Common smut in maize, caused by Ustilago maydis, reduces grain yield greatly. Agronomic and chemical approaches to control such diseases are often impractical or ineffective. Resistance breeding could be an efficient approach to minimize the losses caused by common smut. In this study, quantitative trait loci (QTL) for resistance to common smut in maize were identified. In 2005, a recombinant inbred line (RIL) population along with the resistant (Zong 3) and susceptible (87-1) parents were planted in Beijing and Zhengzhou. Significant genotypic variation in resistance to common smut was observed at both locations after artificial inoculation by injecting inoculum into the whorl of plants with a modified hog vaccinator. Basing on a genetic map containing 246 polymorphic SSR markers with an average linkage distance of 9.11 cM, resistance QTL were analysed by composite interval mapping. Six additive-effect QTL associated with resistance to common smut were identified on chromosomes 3 (three QTL), 5 (one QTL) and 8 (two QTL), and explained 3.2% to 12.4% of the phenotypic variation. Among the 6 QTL, 4 showed significant QTL x environment (Q x E) interaction effects, which accounted for 1.2% to 2.5% of the phenotypic variation. Nine pairs of epistatic interactions were also detected, involving 18 loci distributed on all chromosomes except 2, 6 and 10, which contributed 0.8% to 3.0% of the observed phenotypic variation. However, no significant epistasis x environment interactions were detected. In total, additive QTL effects and Q x E interactions explained 38.8% and 8.0% of the phenotypic variation, respectively. Epistatic effects contributed 15% of the phenotypic variation. The results showed that besides the additive QTL, both epistasis and Q x E interactions formed an important genetic basis for the resistance to Ustilago maydis in maize.
The traditional methods of waste munitions treatment are expensive and also have potential risks during the treatment process. The supercritical fluid extraction technique has been a rapidly developing technique in the chemical industry in recent years. CO2 is used as the solvent, which has some advantages, such as low pollution, low cost, good chemical stability and can be operated under low temperature conditions. This research explored the feasibility of reclaiming TNT from waste munitions by supercritical CO2 fluid extraction. It was found interestingly that the melting point of TNT can be lowered in supercritical CO2 fluid. Therefore, the melting process of TNT was observed under different temperature and pressure conditions to determine the best operating conditions for stripping-down TNT from waste munitions. Afterwards, simulated warheads with weight loadings of 60 g, 500 g and 1 kg of TNT were prepared and stripping-down tests from the simulated warheads were carried out using supercritical CO2 fluid at temperatures lower than the normal melting point of TNT. The results showed that TNT could be completely removed from the simulated warheads and the optimum operating conditions were determined as 55 °C and 25 MPa. This study will contribute to the feasibility evaluation of stripping-down TNT-based high explosives.
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