【作者】 吴伟；

【导师】 彭少兵； 黄见良；

【作者基本信息】 华中农业大学 ， 作物栽培学与耕作学， 2012， 博士

【摘要】 水稻群体大小及其空间构型与纹枯病流行、倒伏抗性和产量形成密切相关,研究群体结构与它们之间的内在关系,可以为合理调控栽培措施提供理论与技术支撑。本研究以高产杂交稻品种两优287和T优207为试验材料,自2008-2010年在大田条件下采用裂区试验设计,通过不同氮素水平和移栽密度构建不同群体结构,并设置纹枯病接种处理和打药处理来研究不同群体结构下双季稻纹枯病流行、倒伏抗性和产量的变化特点及其相互关系,主要研究结果如下：(1)在自然发病区病情指数均随施氮水平和移栽密度的增加而增加。高氮高密条件下具有高茎蘖数、高叶面积指数和高生物量的冠层则具有较为密集的群体结构。密集的群体结构叶片相交频率较大且群体透光率较低,促进了纹枯病的流行。人工接种纹枯病后,由于提供了足够的菌源,纹枯病的流行并不受到蔸与蔸之间的传播速度的影响,它主要受到蔸内垂直扩散速度的影响。即纹枯病扩展的微环境(蔸内)并没有发生较大的改变,因此由氮素水平或移栽密度所构建的群体结构在接种条件下对纹枯病的流行影响较小。(2)采用牙签接种方法进行接种并调查接种后病斑长度可以高效准确地评价纹枯病抗性水平。在接种条件下,不同的氮素水平与移栽密度均对纹枯病病斑长度无显著性影响,并且病斑长度与茎蘖数、叶面积指数和生物量相关性均不显著。群体结构对纹枯病抗性的影响不显著,因此,在自然发病条件下,群体结构主要通过改变叶片相交频率对纹枯病流行产生显著影响。(3)合理调控氮肥用量和适宜的移栽密度可以改善水稻株型如提高叶基角来提高群体透光率和降低叶片相交频率从而在一定程度上控制纹枯病的流行。(4)高氮条件下茎秆倒伏指数上升,茎秆抗折力显著下降,对单位长度干重和茎秆直径无显著影响；密植条件下,茎秆抗折力、弯曲力矩、直径、和单位长度干重均明显下降,同时倒伏指数增加。即随着群体大小的增加,茎秆倒伏指数逐渐增加,群体发生倒伏的风险要明显增大。(5)通过提高茎秆抗折力可以降低倒伏指数从而提高水稻抗倒能力。双季稻茎秆抗折力与茎秆直径和单位节间干重都呈显著正相关,而倒伏指数与茎秆直径和单位节间干重都呈显著负相关,即可以通过提高茎秆直径和单位节间干重来提高茎秆抗折力。通过改善群体透光率,例如通过影响群体内部叶片分布规律,提高叶基角,即可以在相似的群体大小条件下提高群体透光率,同时茎秆基部节间抗折力增加,倒伏指数降低。(6)早稻产量在氮水平为120-180kg N ha-’并且密植(13.3×20cm)条件下最高。对于晚稻,中密(13.3×26.7cm)和120kg N ha-1有利于获得高产。晚稻倒伏发生的风险要明显高于早稻,其倒伏指数在2009和2010年分别比早稻高58%和45%,选择适宜的密度和氮施用量还可以有效防止晚稻倒伏的发生。(7)早稻产量显著低于晚稻,其在2008、2009和2010年分别比晚稻低46%、38%和21%。原因主要由于早稻营养生长期温度过低导致水稻前期生长缓慢,在抽穗期干物质积累不够,早稻库容显著低于晚稻。另外,早稻灌浆期日平均温度要明显高于晚稻,并且早稻在开花前后各一周内容易出现极端高温(大于34℃),这极易导致早稻结实率降低,最终导致早稻产量的下降。(8)纹枯病的流行显著降低了茎秆抗折力,倒伏指数明显增加。纹枯病对群体茎蘖数的影响较小,对水稻生育后期叶面积指数和干物质积累的影响较大。特别在群体较大的情况下(高密或高氮)效果更明显,均显著地提高了群体叶面积指数和干物质积累。(9)纹枯病接种和不防治纹枯病均明显降低了双季稻产量,一般在高氮或高密植条件下产量损失较大并且其绝对产量最低,纹枯病接种处理在2009和2010年共4季中产量损失最高分别达到了30.1%、23.8%、23.7%和48.6%。纹枯病的流行主要是通过降低干物质积累量而非通过降低收获指数来影响产量的。另一方面纹枯病的流行主要是通过降低结实率而非通过降低单位面积颖花数和千粒重来影响产量。更多还原

【Abstract】 The canopy structure had a deep influence on rice grain yield and lodging-resistance. Meanwhile, canopy structure and its micro-climatic are essential factors for disease development. Canopy structure may affect sheath blight epidemic directly or indirectly. So, in order to settle present problem, we must investigate the relationships of canopy structure with sheath blight epidemic, lodging-resistance and grain yield performance. Field experiments were conducted in both early and late seasons in2008,2009and2010. The effects of nitrogen rate, hill density, fungicide treatment, and inoculation with R. solani on sheath blight severity, lodging-related traits and grian yield performance were investigated. The main results are as follows:(1) Sheath blight index increased with the increase of nitrogen rate and hill density. Tiller number, leaf area index and biomass production was high under dense canopy structure due to high nitrogen and dense density in non-inoculated plants. Dense canopy structure led to higher leaf contact frequency and lesser light transmittance, which was conducive to sheath blight epidemic. In inoculated plants, however, sheath blight severity was not necessarily restricted by autoinfection because enough hypha was available in infected tillers, which is mainly controlled by vertical spread of the pathogen within each hill. Micro-climate within a hill favorable to sheath blight development regardless of nitrogen rate and hill density was not changed. So, canopy structure due to difference in nitrogen rate and hill density has less effect on sheath blight epidemic.(2) An effective inoculation method with short woody toothpicks is a critical component of an accurate disease assay for quantifying levels of sheath blight resistance. Nitrogen rate and hill density have no significant effect on lesion length in infected plants, and the relationships of lesion length with tiller number, leaf area index and biomass production was not consistent and significant. These results suggest that canopy structure deep influences sheath blight epidemic under the common field conditions due to change in leaf contact frequency, light transmittance, leaf area index, tiller number and biomass production, but has little effect on plant resistance to sheath blight in the severe infection condition.(3) Adaptation of ’healthy’ canopy structure resulting from appropriate crop management practices such as rational use of fertilizers and optimum planting density can suppress sheath blight. Improving plant traits such as erect leaves based on crop management or breeding selection is an efficient way to control disease infestation.(4) Lodging index increased and breaking resistance decreased with the increases of nitrogen rate. Nitrogen rate have no consistent effect on dry weigh per unit length and stem diameter. Breaking resistance, bending moment, stem diameter and dry weight per length decreased with the increases of hill density, following by an increase in lodging index. So, lodging index increased with the increases of canopy structure.(5) It’s feasible to decrease lodging index with increase in breaking resistance. Correlation analysis revealed that breaking resistance was positively related with stem diameter and dry weight per unit length significantly; lodging index was negatively related with stem diameter and dry weight per unit length significantly. So, it is feasible to increase breaking resistance with increase in stem diameter and dry weight per unit length. Improvement light transmittance such as increasing leaf angle, can affect the leaf distributing in canopy under the same canopy structure, and then breaking resistance increased.(6) In early season, the attainable yield was higher under dense planting (13.3×20cm) when N was applied at a rate of120-180kg ha-1. However, the effect of hill density on grain yield was relatively small for late season, while moderate hill density (13.3×26.7cm) and low nitrogen rate (120kg ha-1) were recommended for their advantages in terms of grain yield and lodging resistant. The loding index of late season was higher than those of early season by58%and45%in2009and2010, respectively.(7) Remarkably higher grain yields were achieved in late season than in early season, as late season had advantages over early season in sink size and biomass production. The comparatively less yield under early season rice resulted due to the slower growth during vegetative phase, which can be ascribed to the lower temperature rather than reduced mean daily radiation. In addition, the averaged air temperature during grain filling and the number of days with maximum temperature above34℃around flowering stage were significantly greater in early season than in late season across the three years, which might have led to a decrease in grain-filling percentage.(8) The direct effect of sheath blight infestation on lodging resistance was found by using fungicide treatment and inoculation of R. solani. Sheath blight development does not affect tiller number. But, it has a great effect on leaf area index and biomass production after flowering. Compared with control, fungicide treatment has significantly increased leaf area index and biomass production, especially under dense canopy structure.(9) Compared with control, inoculation with R. solani treatment has decreased grain yield significantly. Generally, the yield loss was great high under high nitrogen and dense planting, following by the lowest attainable yield. The maximum yield loss by sheath blight inoculation in early-and late-season of2009and2010were30.1%,23.8%,23.7%and48.6%. Sheath blight infestation caused yield loss is driven mainly by the decreased biomass production, rather than decreased harvest index. On the other hand, sheath blight epidemic raised yield loss is contributed by the decreased grain filling, rather than spikelets per m2or grain weight.更多还原