短期培养对玻璃化冷冻小鼠2-细胞胚胎低渗抵抗力的修复作用

为研究短期培养对玻璃化冷冻小鼠2-细胞胚胎低渗抵抗力的修复作用,对玻璃化冷冻小鼠2-细胞胚胎解冻后进行短期(2～4 h)培养,然后使用20%的低渗PBS液于25℃条件下处理20 min,观察48 h发育率、囊胚率和移植后妊娠率、产仔率.获得93%的48 h发育率和48%的囊胚率,显著高于低渗处理前未培养组(47%和9%)(P＜0.05).证明解冻后的短期培养中可以有效修复玻璃化冷冻对小鼠2-细胞胚胎低渗抵抗力的损伤.     

Tomato early blight (Alternaria solani): the pathogen, genetics, and breeding for resistance

Alternaria solani causes diseases on foliage (early blight), basal stems of seedlings (collar rot), stems of adult plants (stem lesions), and fruits (fruit rot) of tomato. Early blight is the most destructive of these diseases and hence receives considerable attention in breeding. For over 60 years, breeding for early blight resistance has been practiced, but the development of cultivars with high levels of resistance has been hampered by the lack of sources of strong resistance in the cultivated tomato and by the quantitative expression and polygenic inheritance of the resistance. In some accessions of wild species, high levels of early blight resistance have been found, but breeding lines still have unfavorable horticultural traits from the donor parent. Recently, the first linkage maps with loci controlling early blight resistance have been developed based on interspecific crosses. These maps may facilitate marker-assisted selection. This overview presents the current knowledge about the A. solani–tomato complex with respect to its biology, genetics, and breeding.     

紫花苜蓿品种在河北低平原区的引进筛选试验研究

在河北低平原区对引进的11个紫花苜蓿品种进行了三年的比较试验。结果表明：保定苜蓿鲜草产量最高，其次是中苜1号、WL323ML；中苜1号干草产量最高，其次是WL323ML、保定苜蓿；WL323ML粗蛋白质产量最高，其次是顶点、中苜1号。保定苜蓿、中苜1号株高、鲜干比、茎叶比明显较低。保定苜蓿、中苜1号抗涝性较强，但抗倒性较差。各品种抗寒性、抗旱性均较强，无明显差异。综合分析WL323ML表现最优，宜作为河北低平原区进行推广的首选品种。     

月季功能基因研究与应用进展

月季是花中皇后.为了充分利用月季优良农艺性状的相关基因来培育具有新奇花色、浓郁芳香、瓶插期长、抗逆性强的新品种,对月季功能基因研究方法、花色代谢相关基因、花香相关基因、乙烯信号传导相关基因、抗根癌病和白粉病基因的研究进展加以综述;对月季转基因育种发展前景做了评价.     

Cytochrome P-based resistance mechanism and pyrethroid resistance in the field Anopheles albimanus resistance management trial

The relative rates of cytochrome P⁴⁵⁰ selection in southern Mexican Anopheles albimanus populations were investigated during a 3 years indoor residual house spraying intervention with a pyrethroid (PYR) or DDT, a mosaic of organophosphate (OP)-PYR, and the annual rotation of OP-PYR-carbamate (CARB). This insecticide resistance mechanism, initially evenly spread in the mosquito population, correlated with PYR resistance during the second treated year, when cytochrome P⁴⁵⁰ contents increased in most villages of the PYR, rotation and mosaic schemes. However, by the third year, mean cytochrome P⁴⁵⁰ contents declined to susceptible levels in mosquitoes of the rotation and one mosaic group but not in the PYR-treated villages. In DDT-treated villages, a continuous decrement of cytochrome P⁴⁵⁰ levels occurred since the first treatment year, and susceptible levels were observed at the end of the intervention. Most correlations of cytochrome P⁴⁵⁰ levels and PYR resistance were lost during the third year, indicating that another mechanism evolved in resistant mosquito populations.     

Fipronil resistance mechanisms in the rice stem borer, Chilo suppressalis Walker

Fipronil resistance mechanisms were studied between the laboratory susceptible strain and the selective field population of rice stem borer, Chilo suppressalis Walker in the laboratory. The borer population was collected from Wenzhou county, Zhejiang province. After five generations of selection, fipronil resistance ratio was 45.3-fold compared to the susceptible strain. Synergism experiments showed that the synergistic ratios of PBO, TPP and DEF on fipronil in susceptible and resistant strains of C. suppressalis were 7.55-, 1.93- and 2.91-fold, respectively, and DEM showed no obvious synergistic action on fipronil. Activities of carboxylesterase and microsomal-O-demethylase in the resistant strain were 1.89- and 1.36-fold higher that in susceptible strain, and no significant difference of glutathione-S-transferase activity was found between the resistant and susceptible strains. The K_m and V_max experiments also demonstrated that fipronil resistance of C. suppressalis was closely relative to the enhanced activities of carboxylesterase and microsomal-O-demethylase. Moreover, cross-resistance between fipronil and other conventional insecticides and the multiple resistant properties of the original Wenzhou’s population were also discussed.     

Various mechanisms responsible for permethrin metabolic resistance in seven field-collected strains of the German cockroach from Iran, Blattella germanica (L.) (Dictyoptera: Blattellidae)

Insecticide resistance in the German cockroach can be mediated by a number of mechanisms, the most common being enhanced enzymatic metabolism. Seven field-collected strains of German cockroach, Blattella germanica (L.) with various levels of resistance to pyrethroids, five out of which were also cross-resistant to DDT were used in this study. The investigation of possible mechanisms responsible for permethrin resistance was carried out using the synergists PBO, DEF and DMC and biochemical assays, including general esterases, glutathione S-transeferases and monooxygenases assays, using an automated microtitre plate reader. PBO and DEF, the inhibitors of cytochrome p450 monooxygenases and general esterases, respectively, affected permethrin resistance to varying degrees depending on the strain. DDT resistance in five strains were not completely eliminated by the synergist DMC, an inhibitor of glutathione S-transferase enzymes, suggesting that a further non-metabolic resistance mechanism such as kdr-type may be present. This suggestion was further supported by GST assay data, where a little elevation in GST activity was detected in only two strains. The synergist data supported by biochemical assays implicated that cytochrome p450 monooxygenases or hydrolases are involved in permethrin resistance in some strains. However, these results implicated both enhanced oxidative and hydrolytic metabolism of permethrin as resistance mechanism in the other strains. The results of synergist and biochemical studies implicated that all the field-collected permethrin resistant strains have developed diverse mechanisms of resistance, although these strains have been collected from the same geographic area. The change in resistance ratios of some strains by using PBO or DEF is discussed. It is of interest to note that because resistance to permethrin was not completely eliminated by DEF and PBO, it is likely that one or more additional mechanisms are involved in permethrin resistance in every strain studied.     

Resistance mechanisms and associated mutations in acetylcholinesterase genes in Sitobion avenae (Fabricius)

Wheat aphid, Sitobion avenae (fabricius), is one of the most important wheat pests and has been reported to be resistant to commonly used insecticides in China. To determine the resistance mechanism, the resistant and susceptible strains were developed in laboratory and comparably studied. A bioassay revealed that the resistant strain showed high resistance to pirimicarb (RR: 161.8), moderate reistance to omethoate (32.5) and monocrotophos (33.5), and low resistance to deltamethrin (6.3) and thiodicarb (5.5). A biochemistry analysis showed that both strains had similar glutathione-S-transferase (GST) activity, but the resistant strain had 3.8-fold higher esterase activity, and its AChE was insensitive to this treatment. The I₅₀ increased by 25.8-, 10.7-, and 10.4-folds for pirimicarb, omethoate, and monocrotophos, respectively, demonstrating that GST had not been involved in the resistance of S. avenae. The enhanced esterase contributed to low level resistance to all the insecticides tested, whereas higher resistance to pirimicarb, omethoate, and monocrotophos mainly depended on AChE insensitivity. However, the AChE of the resistant strain was still sensitive to thiodicarb (1.7-fold). Thus, thiodicarb could be used as substitute for control of the resistant S. avenae in this case. Furthermore, the two different AChE genes cloned from different resistant and susceptible individuals were also compared. Two mutations, L436(336)S in Sa.Ace1 and W516(435)R in Sa.Ace2, were found consistently associated with the insensitivity of AChE. They were thought to be the possible resistance mutations, but further work is needed to confirm this hypothesis.     

Susceptibility of citrus species to Alternaria alternata, the causal agent of the Alternaria brown spot

Alternaria alternata, the causal agent of Alternaria brown spot (ABS), causes necrosis on leaves, twigs, and fruit, reducing the productivity and quality of fruits. Tangerines and their hybrids are highly susceptible to the disease. Species, hybrids, and cultivars of Citrus from the germplasm bank of the Estação Experimental de Citricultura de Bebedouro, São Paulo, Brazil, were evaluated in 2004 and 2005 with respect to their resistance to A. alternata, both through natural infection and by inoculation. Detached leaves were also used to demonstrate susceptibility or resistance to the disease. Ten cultivars of Satsumas (Citrus unshiu), and 14 cultivars of Clementine mandarin (C. clementina) did not show any symptoms of the disease in their leaves, either through natural infection or when inoculated in the field. The Burguess SRA-412, Wallent SRA-438, Carvalhais, Ampefy SRA-459, Ananas SRA, and Macaque SRA-426 mandarin hybrids (C. reticulata) did not show symptoms of the disease under natural or artificial infection in the field. Some cultivars of C. deliciosa, C. tangerina, C. erythrosa, and C. temple showed symptoms of the disease, even though no previous record of their susceptibility to Alternaria brown spot had been previously reported. The hybrids Fairchild, Nova, Page, Fortune, and Sunburst were susceptible to the disease. However, Fremont mandarin (a crossing between C. clementina and C. reticulata), Encore (C. nobilis × C. deliciosa), and Fallglo (C. reticulata × C. paradisi) did not show symptoms in field, and few symptoms were verified in detached leaves. These materials are promising for the cultivation of tangerines, and will enable genetic improvement for the development of cultivars resistant to Alternaria brown spot.