Tolerance evaluation of rice varieties to the brown planthopper,Nilaparvata lugens feeding

The brown planthopper,Nilaparata lugens(Stl)(BPH)is one of the most important insect pests of rice in China and other east-southern Asian countries.Untilization of rice resistance varieties is one of the most econnomic and effective ways for

Evaluation of Salt Tolerance in Nine Shandong Soybean Cultivars at the Germination Stage

[Objectives] Salt stress is an important abiotic stress affecting soybean yield. This study aimed to screen salt-tolerant soybean varieties to improve the utilization efficiency of saline-alkali land. [Methods]Under three concentrations of salt stress（ 5,10 and 15 g/L）,salt tolerance of nine Shandong soybean cultivars was identified at the germination stage. The number of germinated seeds,relative germination rate,plant height,radicle length and number of fibrous roots were recorded to analyze the relative salt damage index and evaluate the salt tolerance of different soybean cultivars. [Results]With the increase of salt concentration,the number of germinated seeds,plant height and number of fibrous roots showed a decreasing trend with significant differences among different soybean cultivars. Under three concentrations of salt stress,Shengdou 10,Lindou 10 and Hedou 28 exhibit relatively strong salt tolerance,indicating that these cultivars are relatively salt-tolerant and highly salt-tolerant cultivars; Hedou 12,Gaofeng 1,Weidou 9 and Qihuang 34 are moderately salt-tolerant cultivars; Qihuang 30 and Qihuang 31 are relatively sensitive to salt solution under 15 g/L NaC l stress. [Conclusions] This study provided high-quality germplasm materials for the improvement of salt tolerance of soybean varieties.

Evaluation on Sixty-eight Rice Germplasms in Cold Tolerance at Germination Stage

Sixty-eight rice germplasms were used for cold tolerance evaluation at the germination stage in laboratory. Seeds of rice germplasms germinated at three different temperatures containing low temperature （constant 13°C for 28 days）, alternative temperature （a temperature cycle of 12 h at 20°C and 12 h at 23°C for 14 days） and control （constant 26°C for 7 days）. Analysis of variance revealed that temperature had a significant effect on germination rate, coleoptile length and radicle length. Germination rate was strongly affected by the low temperature and alternative treatments. Stress of low temperature at the germination stage on the tested rice germplasms caused a reduction in final germination rate and the lengths of coleoptile and radicle. The normal and healthy seeds began to germinate within 36 h after imbibition and germination were completed on the 7th day in the control, but delayed under the low and alternative temperature treatments. The low and alternative temperature treatments delayed the growth of coleoptile and radicle compared to the control, and the average lengths of coleoptile and radicule were strongly inhibited with the decreasing temperature in all of the tested germplasms. Taichung, a semi-dwarf, low amylose content and early maturing rice variety, showed a significantly higher germination rate at the three temperature treatments and its coleoptile length was significantly higher than other germplasms.

Predictive current control of multi-pulse flexible-topology thyristor AC-DC converter

This paper proposes a novel multi-pulse flexible-topology thyristor rectifier(FTTR) that can operate over a large voltage range while maintaining a low total harmonic distortion(THD) in the input current.The proposed multi-pulse FTTR has two operating modes:parallel mode and series mode.Irrespective of the mode in which it operates,the multi-pulse FTTR maintains the same pulses in the load current.To mitigate the harmonic injection into the AC mains,the topology-switching mechanism is then proposed.In addition,predictive current control is employed to achieve fast current response in both the transience and the transitions between modes.To verify the effectiveness of the multi-pulse FTTR as well as the control scheme,performance analysis based on an 18-pulse FTTR is investigated in detail,including fault tolerance evaluation,current THD analysis based on IEEE standard,and potential applications.Finally,a simulation model and the corresponding laboratory setup are developed.The results from both simulation and experiments demonstrate the feasibility of the proposed multi-pulse FTTR as well as the control scheme.