Basic Characteristics Of Conventional Japonica Rice Cultivars With Different Panicle Weight

To analysis evolution trend and differences of related traits among conventional japonica rice cultivars with different panicle weight and the basic characteristics of related traits in conventional japonica rice cultivars with large panicle type, and to provide some reference basis for genetic improvement and high yield cultivation of conventional japonica rive cultivars, a total of 94 conventional japonica rice cultivars(lines) were solution-cultured in 2008 and 2009, respectively. Leaf-area-index (LAI), root morphology, root physiological activity, dry matter weight of different rice plant organs, nitrogen content at heading and maturity stages, grain yield and yield components and panicle traits were measured. Based on single panicle weight by the MinSSw method, these tested rice cultivars were clustered into 6 types in the alignment from low to high (A, B,C, D, E and F). Main results were as follows:1. Great differences in single panicle weight were detected among tested rice cultivars. The single panicle weight ranged from 0.79-3.59 g panicle -1 in 2008 and 1.01-3.53 g panicle -1 in 2009. The maximum of single panicle weight was increased by 354.2% and 249.5%, compared with the minimum of single panicle weight in 2008 and 2009, respectively. The mean value of single panicle weight of A, B, C, D, E and F type was 1.14, 1.69, 2.04, 2.38, 2.70, 3.50 g panicle -1 in 2008 and 1.35, 1.65, 1.92, 2.18, 2.61. 3.14 g panicle -1 in 2009, respectively. The rice numbers of A, B, C, D, E and F type was 19, 17, 16, 22, 13 and 4 in 2008 and12, 19, 21, 26, 10 and 6 in 2009, respectively. Significant differences in single panicle weight were observed between conventional rice cultivars with different panicle weight.2. Significant differences in the average grain yield between conventional rice cultivars with different panicle weight were detected. Panicle weight was significantly and positively correlated with grain yield (r=0.572** in 2008 and 0.612** in 2009). Enlargement of panicle type and increment of panicle weight were beneficial to increase grain yield in conventional Japonica rice cultivars.3. The panicle numbers per unit area and spikelets numbers per panicle significantly differed between conventional rice cultivars with different panicle weight, while the filled grain percentage didn't significantly differ between these rice cultivars. And, 1000-filled grain weight strongly differed in 2008, while not in 2009 between these rice cultivars. The rice cultivars with larger panicle type showed less panicles numbers per unit area, more spikelets numbers per panicle and higher 1000-filled grain weight, while less filled grain percentage than the rice cultivars with partial large panicle. This result indicated that too large panicle type was not helpful to improve filled grain percentage. A further analysis showed that the 1000- filled grain weight of primary rachis branch and that of secondary rachis branch in rice cultivars with larger panicle type were higher than those in the rice cultivars with small panicle weight. While, the filled grain percentage of the primary rachis branch and that of secondary rachis branches in cultivars with larger panicle type were lower than those in the rice cultivars with small panicle type. Too much of spikelet density were an important factor for the lower filled grain percentage of the primary rachis branch and that of second rachis branch, especially that of second rachis branch.4. Sink capacity, LAI, biomass production, dry matter weight at heading stage, total nitrogen uptake, and nitrogen uptake at heading stage of rice cultivars with larger panicle type were significantly higher than rice cultivars with other panicle type. Harvest index and nitrogen use efficiency for gain yield of rice cultivars with larger panicle type were higher than other rice types, except for that of rice cultivars with medium partial large panicle type.5. There were significant differences in panicle length, spikelet density, primary and secondary rachis branch numbers and ratio of secondary rachis branches numbers to primary rachis branch numbers between rice cultivars with different panicle Weight. The panicle weight showed significant relationships with panicle length, spikelet density, primary and secondary rachis branch numbers and ratio of secondary rachis branches numbers to primary rachis branch numbers, respectively. The rice cultivars with large panicle type had longer panicle length, higher spikelet density, higher primary and secondary rachis branch numbers and ratio of secondary rachis branches number to primary rachis branches number.6. Great differences in root dry weight per plant, root active absorption area per plant were detected between rice cultivars with different panicle weight. Total length of adventitious roots per plant, root dry weight per plant, total root absorption area per plant and root active absorption area per plant were higher in the rice cultivars with larger panicle type than other rice types.Significant differences in the roots number per panicle, root dry weight per panicle, length of adventitious roots per panicle, total root absorption area per panicle, root active absorption area per panicle, and root activity per panicle were observed between rice cultivars with different panicl weight. The root traits per panicle in rice cultivars with large panicle type were better than that in rice cultivars with small panicle type.There were significant differences in maximum root length, modal root length, single adventitious root, single adventitious root diameter and single root dry weight between rice cultivars with different panicle weight. The rice cultivars with large panicle type had longer maximum root length, modal root length and single adventitious root, and higher single root diameter and single root dry weight than other rice types, except for rice cultivars with medium partial panicle type. Shoot-root ratio at maturity stage greatly differed between rice cultivars with different panicle weight. This trend was more obvious in 2008 than that in 2009. The rice cultivars with large panicle type showed higher shoot-root ratio than other rice types.The correlation analysis indicated that panicle weight were significantly correlated with root traits per plant (including adventitious root length per plant, root dry matter per plant, total root absorption area per plant, root active absorption area per plant and root activity per plant) and root trait per panicle (including root number per panicle, root dry weight per panicle, adventitious root length per panicle, total root absorption area per panicle, root active absorption area per panicle and root activity per panicle) and root traits per root (including the maximum root length, modal root length, single adventitious root length, single adventitious root diameter and single adventitious root dry weight) and shoot-root ratio. A further analysis showed that the root traits per plant was affected by both root traits per panicle and panicle numbers , while, the correlation trend of root traits per panicle to root traits per hill was higher than panicle number per plant to root traits per hill.In summary, root traits per plant, root traits per panicle, single adventitious root and shoot-root ratio in the rice cultivars with large panicle type were superior to those in the rice cultivars with small panicle type, especially root traits per panicle.