Inhibition of sexual maturation in tank reared haddock (Melanogrammus aeglefinus) through the use of constant light photoperiods

The haddock (Melanogrammus aeglefinus) is believed to be a potential candidate for aquaculture in the Atlantic coastal countries including the UK, Norway and Canada. However, under culture conditions, haddock will sexually mature prior to the attainment of a suitable harvest weight. Therefore, a long term tank based experiment was performed where three populations of haddock (hatched spring 2002, approximately 150 fish per population) were exposed to either a simulated natural photoperiod (SNP) or SNP until January or July 2003 and thereafter continuous illumination (Jan LL or July LL respectively) with individual growth rate and maturation status being recorded until July 2004 (27 months post-hatch). While the SNP treated population matured in the spring of 2004 (two years post-hatch) with 88% of the population being observed to release gametes, no mature individuals were observed in either of the LL treated populations and furthermore there was no evidence of gonadal development or elevation in sex steroids (testosterone, estradiol-17β or calcium). The application of LL appeared to directly stimulate the growth rate of haddock (e.g. 14 to 27% increase in weight thermal growth coefficient) and improve food conversion rates. At the end of the trial there was an approximate 50% increase in wet weight (SNP: 647 ± 53 g, Jan LL: 982 ± 34 g and July LL 985 ± 33 g), however no significant difference in weight in relation to the length of LL exposure was observed. Plasma melatonin analysis revealed that the natural diel rhythm had been inhibited in both LL treated populations. Along with highlighting the similarity in reproductive entrainment between haddock and other gadoids, these results demonstrate how photoperiod manipulation could be used as a management strategy to improve growth performance in farmed haddock stocks.     

玉米温热杂交种光周期敏感相关性状的遗传模型研究

【目的】分析玉米温热杂交种的光周期敏感特性及相关性状的遗传模型。【方法】以9份北方温带选系和8份含热带、亚热带种质的南方选系,按NCⅡ设计组配72个温热杂交种,分别在北京和雅安进行田间试验。【结果】供试温热杂交种总体均表现出较强的光周期敏感性,ASI等10个性状为温热杂交种光周期敏感性相关性状。其遗传模型大多数符合加性-显性遗传模型,少数属于加性-显性-上位性遗传模型;多数性状以加性效应为主,非加性效应为辅,随着日照变长,加性效应的主导地位更加突出。【结论】将热带、亚热带玉米种质利用于温带玉米遗传改良及育种时,应注重相关性状的加性基因效应。     

Growth performance and physiological responses in striped knifejaw, Oplegnathus fasciatus, held under different photoperiods

The growth performance and stress response in striped knifejaw, Oplegnathus fasciatus (body weight 100–300 g) reared under four photoperiods (6L:6D, 12L:12D, 16L:8D and 24L:0D) were investigated. Fish were fed a commercial diet to apparent satiation, two times a day for 8 weeks. A trial of acute handling and confinement stress was also carried out to investigate the stress-induced levels of different stress indicators in O. fasciatus. Blood was also collected from undisturbed fish which was considered as control. Although there were no significant differences in weight gain, specific growth rate (SGR) and feed conversion efficiency (FCE) in fish exposed to 6L:6D, 16L:8D and 24L:0D photoperiods, all parameters in these photoperiods were significantly higher than those of 12L:12D photoperiod (P < 0.05). There was no significant difference in protein retention efficiency (PRE) between fish exposed to 16L:8D and 24L:0D photoperiods, but PRE in both photoperiods was significantly higher than that of 12L:12D photoperiod.Acute stress significantly increased the plasma levels of cortisol (110.3 ng ml^− 1) and glucose (195.4 mg dl^− 1), and decreased plasma levels of total protein (0.8 g dl^− 1); however, all parameters were returned back to the levels indistinguishable from those of control, undisturbed fish within 24 h. The levels of cortisol, glucose and total protein in fish exposed to different photoperiods during the study were far from the stress-induced levels (P < 0.05). The results demonstrated that the growth performance of O. fasciatus reared from 100 to 300 g can be stimulated significantly by using the manipulated photoperiods where feeding time may be playing an important role to increase food intake and feed conversion efficiency. It also revealed that the artificial photoperiods did not cause significant stress response in fish.     

春化和光周期基因在陕西小麦品种中的分布

为了解陕西小麦品种中春化基因和光周期基因的分布特点,采用STS标记检测了陕西境内173份小麦品种春化基因Vrn-A1、Vrn-B1、Vrn-D1、Vrn-B3和光周期基因Ppd-D1位点的显性等位变异组成.结果表明,4个春化基因位点显性等位变异在陕西小麦中的平均分布频率不同,顺序为Vrn-D1(38.2%)＞Vrn-B1(16.2%)＞Vrn-A1(1.2%)＞Vrn-B3(0%).春化显性等位变异在陕西境内各麦区的分布频率也不同:归属于北部冬麦区的小麦品种4个春化位点均处于隐性状态;归属于黄淮冬麦区的小麦品种显性等位变异分布比例顺序为Vrn-D1(41.7%)＞Vrn-B1(19.1%)＞Vrn-A1(0%)=Vrn-B3(0%);归属长江中下游麦区的为Vrn-D1( 40.3%)＞Vrn-B1(16.1%)＞Vrn-A1(0%)=Vrn-B3(0%),归属西南冬麦区的为Vrn-D1(54.6%)＞Vrn-A1(18.2%)=Vrn-B1(18.2%)＞Vrn-B3(0%).在光周期Ppd-D1位点,99.4%的品种携带对光周期反应不敏感的显性等位变异Ppd-D1a.陕西境内推广的小麦品种中存在7种春化和光周期基因显性等位变异组合,即Vrn-D1、Ppd-D1a、Vrn-B1/Ppd-D1a、 Vrn-D1/Ppd-D1a、Vrn-A1/Vrn-B1/Ppd-D1a、Vrn-A1/Vrn-D1/Ppd-D1a 和Vrn-B1/Vrn-D1/Ppd-D1a,平均分布频率为0.6%、49.7%、11.6%、32.3%、0.6%、0.6%和4.6%.5个位点显性等位变异组合在陕西境内不同麦区分布也不同:归属于北部冬麦区的检测小麦品种中,均携带单一显性等位变异Ppd-D1a;归属于黄淮冬麦区的小麦品种中,显性等位变异组合出现5种类型,即Vrn-D1、Ppd-D1a、Vrn-B1/Ppd-D1a、 Vrn-D1/Ppd-D1a和Vrn-B1/Vrn-D1/Ppd-D1a,比例分别为1.2%、45.2%、13.1%、34.5%和6.0%;归属于长江中下游冬麦区的小麦品种中存在4种显性等位变异组合类型,即Ppd-D1a、Vrn-B1/Ppd-D1a、 Vrn-D1/Ppd-D1a和Vrn-B1/Vrn-D1/Ppd-D1a,分别占45.2%、14.5%、37.1%和3.2%;归属于西南冬麦区的小麦品种中存在5种类型,分布比例次序为Ppd-D1a(36.3%)=Vrn-D1/Ppd-D1a(36.3%)＞Vrn-A1/Vrn-B1/Ppd-D1a(9.1%)=Vrn-A1/Vrn-D1/Ppd-D1a(9.1%)=Vrn-B1/Vrn-D1/Ppd-D1a(9.1%).这些信息为陕西选育广适性小麦品种提供了依据.     

Effects of different artificial photoperiods and temperatures on haematological parameters of rainbow trout (Oncorhynchus mykiss)

This study assessed the effects of two artificial photoperiods (LD 24:0 and LD 12:12) and three temperature regimes (9, 11, and 18°C) for 30 days on haematological parameters of trout (Oncorhynchus mykiss) kept in freshwater. Samples were taken at days 7, 14, and 30 during exposure to treatments. A higher mortality (22%) and lower oxygen concentration (<8.0 mg/l) were associated with the combination of photoperiod LD 24:0 and 18°C. The LD 24:0 photoperiod (independently of temperature) increased the haematocrit and the number of erythrocytes at days 7, 14, and 30 (P < 0.01). A temperature of 18°C (independently of photoperiod regimes) diminished the number of total leucocytes, lymphocytes and thrombocytes (P < 0.01). The LD 24:0 photoperiod (also independently of temperature) lowered the number of lymphocytes only after 14 days of experimentation (P < 0.01). Interaction between artificial photoperiod and temperature was only observed at day 14 for polychromatophils (P < 0.01). These results resemble the effects of stress caused by elevated temperatures and the application of continuous light photoperiods, indicating that survival risks may develop in trout farming when this combination is met.     

Growth and age at first maturity in turbot and halibut reared under different photoperiods

The effect of extended photoperiods on growth and age at first maturity was investigated in 166 (79 females and 87 males) individually tagged Atlantic halibut Hippoglossus hippoglossus and in 114 (50 females and 64 males) individually tagged turbot Scophthalmus maximus. The halibut were reared at 11 °C on four different light regimes from 10 February to 6 July 1996: simulated natural photoperiod, (LDN), continuous light (LD24:0), constant 8 h light and 16 h darkness (LD8:16) and LD8:16 switched to continuous light 4 May 1996 (LD8:16–24:0). From 6 July 1996 to 9 February 1998 the LD24:0 and LD8:16–24:0 were reared together under continuous light and the LDN and LD8:16 together under natural photoperiod. The turbot were reared at 16 °C on three different light regimes: constant light (LD24:0), 16 h light:8 h darkness (LD16:8), or simulated natural photoperiod (LDN). After 6 months on the different photoperiods, the turbot was reared together on LDN for approximately 12 months until first maturation. Juveniles subjected to continuous light (halibut) or extended photoperiods (halibut and turbot) exhibited faster growth than those experiencing a natural photoperiod or a constant short day. Moreover, when the photoperiod increased naturally with day-length or when fish were abruptly switched from being reared on short-day conditions to continuous light, a subsequent increase in growth rate was observed. This growth enhancing effect of extended photoperiods was more apparent on a short time scale in Atlantic halibut than in turbot, but both species show significant long-term effects of extended photoperiods in the form of enhanced growth. In both species lower maturation of males was seen in groups exposed to extended or continuous light compared to LDN and this could be used to reduce precocious maturation in males leading to overall increase in somatic growth. This revised version was published online in August 2006 with corrections to the Cover Date.     

小麦光周期基因在我国不同麦区中的组成分布

为明确光周期基因在我国小麦品种中的组成分布特点,利用已有的特异性分子标记对我国977份小麦品种的光周期基因Ppd-A1、Ppd-B1和Ppd-D1进行检测,分析比较不同麦区中光周期基因的组成分布特点。结果表明,在Ppd-A1位点有5份材料无PCR扩增条带(0.5%),其余972份材料都为光周期敏感型Ppd-A1b(99.5%);在Ppd-B1位点仅青春37为光周期不敏感型Ppd-B1a(0.1%),有3份材料无PCR扩增条带(0.3%),其余973份材料为光周期敏感型Ppd-B1b(99.6%);在Ppd-D1位点有789份材料为光周期不敏感型Ppd-D1a(80.8%),其余188份材料为光周期敏感型Ppd-D1b(19.2%)。在东北春麦区、新疆冬春兼播麦区、青藏春冬兼播麦区等高纬度麦区,小麦品种多携带光周期敏感型基因Ppd D1b;在北部冬麦区、黄淮冬麦区、长江中下游冬麦区,不敏感型Ppd-D1a基因分布频率较高;Ppd-D1a基因分布频率总体呈现以黄淮冬麦区为最高,向其他方向麦区呈现下降的趋势。在Ppd-A1位点和Ppd-B1位点发现的无PCR扩增条带的新等位变异,丰富了小麦育种种质资源的多样性,为选育适应不同环境条件的品种奠定了材料基础,是进一步研究的重要材料。     

广州的短日照对短光低温不育水稻宜D1S育性转换的影响

本试验通过在广州对宜D1S的周年育性观察及人工短日处理对其育性转换的影响分析得到：(1)宜D1S是一个光敏性较强的材料，在广州一年中具有明显的从不育→可育→不育的育性转换特点。(2)宜D1S的光敏期为幼穗分化Ⅰ期～Ⅲ期。在常温下光敏期适当的短日处理可使育性趋于完全不育，但在高温下光敏期短日不育效应被削弱。作者认为     

光周期对春夏大豆品种生育阶段的影响

作者于１９９０－１９９１年，在哈尔滨和长沙两地采用８小时和１６小时光，周期诱导，研究黑河５，黑农３３，晋豆１和湘春１４四个品种光周期反应。结果表明：１，各品种短光强弱顺序，在哈尔滨是晋豆１＞湘春１４＞黑河５＞黑农３３；长沙则为黑河５＞湘春１４＞，黑河３３＞晋豆１。２，在哈尔滨经８小时光周期诱导，Ｖｅ－Ｒ８期黑河５和黑波农３３日数化自然光照缩短，主要是Ｖｅ－Ｒ１－Ｒ１－Ｒ３期日数缩短所致，晋豆１和湘     

黑龙江春小麦品种对光周期反应特性研究

[目的]探讨不同光周期对春小麦生育进程及其主要产量因素的影响。[方法]将待测小麦种子洗净消毒后,置于温度为25℃、相对湿度为80%的恒温恒湿培养箱内进行种子萌动处理。种子露白后,置于0~2℃低温黑暗处处理15 d。[结果]光周期延长时,出苗至成熟的天数减少且光反应敏感品种的出苗至拔节和拔节至抽穗期缩短极为显著。在短日照下,光反应迟钝品种的分蘖数略有变化,而光反应敏感品种的分蘖数增加极为显著。光反应敏感品种的株高变化幅度、穗长可调幅度明显大于光反应迟钝品种,短日照下光反应敏感品种的株高增加10 cm以上。[结论]延长发育期的光照时间有利于增加光反应敏感春小麦品种的小穗数和小花数,从而形成大穗。