid isolated form maize plant could be recovered intact.     

Comparative expression profiles of maize genes from a water stress-specific cDNA macroarray in response to high-salinity, cold or abscisic acid

cDNA macroarray has become a useful tool to analyze expression profiles and compare the similarities and differences of various expression patterns. We have prepared a cDNA macroarray containing 190 maize expressed sequence tags (ESTs) specifically induced by water stress to analyze the expression profiles of maize seedlings under abscisic acid (ABA) treatment, high-salinity and cold stress conditions. The results indicated that 48 ESTs in leaves and 111 ESTs in roots were significantly up-regulated by ABA treatment, 36 ESTs in leaves and 41 ESTs in roots by high-salinity stress, 14 ESTs in leaves and 18 ESTs in roots by cold induction, whereas 22 ESTs were induced under all 3 stresses. Results from the hierarchical cluster analysis suggest that the leaves and roots of maize seedlings had different expression profiles after these stresses. The overlap analysis of different stress-induced ESTs indicated that there is more crosstalk between water stress and ABA and high-salinity stress than between water stress and cold stress. It will be helpful to study the precise function of the corresponding overlapping-induced genes for understanding the relationship and crosstalk between different stress signal pathways.     

Response of soil properties and maize yield to simulated erosion by artificial topsoil removal

The study was aimed at identifying the soil properties responsible for maize yield decline on eroded soils and at quantifying their relationship with yield. Topsoil was artificially removed to incremental depths of 0, 5, 10, 15 and 20 cm to simulate various degrees of erosion. Maize growth and yield were monitored on the plots and soil physical and chemical properties were determined after two years (4 seasons) of cultivation. Soil pH was significantly higher on the control plot and decreased with increased depth of topsoil removal. Bulk density (BD) increased with depth of topsoil removal from a mean value of 1.38 g cm⁻³ under control to 1.55 g cm⁻³ at 20 cm depth of removal, while cone index of penetrometer resistance (CI) correspondingly increased from 1.09 g cm⁻² to 1.37 g cm⁻². Maize yield significantly decreased in the first year from 3.2 t ha⁻¹ on the control plot to 0.12 t ha⁻¹ where 20 cm of topsoil was removed and correspondingly from 1.85 to 0.09 t ha⁻¹ in the second year of cropping. Maize yield decreased exponentially with increase in depth of topsoil removal (r ²=0.99, P<0.01) with an average of 55% yield loss on the removal of just 5 cm topsoil. Soil organic carbon (SOC), BD, CI, field capacity (FC), pH and exchangeable Mg²⁺ were significantly correlated to maize yield parameters. However, factor analysis showed that the combination of SOC and exchangeable Mg²⁺ with soil physical properties (BD, FC, CI and depth of topsoil removal) explained 99% of variation in maize grain yield. The need for conservation farm practices is recommended on the soil to prevent soil degradation. Section Editor: L. Wade