Effect Of Genome-Doubling On Rice Traits And Study On The Related Mechanism

The study on potential value of polyploidy rice is one of the important research directions in genetic improvement of rice. To clarify the potential value of genome-doubling in rice breeding, the variation of morphology, physiology and quality traits between diploid rice lines (630-2X, SP-2X) and their autotetraploid rice lines (630-4X, SP-4X) and the variation mechanism of these traits were firstly and systematically studied by field experiment and trait measure; also response of diploid and autotetraploid rice lines to N+ ion implantation. The results showed that 34 traits of the two diploid rice lines showed increasing trend after their genome were doubled, accounting about for 70.8% of all investigated traits, these traits were mainly morphology traits and some quality traits such as protein and some trace elements contents in grain. And 7 traits of the two diploid rice lines showed reducing trend after their genome were doubled, about for 14.6% of all investigated traits, these traits related to plant growth and development such as photosynthetic rate etc. Plant height, primary xylem of lateral root and protein, P, Ca, F, Na contents of 630-2X line showed increasing trend after its genome was doubled, but SP-2X line presented opposite effect.The photosynthesis was assayed further in two diploid and corresponding autotetraploid rice lines. The results showed that PN of autotetraploid rice lines were lower than those of the corresponding diploid rice lines during the moderate light, whereas higher than those of the corresponding diploid rice lines during the weak or excessively strong light. This means that autotetraploid rice lines could maintain a certain photosynthetic advantage in extreme conditions.The autotetraploid rice lines had higher PN, Fv/Fm, ΦPSⅡ and SOD, POD, CAT, PEPC activities, and lower MDA content, O2·-produce rate than those of corresponding diploid rice lines under drought stress, which made the autotetraploid rice lines more tolerant to drought stress than corresponding diploid rice. Furthermore, variations of morphological and physiological traits in root also affect the growth and drought resistance of autotetraploid rice lines. In the early stage of growth, autotetraploid rice did not have the obvious advantage, even worse than the corresponding diploid rice lines in root growth. But in the jointing, heading, and maturity stages, two autotetraploid rice lines had higher amount than two corresponding diploid lines in root dry weight, ratio of root to shoot, root volume, total absorbing surface area of root, active absorbing surface area of root, and root oxidation ability of a-NA, which increases drought resistance ability of autotetraploid rice lines.Genome-doubling increased the activities of ADPG-PPase, Q-enzyme and SSS, which caused increase in starch content of autotetraploid rice lines. Genome-doubling had different effects on protein contents in different rice lines. For autotetraploid rice line 630-4X, genome-doubling increased activities of its GOT, GPT and GS at all grain filling stage, resulting increase of its protein content. And for autotetraploid rice line SP-4X, genome-doubling reduced its GS activity, which became the bottleneck of protein synthesis, leading to decrease of its protein content.N+ beam implantation had increase effect on most of the traits of diploid rice lines, while had decrease effect on most of the traits of autotetraploid rice lines. For diploid rice, there were significant increase in 19 traits and reduction in 6 traits. And for autotetraploid rice, there were significant increase in 10 traits and reduction in 15 traits, thus autotetraploid rice was also sensitive to N+beam implantation. N+ beam implantation could decrease contents of 8 mineral elements of autotetraploid rice line.