Fundamental Traits Of High Yield Varieties And Its Causes In Indica Rice(Oryza Sativ L.)

A large quantity of research works have been done on the effects of yield components, source-sink relationship, dry matter production and distribution, root characteristics, nutrient uptake and utilization, etc on grain yield in rice(Oryza sativa L.). But as concerned the materials used in the comparative studies of the same type of rice, the test cultivar's number was limited and the materials generally came from given rice-developed regains with a small span of breeding period. As concerned the contents, previous studies have mainly investigated the effects of yield components, source-sink relationship and dry matter production and distribution, on the grain yield formation, while few research works have been done about the effects of root traits, nutrient uptake and utilization, on grain yield formation, and studies have almost never been reported that used the same materials to analysis the effects of yield components, source-sink relationship, dry matter production and distribution, root traits, nutrient uptake and utilization, on grain yield formation. In order to investigate the main factors influencing grain yield of Indica rice, 88 varieties in 2001 and 122 combinations in 2002 from home and abroad were selected to represent different breeding age from 1930's to 1990's, respectively. These cultivars were cultivated in continuously flowing nutrient solution to measure root morphological characteristics, root activity, yield components, leaf area index (LAI), dry matter production, sink capacity, grain yield and plant nitrogen content at the critical growth stages of rice, and to calculate sink capacity per leaf area, sink capacity per dry matter, nitrogen uptake, harvest index(HI), nitrogen use efficiency for dry matter production(NUEp), nitrogen use efficiency for grain yield output( NUEg)and nitrogen harvest index (NHI), etc. Combined analysis the effects of these traits on grain yield of Indica rice by MinSSw dynamic clustering method, correlation analysis, multivariate stepwise regression analysis and path analysis to investigate the main factors influencing grain yield of Indica rice. This may do great help to the program ofbreeding of high-yield Indica 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 237.72-1012.76 g.m-2 in 2001 and 140.14-1568.36 g.m-2 in2002, respectively. Thus, these Indica cultivars were classified into 6 types using one of dynamic clustering methods, MinSSw, based on the grain yield from low to high. The average gram yields of these types were 310.73, 469.60, 548.02, 635.67, 763.97 and 944.44 g.m-2 in 2001, respectively, and 306.64, 464.79, 601.51, 721.92, 903.94 and 1194.84 g.m-2 in 2002, 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 are calculated. based on the results of classification above. For average values of relevant traits of high yielding types of varieties: (1) Basic traits of yield components of high yielding types of varieties in Indica rice were having more panicles per area, more spikelets per panicle, higher ripe grain percentage and 1000-gram weight, and the range of coefficient of variation(CV) of these traits among high yielding types of varieties was relatively small and stable. (2) Basic traits of source-sink relationship of high yielding types of varieties in Indica rice were having higher LAI at heading, larger sink capacity per area, large sink capacity per leaf area, and the range of CV of these traits among high yielding types of varieties was relatively small and stable. (3) Basic traits of dry matter production and distribution of high yielding types of varieties in Indica rice were having large dry matter production before and after heading, large biomass, high proportion of dry matter production after heading, high HI, and the range of CV of these traits among high yielding types of varieties was relatively small and st...