Feeding damage effects of three aphid species on wheat root growth

Cereal aphid infestations have considerable impact upon productivity and profitability of United States agriculture. A comparison study of the influence of different aphid species (Russian wheat aphid, Duraphis noxia Mordvilko; greenbug, Schizaphis graminum Rondani; and bird cherry oat aphid, Rhopalosiphum padi L.) upon shoot characteristics and root growth of hard red spring wheat (Triticum aestivum L.) was conducted in an attempt to better understand the mechanisms of yield loss in aphid damaged plants. Plants infested with aphids showed similar reductions in shoot growth regardless of aphid species. Shoot chlorophyll concentrations were lowest in greenbug‐infested plants. Root length and dry weight were also equally reduced by feeding damage by the three aphid species. Upon removal of the aphids, shoot dry weights of plants damaged by each aphid species remained unchanged for 10 days. Shoot dry weights for aphid‐damaged plants were about half the magnitude seen in the control plants after 15 days. Chlorophyll concentrations seen in greenbug and Russian wheat aphid‐infested plants initially were lower than the concentrations seen in bird cherry oat aphid‐infested and control plants. Within 10 days after aphid removal, however, chlorophyll concentrations across all treatments were essentially equal. Root lengths in plants previously infested with greenbugs or Russian wheat aphids were lower than control plants four days after aphid removal. Within 10 days after aphid removal, root lengths in plants previously infested with greenbugs or Russian wheat aphids did not differ from control plants. Root lengths in plants previously damaged by bird cherry oat aphids did not reach the same magnitude as that of the other treatments until 27 days after aphid removal. These results indicate that aphid feeding damage to wheat plants can have significant effects on root growth, suggesting that crop management practices that promote root growth could play important roles in improving plant tolerance to aphid damage.     

Nitrogen relations in winter wheat cultivars differing in grain protein percentage and stature

Accumulation of reduced nitrogen and its partitioning between vegetative tissue and grain are two important aspects of the nitrogen economy of wheat (Triticum aestivum L.). The objectives of this study were to 1) determine the range of nitrogen harvest index (NHI) among four hard red winter wheat cultivars differing in grain protein percent (GPP) and the influence of NHI on grain protein percent, and 2) to contrast the partitioning of nitrogen and dry matter to the component parts of the plant throughout growth and development. Plants were grown in a nutrient solution and nitrogen salts were withheld from the solution when the wheat reached anthesis. High nitrogen percentage of plant parts tended to correlate positively with grain protein percentage at first node and anthesis stages, but correlated negatively at latter stages. Dry weight was important in the accumulation of nitrogen; however, neither dry weight nor total plant nitrogen was correlated with GPP. Nitrogen harvest index was correlated strongly and positively with GPP and was independent of plant stature. The selection of parents with high NHI could be an important criterion in breeding programs to increase GPP of wheat.     

Nitrogen Fixation,Ureide, and Nitrate Accumulation Responses to Soybean Aphid Injury in Glycine max

There is little information available about soybean aphid (Aphis glycines Matsumura) effects on the physiology and mineral nutrition of soybean (Glycine max [L.] merr.). Controlled-environment studies were conducted to measure soybean aphid infestation effects on dry weight, nitrogen (N) fixation, ureide-N, and nitrate-N concentration and accumulation. Plants grown in perlite using –N nutrient solution culture were infested at the 3rd trifoliolate (V3) stage and measured for N fixation, nodule characteristics, and ureide-N concentration at the full pod (R4) stage. When compared to uninfested control plants, aphid infestation reduced total nodule volume per plant by 34%, nodule leghemoglobin per plant by 31%, plant N fixation rate by 80% and shoot ureide-N concentration by 20%. Soil-grown plants were infested at the first trifoliolate (V1) stage and shoots were measured for dry weight, nitrate-N, and ureide-N at the full bloom (R2) stage. Infestation reduced shoot dry weight by 63%, increased nitrate-N concentration by 75%, but did not significantly affect ureide-N concentration. Because nutrient concentration is a single-point measurement that results from the integration of two dynamic processes, nutrient accumulation and dry matter production, we conclude that aphid-induced reductions in N fixation, coupled with decreased dry weight accumulation, caused shoot ureide-N concentration to remain unchanged in aphid-injured plants when compared to uninfested plants. Because nitrate-N concentration was greater in aphid-damaged shoot tissue, we further conclude that nitrate-N accumulation was less sensitive to aphid injury than dry weight accumulation.     

Nutrient solution nitrogen form and barley yellow dwarf virus disease tolerance in oat and wheat

Abstract

The form of nutrient solution nitrogen (either NH₄‐N or NO₃‐N or mixtures of the two) provided to plants influences the severity of many crop diseases. This greenhouse study was conducted to determine how growth, grain yield, and yield components of oat (Avena sativa L.) and wheat (Triticum aestivum L.) plants given nutrient solutions containing different ratios of NO₃‐N to NH₄‐N would react to barley yellow dwarf virus (BYDV) infection. Fifteen‐day‐old seedlings (2nd leaf stage) were either infected with BYDV (PAV strain) or left uninfected. Nutrient solution treatments (started 19 d after germination) provided three ratios of NO₃‐N to NH₄‐N (100% NO₃, 50:50 NH₄:NO₃, or 100% NH₄) for a 30‐d period, after which plant height and tillers plant^?1 were measured. Oat and wheat plants given NH₄ had fewer tillers than plants given the other nutrient solution treatments. BYDV‐infected oat and wheat plants were shorter than uninfected plants. All pots then received NO₃ nutrient solution until plant maturity, after which days to anthesis, primary tiller height, grain yield and yield components were measured. In the NH₄ nutrient solution treatments, BYDV infection significantly reduced individual kernel weight in oat and primary tiller height in wheat. These same measures were not significantly affected by BYDV infection in the NO₃ or NH₄NO₃ nutrient solution treatments. There were no other significant nutrient solution by BYDV infection interactions for any other dependent variable measured. Nutrient solution treatments had no significant effect on grain yield, but BYDV infection reduced grain yield by 45% in oat and 46% in wheat. In conclusion, nutrient solution N form interacted with BYDV infection to alter disease tolerance in oat (kernel weight) and wheat (primary tiller height), but these alterations had no effect in ameliorating grain yield loss caused by BYDV disease.     

施硅降低麦长管蚜对小麦寄主选择偏好的化学机理

[目的]从施硅对小麦挥发物释放影响的角度,探究施硅提高作物抗虫能力的作用机理.[方法]采用水培试验方法,供试小麦品种为'郑麦1036',供试蚜虫为黄淮地区的优势种麦长管蚜(Sitobion avenae),供试营养液为Hoagland营养液.设置不施硅不接蚜虫对照(CK)、不施硅接蚜虫(A)、施硅不接蚜虫(Si)、施硅...     

How to reduce the incidence of black bean aphids (Aphis fabae Scop.) attacking organic growing field beans (Vicia faba L.) by growing partially resistant bean varieties and by intercropping field beans with cereals

Abstract

There is an increasing demand for organically grown pulses and cereal grains in Denmark, which is expected to cause a change in the typical organic farm structure away from dairy farming and towards arable farming. Spring field beans (Vicia faba) could be a popular break crop in organic agriculture. The black bean aphid (Aphis fabae) is generally considered to be a serious pest of spring-sown field beans in northern Europe, and field studies have shown that yield losses can exceed more than 50% due to attacks from the black bean aphid.

The use of insecticides in organically grown field bean crops is not permitted, but it has been known for a long time that the black bean aphid infests different varieties of beans to a very different extent. Therefore, partial resistance to the black bean aphid is one method of stabilizing yields. Another method of cultural pest control is intercropping and a third method could be a combination of both. Six field experiments involving the three methods were carried out. There was a significant difference between the number of aphids per plant on the three investigated bean varieties, where ‘Colombo’ was the most susceptible, ‘Quattro’ was intermediate, and ‘Caspar’ the most resistant variety. ‘Colombo’ intercropping with spring wheat and spring barley reduced the numbers of aphids per plant significantly, and also the number of plants infested. The harvesting of all crops took place during the last fourteen days of August.

It can be concluded that the growing of partial host plant resistant varieties of field beans or the intercropping of field beans with spring cereals separately will reduce the infestation with black bean aphids. If both methods are used, the reduction of infestation will be even higher and consequently also the yield.     

适宜钾浓度降低小麦蚜虫密度的生理代谢机理

【目的】从对植物基础代谢影响的角度,研究施钾降低麦株蚜虫密度的作用机理,为田间小麦蚜虫的生态调控提供科学依据。【方法】采用水培试验,设置5个钾水平（KCl 0.005、0.05、0.5、2、10 mmol/L）,每个钾水平均进行蚜虫侵染和不侵染处理,每个处理重复3次,并于麦株五叶一心时进行蚜虫侵染,将虫龄大小一致的成年无翅蚜虫接种在小麦的最新完全展开叶上,每株小麦用5头蚜虫侵染。然后,分别于蚜虫侵染4天和8天两个时间节点调查麦株蚜虫密度并取样,分析钾水平和蚜虫取食对小麦叶片游离氨基酸、可溶性蛋白和可溶性糖含量的影响。【结果】钾水平在0.005~0.5 mmol/L范围内,蚜虫侵染后第4天,单位干物质重的蚜虫密度随着钾水平的提高显著降低,进一步提高钾水平,蚜虫的群体密度差异并不显著;而在蚜虫侵染后第8天,蚜虫的群体密度随着钾水平的升高而显著降低。随着钾水平提高,未被蚜虫侵染的小麦植株其游离氨基酸含量呈降低趋势,而可溶性蛋白和可溶性糖含量则呈先升高后降低趋势;被蚜虫侵染的小麦植株其游离氨基酸和可溶性蛋白含量的变化趋势不变,而可溶性糖含量则呈持续增加趋势。同一测定时间与不接虫处理相比,接虫处理随着钾水平的提高,蚜虫侵染诱导的游离氨基酸和可溶性蛋白含量降低,而可溶性糖含量增加。两个时间节点相比,随时间推移,不接虫处理游离氨基酸、可溶性蛋白、可溶性糖含量的平均增幅分别为2.6%、18.1%、2.0%,而接虫处理上述指标平均增幅分别为67.3%、20.9%、22.9%,与不接虫处理相比,接虫处理麦株游离氨基酸和可溶性糖含量增幅较大。此外,蚜虫侵染诱导的游离氨基酸、可溶性蛋白和可溶性糖含量的增加量,都与相应时间节点的蚜虫群体密度显著或极显著相关,其中,接虫4天和接虫8天的相关系数分别为0.948、0.920、-0.908和0.944、0.985、-0.991。而组成型的可溶性蛋白和可溶性糖含量与相应时间节点蚜虫群体密度间相关性不显著,游离氨基酸含量却与之呈极显著正相关,接虫4和8天的相关系数分别为0.995和0.944。【结论】提高钾水平可能通过降低小麦组成型游离氨基酸的含量,降低蚜虫取食诱导型游离氨基酸和可溶性蛋白积累,提高诱导型可溶性糖的积累,共同降低麦长管蚜密度。     

The influence of nitrogen nutrition on plant response to greenbug infestation 1

The influence of nitrogen nutrition and greenbug (Schizaphis graminum Rondani) infestation on growth, chlorophyll content, soluble amino acids, and soluble protein of barley plants (Hordeum vulgare L.) was studied in growth chamber experiments. Plants were grown for 21 days using complete or minus nitrogen nutrient solution. First leaves were then fitted with cages containing eight apterous adult greenbugs. After 7 days, the greenbugs were removed and the plants harvested. The plants given complete nutrient solution grew more rapidly than those given minus nitrogen. Plants grown with minus nitrogen had fewer greenbugs per plant but had much higher numbers of greenbugs per square centimeter of total plant leaf area than plants given complete nutrient solution. All leaves of infested plants grown with minus nitrogen had decreased dry weight, decreased chlorophyll, and increased soluble amino acids when compared with minus nitrogen uninfested plants. Infestation of first leaves of plants grown on complete nutrient solution increased soluble amino acids in all leaves. However, there was little change in the dry weight or chlorophyll level in leaves other than the first leaf. It is concluded that adequate nitrogen nutrition produces plants that can better withstand localized greenbug feeding damage than plants deficient in nitrogen.     

平水年和欠水年渭北旱地冬小麦临界氮浓度稀释曲线构建

降雨波动大和过量施氮是限制渭北旱地冬小麦生产中氮肥高效利用和高产稳产的主要因子。该研究旨在构建2种降雨年型下冬小麦临界氮浓度稀释曲线,分析氮营养指数诊断冬小麦氮素营养状况的可行性,为考虑降雨条件下旱地冬小麦精准施氮提供理论依据。于2017—2021年在陕西合阳县开展4 a定位施氮试验,以晋麦47为试验材料,设置0、60、120、180、240 kg/hm² 5个施氮水平,其中2017—2018年和2020—2021年为平水年,2018—2019和2019—2020年为欠水年。研究2种降雨年型下施氮量对冬小麦氮素利用、产量及产量构成因素的影响,基于2种降雨年型下地上部生物量与植株氮浓度之间的关系,构建临界氮浓度稀释曲线模型和氮营养指数(nitrogen nutrition index,NNI)优化施肥方案。结果表明:1)施氮量、降雨年型及其二者互作效应对穗数、千粒质量、产量影响显著或极显著。2)2种降雨年型下冬小麦临界植株氮浓度和地上部生物量均符合幂函数关系,但模型参数之间存在差异(模型参数a在平水年和欠水年分别为3.33、2.79 g/kg,参数b在平水年和欠水年...     

Interactive effects of salinity and macronutrient level on wheat. II. Composition

Results of several studies show interactive effects of salinity and macronutrients on the growth of wheat plants. These effects may be associated with the nutrient status in plant tissues. The objective of this study was to investigate interactive effects of salinity and macronutrients on mineral element concentrations in leaves, stems, and grain of spring wheat (Triticum aestivum L. cv. Lona), grown in hydroponics, and the relation of these effects to yield components. Eight salinity levels were established from 0 to 150 mM NaCl, and 1, 0.2, and 0.04 strength Hoagland macronutrient solution (x HS) were used as the macronutrient levels. Sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chlorine (Cl), and phosphorus (P) in leaves, stems, and grain, NO₃ in leaves and stems, and total nitrogen (N) in grain were determined. Supplemental Ca, Mg, K, and NO₃ added to 0.2 x HS increased mineral concentrations in leaves and stems, but did not improve growth or yield in salinized wheat plants except moderately at 100–150 mM NaCl. In contrast, growth or yield was improved significantly when the concentration of macronutrients was increased from 0.04 to 0.2 × HS. In contrast to leaves and stems, mineral concentrations in grain increased (Na, Cl) or decreased (Ca, Mg, K) only slightly or were not affected (K) by salinity except at high salinity and low macronutrient level. Nitrogen and P concentrations in grain were not affected by salinity. Sodium and Cl concentrations in leaves and stems increased significantly, whereas K and NO₃ decreased significantly, with an increase in salinity regardless of the macronutrient level. The latter was also observed for Ca and Mg in leaves. Extreme Na/Ca ratios in plant tissues negatively affected grain yield production at high salinity with medium or high macronutrient levels and at low macronutrient level together with medium salinity. Even though strong and significant correlations between mineral concentration at grain maturity in leaves, stems, and grain and various yield parameters were observed, our results are inconclusive as to whether toxicity, nutrient imbalance, nutrient deficiency, or all of these factors had a strong influence on grain yield.     

Winter wheat fertilizer nitrogen use efficiency in grain and forage production systems

Abstract

Nitrogen use efficiency (NUE) is known to be less than fifty percent in winter wheat grain production systems. This study was conducted to determine potential differences in NUE when winter wheat (Triticum aestivum L.) is grown strictly for forage or grain. The effects of different nitrogen rates on plant N concentrations at different growth stages and on grain yield were investigated in two existing long‐term winter wheat experiments near Stillwater (Experiment 222) and Lahoma (Experiment 502), OK. At both locations in all years, total N uptake was greater when wheat forage was harvested twice (Feekes 6 and flowering) compared to total N uptake when wheat was grown only for grain. Percent N content immediately following flowering was much lower compared to percent N in the forage harvested prior to flowering, indicating relatively large losses of N after flowering. Averaged over locations and years, at the 90 kg N ha^?1 rate, wheat produced for forage had much higher NUE (82%) compared with grain production systems (30%). While gaseous N loss was not measured in this trial, the higher NUE values found in the forage production systems were attributed to harvesting prior to anthesis and the time when plant N losses are known to be greater.     

施硅提高玉米抗蚜性的组成型和诱导型生理代谢机制

  【目的】  禾谷缢管蚜 (Rhopalosiphum padi) 是危害玉米的主要害虫之一,其生长繁殖严重影响了玉米的产量和品质。分析施硅 (Si) 诱导玉米植株对蚜虫的抗性对玉米正常生长尤为重要。本研究从玉米抗氧化系统、次生代谢和信号传导途径3个方面,探究了施硅提高玉米抗蚜性的生理代谢机制。  【方法】  采用玉米水培试验方法,共设置4个处理:不施硅不接蚜虫 (–Si–A)、不施硅接蚜虫 (–Si+A)、施硅不接蚜虫 (+Si–A)、施硅接蚜虫 (+Si+A)。分别于蚜虫侵染后48、60、72、96、120 h,调查玉米植株蚜虫密度,并取样分析玉米植株抗氧化系统 (CAT、SOD、H₂O₂和MDA)、次生代谢 (PAL、PPO、LOX和木质素含量) 和信号传导物质 (JA、SA) 含量,以未接虫玉米3个系统中的相关成分含量为组成型抗性,以接虫前后各成分含量的差值为诱导型抗性,讨论了硅对玉米抗蚜组成型和诱导型抗性的影响。  【结果】  随着蚜虫侵染后时间的延长,蚜虫密度增加,与侵染后48 h相比,在–Si处理下,侵染后60～120 h时蚜虫数量显著增加了12.50%～40.18%;+Si处理下,侵染后60～120 h蚜虫数量显著增加了12.36%～49.44%;在侵染后48～120 h相同时间点下,与不施硅处理相比,施硅处理的蚜虫种群密度显著降低了15.29%～20.64%。整个培养时间内,与不施硅处理相比,施硅处理的玉米抗氧化系统中组成型CAT、SOD活性均显著提高,组成型H₂O₂、MDA含量分别降低了4.41%～15.35%、5.35%～17.95%,诱导型CAT活性显著增加 (除侵染后72 h外),诱导型SOD活性显著降低,诱导型H₂O₂含量先提高后降低;施硅处理显著提高了次生代谢中组成型PAL、LOX和PPO活性、木质素含量,降低了诱导型PPO活性、木质素含量,诱导型PAL活性表现为先提高后降低,诱导型LOX活性表现为先降低后升高随后又降低;施硅处理显著提高了信号传导中组成型JA、SA含量,增加了诱导型SA含量43.77%～117.48%,降低了诱导型JA含量。同一时间点,无论是否施硅,组成型CAT、SOD活性、H₂O₂和MDA含量、PAL、LOX和PPO活性、木质素、JA和SA含量均显著高于诱导型。PCA与相关性分析结果表明,组成型和诱导型CAT、SOD活性和诱导型H₂O₂、SA含量为体现玉米抗蚜虫的组成型和诱导型抗性的较优指标。  【结论】  施硅可显著降低蚜虫的密度,并显著提高玉米抗氧化系统、次生代谢和信号传导途径各物质的组成型与诱导型抗性,因此,施用硅肥为玉米田间蚜虫的生态调控提供了理论基础和科学依据。     

Tillering,nutrient accumulation,and yield of winter wheat as influenced by nitrogen form 1

When grown with mixtures of nitrate‐nitrogen (NO₃‐N) and ammonium‐nitrogen (NH₄‐N) (mixed N) spring wheat (Triticum aestivum L.) plants develop higher order tillers and produce more grain than when grown with only NO₃. Because similar work is lacking for winter wheat, the objective of this study was to examine the effect of N form on tillering, nutrient acquisition, partitioning, and yield of winter wheat. Plants of three cultivars were grown to maturity hydroponically with nutrient solutions containing N as either all NO₃, all NH₄, or an equal mixture of both forms. At maturity, plants were harvested; separated into shoots, roots, and grain; and each part analyzed for dry matter and chemical composition. While the three cultivars varied in all parameters, mixed N plants always produced more tillers (by a range of 16 to 35%), accumulated more N (28 to 61%), phosphorus (P) (22 to 80%), and potassium (K) (11 to 89%) and produced more grain (33 to 60%) than those grown with either form alone. Although mixed N‐induced yield increases were mainly the result of an increase in grain bearing tillers, there was cultivar specific variation in individual yield components (i.e., tiller number, kernels per tiller, and kernel weight) which responded to N form. The presence of NH₄ (either alone or in the mixed N treatment), increased the concentration of reduced N in the shoots, roots, and grain of all cultivars. The effect of NH₄ in either treatment on the concentrations of P and K was variable and depended on the cultivar and plant part. In most cases, partitioning of dry matter, P, and K to the root decreased when NH₄ was present, while partitioning of N was relatively unaffected. Changes in partitioning between the shoot and grain were affected by N treatment, but varied according to cultivar. Based on these data, the changes in partitioning induced by NH₄ and the additional macronutrient accumulation with mixed N are at least partially responsible for mixed‐N‐induced increases in tillering and yield of winter wheat.     

Effect of nitrogen rate on plant nitrogen loss in winter wheat varieties 1

Gaseous nitrogen (N) loss from winter wheat (Triticum aestivum L.) plants has been identified, but has not been simultaneously evaluated for several genotypes grown under different N fertility. Two field experiments were initiated in 1993 and 1994 at the Agronomy Research Station in Stillwater and Perkins to estimate plant N loss from several cultivars as a function of N applied and to characterize nitrogen use efficiency (NUE). A total of five cultivars were evaluated at preplant N rates ranging from 30 to 180 kg·ha^‐1. Nitrogen loss was estimated as the difference between total forage N accumulated at anthesis and the total (grain + straw) N at harvest. Forage, grain, straw yield, N uptake, and N loss increased with increasing N applied at both Stillwater and Perkins. Significant differences were observed among varieties for yield, N uptake, N loss, and components of NUE in forage, grain, straw, and grain + straw. Estimates of N loss over this two‐year period ranged from 4.0 to 27.9 kg·ha^‐1 (7.7 to 59.4% of total forage N at anthesis). Most N losses occurred between anthesis and 14 days post‐anthesis. Avoiding excess N application would reduce N loss and increase NUE in winter wheat varieties. Varieties with high harvest index (grain yield/total biomass) and low forage yield had low plant N loss. Estimates of plant loss suggest N balance studies should consider this variable before assuming that unaccounted N was lost to leaching and denitrification.     

两种冬小麦对铝毒响应的敏感性差异研究

A experiment was carried to evaluate the effects of Al on growth, accumulations of free proline and amino acid in 2 wheat cultivars (Triticum aestivum L.), Yangmai No.5 and Jian 864, differing in Al sensitivity. Plants grew initially in a nutrient solution without Al for 13 days before the addition of Al and finally in a nutrient solution containing 0.5mmol Al (L^-1) for 19 days. The results showed that there were marked decreases in dry weight, relative growth rate (RGR) and net assimilation rate (NAR) of Al-treated seedlings compared with control plants. The Al effects were more evident in Yangmai No.5 than Jian 864. Leaf area ratio(LAR) was little affected by Al. RGR was highly correlated with NAR rather than LAR. Aluminum increased the concentrations of free proline and total free amino acid in shoots of both the cultivars. The increases were greater in Yangmai No.5 than in Jian 864. The percentage of free proline in total amino acid in shoots was not affected by Al treatment. It was possible that accumulation of proline was merely a symptom of Al injury. The concentrations of total nitrogen in Al-treated plants did not significantly differ from those of control plants. Nitrate reductase activity (NRA) in leaves was severely decreased by Al, and a greater decrease was noted in Yangmai No.5 than in Jian 864, but NRA in roots of both the cultivars was not affected. The decreases in NRA might be an indirect (accumulation of amino acid) rather than a direct result of Al toxicity.     

Phytosiderophore release by Sorghum,wheat, and corn under zinc deficiency 1

Zinc (Zn) deficiency is more common in corn (Zea mays L.) than in sorghum [Sorghum bicolor (L.) Moench] or wheat (Triticum sp.). The ability of wheat to withstand low soil Zn conditions is related to increased release of phytosiderophore from its roots. The reasons for sorghum's ability and corn's inability to utilize low levels of soil Zn have not been explored adequately. The objectives of this research were to 1) ascertain if Zn deficiency could be induced in sorghum, wheat, and corn grown in a chelator‐buffered nutrient solution and 2) determine relative releases of phytosiderophore from roots of sorghum, wheat, and/or corn under Zn‐deficiency conditions. Sorghum, wheat, and corn were grown hydroponically in the greenhouse with a chelator‐buffered nutrient solution designed to induce Zn deficiency, while supplying adequate amounts of other nutrients. Root exudates were collected over time to measure phytosiderophore release. Shoot Zn concentrations and shoot and root dry matter yields were determined also. The technique was effective for inducing Zn deficiency in sorghum, wheat, and corn, as evidenced by reduced shoot and root dry matter yields, shortened internodes, reduced shoot Zn concentrations, and plant Zn concentrations below the suggested critical values for these species. Sorghum and wheat plants increased the release of phytosiderophore in response to Zn deficiency, but com did not. The total amount of phytosiderophore released by the roots was in the order wheat>sorghum>corn. The absence of a “phytosiderophore”; response to Zn deficiency of corn, coupled with the evidence that this species requires, or at least accumulates, more Zn than wheat or sorghum, provides an explanation as to why Zn deficiencies are more prevalent for corn than wheat or sorghum under field conditions.     

Bacterial inoculants for rice: effects on nutrient uptake and growth promotion

Beneficial soil bacteria are able to colonize plant root systems promoting plant growth and increasing crop yield and nutrient uptake through a variety of mechanisms. These bacteria can be an alternative to chemical fertilizers without productivity loss. The objectives of this study were to test bacterial inoculants for their ability to promote nutrient uptake and/or plant growth of rice plants subjected to different rates of chemical fertilizer, and to determine whether inoculants could be an alternative to nitrogen fertilizers. To test the interaction between putatively beneficial bacteria and rice plants, field experiments were conducted with two isolates: AC32 (Herbaspirillum sp.) and UR51 (Rhizobium sp.), and different nitrogen fertilization conditions (0%, 50%, and 100% of urea). Satisfactory results were obtained in relation to the nutrient uptake by plants inoculated with both isolates, principally when the recommended amount of nitrogen fertilizer was 50% reduced. These bacterial strains were unable to increase plant growth and grain yield when plants were subjected to the high level of fertilization. This study indicated that the tested inoculant formulations can provide essential nutrients to plants, especially when the levels of nitrogen fertilizers are reduced.     

Optimizing Vermicompost Concentrations for the N Nutrition and Production of the Legume Lupinus angustifolius

ABSTRACT

Vermicomposts (VCs) are the solid excreta of earthworms known to contain plant available nutrients, large amounts of microbial life and diversity, and plant growth regulating hormones. VCs may play an integral role in the nitrogen nutrition of Lupinus angustifolius and function to reduce the reliance of legume crops on chemical fertilizers. The aim of the present study was to determine the role of varying concentrations of chicken manure VC on the biomass production and N nutrition of the legume, L. angustifolius. The effect of increasing concentrations of VCs has been investigated, in conjunction with commercial rhizobia inoculum additions on the biomass yield of L. angustifolius. Plants were germinated and allowed to establish for 10 days in various mixtures of VC, rhizobia inoculum, and quartz sand under glasshouse conditions. After cultivation of a further 30 days, the plants were harvested and analyzed for tissue nutrient concentrations. The VC-containing substrates were assessed for wide-spectrum soil analyses and microbial diversity via Biolog EcoPlates. The combined treatments of 5% VC and rhizobia inoculation yielded the greatest biomass response. Furthermore, the addition of VC allowed for bacterial nitrogen fixation within non-rhizobia treatments. Nematode numbers and diversity grew with increases in VC concentrations, likely driven by similar increases in abundance of their microbial prey. However, changes in VC concentration had no effect on bacterial guild structure. In conclusion VC concentrations should be an important consideration for substrate nutrient availability, microbial abundance, and bacterial nitrogen fixation.     

Growth and Ca,Mg, K,and P uptake by triticale,wheat, and rye at four al levels

This study was conducted to determine relationships between Al toxicity and mineral uptake of triticale (X Triticosecale, Wittmack), wheat (Triticum aestivum L.), and rye (Secale cereale L.). Two culti‐vars of each species were grown in 1/5‐strength Steinberg solution with 0, 3, 6, or 12 ppm Al added. The solutions were adjusted to pH 4.8 at transplanting and were not adjusted thereafter. The plants were grown in a growth chamber for 19 days before harvesting to determine nutrient solution pH, dry weights, and Al, Ca, Mg, K, and P levels in plants. Increasing Al concentration reduced the final pH of solutions. The addition of 12 ppm Al severely reduced the growth and increased Al concentration of plant tops. The Al levels in roots generally increased with increments of added Al up to 6 ppm. Increasing Al decreased the uptake of Ca, Mg, and P by plant tops more than that of K. Regression analyses indicated that Al toxicity was associated with increasing K/Ca + Mg equivalent ratios and decreasing P concentration in plant tops. Differences between species were: higher Al concentration in rye than wheat with 6 and 12 ppm Al, higher translocation of Ca from roots to tops in wheat than in rye and Mg in triticale and wheat than rye; K/Ca + Mg equivalent ratios associated with 50% reduction in top growth followed the order: triticales > tolerant wheat > sensitive wheat > rye. Differences in mineral uptake associated with Al toxicity in wheat were more indicative of differential Al sensitivity in wheat than in triticale and rye which have higher internal Al tolerance.     

Effect of 6-methoxybenzoxazolin-2-one (MBOA) on the reproduction rate of the grain aphid (Sitobion avenae F.)

Partial host-plant resistance could make a substantial contribution to reducing the damage caused by economically important grain aphids and, therefore, to reduced insecticide use. Naturally occurring hydroxamic acids, in particular 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), have been shown to be involved in the resistance of cereals to insects. DIMBOA is unstable in aqueous solutions and has been reported to decompose to 6-methoxybenzoxazolin-2-one (MBOA). MBOA was tested on grain aphids living on artificial diet incorporated with MBOA. From 0 to 0.1 mM, the intrinsic rate of increase (rm) increased. From 0.1 to 0.3 it decreased by 73%. The rm was calculated to be 0 at 1.0 mM. Consequently, even low concentrations of MBOA may reduce the aphid multiplication to a level below the economic damage threshold. Therefore, it is possible to breed wheat varieties with a sufficiently high content of DIMBOA to decrease grain aphid populations.