Effect of N supply on stalk quality in maize hybrids

The identification of maize nitrogen (N) response for stalk quality is valuable in stalk breeding improvement, stalk lodging resistance and for use in bioenergy. This study analyzed the effect of two N levels and estimated quantitative genetic parameters for stalk quality in summer maize in the north China plain (NCP). Thirty hybrids were sampled and tested from three to four geographic locations under high nitrogen (HN) (225 kg N ha⁻¹) and low nitrogen (LN) (0 kg N ha⁻¹) during 2006–2008. Compared to HN level, stalk crude protein (CP) was significantly reduced (22.06%) under LN level. Ether extract (EE), ash content (AC), in vitro dry matter digestion (IVDMD) and lignin content (LC) were lower under LN level. Cellulose content (CC), neutral detergent fiber (NDF) and acid detergent fiber (ADF) were increased with a reduction in N, however N did not significantly affect EE, ADF and LC. An increase in NDF and ADF content under low vs. high N level was mainly attributed to a reduction in CC. ADF and NDF exhibited positive correlation and both showed a positive correlation with CC but a negative correlation with LC, IVDMD and CP. Negative correlations between IVDMD and CC, IVDMD and LC, and CP and CC were also detected. The interaction variance of genotype × year × location (σ²_GYL) for each N level, with the exception of σ²_GYL for CC under HN, was significant and most stalk quality traits were evaluated in different locations and years. The estimates of genetic variance (σ²_G) and heritability (h²) were greater under HN, with the exception of LC and EE. The interaction of genotype × nitrogen (σ²_GN) for CP was more important than σ²_G. The genotypic correlation coefficients (r_G) for performance in different stalk quality traits between HN and LN were significant. However, it was necessary to evaluate both HN and LN for IVDMD. For other stalk quality traits, breeding maize under HN levels may serve to develop hybrids well adapted to high and/or low N level. The response to N trend was similar between high oil and normal maize hybrids.     

摘穗与秸秆粉碎复式作业机构设计与试验

设计了一种摘穗与秸秆粉碎复式作业机构.该机构主要由摘穗板、一对拉茎辊和一个切割刀辊组成.拉茎辊带有凸棱,凸棱上按一定间隔设有开口,切割刀辊上装有缺口圆盘刀片,刀片与拉茎辊凸棱的开口配合,茎秆下拉时,切割刀辊将茎秆切碎,一套机构实现摘穗和秸秆切碎2个功能.建立了茎秆下拉运动方程,分析了茎秆在机构间的运动规律,理论上证明了茎秆下拉的运动轨迹具有较好的直线度.初步试验表明,该机构的摘穗效果良好,籽粒损伤率和果穗损失率低、茎秆折断减少,功耗是摘穗机构与秸秆切碎机构分置时的35％,节能效果显著.     

玉米抗禾谷镰刀菌的转录组分析

赤霉菌茎腐病是由禾谷镰刀菌(Fusarium graminearum,有性态,Gibberella zeae)引起的一类土传性病害,严重危害玉米的产量和品质。本研究依据玉米第10和第1染色体上的2个抗茎腐病QTL,qRfg1和qRfg2,培育近等基因系NIL-R (2个QTL位点均为抗病等位基因)和NIL-S (2个QTL均为感病等位基因)。在成株期和幼苗期接种禾谷镰刀菌,两近等基因系的抗性差异均显著。用2个近等基因系的幼根接种禾谷镰刀菌,进行转录组分析研究。结果表明,与NIL-S相比,NIL-R在接种禾谷镰刀菌后,乙烯(ethylene,ET)合成、信号途径基因,病程相关蛋白、脱氧雪腐镰刀菌烯醇毒素(deoxynivalenol,DON)解毒基因等呈现特异上调表达。与NIL-S相比,有1170个基因在NIL-R对照组中表达量较高,其中水杨酸(salicylic acid,SA)、茉莉酸(jasmonic acid,JA)和乙烯合成和信号介导途径以及苯丙烷合成途径中的基因显著富集;接种禾谷镰刀菌6 h或18 h后,病程相关蛋白、激素JA和ET合成基因、DON解毒基因在NIL-R中表达量较高。     

免耕栽培不同秸秆覆盖量下土壤温度变化研究

试验采用微区定位方法, 研究免耕栽培条件下不同秸秆覆盖量对大豆田土壤温度的影响。结果表明： 秸秆覆盖平作免耕栽培处理间随秸秆覆盖量增加, 土壤温度呈下降趋势, 较 0%秸秆覆盖常规秋翻垄作对照比, 0、 30、 60、 100%秸秆覆盖免耕处理分别降低 0.35~4.39、 0.45~4.55、 0.57~5.34、 0.77~6.14℃; 各生育时期间以苗期各处理土温与对照差异最大, 开花以后土温差异变小; 各处理不同土层间降温幅度为0.46~3.62℃, 仍以苗期降幅最大为 3.62℃。因此, 在高纬度寒地应用秸秆还田免耕技术关键是在苗期采用增温措施, 促进幼苗发育。     

秸秆还田对农田棕壤氧化亚氮排放动态的影响

通过田间试验,采用静态箱法对不同量秸秆还田(单施氮肥、半量秸秆还田、全量秸秆还田)下不同时期土壤氧化亚氮排放动态进行了研究。结果表明,和单施氮肥相比,秸秆覆盖还田提高了土壤氮素积累,也同时影响土壤N_2O排放动态。在玉米生长期间,半收获量秸秆还田增加了7.8%的N_2O排放,全量秸秆还田降低了2.2%的N_2O排放,与土壤铵态氮变化一致;玉米收获后,秸秆还田显著增加了N_2O排放,增幅分别为6.7%(半量秸秆还田)和22.6%(秸秆全量还田)。试验期间单施氮肥、半量秸秆还田和全量秸秆还田三个处理N_2O排放的年累计量分别为1183 g hm~(-2)、1269 g hm~(-2)和1294 g hm~(-2)。尽管秸秆还田增加了总的N_2O排放,但是,由于秸秆增加了土壤氮素的投入,当以N_2O损失的氮素占总氮素投入的比例进行估算时,全量秸秆还田损失率最低为0.52%、半量秸秆还田为0.57%、单施氮肥为0.59%。由此可见,秸秆还田在增加土壤肥力的同时,降低了单位氮素的氧化亚氮损失,有利于氮素在土壤中的保留。     

免耕覆盖还田下玉米秸秆氮素的去向研究

采用田间微区试验,以15N标记的玉米秸秆为研究对象,研究了免耕覆盖还田下玉米秸秆氮素经过4个生长季后的作物累积利用率、在土壤(0~60 cm)的残留率以及损失情况。试验共设2个处理:TS1为第1年15N标记秸秆覆盖还田,此后秸秆不还田;TS2为第1年15N标记秸秆覆盖还田,此后每年以非标记秸秆还田。结果表明:经过4个生长季后,两个处理间的玉米籽粒、秸秆的累积产量及总氮素吸收量的差异均不显著。在TS1处理中,秸秆氮素在籽粒和秸秆中的累积回收率分别为14.2%和6.7%,并分别高于TS2处理的12.4%和5.8%。与作物的累积回收率相比,更多的秸秆氮素被保持在土壤中。在TS1和TS2处理中,秸秆氮素在土壤中的残留率分别为40.9%和73.8%,而损失率分别为38.6%和8.1%。与TS1处理相比,TS2处理中较高的土壤微生物生物量碳和氮以及较低的矿质态秸秆氮的含量,说明连续秸秆还田在一定程度上提高了最初还田秸秆氮素在土壤中的微生物固持并降低了秸秆氮素的淋失风险,从而显著提高秸秆氮素在土壤-植物系统中的总回收率。因此,在温带农田生态系统中,长期的免耕结合秸秆覆盖还田可促进秸秆氮素的积累,这对提高和保持土壤氮素含量和稳定性具有重要的意义。     

省沽油果实性状表型多样性分析

[目的]了解省沽油果实性状表型多样性变异规律。[方法]对河南桐柏县、湖北大悟县和安徽石台县省沽油各生长和结实性状进行调查分析,并对省沽油果柄长、果长、果宽、果厚和每果实种子数等指标的表型变异模式进行探讨。[结果]结实性状变异幅度较大的是每果序果实数和每果实种子数,其次是果厚,种子百粒重,果长和果宽相对较小。方差分析表明,省沽油果柄长、果长、果宽、果厚种源间差异均达到显著水平。方差分量分析表明,省沽油各性状种源间方差分量(0.14%~9.10%)均小于种源内个体间(4.92%~40.55%)。[结论]在对省沽油结实性状进行选择时种源内的单株选择具有较好的选择效果。     

提高玉米秸秆利用率的研究技术进展

玉米秸秆作为一种可再生资源,是仅次于油、煤、气的第四大能源。中国玉米秸秆资源极其丰富,但利用率低。本研究通过对玉米秸秆的利用现状、问题和有效利用方式进行综述,归纳出玉米秸秆的利用领域、主要处理方法和关键突破技术,指出秸秆的生物处理方法是未来研究的重点,而利用纤维分解菌是提高玉米秸秆瘤胃降解率的关键。     

玉米组合M9916×D472抗镰孢茎腐病的六世代联合数量遗传研究

以玉米自交系M9916×D472组成的六世代群体为材料,利用六世代数量性状主基因+多基因混合遗传模型多世代联合分析方法,研究玉米茎腐病抗性的遗传机制。结果表明,分离世代的次数频率分布在F2群体中呈近似于抛物线状的正态分布,在B1和B2群体中呈偏正态分布。通过AIC值适合性检验,该性状符合1对加-显主基因+加-显-上位性多基因遗传D模型,主基因加性效应值为5.29,显性效应值为6.79,两者效应值均相对较高,加性与显性效应比率为78%;多基因加性效应值为2.98,明显低于显性效应值6.88,说明显性效应起主导作用。多基因加性互作效应明显,加、显互作上存在一定抑制作用,显性互作效应不明显,加性互作效应在上位性方面起主导作用。回交群体中主基因的遗传率介于39.9%~41.3%,多基因遗传率介于33.8%~36.7%,主基因遗传率相对较高;自交群体中多基因遗传率为53.8%,大于主基因遗传率32.8%,说明在进代过程中主基因遗传率不断下降。在抗茎腐病的育种中,应注重早代抗病材料的选择,对现有重要的感病材料可利用回交方法进行有效改良。     

Agronomic comparisons of sugarcane varieties derived from tissue culture (NovaCane®) and conventional propagation under rainfed conditions

Tissue-cultured (TC) sugarcane (Saccharum spp.) plants have been shown to possess an altered phenotype (high tillering and thin stalks) relative to conventionally propagated sugarcane from setts (Conv) in the first vegetative propagation stage (Stage 1). It is currently unclear if these effects are genotype specific, and whether they would persist in ratoon crops and the subsequent vegetative propagation stage (Stage 2). A field experiment was conducted to ascertain growth and yield differences between TC and Conv plants for different varieties (N12, N31, N41, and N48) across two crops (plant and first ratoon), and two plant spacings (30 cm and 50 cm) in Stage 1. A second field experiment evaluated agronomic performance of TC and Conv crops in Stage 2, established at three planting rates (PRs) (low, medium, and high).

Plants produced from TC in both Stage 1 and Stage 2 produced significantly higher number of stalks that were thinner compared with Conv plants for selected varieties. Cane and estimated recoverable crystal (ERC) yields were statistically similar between TC (Stage 1) and Conv plants, whereas TC (Stage 2) plants significantly improved cane and ERC yields compared with Conv Varieties responded differently to the TC process (N41 and N48 TC plants did not show phenotypic variation relative to Conv). Plant spacing (Stage 1) and PRs (Stage 2) had no significant effects on agronomic traits. The TC plants can be used as planting materials for commercial production without any negative effects on productivity. This is despite the persistence of the reduced stalk diameter and increased stalk population phenotype. Routine screening for phenotypic responses to TC is recommended to sensitize growers to expected phenotypic changes of new variety releases.