氮肥对水稻品种-稻瘟菌小种相对寄生适合度的影响

INFLUENCE OF NITROGEN APPLICATION ON RELATIVE PARASITIC FITNESS OF CULTIVAR-RACE COMBINATIONS OF RICE BLAST DISEASE

选择具有不同抗病性水稻品种 -稻瘟菌小种组合 ,在室内、田间分别设 7个、3个不同氮肥水平 ,测定不同组合不同氮肥水平下品种 -小种相对寄生适合度 ,方差分析结果表明 ,施氮量对品种小种相对寄生适合度的影响较小。相对寄生适合度可以作为一项较为稳定的参量用于水稻品种与稻瘟病小种互作研究。

Rice blast, caused by Magnaporthe grisea , is one of the most important crop diseases in China. Resistance break down often happens, especially firstly occurs in those fields supplied with a high dose of nitrogen fertilizer. In the simulation study on race dynamics and cultivar race interaction on population level, the influence of nitrogen application on the relative parasitic fitness of cultivar race combinations must be realized as quantitatively as possible. Greenhouse experiment pertaining to seedlings of 6 cultivars(cv)×3 races ×7 levels of nitrogen(N) applications×3 replications and field experiment pertaining to 4 cv ×3 races × 3 doses of N applications (corresponding to 0,105, and 210 kg of pure N per hectare)×3 replications were conducted in 1998. In greenhouse experiment, 10 days after inoculation by spraying equal volume of spore suspension, number of lesions on unit leaf area, infection probability and area of sporulation per lesion were recorded. In field experiment, equal amount of spore suspension was inoculated onto the 10 leaves in the center point of each plot(1m×1m, one cv) and disease index was recorded for each plot every 5 days after disease apparition. Two main points were showed by the results. Firstly, the pattern of response of disease intensity to the amount of N application appeared similar to a parabola, disease intensity increasing with the increasing N from very low to medium high but decreasing with further increasing N. Secondly, the influence of amount of N application on relative parasitic fitness mightbeveryslightorevendinkyinmanycultivar racecombinations.Basedontheresults mentioned above, it is obvious that N application must be comprised in the construction of the simulation model for rice blast because it is an important factor influencing the rate of pathogen multiplication no less than meteorological ones. Furthermore, at present the estimation of relative parasitic fitness of cultivar race combinations would be better undertaken under moderate to high amount of N supply in order to reveal the highest range of F value that may leads to cultivar resistance break down. As for how and why different cultivar race combinations react to N application differently in manifesting parasitic fitness, further studies are needed.