Competitive Relation Between Weedy Rice And Cultivated Rice

Rice is one of the most important cereal crops, however, more and more weeds are occurring in rice fields, particularly the conspecific weedy rice. Weedy rice is one of the most notorious weeds found in rice-planting areas all over the world. It commonly causes reduction of rice yield and affects grain quality. Because of the affinity of weedy and cultivated rice, weedy rice is more difficultly controlled than other weeds in rice fields. On the other hand, as a primary gene pool of cultivated rice, weedy rice may provide a large amount of gene resources for rice breeding. The change of cultivation methods and weed managements accelerate the growth and spread of weedy rice. In recent years, therefore, weedy rice has increasingly affected rice production in many regions of the world. With the popularizing of direct seeding and the extensive weed management, weedy rice has spread rapidly and seriously affected rice production, including southern and northeastern China. Controlling weedy rice has become an urgent problem. At present, a lot of people are interesting in how to use weedy rice in breeding and resist to adversity in our country, effects of weedy rice density on yield and quality of cultivated rice and the competition relation between them were little studied on this. In order to provide some references for weedy rice control, a pot experiment was conducted to study the relationship between weedy rice and cultivated rice, two field experiment was conducted to study the performance of weedy rice and the effect of weedy rice on cultivated rice in transplanted plots. Our results showed that:1.Weedy rice was provided with competition ability more than cultivated rice, after transplanting pot experiment also can make sure this result. With the number of weedy rice increasing, tillers, leaf area, and dry weight decreased significantly, leaf length and width were not influenced by weedy rice numbers. Chlorophyll content and photosynthesis of cultivated leaf decreased with increasing weedy rice numbers in some degree.The root numbers, root volume, and root dry weight of cultivated rice were gradually decreased with increasing weedy rice numbers, the total absorption area and active area were decreased significantly in competition with weedy rice. The root numbers, root volume, and root dry weight of weedy rice were gradually increase, the total absorption area and active area were increased significantly in competition with cultivated rice.The significant decrease of yield in cultivated rice was induced by increasing weedy rice numbers. Considering the yield components, the effect of plant numbers seemed to be the most significant on the number of rice panicles, the spikelets per panicle and percent of filled-grain were seconded, while the 1000- grain weight did not seem to be influenced. Weedy rice yield increased in competition with cultivated rice, the number of rice panicles and spikelets per panicle were increased significantly, percent of filled-grain and the 1000-grain weight did not seem to be influenced. The grain of primary branch, the number of secondary branch, and grain of secondary branch of cultivated rice were decreased significantly by weedy rice competition.The relative yield, relative yield total, and aggressivity of cultivated rice were decreased significantly by weedy rice competition, this showed cultivated rice were inferior to weedy rice in competition. The relative yield and relative yield total of weedy rice showed decreased in some degree, aggressivity increased by weedy rice numbers.2.With the spontaneity weedy rice density increasing, tillers, leaf area, and dry weight decreased significantly, leaf length and width were not influenced by spontaneity weedy rice density. Chlorophyll content and photosynthesis of cultivated leaf decreased with increasing spontaneity weedy rice density in some degree.The significant decrease of yield in cultivated rice was induced by increasing spontaneity weedy rice density. Considering the yield components, the effect of weedy rice density seemed to be significant on the number of rice panicles and spikelets per panicle, was one of the main reasons causing yield loss of cultivated rice. The brown rate, milled rate, whole milled rate, and score were decreased significant, the protein content, chalky, and chalky grain rate were increased significantly by increasing spontaneity weedy rice density. The rice rate, score, and appearance quality were inclined, finally the commodity value were debased.3.The plant height and stem length of cultivated were lesser influenced than stem width by different weedy rice density. With the weedy rice density increasing, tillers, leaf area, and dry weight decreased significantly, leaf length and width were not influenced by weedy rice density. Chlorophyll content, MDA content, Praline content and SOD content of cultivated leaf changed lesser in competition with weedy rice. Soluble sugar content and photosynthesis of cultivated leaf decreased with increasing weedy rice densityIncreasing weedy rice density made delay to starting filling time ,shorten the peak filling time, reducing the filling rate, prolong the filling time, slower the increasing weight speed, were make against accumulating dry weight, finally grain weight were induced decline. The secondary branch grain filling of cultivated seems to be significant than primary branch, and the effects on bottom grain more than middle-upper grain by increasing weedy rice density.The results showed that the significant decrease of yield in cultivated rice was induced by increasing weedy rice density. Considering the yield components, the effect of weedy rice density seemed to be significant on the number of rice panicles and spikelets per panicle, was one of the main reasons causing yield loss of cultivated rice. Milling quality, nutrient quality, and taste quality of cultivated rice decreased with the increasing of weedy rice density, while apparent quality did not show the same trend. The PKV, HPV, and CPV were decreased by increasing weedy rice density, and other characters of RVA were not easy to be influence. The correlation analyze showed that the secondary branch grain yield and quality seems to be influenced by increasing weedy rice density.Effects of different weedy rice density on cultivated yield difference were not apparent by weedy rice density lower 30%. When weedy rice density excess 40%, the cultivated yield significant decreased. The brown rate, milled rate, whole milled rate, and score were decreased significant, the protein content and chalky grain rate were increased significantly.4.The daily mean temperature, minimum temperature, and minimum humidity increased in some degree, but the maximum temperature, daily temperature range, maximum humidity, and daily humidity range decreased in the cultivated rice population with increasing weedy rice density. The illumination, at 60 cm and 90 cm from ground of cultivated rice seems to be decreased with the increase of weedy rice density and that at 30 cm was not influenced by this parameter. The yield and quality of cultivated rice with the population temperature, humidity,and illumination are closely related to the change.