| Drought is one of the major problems facing agricultural production. Rice(Oryza sativa.) is the major water-intensive crops and it’s study of drought tolerance is important to increase grain yield. Drought resistance of plant is a very complex trait and is affected by the impact of environmental and genetic background significantly. the typical high yield drought tolerant rice resources scarce, so has been slow Due to the typical high-yielding drought-tolerant rice scarcity of resources, so the research progress around the rice drought resistance mechanism has been slow. In 1995, Zhu Qisheng team of Anhui academy of agricultural sciences used the method of soaking embryo, DNA of Alternanthera philoxeroides Griseb was extracted and introduced into rice, bred a new drought-tolerant variety Lvhanl, which has been in production on a large scale.It’s promotion area was 80% of the total area of upland rice in the country, which showed greater adaptation in many Asian and African countries. However, the mechanism of drought resistance was not clear yet. In this paper, the Lvhanl was taking as the primary research material, and the morphological and physiological characteristics of drought difference of the Lvhanl from its original receptor Rice 6527 was compared and analysed. We conducted it’s comprehensive assessment of drought tolerance in the field with 105 upland rices gathered in different regions of 17 countries; On this basis, study on the drought-related characteristics QTL analysis to exploratory Indica upland rice drought-tolerant mechanism, the main research results were as follows:1. The morphological and economic traits differences of Lvhanl and 6527 under drought stressUsing 25% PEG to imitate drought treatment, and investigating the situation of germination and roots of Lvhanl and 6527 varieties after 7 days, the results showed that the germination rate of Lvhanl was beyond 20 percentage than 6527, Analysis of variance showed that Lvhanl,6527 and Brazilian upland rice stem length had reached extremely significant level (P< 0.01), root and stem ratio of Lvhanl was 1.2, more 37.5 percentage than 6527. As for save-water test show:under the condition saved water 60% management, decrease amplitude of 1000-grain weight, seed setting rate, plant height and efficient panicle of Lvhanl was smaller than CK, but the difference was not significant level. However, decrease amplitude of plot yield, the total seed number of panicle, theoretical yield and actual grain number of panicle was most, and all exceeded 25%, the difference was extremely significant (P< 0.01)2. The difference of Lvhanl and 6527 varieties of physiology and character in drought resistanceAfter drought treatment, the RWC of Lvhanl and 6527’s leaves were decreased, and decrease amplitude of 6527 was more than Lvhanl. Temperature change of leaves presented fluctuant trend, the change of Lvhanl was as consistent as 6527, and decrease amplitude of 6527 was smaller. Change trend of chlorophyll in Lvhanl variety presented decreased, slowly decreased, increased, then decreased, chlorophyll content change of 6527 was lower than control. Proline content was increased, and rising amplitude was different between Lvhanl and 6527, the rising amplitude of Lvhanl was more than 6527 under the same treatment. The rising amplitude of MDA content in 6527 was bigger than Lvhan1, there was difference among different treatment time. Soluble protein content in leaves was lower than control, but the difference was not significant. POD activity presented a trend with increased, then decreased, but the change amplitude was different, POD activity value was most after drought treatment 14 days, and the difference was extremely significant (P<0.01) compared with control.Drought treatment 8-14d, superoxide dismutase (SOD) activity of the three varieties showed up-down-up-down trends; Drought treatment 8d, SOD values of the three species were close; Drought 12d, SOD values of the three species appeared obvious difference:upland rice was higher than paddy rice, especially Lvhanl was up to 1.59 U/ mg prot, than rice 6527 was 0.93 U/mg prot, higher than 70.97%.3. Comprehensive evaluation of Lvhanl variety drought resistanceSimilarity-difference analysis methods used for from 17 different countries such as Brazil,105 upland rice varieties and 1 rice varieties, including 26 belong to Japonica rice varieties and 80 Indica rice varieties, drought-tolerant comprehensive analyses, the plant height, spike length, panicle, panicle total grain number per plant, seed setting rate, grain weight and other agronomic and economic index as the comprehensive evaluation index, the results show that:Lhanl is "good", the difference and analysis of sorting for the 11th, show that the varieties belonging to the drought resistance of good varieties.4. QTL mapping analysis of drought tolerance related traitsWith Lvhanl and "Nipponbare" Building F2 mapping population Indica and Japonica constructed a molecular linkage map, covering rice full-length genome 1674.2 cM, the average interval was 19.47 CM, distributed on 12 chromosomes. There had two QTL loci of leaf water content on the fourth and sixth chromosome, the contribution rate of phenotypic variation was 4.81%-6.43%. The contribution rate of qDT-4 on the fourth chromosome was the maximum, and explained 6.43%, LOD value reached to 2.7, as the main effect QTL, additive effect was 0.54. Mode of action presented additive effect, and the QTL located in 4-27M and 4-23M, closed to 4-27M. qDT-6 on the sixth chromosome was explained 4.81%, LOD value reached to 2.0, additive effect was 0.61, and the QTL located between in 6-3M and RM267. |
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