Root Characteristics Of Japonica Rice With High Yield And Its Influence On Yield

In order to investigate the main root characteristics influencing grain yield of japonica rice, 45 varieties in 2006 and 92 combinations in 2007 from home and abroad were selected to be cultivated in continuously flowing nutrient solution to measure root morphological characteristics, root activity, yield components, grain yield at the critical growth stages of rice. Combine analysising the effects of these characteristics on grain yield of Japonica rice by MinSSw dynamic clustering method, correlation analysis, multivariate stepwise regression analysis and path analysis to investigate the main root characteristics influencing grain yield and yield components of Japonica rice. This may do great help to the program of breeding of high-yield Japonica rice and high yielding-cultivation. Main results were as follows:1. Significant difference of grain yield per unit area was found, with the variation of 224.75-523.34g·m^-2 in 2006 and 391.29-1374.18g·m^-2 in 2007, respectively. Thus, these Japonica cultivars were classified into 6 types using one of dynamic clustering methods, MinSSw, based on the grain yield from low to high. The average grain yields of these types were 224.75, 281.70, 344.52, 396.79, 467.43 and 523.34 g?m^-2 in 2006, respectively; 391.29, 595.82, 760.43, 918.07, 1086.01 and 1374.18 g?m^-2 in 2007, respectively. Grain yield varied significantly among different types of yield at the same year.2. Average values of relevant traits of different types of grain yield were calculated based on the results of classification above. Ripe grain percentage varied significantly among different types of yield in 2006. But panicles per area, spikelets per panicle and 1000-grain weight didn't vary significantly in 2006. The differences of panicles per area, spikelets per panicle, ripe rain percentage and 1000-grain weight among different types of yield in 2007 were significant (p<0.05 or p<0.01). Basic characteristics of yield components of high yielding types of varieties in Japonica rice had more panicles per area, higher ripe grain percentage and 1000-grain weight in 2007; Medium yielding types of varieties in Japonica rice had more spikelets per panicle than high yielding ones, high yielding ones had more spikelets per panicle than low yielding ones.3. Average values of root traits of different types of grain yield were calculated based on the results of classification above. Root characteristics of high yielding types of varieties in Japonica rice at heading were having high root dry weight per unit area, long total length of adventitious roots, high shoot and root dry matter ratio significantly, but adventitious roots per area, length per adventitious root, dry weight per adventitious root, diameter per adventitious root, root dry weight per length, length of the longest adventitious root of high yielding Japonica rice at heading were not significantly different from those of low yielding. Total root active absorption area per area, root total activity per area of high yielding Japonica rice were significantly higher than those of low yielding ones, but the differences of total root absorption area per area, root activity per unit dry weight of adventitious roots at heading between high and low yielding rice were not significant.4.The analysis on the relationship between single root trait and grain yield showed that: (1) Relationship between some root traits and grain yield could be simulated by linear equation at 0.01 or 0.05 significant level. These root traits included number of adventitious roots per area, total length of adventitious roots per area, root dry weight per area, root active absorption area per area, root total activity per area, shoot and root dry matter ratio, dry weight per adventitious root, length of the longest adventitious root; Relationship between some root traits and grain yield could not be simulated by linear equation which were not significant, these root traits included length per adventitious root, dry weight per unit length of adventitious root, diameter per adventitious root, root activity per unit dry weight of adventitious roots; (2)A further analysis on different effects of rice traits on grain yield was done by path analysis. The results were as follows: root dry weight per area, shoot and root dry matter ratio played the most important role on grain yield in two years, it was concluded that root dry weight per area was probably the most important factor affecting grain yield, followed by shoot and root dry matter ratio, which played less important role on grain yield.5. The promotion of shoot root dry matter ratio could increase panicles per area of Japonica rice significantly; Length per adventitious root, dry weight per adventitious root, length of longest adventitious root at heading could increase spikelets per panicle significantly; The promotion of dry weight per adventitious root could increase 1000-grain weight significantly; It was possible that the promotion of length per adventitious root, the length of the longest adventitious root may increase 1000-grain weight. The number of adventitious roots, shoot root dry matter ratio, dry weight per adventitious roots had no close relationship with spikelets per panicle; The number of adventitious roots, total length of adventitious roots, shoot root dry matter ratio, dry weight per unit length of adventitious root and length of the longest adventitious root had no close relationship with ripe grain percentage.6. Root active absorption area of Japonica rice had no significant effect on panicles per area, spikelets per panicle or 1000-grain weight; Root total activity per area had little effect on spikelets per panicle or ripe grain percentage; Root activity per unit dry weight of adventitious roots had little effect on 1000-grain weight or ripe grain percentage; The promotion of total root absorption area was possible to increase panicles per area; With the increase of root activity per unit dry weight of adventitious roots, spikelets per panicle may decrease; The increase of root active absorption area may increase ripe grain percentage of Japonica rice; The increase of root total activity per area may increase 1000-grain weight, too.