旱地小麦理想株型与生长冗余

自1968年Donald提出作物理想株型(ideotype)以来,众多学者在如何减少生长冗余、塑造理想株型方面做了大量努力,在旱地小麦育种策略和栽培管理模式创新方面取得了一定进展。而该方面的进展有限,不同领域的研究者对理想株型和生长冗余的认识存在严重分歧。综述了近年来旱地小麦理想株型研究进展,以过去20年黄土高原雨养农业区的观测数据为主进行了集成分析,将产量分别与根系生物量、地上生物量和株高等指标进行回归分析,勾画了旱地小麦在根系、茎秆和分蘖等器官中生长冗余的演变趋势,对生长冗余产生的生态学机制展开了分析,并对理想株型与生长冗余的互作关系进行了讨论。已有的研究进展表明,旱地小麦理想株型演变是一个不断消减生长冗余,但又无法完全消除冗余的复杂过程,一定程度的冗余存在是理想株型发生的物质基础。旱地小麦理想株型育种必须以基因型和环境互作关系为基础,通过减少个体间的竞争强度和个体大小不整齐性,促进物质和能量更多地向籽粒迁移,最终提高种群产量。综上所述,旱地小麦理想株型选择需建立在生长冗余理论基础上,根据生态学基本原理对基因型和表现型进行耦合分析与选择权衡。     

宁夏引黄灌区秸秆还田对麦田土壤硝态氮淋失的影响

以宁夏引黄灌区为例,探索秸秆还田条件下冬小麦土壤硝态氮淋失规律。试验设置常规施肥(CK)、常规施肥条件下施用4500kg/hm2(T1,半量还田)和9000 kg/hm2(T2,全量还田)秸秆3个处理。利用树脂芯法吸附10、20、30、60cm和90cm土层的硝态氮流失量。结果表明:硝态氮(纯N)淋失量6.26—12.85 kg/hm2,是冬小麦施用化肥氮量的2.78%—5.71%。与对照CK相比,T1和T2在10cm土层减少0.09%和3.97%;20cm土层减少8.51%和9.81%;30cm土层减少2.25%和10.34%;60cm土层减少23.85%和13.08%;90cm土层减少27.65%和20.73%。10cm和20cm土层,处理与对照以及处理之间均未到显著性差异(P0.05);30cm处理,T1与CK以及T1与T2未达到显著性差异,但T2与CK达到显著性差异表明全量还田效果最好;60cm土层,处理与对照、以及处理之间均达到显著性差异;90cm土层,处理与对照之间达到显著性差异,处理之间未达到显著性差异。硝态氮淋失主要发生在冬小麦返青至灌浆期间,占全生育期淋失量的52.95%—67.79%。T1、T2冬小麦产量增产率分别为10.11%与11.51%。可见,稻秆还田能够减少灌区土壤硝态氮淋失量。     

窄行匀播对晚播冬小麦群体环境、个体性状和物质生产的影响

为了明确行距和行内种子分布形式对华北平原晚播冬小麦群体生长的影响,以济麦22为试验材料,在晚播条件下设置3种行距(10、15、20 cm)和2种行内种子分布形式[随机分布(R)和均匀分布(A)]处理,考察了不同处理冬小麦的冠层结构与环境特征、个体性状、生物量累积及产量性能。结果表明:在相同播种量下较小行距比较大行距、种子均匀分布比非均匀分布群体叶面积较大,冠层下部漏光较少,温度较低且相对湿度较高;缩小行距或增加行内种子分布均匀度使群体内个体间植株性状差异缩小,穗层分布趋向均匀,花后物质积累量增加,穗粒重增加,最终产量提高。10 cm行距的产量高于15 cm行距、显著高于20 cm行距;在15 cm和20 cm行距下植株均匀分布处理产量显著高于非均匀分布处理的产量。综合研究认为,窄行匀播是华北平原干旱缺水地区提高晚播小麦群体产量的有效措施。     

植物维生素B_6从头合成与代谢转换研究进展

维生素B6是一组可相互转换的吡啶衍生物的总称,包括吡哆醇、吡哆胺、吡哆醛、磷酸吡哆醇、磷酸吡哆胺和磷酸吡哆醛。其中,磷酸吡哆醛是140多种细胞酶的辅酶。至今发现两种VB6从头合成途径,DXP(1-脱氧-D-木酮糖-5-磷酸)依赖途径和DXP非依赖途径,前者仅存在于大肠杆菌和少量其他细菌,后者存在于其他所有VB6自养生物。除了VB6的从头合成,所有细胞生物体内还存在一条相似的补救途径,补救途径实现VB6各型的代谢转换。该文对近年来国内外有关植物VB6从头合成和代谢转换研究进展进行综述。     

屋面绿化卷材根系层土壤温度变化特征

根据3种厚度屋面绿化卷材根系层土壤温度、自然条件下的土壤温度和附近气象站大气温度观测资料,采用对比分析、线性回归等方法,对不同屋面绿化卷材根系层土壤温度的变化特征进行了研究。结果表明:屋面绿化卷材根系层土壤温度年变化规律与大气温度年变化规律基本一致;卷材具有一定的隔热保温作用,且随着薄膜厚度的增加,绿化卷材保温隔热效果越明显;不同型号卷材根系层土壤温度的日变幅随薄膜厚度的增加而减小;根系层土温日变幅与厚度关系可拟合成指数函数;不同厚度屋面卷材根系层土壤温度同大气温度之间均存在极显著的线性关系。     

调亏灌水和分蘖干扰对冬小麦生长的补偿效应

为探索抑制个体功能的生长冗余以实现群体性能优化并挖掘作物高产潜力的途径,通过桶栽试验,选择分蘖能力中等的小偃22号和分蘖能力较强的郑麦7698,对比研究2种灌水模式（全生育期充分灌水和分生育期调亏灌水）和3种分蘖干扰（从拔节期开始去除所有小分蘖,仅保留主茎和1个大分蘖;抽穗期去除所有无效分蘖;以不作任何干扰为对照）,来模拟不同水分供应和不可预测干扰对冬小麦生理生长、产量和水分利用效率的补偿机制.结果表明： 2个冬小麦品种均存在生长冗余.与小偃22号相比,郑麦7698有效分蘖数较高,但穗部性状较差.调亏灌水和抽穗期去除无效分蘖均可减少生长冗余,弱化竞争能力,改变源 库关系,提高资源分配.但冗余消除过度（拔节期干扰）则会破坏植株固有的根冠平衡和功能结构,导致生长的不足补偿.与对照相比,调亏灌水联合抽穗期去除无效分蘖可在时空尺度上充分开发和利用作物自身调控潜力实现补偿生长,在不显著影响籽粒产量的同时可提高水分利用效率20.4%～25.4%,是适宜的减冗增效措施.     

未来气候变化对河南省冬小麦需水量和缺水量的影响预估

采用美国农业部土壤保持局推荐的方法计算有效降水量,应用Penman-Monteith模型和作物系数法计算需水量,在对河南省1981—2010年冬小麦生育期内有效降水量、需水量和缺水量分析的基础上,结合《排放情景特别报告》的两种排放情景A2(强调经济发展)和B2(强调可持续发展)预估的未来气候情景,探讨了未来气候情景下河南省冬小麦的有效降水量、需水量和缺水量的时空演变规律及其主要气候影响因素.结果表明: 从整体上看,相对于基准时段(1981—2010年),A2和B2情景下,不同时段冬小麦全生育期的有效降水量、需水量和缺水量均表现出增加趋势,有效降水量均以2030s时段增加最多,分别增加33.5%和39.2%;需水量均以2010s时段增加最多,分别增加22.5%和17.5%,年代间呈现明显递减趋势;缺水量在A2情景下以2010s时段增加(23.6%)最多,B2情景下以2020s时段增加(13.0%)最多.偏相关分析表明,A2和B2情景下,太阳总辐射是影响河南省冬小麦需水量和缺水量变化的主要气候因素.由于地理环境和气候条件的差异,不同时段河南省冬小麦全生育期有效降水量、需水量和缺水量的距平百分率在空间分布上具有差异.未来河南省水资源可能更趋于短缺.     

种植密度和施氮水平对小麦吸收利用土壤氮素的影响

2011-2013小麦季,在大田条件下设置2个氮肥水平(180和240kgN· hm-2)和3个种植密度(135、270和405万·hm-2),并将15N-尿素分别标记在20、60和100 cm土层处,研究种植密度-施氮互作对小麦吸收、利用土壤氮素及硝态氮残留量的影响.结果表明:种植密度从135万·hm-2增加至405万·hm-2,小麦在20、60和100 cm土层的15N吸收量分别增加1.86、2.28和2.51 kg·hm-2,地上部氮素积累量和吸收效率分别提高12.6％和12.6％,氮素利用效率降低5.4％;施氮量由240 kg N·hm-2降至180 kg N·hm-2,小麦在20、60 cm土层的15N吸收量分别降低4.11和1.21 kg·hm-2,在100 cm土层的15N吸收量增加1.02 kg·hm-2,地上部氮素积累量平均降低13.5％,氮素吸收效率和利用效率分别提高9.4％和12.2％.施氮180kg N·hm-2+种植密度为405万·hm-2处理与施氮240 kg N·hm-2+种植密度为270或405万·hm-2处理相比,其籽粒产量无显著差异,深层土壤氮素的吸收量显著提高,氮素吸收效率和利用效率分别提高13.4％和11.9％,O～ 200 cm土层的硝态氮积累量及100～ 200 cm土层硝态氮分布比例降低.在适当降低氮肥用量条件下,通过增加种植密度可以促进小麦吸收深层土壤氮素,减少土壤氮素残留,并保持较高的产量水平.     

Identification of New Sources of Resistance to Septoria Tritici Blotch Caused by Zymoseptoria tritici

Twenty‐nine synthetic hexaploid wheats (SHWs) were evaluated for resistance to five isolates of Zymoseptoria tritici, a devastating wheat pathogen worldwide. The five Z. tritici isolates varied in their virulence spectra towards wheat genotypes, indicating that they have distinct set of avirulence genes. New isolate‐specific resistances were identified that could be used in wheat breeding programmes. Comparing with the previous studies, the number of specific resistances identified in this study is considerable. Among 150 interactions, 78 isolate‐specific resistances were identified. Interestingly, 21 wheat genotypes showed specific responses to one or more isolates tested. Of these, 12 genotypes were highly resistant to all isolates, indicating that they possess known or novel effective resistance genes. The Stb15 and Stb16/Stb17 are effective resistance genes towards isolates used in this study, indicating that the conferred resistance in these genotypes is due to the presence of either of these genes in combination or individually. Alternatively, they may carry novel broad‐spectrum resistance gene(s) that their identification is of interest. Our data suggest that the presence of complete resistance to various Z. tritici isolates in SHWs justifies the need for more in‐depth research to characterize the likely novel genes.     

Microbiota in Wheat Roots,Rhizosphere and Soil in Crops Grown in Organic and Other Production Systems

Culturable microbial communities and diseases were compared in organic, integrated and conventional systems of winter wheat production and monoculture. Particular emphasis was placed on the density and diversity of cereal pathogens and their potential antagonists, and on the association of the active microbial populations with the health and productivity of wheat. In roots, rhizoplane and rhizosphere, fungi tended to be most abundant in the integrated system or monoculture, and bacteria in the organic system. The dominant fungal groups (with individual frequency >5%) included root pathogens (Fusarium, Gibberella, Haematonectria and Ilyonectria) and known pathogen antagonists (Acremonium strictum, Clonostachys, Chaetomium, Gliocladium and Trichoderma spp.). The 50 subdominant species (with individual frequency 1–5%) included the pathogens Alternaria, Cladosporium (leaf spot), Gaeumannomyces graminis (take‐all), Glomerella graminicola (anthracnose), Oculimacula yallundae (eyespot), Phoma spp. (leaf spots), and Pythium and Rhizoctonia (root rot). The 40 subrecedent species (with individual frequency <1%) included minor pathogens (Botrytis, Coniothyrium, Leptosphaeria). Antagonists in roots, rhizoplane and rhizosphere were most frequent in the organic system and least frequent in monoculture, suggesting that these systems had the most and least disease‐suppressive habitats, respectively. The other two systems were intermediate, with microbial communities suggesting that the conventional system produced a slightly more suppressive environment than the integrated system. The highest grain yield, in the integrated system, was associated with high abundance of fungi, including fungal pathogens, lowest abundance of Arthrobacter, Pseudomonas and Streptomyces in roots, rhizoplane and soil, and relatively high stem‐base and leaf disease severity. The lowest grain yields, in the organic system and monoculture, were associated with less abundant fungi and more abundant Pseudomonas. There is no clear indication that yields were affected by diseases.