Comparative study on the utilization of crystalline methionine and methionine hydroxy analogue calcium by Pacific white shrimp (Litopenaeus vannamei Boone)

The objective of this study was to compare the supplemental effects of crystalline DL‐methionine (DL‐Met) and methionine hydroxy analogue calcium (MHA‐Ca) on growth performance of Pacific white shrimp. Eight isoproteinic (355.3 ± 2.0 g/kg diet) and isolipidic (70.0 ± 2.2 g/kg diet) diets were prepared as positive diet (20% fish meal), negative diet (15% fish meal) and DL‐Met, MHA‐Ca‐supplemented diets with the supplementation of 0.03%, 0.06%, 0.09% DL‐Met and 0.04%, 0.07%, 0.1% MHA‐Ca in negative diet respectively. Pacific white shrimp (0.92 ± 0.03 g) were fed one of the eight diets for 49 days. The results showed that dietary DL‐Met did not affect weight gain (WG) and feed conversion ratio (FCR) (p > 0.05), but the supplementation of 0.1% MHA‐Ca significantly increased WG, protein and lipid retention, and reduced FCR (p < 0.05) when compared to the negative group, and reached the similar levels as the positive control. The total free amino acids (TFAA) in haemolymph of MHA‐Ca groups and PC, NC group peaked at the 3rd hr after feeding, but the peaking time of DL‐Met groups was advanced to the 2nd hr. Activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in haemolymph of all MHA‐Ca groups peaked at the 2nd hr, but DL‐Met groups peaked at the 1st hr after feeding. The above results indicated that the supplementation of 0.1% MHA‐Ca in a low fish meal diet could improve the growth performance and feed utilization of Pacific white shrimp, but dietary DL‐Met did not significantly affect the growth.     

Population structure,genetic diversity,and sexual state of the rice brown spot pathogen Bipolaris oryzae from three Asian countries

Bipolaris oryzae causes brown spot in rice (Oryza sativa) inflicting substantial grain yield losses worldwide. Knowledge of the population structure, genetic diversity and sexual recombination of the fungal pathogen can help to implement effective disease management strategies. In this study, B. oryzae isolates sampled from Iran, the Philippines and Japan were analysed with 12 simple‐sequence repeat (SSR) markers, newly developed from the genome sequence of the fungus. Among the 288 B. oryzae isolates genotyped, 278 unique haplotypes were identified. High genotype numbers (richness) with even distribution (evenness) were found within the collection sites. Both mating types, MAT1‐1 and MAT1‐2, were present in each collection area, and the sexual state was induced under controlled conditions with production of viable ascospores. However, the tests of linkage disequilibrium rejected of the hypothesis of random mating. Discriminant analysis of principal components (DAPC) revealed that the B. oryzae collection formed three clusters, each consisting of isolates from different collection sites. Analysis of molecular variance (amova ) showed that genetic variation among clusters was 18.7%, with the rest of the variation distributed within clusters (R_ST = 0.187, P < 0.001). Statistically significant pairwise genetic differentiation was found between the clusters. These results show that Asian B. oryzae isolates are genetically diverse, and, overall, distributed in three groups. These findings will be helpful in managing the disease and guide the use of representative isolates needed for selection of resistant rice varieties.     

桑树修复土壤重金属污染的研究进展

重金属污染修复已成为当前国际环境科学研究的热点问题,利用桑树修复土壤重金属污染也是一种有效的植物修复技术。笔者简单介绍了土壤重金属与植物修复技术的概念,并阐述了桑树的生长特性,桑树生长与土壤中镉、铅、锌、砷等重金属元素的关系,并结合江西省土壤重金属污染的形势,探讨了桑树作为江西省土壤重金属污染修复树种的潜力。     

不同抗旱措施对东试早柚光合生理特性及产量的影响

以东试早柚为试材,采用常规管理为对照,开展黑地膜、白地膜、杂草覆盖和添加保水剂措施的田间比较试验,研究不同抗旱措施对柚子物候期光合生理特性及其产量的影响。结果表明,柚子各物候期叶片的净光合速率（Pn）、蒸腾速率（Tr）和气孔导度（Gs）均以黑地膜和白地膜处理最高,其次为草覆盖和保水剂处理,对照表现为最低。各抗旱措施柚子叶片的水分利用效率（WUE）均高于对照,从柚子现蕾期（1月）至壮果期（6月）以草覆盖和保水剂处理的WUE最高,而在柚子成熟期（7~9月）以黑地膜处理的WUE最高,对照的WUE表现最低。总的看来,不同抗旱措施均明显提高了全物候期柚子叶片的Pn及WUE;各抗旱措施处理以黑地膜处理的座果率和产量较对照均增加最为显著,较对照分别提高了91.7％和56.9％,白地膜和草覆盖的座果率及保水剂处理的产量居中,分别较对照提高了29％和47％、36.5％和31.9％,而对照的座果率与产量均最低。各抗旱措施效果从高到低依次为：黑地膜>白地膜>草覆盖>保水剂>对照。     

浅谈我国的水产饲料行业标准

<正>我国是产量位居世界第一的水产养殖大国,在我国水产养殖业的发展过程中,水产饲料工业发挥了至关重要的作用。饲料是进行养殖生产最为重要的物质     

花生油乳液稳定特性研究

本实验研究了三聚甘油单硬脂酸酯(C-18A)、四聚甘油单硬脂酸酯(D-18A)、六聚甘油单硬脂酸酯(F-18A)、六聚甘油六硬脂酸酯(F-18F)、卵磷脂、分子蒸馏单甘酯(单甘酯)和两种蔗糖酯(SE11、SE15)共八种常用的非离子型乳化剂对花生油O/W型乳状液的表面张力及粒径的影响,并采用Box-Behnken响应面设计.以脂肪上浮速率为响应值,对乳化剂进行了复配.结果表明,八种乳化剂中卵磷脂及单甘酯在降低乳液表面张力方面效果最好,SE11及SE15在降低乳液粒径方面效果最好(P<0.05).响应面中各因素对乳液脂肪上浮速率影响的显著程度依次为SE15、卵磷脂、单甘酯,最佳乳化剂配方为单甘5g/L、卵磷脂7g/L、SE15 5g/L,该配方下乳状液的脂肪上浮速率为0.1643%/s.     

不同氮素籽粒生产效率油菜品种苗期叶片光合特性差异

2007-2008年度通过对不同氮肥水平下28个品种苗期叶片叶绿素含量和光合参数以及氮素籽粒生产效率的测定,结果表明：（1）不同品种氮素籽粒生产效率差异较大,施用氮肥氮素籽粒生产效率显著降低。（2）多数品种施用氮肥叶片叶绿素含量(SPAD值),净光合速率(Pn)增加;PSⅡ最大光化学量子产量(Fv/Fm),光化学淬灭系数(qP)增加,非光化学淬灭系数(qN)减小。（3）叶片叶绿素含量(SPAD值)与净光合速率(Pn)之间,净光合速率(Pn)与PSⅡ最大光化学量子产量(Fv/Fm)之间都表现显著正相关关系。（4）氮素籽粒生产效率与苗期叶片PSⅡ最大光化学量子产量(Fv/Fm)呈显著正相关,不施氮肥条件下氮素籽粒生产效率与SPAD值呈显著正相关。     

不同生态类型大豆品种光周期反应的鉴定

通过设置短日照(12h)和长日照(16h)两种光照处理,对58个近年育成的不同生态类型大豆品种(系)进行光周期反应鉴定.结果表明.大豆光周期反应敏感性强弱依次为南方夏大豆、南方春大豆、黄淮海夏大豆、北方春大豆,品种的光周期反应敏感性随着主产地纬度的降低而增强;本试验建立了一种以短日开花促进率为评价指标的光周期反应敏感性的鉴定方法,该方法准确、简便、周期短、成本低廉.     

粘胶涂干防治榆紫叶甲试验

为了阻止榆紫叶甲成虫上树为害,采用无毒粘胶涂干方法对害虫进行了防治试验,并与采用无公害农药——触破进行涂毒环和直接喷洒百虫杀两种防治方法的效果进行了比较。结果显示:粘胶涂干法的防治效果最好,其防治率可达90%以上,明显高于涂毒环的防治率(32.63%)和喷药的防治率(68.90%);且粘胶涂干法的有效防治期长,在整个春季对越冬代成虫都有持续的阻隔上树作用;涂粘胶的最佳宽度为5cm,其防治率可达89.57%。     

鸡蛋中臭鼻克雷伯氏菌的分离与鉴定

从市售鲜鸡蛋内容物中分离到一株革兰氏阴性杆菌,经形态学观察、培养特性观察及生化试验鉴定该菌为臭鼻克雷伯氏菌。药敏试验表明该菌对先锋霉素、链霉素、氯霉素和庆大霉素敏感。动物实验结果表明,该菌对小白鼠有致病力。一般情况下臭鼻克雷伯氏菌属于条件致病菌,从鸡蛋中分离出致病菌株,在公共卫生方面具有重要意义。