玉米田蚜虫种群的空间动态

【目的】明确我国黄淮海地区玉米蚜虫种类及其空间分布,掌握玉米蚜虫田间发生规律。【方法】采用系统调查法于2009—2010年在河北廊坊对春玉米、夏玉米上玉米蚜虫种群的发生动态进行了研究。【结果】结果表明,该地区取食为害玉米的蚜虫有5种;玉米蚜Rhopalosiphum maidis(Fitch)和禾谷缢管蚜R.padi(L.)混合发生,为玉米田蚜虫的优势种群。【结论】几种蚜虫的混合种群在玉米田间的动态分布始终呈聚集分布;二项分布k和聚集型指标m~*/x判断表明,随着玉米的生长发育,玉米蚜虫表现扩散-聚集-再扩散-再聚集的趋势。     

Molecular dynamics simulations of the auxin‐binding protein 1 in complex with indole‐3‐acetic acid and naphthalen‐1‐acetic acid

Auxin‐binding protein 1 (ABP1) is suggested to be an auxin receptor which plays an important role in several processes in green plants. Maize ABP1 was simulated with the natural auxin indole‐3‐acetic acid (IAA) and the synthetic analog naphthalen‐1‐acetic acid (NAA), to elucidate the role of the KDEL sequence and the helix at the C‐terminus. The KDEL sequence weakens the intermolecular interactions between the monomers but stabilizes the C‐terminal helix. Conformational changes at the C‐terminus occur within the KDEL sequence and are influenced by the binding of the simulated ligands. This observation helps to explain experimental findings on ABP1 interactions with antibodies that are modulated by the presence of auxin, and supports the hypothesis that ABP1 acts as an auxin receptor. Stable hydrogen bonds between the monomers are formed between Glu40 and Glu62, Arg10 and Thr97, Lys39, and Glu62 in all simulations. The amino acids Ile22, Leu25, Trp44, Pro55, Ile130, and Phe149 are located in the binding pocket and are involved in hydrophobic interactions with the ring system of the ligand. Trp151 is stably involved in a face to end interaction with the ligand. The calculated free energy of binding using the linear interaction energy approach showed a higher binding affinity for NAA as compared to IAA. Our simulations confirm the asymmetric behavior of the two monomers, the stronger interaction of NAA than IAA and offers insight into the possible mechanism of ABP1 as an auxin receptor. Proteins 2014; 82:2744–2755. © 2014 Wiley Periodicals, Inc.     

Western Flower Thrips (Frankliniella occidentalis) Transmits Maize Chlorotic Mottle Virus

Maize chlorotic mottle virus (MCMV) is one of the co‐infection pathogens that cause corn (maize) lethal necrosis, but the transmission mechanism of MCMV is not yet clear. In order to determine the ability of western flower thrips (Frankliniella occidentalis; WFT) to transmit MCMV, imported maize seeds from Thailand were germinated in an insect‐free greenhouse and the seedlings were tested for the transmission by WFT of chlorotic mottle virus disease. The thrips (WFT), starved for 48 h then allowed to feed for 30 min on maize plants infected with MCMV or asymptomatic maize plants, were transferred to healthy seedlings. After 35 days, the seedlings with WFT from diseased maize plants showed chlorotic mottle symptoms, whereas seedlings with WFT from asymptomatic maize plants remained healthy. A single band of 711 bp was amplified by RT‐PCR using primers MCMV‐F/MCMV‐R from the MCMV‐infected plants and WFT collected from the diseased plants. Sequencing of the amplified product and further sequence comparison indicated that the two viruses from both sources showed 99% similarity of nucleotides and they should be regarded as identical. In addition, isometric particles c. 30 nm in diameter, characteristic of MCMV, were found in the WFT samples from diseased maize plants. Thus, it is concluded that WFT transmits MCMV. Our findings suggest that corn lethal necrosis disease can be controlled or minimized by the eradication of WFT from the field or greenhouses.     

Temperatures and the growth and development of maize and rice: a review

Because of global land surface warming, extreme temperature events are expected to occur more often and more intensely, affecting the growth and development of the major cereal crops in several ways, thus affecting the production component of food security. In this study, we have identified rice and maize crop responses to temperature in different, but consistent, phenological phases and development stages. A literature review and data compilation of around 140 scientific articles have determined the key temperature thresholds and response to extreme temperature effects for rice and maize, complementing an earlier study on wheat. Lethal temperatures and cardinal temperatures, together with error estimates, have been identified for phenological phases and development stages. Following the methodology of previous work, we have collected and statistically analysed temperature thresholds of the three crops for the key physiological processes such as leaf initiation, shoot growth and root growth and for the most susceptible phenological phases such as sowing to emergence, anthesis and grain filling. Our summary shows that cardinal temperatures are conservative between studies and are seemingly well defined in all three crops. Anthesis and ripening are the most sensitive temperature stages in rice as well as in wheat and maize. We call for further experimental studies of the effects of transgressing threshold temperatures so such responses can be included into crop impact and adaptation models.     

Roothairless5, which functions in maize (Zea mays L.) root hair initiation and elongation encodes a monocot‐specific NADPH oxidase

Root hairs are instrumental for nutrient uptake in monocot cereals. The maize (Zea mays L.) roothairless5 (rth5) mutant displays defects in root hair initiation and elongation manifested by a reduced density and length of root hairs. Map‐based cloning revealed that the rth5 gene encodes a monocot‐specific NADPH oxidase. RNA‐Seq, in situ hybridization and qRT‐PCR experiments demonstrated that the rth5 gene displays preferential expression in root hairs but also accumulates to low levels in other tissues. Immunolocalization detected RTH5 proteins in the epidermis of the elongation and differentiation zone of primary roots. Because superoxide and hydrogen peroxide levels are reduced in the tips of growing rth5 mutant root hairs as compared with wild‐type, and Reactive oxygen species (ROS) is known to be involved in tip growth, we hypothesize that the RTH5 protein is responsible for establishing the high levels of ROS in the tips of growing root hairs required for elongation. Consistent with this hypothesis, a comparative RNA‐Seq analysis of 6‐day‐old rth5 versus wild‐type primary roots revealed significant over‐representation of only two gene ontology (GO) classes related to the biological functions (i.e. oxidation/reduction and carbohydrate metabolism) among 893 differentially expressed genes (FDR <5%). Within these two classes the subgroups ‘response to oxidative stress’ and ‘cellulose biosynthesis’ were most prominently represented.     

大田淹水对夏玉米叶片衰老特性的影响

选用登海605(DH605)和郑单958(ZD958)为试验材料,在大田条件下研究了不同淹水时期(三叶期、拔节期和开花后10 d)和持续时间(3 d、6 d)淹水对夏玉米叶片衰老特性的影响.研究表明: 淹水胁迫后超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)等保护酶活性以及可溶性蛋白含量较不淹水对照显著下降,而丙二醛(MDA)含量显著升高,三叶期淹水6 d后DH605和ZD958的含量较对照分别升高35.3%和34.1%.淹水胁迫后叶片叶绿素含量降低,产量显著下降.三叶期淹水6 d对夏玉米产量的影响最大,DH605和ZD958较对照分别减产32.1%和35.2%.不同生育期中,三叶期淹水造成的影响最大,拔节期次之,开花后10 d淹水造成的影响较小,且影响程度随淹水持续时间的延长而加剧.     

Bioremediation of Cadmium-Contaminated Soil through Cultivation of Maize Inoculated with Plant Growth–Promoting Rhizobacteria

A pot experiment was conducted to study the effect of single and co-inoculation of Bacillus mycoides and Micrococcus roseus strains, indigenous to heavy metal (HM)–contaminated soils, on the growth and essential-nutrient and Cd uptake of maize in a soil polluted with 100 and 200 mg Cd kg^?1. Increasing Cd levels significantly decreased shoot and root dry weights, and shoot P, Fe, Zn, and Mn uptake. All bacterial treatments significantly increased biomass and shoot nutrient uptake of plant compared with control in the soil polluted with Cd. Inoculation of plants with B. mycoides and consortium of two bacteria significantly increased, whereas M. roseus significantly decreased, shoot and root Cd uptake, and Cd transfer and translocation factors compared with control in Cd-polluted conditions. The results showed that B. mycoides and consortium of two bacteria had an effective role in phytoextraction and M. roseus was the most effective treatment in phytostabilization of Cd.     

High temperature combined with drought affect rainfed spring wheat and barley in South-Eastern Russia: I. Phenology and growth

Heat stress, when combined with drought, is one of the major limitations to food production worldwide, especially in areas that use rainfed agriculture. As the world population continues to grow, and water resources for the crop production decline and temperature increases, so the development of heat- and drought-tolerant cultivars is an issue of global concern. In this context, four barley and two wheat genotypes were evaluated in south-eastern Russia to identify heat- and drought-tolerant genotypes for future breeding programmes by identifying suitable sowing times for specific genotypes. High temperature stress, when combined with drought during late sowing, decreased the days to visible awns, days to heading and days to ripe harvest, finally negatively affecting the growth and development of plants and resulting in a lower plant population m⁻², tillers plant⁻¹, plant height and dry matter production m⁻². On the other hand, low temperature in combination with early sowing increased the number of days to germination, reduced seedling stand establishment and tillering capacity, finally affecting the growth and development of the crops. Compared to overall performance and optimum sowing date, barley genotypes ‘Zernograd.770’ and ‘Nutans’, and wheat genotype ‘Line4’ performed best in both late (high temperature with drought) and early (low temperature) stress conditions.