松材线虫萎蔫病生物学特性及治理技术的初步研究

松材线虫萎蔫病病原是松材线虫(Bursaphelenchus xylophilus),而松褐天牛(Monochamus alternatus)是主要传病媒介。根据南京地区自然规律、线虫和天牛的生物学特性,采用了树干注药、薰蒸杀灭病死木中的传病媒介、喷洒菊酯微胶囊农药、加强营林技术管理和制定严格的植物检疫制度等综合防治方法,能有效地防治松材线虫萎蔫病。     

基于多光谱与高光谱遥感数据的冬小麦叶面积指数反演比较

近年来,高光谱遥感数据广泛应用于农作物叶面积指数(LAI)反演。与常用的多光谱遥感数据相比,高光谱数据能否提高农作物LAI反演的精度和稳定性还存在争议。针对这一问题,该研究利用实测冬小麦冠层高光谱反射率数据,构造了不同光谱分辨率和波段组合的5种光谱数据。基于ACRM(a two-layer canopy reflectance model)模型、2套参数化方案及上述5种光谱数据,对冬小麦LAI进行反演,分析光谱分辨率、高光谱数据波段选择、模型参数不确定性3方面因素对LAI反演精度与稳定性的影响。研究结果表明:当波段选择适宜、模型参数不确定性较小且光谱数据分辨率较高时,LAI反演精度与稳定性更高,提高光谱分辨率对LAI反演精度的改进作用随光谱分辨率的升高而降低;反之,当高光谱数据波段选择不当或者模型参数不确定性较大时,提高光谱数据的分辨率并未提高LAI反演精度。该研究解释了"高光谱遥感数据能否提高植被参数反演精度"问题,为进一步发挥高光谱数据在农作物LAI反演中的潜力提供了科学参考。     

Selection of species resistant to the wood rot fungus <Emphasis Type="Italic">Phellinus noxius</Emphasis>

Brown root rot, caused by the pathogen Phellinus noxius, has been reported throughout Southeast Asia, Oceania and Africa as a cause of tree decline and mortality. This paper describes how a field survey can be used to quickly select species that are locally resistant to Phellinus noxius by performing qualitative and quantitative analyses.     

Effects of Estradiol and Testosterone on the Expression of Growth‐related Genes in Female and Male Nile Tilapia,Oreochromis niloticus

Nile tilapia exhibits strong sexual growth dimorphism. The potential role of sex steroid hormones in sexual growth dimorphism is not fully understood. We investigated the effects of estradiol (E₂) and testosterone (T) on growth rate, plasma sex hormones, and expression of growth hormone (GH)‐insulin‐like growth factor (IGF) axis genes and muscle regulatory factor (MRF) genes in female and male Nile tilapia. The results revealed that serum concentrations of E₂ and T were significantly higher after correlative injection (P < 0.05). Compared to male fish, female fish had lower growth rates. E₂ increased growth performance in females with no significant effects on males, whereas T significantly increased growth performance in males, with no significant effects on females. In females, E₂ significantly increased expression of ghr1, ghr2, igf1, and igf2, while T decreased igf2 and increased ghr1 and ghr2 expression. In males, T increased expression of igf1, igf2, ghr1, and ghr2, and E₂ decreased expression of igf1, ghr1, and ghr2. Additionally, E₂ and T enhanced the expression of MRF genes (myod1, myod2, myog, and myf5) in female and male fish, respectively. The results suggest that sex steroid hormones play a role in sexual growth dimorphism by regulating the expression of GH‐IGF axis and MRF genes.     

梨矮化中间砧S2 、S5 和PDR54的离体培养研究

 以梨矮化中间砧S2、S5和PDR54试管苗为试材, 探讨了培养基和植物生长调节剂对梨矮化中间砧试管苗增殖和生根的效应。其结果表明: MS培养基较QL、AS和WPM培养基更有利于中间砧茎的增殖, 2～3 mg·L ^{- 1} 6-BA、0.1～0.2 mg·L ^{- 1} IBA和1～2 mg·L ^{- 1} GA₃组合能有效促进S2、S5和PDR54试管苗的增殖, 其增殖倍数达3.71～5.83。综合各品种增殖倍数、茎高度以及茎质量等指标表明, MS + 3.0 mg·L ^-1 6-BA + 0.2 mg·L^-1 IBA + 2.0 mg·L^-1 GA₃是S2的最佳增殖培养基; MS + 2.0 mg·L^-1 6-BA + 0.1 mg·L^-1 IBA + 1.0 mg·L^-1 GA₃是S5和PDR54增殖的最佳培养基。同时, S2、S5和PDR54增殖的试管苗在不同的生根条件下分别获得了67%、50%和86%的生根率。     

Coexisting invasive gobies reveal no evidence for temporal and trophic niche differentiation in the sublittoral habitat of Lake Erhai,China

Niche differentiation facilitates the coexistence of species within a community through avoidance of competition via mechanisms involving spatial, temporal and/or trophic dimensions. Where invasive species coexist in their non‐native range, niche differentiation could allow their persistence at higher levels of abundance. Here, we tested whether there was temporal and/or trophic niche differentiation between two congeneric invasive goby species (Rhinogobius cliffordpopei and Rhinogobius giurinus) in the sublittoral habitat of Lake Erhai (south‐west China) through quantifying their diel and seasonal rhythm of locomotion activities, feeding activities and diet composition. Both species displayed two similar diel peaks in activity and two main feeding periods (6:00–10:00 and 18:00–22:00), with rhythms of locomotion and feeding activity not differing significantly between the species in each season. Their diets had a high degree of overlap, being primarily composed of macrozooplankton, aquatic insects and shrimp larvae, with no diel changes across the seasons. Thus, in this habitat, there was no clear temporal or trophic niche differentiation between the invasive congeners, indicating their coexistence with high temporal and trophic overlap. In conjunction with data from the littoral and profundal habitats, the gobies revealed different strategies across the habitats (e.g. spatial segregation, trophic niche differentiation) that minimised their competitive interactions and promoted their coexistence. This suggests that the interactions of invasive fishes during the integration into native communities can be context dependent, varying according to factors including habitat and the availability of food resources.     

Light and electron microscopic evidence of white spot disease in the giant tiger shrimp, Penaeus monodon (Fabricius), and the kuruma shrimp, Penaeus japonicus (Bate), cultured in Taiwan

Since 1992, mass mortalities among cultured giant tiger shrimp, Penaeus monodon (Fabricius), and kuruma shrimp, Penaeus japonicus (Bate), have been observed in Taiwan. The condition is known as 'white spot disease' (WSD), based on the characteristic white spots on the cuticle of diseased shrimp. With the scanning electron microscope, two sizes of white spots were observed. Each spot represented a protrusion on the inside surface of the carapace. The composition of white spots was similar to that of the cuticule, most calcium, as determined with an energy dispersive spectrometer. Histological studies of moribund, infected specimens revealed degenerated cells, characterized by hypertrophied nuclei, in various meso- and ectodermal tissues. Infected tissues included cuticular epidermis, connective tissue, lymphoid organ, antennal gland, and haematopoietic, gill and nervous tissue. Nuclei were Feulgen-positive and no occlusion body was found in the necrotic tissue. Transmission electron microscopy revealed the presence of rod-shaped and enveloped virions in the hypertrophied nuclei. The virions measured 298 ± 21 × 107 ± 8 nm in the giant tiger shrimp and 248 ± 12 × 104 ± 8 nm in the kuruma shrimp. In an experimental infection trial, cumulative mortality was 40% within 14 days under stress conditions. No mortality was observed in controls or in non-stressed infected shrimp. Experimental infections show that environmental stressors such as ammonia may enhance the severity of WSD virus infections in cultured shrimp.     

白令海阿留申海盆区夏季理化环境特征及其与狭鳕分布和移动的关系

１９９３年６～８月，“北斗”号渔业资源调查船在白令海阿留申海盆区进行了狭鳕资源声学调查及渔场环境调查。应用本航次调查资料，本文阐述了调查海区温度、盐度及溶解氧分布特征，并分析了狭鳕分布和移动与理化环境的关系。结果表明：（１）阿留申海盆区为大面积低温水所覆盖，水温在１０℃以下。温盐水平分布特征为公海区低温高盐，调查区的其余水域则为高温低盐。溶解氧水平分布比较均匀，表层溶氧含量在１０ｍｇ／Ｌ左右；（２）温跃层位于２５米和５０米之间，一强冷水团控制着１００米到２００米左右的水层，其水温在３℃以下。盐度随深度增加而增加，溶解氧随深度的增加而降低；（３）狭鳕当年生幼鱼主要分布在海盆水系和东大陆架水系的混合区内，１００米层幼鱼密集区水温在３～５℃，盐度在３２．９～３３．１，溶解氧在８～９ｍｇ／Ｌ；（４）夏季狭鳕成鱼主要在冷水团范围以内垂直移动，２００米层成鱼密集区水温为３～４℃，盐度为３３．２～３３．６，溶解氧为６～８ｍｇ／Ｌ。