240份玉米自交系纹枯病抗性鉴定与评价

在人工接种条件下,连续3年对240份玉米自交系纹枯病抗性进行鉴定和评价,分析了玉米纹枯病抗性与主要农艺性状的相关性。结果表明,玉米纹枯病抗性资源较为缺乏,240份自交系中无免疫或高抗的材料,有中抗自交系4份、感病自交系18份、高感自交系218份。旅大红骨、Reid、PA和塘四平头类群自交系中未发现玉米纹枯病抗源,PB类群和Lancaster类群自交系纹枯病抗性相对较好,今后应主要从这两类种质中寻找玉米纹枯病抗源。玉米纹枯病病情指数与株高、穗位高、穗位高/株高、穗下节间数和穗下平均节间长均呈极显著负相关,这些表型可以作为非接种条件下筛选抗玉米纹枯病种质的参考指标。     

基于相对叶绿素含量的玉米自交系氮敏感性鉴定与评价

氮敏感性鉴定与评价是培育耐低氮与氮高效利用玉米品种的重要的研究内容。本研究采用前期建立的快速无损伤测定SPAD值分析相对叶绿素含量的模型,于低氮与正常供氮大田试验处理下,对我国玉米育种与生产上重要的 189 份玉米自交系开展了低氮与正常供氮条件下不同时期与不同部位叶片的相对叶绿素含量分析。方差分析结果表明,低氮与正常供氮条件下,叶绿素含量均存在极显著的基因型与环境差异,基因型差异是氮敏感性差异的重要原因之一。开花期和开花后10天玉米主要功能叶穗三叶(穗位上第1叶、穗位叶、穗位下第1叶)叶绿素含量之间具有极显著正相关;大喇叭口期玉米全展叶叶绿素含量与各时期各部位叶绿素含量之间呈现极显著中度相关。将正常供氮条件下的性状值与低氮胁迫下性状值的差值占正常供氮条件下性状值的百分比定义为氮敏感性。189份玉米自交系氮平均氮敏感指数变幅为23.86%- 36.00%,表现高度耐低氮的材料有合344和昌7-2等40份自交系,高度敏感的材料有CML206和CA375等40份自交系。本研究提供了一种快速高效的种质资源氮敏感性鉴定与评价方法,并为玉米耐低氮与氮高效育种的遗传育种提供了重要分析结果与基础数据。     

玉米鼠耳病及其媒介昆虫二点叶蝉消长动态和玉米受害损失测定

对四川省南充市仪陇县二点时蝉及其所传播的玉米鼠耳病的田间消长规律以及玉米受害后的产量损失状况进行了研究。结果表明：温度低于16℃时,玉米不发病;28℃和31℃时玉米鼠耳病的潜伏期较短,分别为4．85和4．64d。在高、中、低3个海拔高度上,玉米鼠耳病的田间消长动态受二点叶蝉种群发生动态的影响,并于5月下旬至6月上旬达到最大病情指数,分别为5．75、10．97和9．09。玉米的生长和产量均受到玉米鼠耳病发生程度的影响,随着该病病级的上升,玉米株高、地面直径、穗长、穗粗、穗粒数、穗粒重及千粒重均相应下降。通过二元线性回归方程对玉米单穗籽粒重损失率作通径分析,表明在玉米的产量构成中．千粒重下降是导致产量损失的主要因子。     

刈割、施肥和浇水对垂穗披碱草补偿生长的影响

植物的补偿生长特性受放牧强度和生境资源获得性的影响。通过为期2年的野外控制实验,研究了刈割高度(留茬1cm、3cm及不刈割)、施肥(施、不施)和浇水(浇、不浇)处理对垂穗披碱草(Elymus natans)补偿生长的影响,并结合对各处理分株密度、比叶面积、净光合速率和相对生长率的变化研究,探讨了其补偿生长机制。结果表明:刈割后垂穗披碱草分株种群密度显著增加,补偿生长高度显著降低,比叶面积和相对生长率随刈割强度增加而呈上升趋势,叶片净光合速率变化不显著;施肥能显著增加垂穗披碱草的补偿生长高度、比叶面积、叶片净光合速率和相对生长率;浇水处理以及刈割、浇水、施肥处理之间的交互作用均不显著。可见,在刈割条件下,垂穗披碱草具有一定的密度补偿机制,但由于刈割抑制补偿性高生长,导致分株高度出现低补偿。因此,即使刈割后比叶面积和株高相对生长率显著增加,也不一定必然引起株高的超补偿;但施肥可显著提高垂穗披碱草的补偿能力,增加耐牧性,证实了改进后的限制资源模型的预测。     

内蒙古中东部草原不同生境克氏针茅（Stipa krylovii Roshev.）种群的形态差异分析

对内蒙古中东部草原分布的克氏针茅进行了种群内和种群间的形态差异分析。结果表明：（1）种群内不同的形态性状存在不同程度的差异;（2）种群间生殖枝中的一部分形态性状以及营养枝高度和营养枝干重均存在较大差异;（3）每穗小花数、每穗籽粒数、每穗小穗数、生殖枝高、穗干重、生殖枝干重、每穗种子重、种子重/生殖枝重比等性状的变化趋势相同,均表现为随生境条件变差而增加,即在生殖上投入增加以增大适合度;（4）主成分分析表明穗长、种子重/生殖枝重比、每穗小花数、每穗籽粒数、生殖枝高、基盘长、第二芒柱长、营养枝高、千粒重、芒针长是不同种群差异的主要指标。这些形态性状的差异可以看作克氏针茅对不同生境的适应性表现。     

栽培模式和复合肥类型对隆平206农艺性状及干物质积累的影响

该研究用双因素裂区设计,在四种栽培模式和两种类型复合肥条件下,分析了玉米杂交种隆平206的农艺性状及干物质积累的影响。隆平206的株高、生长率均在等行距和宽窄行间差异不显著,但与等行距一穴两株间差异显著;穗位高在等行距和宽窄行[(70+50)cm]间差异不显著,但与宽窄行[(90+30)cm]和等行距一穴两株间差异显著;茎粗在各处理间差异不显著,栽培模式对隆平206穗位上第1叶和穗下第1叶的叶夹角影响显著,对穗上第1叶的叶向值影响显著,对穗下第1叶的叶向值影响不显著,对不同时期穗位节和穗位上节的茎杆强度影响差异显著,对不同时期干物质积累影响差异显著。隆平206在宽窄行[(90+30)cm],地富原玉米专用复合肥时,隆平206农艺性状各指标达最佳状态,栽培模式对隆平206不同时期干物质积累影响差异显著,在拔节期、大喇叭口期、开花期、乳熟期、成熟期,隆平206在栽培模式宽窄行(70+50)cm时干物质积累量均最大。该研究结果为玉米杂交种隆平206的栽培管理和施肥提供了依据。     

1973-2009年中国玉米品种演替过程中根系性状及其对氮的响应的变化

根系在氮素高效吸收过程中起重要作用,但人们对玉米育种过程中不同年代杂交种的根系生长特性及其对氮素供应的响应了解较少．选用中国1973．2009年育成的11个代表性玉米品种,在水培体系下研究了正常供氮（4retool／L）和低氮（0．04mmol／L）下根系与地上部生长差异．结果表明,与低氮处理相比,正常供氮降低根干重、根冠比和根系相对生长速率,但增加总根长和侧根长．对于20世纪90年代之前育成品种,供氮还降低总轴根长．氮处理不影响种子根数．随育种年代演进,地上部相对生长速率表现明显增加,不同氮水平下表现一致．但是,根系相对生长速率仅在正常供氮条件下表现出与育成年代线性相关．相应地,只在正常供氮条件下玉米总根长、侧根长、轴根长表现为随育成年代增加而明显增加．因此,在过去36年的玉米育种进程中,玉米地上部生长势在不同氮供应水平下均得到提高,而根系生长则只在正常供氮条件下得到提高．进一步改良根系在低氮环境下的生长能力可能提高现代玉米品种的氨吸收效率．     

云南两个不同生态区玉米蚜种群动态研究

在2013年5-9月,采取5点取样,对云南省昭通温凉玉米种植区及普洱暖热玉米种植区玉米蚜种群动态进行定期、定点、定株的系统调查,明确云南省两种不同生态条件下玉米种植区玉米蚜发生规律及分布特征,为玉米蚜的防治提供理论依据。结果显示:昭通温凉玉米种植区玉米蚜在玉米各生育期均有发生;玉米蚜在抽雄散粉期主要集中在雄穗为害,籽粒建成期以后转移集中在苞叶及雌穗为害;玉米蚜在玉米田始终呈聚集分布,聚集度呈聚集—扩散—聚集趋势。普洱暖热玉米种植区玉米蚜种群数量在玉米进入籽粒建成期后才有所增长;玉米蚜在籽粒建成期以后主要集中在苞叶及雌穗上为害;玉米蚜在玉米田基本呈聚集分布,聚集度始终呈扩散趋势。两地玉米蚜自然种群消长、垂直分布动态,空间动态均具有一定差异,昭通温凉玉米种植区相对更适宜玉米蚜的发生。     

玉米籽粒重金属铅(Pb2+)含量的QTL定位

铅(Pb²⁺)是现存环境最大量的有毒重金属污染元素,在我国特别是西南地区种植的玉米受重金属Pb²⁺污染日益严重,已严重影响到食物安全。文章利用玉米籽粒Pb²⁺低富集自交系178和籽粒Pb²⁺高富集自交系9782杂交衍生的重组自交系群体为作图群体,利用165对SSR多态性标记,构建了总长度为1499.85 cM、标记间平均距离为9.07 cM的分子遗传图谱,对玉米籽粒Pb²⁺含量性状进行了QTL定位分析,以期为选育籽粒低富集Pb²⁺的玉米新品种提供参考。结果表明,在Pb²⁺浓度为333.32 mg/kg胁迫下,共检测到2个与籽粒Pb²⁺含量相关的QTL,分别位于玉米第1、第4号染色体,其中qPC1位于标记区间umc1661~phi002h之间,表型贡献率为11.13%,加性效应为0.062;qPC4位于umc1117~nc005之间,表型贡献率为5.55%,加性效应为-0.044。性状相关分析结果表明,籽粒中Pb²⁺含量与穗长、穗粗、行粒数、穗重和百粒重等产量性状间均未达到显著水平,表明选育玉米籽粒Pb²⁺低富集的新自交系或杂交种不一定会影响到产量性状,而且籽粒Pb²⁺含量是一个相对独立的遗传性状。     

红穗苔草对天鹅洲湿地淹水时间变化的形态学响应

以天鹅洲湿地的优势种红穗苔草（Carex argyi）作为研究对象,以淹水持续时间作为水位变化的衡量指标,选取3个淹水持续时间不同的位点,研究了淹水时间长短对红穗苔草形态指标的影响。通过野外原位观测试验发现,红穗苔草的株高及叶片的长、宽对淹水时间的长短反应敏感,而单个分株上的绿叶数对淹水时间的长短不敏感。适度的淹水可以显著增加叶片的长度和株高,长期淹水和相对干旱的环境不利于叶片的伸长和株高的增加。短时间淹水处理株高一直维持较高的水平,并保持相对的稳定。淹水会显著增加叶片的宽度,长时间淹水的处理效果更明显,且维持时间较长。长期淹水会提高红穗苔草地上部生物量的分配比例。尽管不同水位点土壤氮含量有显著差异,但是氮对红穗苔草形态指标并无显著的影响。以上实验结果表明,红穗苔草可以通过调节其叶片的形态及地下和地上部分生物量的分配比例来适应淹水胁迫的不利环境,有利于其在水位波动条件下种群的稳定和维持。     

Effects of drought-rewatering-drought on photosynthesis and growth of maize

Aims Our objective was to investigate the responses of maize photosynthesis and growth to repeated drought.Methods Maize seedlings were exposed to different soil water deficit for three weeks, then rewatering for one week, and again to different water deficit for three weeks, to examine the effects of repeated drought on photosynthesis and growth.Important findings After the first water deficit treatments, under severe drought, plant height, total leaf area of individual plant, shoot and root biomass declined significantly, also transpiration rate (T_r), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), net photosynthetic rate (P_n), maximum net photosynthetic rate (A_max), but light compensation point and dark respiration rate increased significantly. Under medium drought, plant height, leaf area, and shoot biomass decreased significantly, but root biomass did not vary, hence, the ratio of roots to shoots (R/S) increased. Moreover, plants did not show significant differences in photosynthetic parameters. After rewatering, photosynthesis and growth rate of plants previously exposed to water deficit could recover to the levels of well-watered plants, but plant height and leaf area did not recover to the levels of the control. When maize were subjected to recurrent drought, plants pre-exposed to medium drought showed no significant difference in plant height, biomass, and photosynthetic parameters, but a significant decrease in leaf area, compared to plants only exposed to second medium drought. Plants pre-exposed to severe drought had significantly higher T_r, G_s, C_i, P_n, A_max, and, apparent quantum yield but significantly lower plant height, leaf area, and biomass than plants without previous exposure. These results indicated that the first severe drought significantly reduced photosynthetic capacity and maize growth, rewatering could recover photosynthesis and growth rate to the levels of well-watered plants, but could not eliminate the adverse influence of the first drought on growth. The first medium drought could stimulate the growth of maize root system and significantly increased R/S, which can enhance maize drought resistance to subsequent repeated drought, and maintain the total biomass in the control level; the first severe drought could enhance maize drought resistance to subsequent repeated drought in the aspect of photosynthesis, but could not compensate for the adverse effect of early drought on plant growth. Hence, in practice, drought hardening should be limited in the level of medium drought, and avoiding severe drought.     

干旱-复水-再干旱处理对玉米光合能力和生长的影响

为了探求玉米(Zea mays)光合作用和生长对重复干旱的响应机制, 采用盆栽试验, 分别测定了不同程度土壤干旱处理3周时、随后复水1周时以及再次不同程度干旱处理3周时玉米幼苗光合参数和生长的变化。第一次土壤干旱处理后, 重度干旱处理显著降低玉米株高、单株总叶面积、地上部分及根系生物量以及叶片的蒸腾速率(T_r)、气孔导度(G_s)、胞间CO₂浓度(C_i)、净光合速率(P_n)和最大净光合速率(A_max), 但显著提高光补偿点和暗呼吸速率; 中度干旱处理同样显著降低玉米株高、叶面积和地上部分生物量, 但对根系生物量无影响, 因而根冠比增大, 对上述光合参数的负效应也不具有显著性。复水可使前期经受中度和重度干旱处理的玉米植株的光合能力和生长速率恢复到正常水分条件下生长的植株的水平, 但株高和叶面积没有恢复到对照水平。当玉米再次经受水分亏缺处理时, 与只遭受第二次中度或重度干旱处理的植株相比, 经历过前期中度干旱处理的植株的株高、生物量和光合参数没有显著变化, 但叶面积显著下降; 经历过前期重度干旱处理植株的T_r、G_s、C_i、P_n、A_max和表观量子效率显著升高, 而株高、叶面积和生物量显著降低。综上所述, 第一次重度干旱处理显著降低玉米叶片的光合能力和生长, 复水可使光合能力和生长速率恢复到正常水分条件下生长植株的水平, 但不能消除前期干旱对生长产生的不利影响。前期中度干旱可以刺激玉米根系的生长和显著提高根冠比, 有利于提高对二次干旱的抵抗能力, 并使总的生物量保持在对照水平, 而前期重度干旱处理虽然在光合作用上能提高植株对二次干旱的抵御能力, 但不能弥补前期干旱处理对生长的不利影响。因此, 在生产实践中, 如果进行抗旱锻炼, 应限制在中度干旱水平, 避免重度干旱。     

特异性适应稻作系统的稗草种群生活史特性

长期进行除草剂药效试验可能会导致田间杂草种群发生适应性进化。本研究在安徽南陵县除草剂药效试验专用稻田中采集了1个稗草种群A,并以从常规稻田采集的3个稗草种群为对照,开展同质园栽培试验。结果表明: 与3个对照种群相比,A种群稗草植株的单株种子产量显著减少,种子千粒重显著增加,幼苗生长速率显著加快,结实分蘖数显著增多,生育期显著缩短;A种群稗草成株的株高、生物量及对除草剂五氟磺草胺的敏感性均显著降低。A种群稗草幼苗3～4叶期时经五氟磺草胺推荐剂量2倍量(有效成分60 g·hm^-2)处理后,其株高、生物量及成熟种子产量(平均每株1066粒)显著降低,而抽穗期、结实分蘖数、单个总状花序的种子数及种子千粒重无显著差异。因此,种子较重、生活史周期短、植株矮小、结实分蘖多及对除草剂五氟磺草胺具有抗药性,使得A种群稗草对稻作系统具有特异适应性,应防止此类种群扩散至常规稻田。     

Jasmonic acid as modulator of lead toxicity in aquatic plant Wolffia arrhiza (Lemnaceae)

The present study was undertaken to test the influence of exogenously applied jasmonic acid (JA) upon the growth and metabolism of Wolffia arrhiza (Lemnaceae), the smallest vessel aquatic plant exposed to lead (Pb) stress. It was found, that JA acted in a concentration-dependent manner. Treatment with JA at the highest concentration 100 μM resulted in the enhancement of heavy metal toxicity leading to increase in metal biosorption and formation of lipid peroxides as well as decrease in fresh weight, chlorophyll a, carotenoid, monosaccharide and soluble protein content. In contrast, this phytohormone applied at 0.1 μM protected W. arrhiza fronds against Pb stress inhibiting heavy metal accumulation, restoring plant growth and primary metabolite level. Moreover, JA at 0.1 μM activated enzymatic (catalase, ascorbate peroxidase, NADH peroxidase) and non-enzymatic antioxidant (ascorbate, glutathione) system in W. arrhiza, and therefore, suppressed oxidative destruction of cellular components induced by heavy metal. The data suggest that JA plays an important role in the growth and metabolism of W. arrhiza exposed to abiotic stressor and its high adaptation ability to metal contamination of aquatic environment.     

Jasmonic acid as modulator of lead toxicity in aquatic plant Wolffia arrhiza (Lemnaceae)

The present study was undertaken to test the influence of exogenously applied jasmonic acid (JA) upon the growth and metabolism of Wolffia arrhiza (Lemnaceae), the smallest vessel aquatic plant exposed to lead (Pb) stress. It was found, that JA acted in a concentration-dependent manner. Treatment with JA at the highest concentration 100 μM resulted in the enhancement of heavy metal toxicity leading to increase in metal biosorption and formation of lipid peroxides as well as decrease in fresh weight, chlorophyll a, carotenoid, monosaccharide and soluble protein content. In contrast, this phytohormone applied at 0.1 μM protected W. arrhiza fronds against Pb stress inhibiting heavy metal accumulation, restoring plant growth and primary metabolite level. Moreover, JA at 0.1 μM activated enzymatic (catalase, ascorbate peroxidase, NADH peroxidase) and non-enzymatic antioxidant (ascorbate, glutathione) system in W. arrhiza, and therefore, suppressed oxidative destruction of cellular components induced by heavy metal. The data suggest that JA plays an important role in the growth and metabolism of W. arrhiza exposed to abiotic stressor and its high adaptation ability to metal contamination of aquatic environment.     

Effect of increased temperature in apical regions of maize ears on starch-synthesis enzymes and accumulation of sugars and starch

Apical florets of maize (Zea mays L.) ears differentiate later than basal florets and form kernels which have lower dry matter accumulation rates. The purpose of this study was to determine whether increasing the temperature of apical kernels during the dry matter accumulation period would alter the difference in growth rate between apical and basal kernels. Apical regions of field-grown maize (cultivar Cornell 175) ears were heated to 25 ± 3°C from 7 days after pollination to maturity (tip-heated ears) and compared with unheated ears (control). In controls, apical-kernel endosperm had 24% smaller dry weight at maturity, lower concentration of sucrose, and lower activity of ADP-Glc starch synthase than basal-kernel endosperm, whereas ADP-Glc-pyrophosphorylase (ADPG-PPase) activities were similar. In tip-heated ears apical-kernel endosperm had the same growth rate and final weight as basal-kernel endosperm and apical kernels had higher sucrose concentrations, higher ADP-Glc starch synthase activity, and similar ADPG-PPase activity. Total grain weight per ear was not increased by tip-heating because the increase in size of apical kernels was partially offset by a slight decrease in size of the basal- and middle-position kernels. Tip-heating hastened some of the developmental events in apical kernels. ADPG-PPase and ADP-Glc starch synthase activities reached peak levels and starch concentration began rising earlier in apical kernels. However, tip-heating did not shorten the period of starch accumulation in apical kernels. The results indicate that the lower growth rate and smaller size of apical kernels are not solely determined by differences in prepollination floret development.     

Determining rates of change and evaluating group-level resiliency differences in hyporheic microbial communities in response to fluvial heavy-metal deposition

Prior field studies by our group have demonstrated a relationship between fluvial deposition of heavy metals and hyporheic-zone microbial community structure. Here, we determined the rates of change in hyporheic microbial communities in response to heavy-metal contamination and assessed group-level differences in resiliency in response to heavy metals. A controlled laboratory study was performed using 20 flowthrough river mesocosms and a repeated-measurement factorial design. A single hyporheic microbial community was exposed to five different levels of an environmentally relevant metal treatment (0, 4, 8, 16, and 30% sterilized contaminated sediments). Community-level responses were monitored at 1, 2, 4, 8, and 12 weeks via denaturing gradient gel electrophoresis and quantitative PCR using group-specific primer sets for indigenous populations most closely related to the alpha-, beta-, and gamma-proteobacteria. There was a consistent, strong curvilinear relationship between community composition and heavy-metal contamination (R(2) = 0.83; P < 0.001), which was evident after only 7 days of metal exposure (i.e., short-term response). The abundance of each phylogenetic group was negatively affected by the heavy-metal treatments; however, each group recovered from the metal treatments to a different extent and at a unique rate during the course of the experiment. The structure of hyporheic microbial communities responded rapidly and at contamination levels an order of magnitude lower than those shown to elicit a response in aquatic macroinvertebrate assemblages. These studies indicate that hyporheic microbial communities are a sensitive and useful indicator of heavy-metal contamination in streams.     

Root development and heavy metal phytoextraction efficiency: comparison of different plant species in the field

Heavy metal phytoextraction is a soil remediation technique which implies the optimal use of plants to remove contamination from soil. Plants must thus be tolerant to heavy metals, adapted to soil and climate characteristics and able to take up large amounts of heavy metals. Their roots must also fit the spatial distribution of pollution. Their different root systems allow plants to adapt to their environment and be more or less efficient in element uptake. To assess the impact of the root system on phytoextraction efficiency in the field, we have studied the uptake and root systems (root length and root size) of various high biomass plants (Brassica juncea, Nicotiana tabacum, Zea mays and Salix viminalis) and one hyperaccumulator (Thlaspi caerulescens) grown in a Zn, Cu and Cd contaminated soil and compared them with total heavy metal distribution in the soil. Changes from year to year have been studied for an annual (Zea mays) and a perennial plant (Salix viminalis) to assess the impact of the climate on root systems and the evolution of efficiency with time and growth. In spite of a small biomass, T. caerulescens was the most efficient plant for Cd and Zn removal because of very high concentrations in the shoots. The second most efficient were plants combining high metal concentrations and high biomass (willows for Cd and Zn and tobacco for Cu and Cd). A large cumulative root density/aboveground biomass ratio (L_A/B), together with a relative larger proportion of fine roots compared to other plants seemed to be additional favourable characteristics for increased heavy metal uptake by T. caerulescens. In general, for all plants correlations were found between L _A/B and heavy metal concentrations in shoots (r=0.758^***, r=0.594^***, r=0.798^*** (P<0.001) for Cd, Cu and Zn concentrations resp.). Differences between years were significant because of variations in climatic conditions for annual plants or because of growth for perennial plants. The plants exhibited also different root distributions along the soil profile: T. caerulescens had a shallow root system and was thus best suited for shallow contamination (0.2 m) whereas maize and willows were the most efficient in colonising the soil at depth and thus more applicable for deep contamination (0.7 m). In the field situation, no plant was able to fit the contamination properly due to heterogeneity in soil contamination. This points out to the importance and the difficulty of choosing plant species according to depth and heterogeneity of localisation of the pollution.     

A Challenge for the Seed Mixture Refuge Strategy in Bt Maize: Impact of Cross-Pollination on an Ear-Feeding Pest,Corn Earworm

To counter the threat of insect resistance, Bacillus thuringiensis (Bt) maize growers in the U.S. are required to plant structured non-Bt maize refuges. Concerns with refuge compliance led to the introduction of seed mixtures, also called RIB (refuge-in-the-bag), as an alternative approach for implementing refuge for Bt maize products in the U.S. Maize Belt. A major concern in RIB is cross-pollination of maize hybrids that can cause Bt proteins to be present in refuge maize kernels and negatively affect refuge insects. Here we show that a mixed planting of 5% nonBt and 95% Bt maize containing the SmartStax traits expressing Cry1A.105, Cry2Ab2 and Cry1F did not provide an effective refuge for an important above-ground ear-feeding pest, the corn earworm, Helicoverpa zea (Boddie). Cross-pollination in RIB caused a majority (>90%) of refuge kernels to express ≥ one Bt protein. The contamination of Bt proteins in the refuge ears reduced neonate-to-adult survivorship of H. zea to only 4.6%, a reduction of 88.1% relative to larvae feeding on ears of pure non-Bt maize plantings. In addition, the limited survivors on refuge ears had lower pupal mass and took longer to develop to adults.     

The effect of endophytic Peyronellaea from heavy metal-contaminated and uncontaminated sites on maize growth,heavy metal absorption and accumulation

Heavy metal (HM) tolerance, effects on maize growth, heavy metal absorption and accumulation by endophytic Peyronellaea from HM-contaminated and uncontaminated sites were studied to evaluate the hypothesis that endophytes from HM-contaminated sites would enhance HM-tolerance in hosts. Although we found that certain endophytes improved tolerance of plants to heavy metals, isolates from the HM-contaminated site were not more tolerant to heavy metals than those from the uncontaminated site. Pot experiments indicated that growth and heavy metal absorption and accumulation by host plants in HM-polluted environments could be affected by inoculation with HM-tolerant endophytic fungi, and isolates showed a high intraspecific variability. However, there was no significant difference in growth between the maize inoculated with the endophytes from the HM-contaminated site and uncontaminated site under lead stress. Similarly, the HM content in the shoots and roots of maize inoculated with the isolates from the HM-contaminated site was not always higher than that in maize inoculated with endophytes from the uncontaminated site. Therefore, based on our experiments it is suggested that HM-tolerance due to endophytes and their effects on host plant growth and heavy metal absorption and accumulation were not correlated with origin of the endophytes.