Establishment of new convenient two-line system for hybrid production by targeting mutation of OPR3 in allopolyploid Brassica napus

The two-line pollination control system,which usually depends on the utilization of thermosensitive or photoperiod genic male-sterile lines,has been widely used in various crops.However,this system is susceptible to instability issues caused by uncontrollable weather fluctuations.A stable and handy two-line pollination control system is highly desirable in many crop species for heterosis exploitation.Oxophytodienoic acid reductase 3(OPR3)was proven to be involved in jasmonate biosynthesis.In the present study,CRISPR/Cas9(Clustered Regularly Interspaced Short Palindromic Repeat)was utilized to mutate two OPR3 homologs in Brassica napus.After two OPR3 homologs were simultaneously mutated,mutants exhibited complete male sterility,and fertility could be easily restored by exogenous MeJA treatment.Hybrids produced from crosses between the opr3 sterile lines and normal varieties exhibited heterosis.This new two-line system based on OPR3 mutation provides higher stability and convenience than traditional systems.By using exogenous MeJA treatment to restore fertility,the system enables more precise control of male fertility transition,which has great potential to significantly contribute to the maneuverable production of hybrid seeds in rapeseed as well as other Brassica species crops.

Mass transfer in gas–liquid stirred reactor with various triple-impeller combinations

The gassed power demand and volumetric mass transfer coefficient(kLa) were investigated in a fully baffled,dished-base stirred vessel with a diameter of 0.30 m agitated by five triple-impeller combinations. Six types of impellers(six-half-elliptical-blade disk turbine(HEDT), four-wide-blade hydrofoil impeller(WH) pumping down(D) and pumping up(U), parabolic-blade disk turbine(PDT), and CBY narrow blade(N) and wide blade(W)) were used to form five combinations identified by PDT + 2CBYN, PDT + 2CBYW, PDT + 2WHD,HEDT + 2WHDand HEDT + 2WHU, respectively. The results show that the relative power demand of HEDT + 2WHUis higher than that of other four impeller combinations under all operating conditions. At low superficial gas velocity(uG), kLa differences among impeller combinations are not obvious. However,when uG is high, PDT + 2WHDshows the best mass transfer performance and HEDT + 2WHUshows the worst mass transfer performance under all operating conditions. At high uGand a given power input, the impeller combinations with high agitation speed and big projection cross-sectional area lead to relatively high values of kLa. Based on the experimental data, the regressed correlations of gassed power number with Froude number and gas flow number, and kLa with power consumption and superficial gas velocity are obtained for five different impeller combinations, which could be used as guidance for industrial design.