【作者】 薛腾；

【导师】 傅俊范；

【作者基本信息】 沈阳农业大学 ， 植物病理学， 2009， 博士

【摘要】 玉米（Zea mays L.）是辽宁省第一大粮食作物,具有重要的经济价值和社会价值。近年来,玉米纹枯病（Rhizoctonia solani Kiihn）的发生与危害呈逐年加重的趋势,给玉米生产造成重大损失。尤其在为提高玉米产量而大力推广新型丰产栽培模式以实现增密增产目标的形势下,玉米纹枯病更成为辽宁玉米高产、丰产的主要限制因素之一。为明晰辽宁不同生态区玉米纹枯病发生的基本情况和病害灾变规律,本研究对病害的发生和流行动态进行了系统调查和监测,结合田间人工接种试验,明确了玉米纹枯病流行的时空动态,并研究了新型丰产栽培模式对纹枯病及叶斑病流行动态的影响,在此基础上构建了病害时空流行动态模拟模型及产量损失估计模型,取得的具体成果如下:1.对辽宁省不同生态区玉米纹枯病的发生情况进行了系统调查和监测。调查结果表明:一般年份,辽宁省玉米纹枯病的发病率在40%-85%,严重年份部分地区的发病率高达90%以上,已由次要病害上升为玉米生产上新的威胁。虽然纹枯病在各生态区均有发生,但发病率和病情指数在地区间和年份间存在显著差异。在丹东、大连等辽南湿润区,病害的发病率常年在80%以上,已成为限制当地玉米生产的最重要的病害之一。2.对采自11个代表地区124株病原菌进行了菌丝融合群鉴定。鉴定结果表明:AGl-IA融合亚群是辽宁省玉米纹枯病的优势菌群,占所有分离菌株的97.6%,另有3株分离自大连瓦房店病害标样的菌株属于AG4-HGI融合亚群,这是首次在在辽宁省玉米纹枯病标样上分离到除AGl-IA融合亚群以外的菌株。3.连续2年对14个辽宁主栽玉米品种进行了纹枯病抗病性鉴定。鉴定结果表明:供试品种中没有高抗或抗病品种,多数表现为感病或高感。不同品种在抗性上存在着显著性差异,其中,丹玉88和屯玉42在2年的试验中均表现为中抗。此外,各品种抗病性不同年份间存在显著差异,气候条件是造成差异的根本原因,对品种的抗病鉴定不能依据一年的数据进行判断,要综合多年的数据分析,才能反映品种的实际抗性水平。4.对病情指数随时间的增长情况进行了模拟,得到了可以反映病害在沈阳地区发生与流行的时间动态的生物数学模型。模拟结果表明:Logistic模型和Gompertz模型能够较好地反映病情指数的变化趋势。无论是品种间还是年度间,Logistic模型的拟合度都要优于Gompertz模型,是模拟玉米纹枯病流行时间动态的最佳模型。模型的表达式为:Xt=（?）,（R²=0.9953）。5.通过连续2年的试验,对玉米纹枯病的空间传播方式进行了研究。首次证明:玉米纹枯病在田间单一生长季内不存在空间传播,或传播距离很短,不能依靠气生菌丝或病健叶接触向邻近植株扩展蔓延,是否可以通过落入土中的菌核经雨水反溅进行空间传播有待进一步验证。这与其他学者的结论和教科书的描述截然不同。试验还首次对玉米纹枯病不同时期的空间分布型进行了研究,结果表明病株在整个生长季内均表现为随机分布,试验结果验证了上述结论。6.首次对玉米纹枯病在不同栽培模式下的流行动态进行了系统研究。研究表明:新型丰产栽培模式之间以及与常规模式之间病害的病情指数存在显著性差异,严重程度从高到低依次为:双株紧靠>双株定向>常规栽培>稀密交错>大垅双行>二比空。不同栽培模式间在病害的指数增长期流行速率不同,二比空和大垄双行的增长速率显著低于其他栽培模式,这是导致发病严重程度明显低于其他栽培模式的根本原因。由试验结果可知,各栽培模式下的病株率基本相同,增长情况也大体一致,这主要是由于纹枯病在田间不存在空间传播再侵染所导致。病株率相同,而病情指数不同,表明病株的病害级别不同。主要原因是新型栽培模式创造了良好的通风透光条件,降低了田间的温湿度,减缓了病菌扩展的速度,从而降低了发病程度。7.对以玉米灰斑病为代表的玉米叶斑病在不同栽培模式下的流行动态进行了研究。结果表明:玉米灰斑病在不同栽培模式下的时间动态大致相同,呈典型的“S”型曲线,且各栽培模式的病情指数也基本一致,没有显著差别,说明新型栽培模式对玉米叶斑病的时间流行动态没有显著影响。玉米灰斑病的空间传播表现为中心式传播规律,幂函数模型Y=a（x²+y²）^b、含有x²+y²形式的圆型分布模型和含有a（x²+y²）+bx+cy+d形式的椭圆型分布模型,是反映病害空间增长过程和分布情况的最佳模型。病害的空间传播受寄主空间分布和风向风速的影响较大,而新型栽培模式良好的通风条件和密植栽培形式,增加了孢子的传播距离,提高了孢子着落在寄主叶片上的概率,促进了叶斑病的传播。8.对玉米纹枯病引致玉米产量损失的机制进行了研究,并在此基础上构建了玉米纹枯病产量损失估计模型。玉米纹枯病引致产量损失的主要机制是降低籽粒饱满度和果穗的结实率。在病害影响下,百粒重和行粒数等产量性状在不发病与病害2级、3级、4级之间有显著差异,在3级与4级间的差异尤为显著,表明病斑越接近穗位,病害对产量的影响越大,尤其是影响到以穗位为中心的棒三叶时表现尤为敏感。拟合不同模拟模型的研究结果表明,三次多项式模型（Cubic model）是模拟病害级别与产量损失率之间关系的最佳模型,模型表达式为:Y=-0.678x³+5.211x²-1.388x+14.733,而幂指数模型是模拟病情指数与产量损失之间关系的最佳模型,模型表达式为:Y=0.969^*x^0.919。更多还原

【Abstract】 Corn is one of the most important crops in Liaoning province and has important economical value and social value. Corn sheath blight, one of the most important diseases on corn, always damages corn production heavily in recent years and becomes the significant limiting factor to increasing production and high yield. To manage and protect the diseases better, it is necessary to study the occurrence and regularities of disease. So we make the systematical investigation and monitoring in the most corn producing areas of Liaoning province. Combined with artificial inoculation method in experimental plot, the result indicates the temporal and spatial dynamics of corn sheath blight. The influences of various high yield planting patterns on the epidemiology of corn disease were studied also. On the basis, the simulation models of epidemic dynamics and yield loss estimation on corn sheath blight was established. The results were as follows:1. The he systematical investigation and monitoring show that the incidence of corn sheath blight is usually about 40%-85% in Liaoning province, and sometimes over 90%. There were highly significant difference of the incidence and diseases index in different regions. In Dandong and Dalian, the warm and humid region of south part, corn sheath blight has become the significant limiting factor to corn production.2. One hundred and twenty-four Isolates of Rhizoctonia spp. were obtained from tissues of corn sheath blight in 11 counties of Liaoning province. According to the hyphal fusion with international standard isolates of anastomosis groups （AGs） of Rhizoctonia, the multinucleate series belong to R. solani AG1-IA and AG4-HGI. The frequency was 97.6%, 2.4%, respectively. In Liaoning province, the predominant anastomosis group is AG1-IA.The isolates of AG4-HGI were first found in corn in Liaoning.3. The resistance identification of sheath blight for 14 principal cultivated varieties of maize was carried out in the field for two years in Shenyang. The results showed that the high resistant and resistant varieties were not found, the percentage of moderate resistant varieties was 14.3%, disease susceptible varieties and highly susceptible varieties was 42.9%, respectively. The resistance of disease affection among these varieties was different, and the disease of each variety was also obviously different between 2007 and 2008. This is mainly due to the difference climate condition.4. The bio-mathematical models, which could reflect the epidemics of corn sheath blight in Shenyang region, were obtained by artificial inoculation and computer simulation. The LOGISTIC model of Y=k /（1+exp （a-b*t）） and the GOMPOERTZ model Y=aEXP（bEXP（ct）） could reflect the dynamic development of corn sheath blight with time. The LOGISTIC modelis the optimistic model, and the model format was as follows:Xt =（?）,（R²=0.9953）.5. The paper studied on the spatial dynamic of corn sheath blight and obtained the results as follow. The spatial transmissions haven’t been observed in one growing period. The disease can’t transmit by aerial hypha or contagium between infected and uninfected leaves. If the pathogen can spread by rainwater splash waits to be proved. The results are completely different from conclusion of other scholar and description in textbooks. A method of indices of aggregation and mean crowding-mean density coefficient were led into the study of spatial patterns of corn sheath blight. All indices indicate that the distribution of the plant of com sheath blight were of the random distribution pattern.6. The epidemic dynamic of disease in new cultivation patterns were studied in this paper. There are obviously differences of the increased rate of disease index among various cultivation patterns in exponential growth phase. The results indicate that the increased rate of disease index in 2-0 cultivation and double-row ridges cultivation was lower than other cultivation patterns. This is the fundamental cause for the disease severity degree was milder than other patterns. Those new cultivation patterns can create good condition for air and light penetration which will slow down the expansion speed of pathogens.7. The results of epidemic dynamic study to maize leaf spot represented by gray leaf spot of maize in various cultivation patterns showed that the season epidemic curve of corn sheath blight in the field fitted s shape. The epidemic dynamic of disease changing trends were the same at different cultivation patterns. Gray leaf spot spread from center to vicinal fields, and the models of Y=EXP （ax+b） and Y=EXP （aEXP（bx+c）） could reflect the disease development with single direction in fields. The Gauss model of Y=EXP （ax²+bx+c）, which were optimal models, reflected the disease dynamic with west-east direction or north-south direction. The Circular model Y=a（x²+y²）^c and Oval model Y=EXP （a（x²+y²） +bx+cy+d） were the optimum 3-Dimensional models by comparison different mathematical models. The spatial dynamic of corn leaf spot was affected by host spatial distribution patterns and performance wind. And those new cultivation patterns could promote the transmission of corn leaf spot.8. The relationship between the disease index of corn sheath blight and the percentage of yield loss was studied. The results showed that the percentage of yield loss increased with the increase of disease index, the 100 kernel weight and kernels per row decreased with the increase of disease index. On the basis of the results achieved above, the yield-loss assessment models for disease grade or disease index and yield loss ratio were established as cubic model （Y= -0.678x³ + 5.211x²-1.388x+14.733） and exponential model (Y= 0.969^*x^0.919).更多还原