基于配合力和遗传距离的甜高粱杂种优势预测

【目的】对甜高粱主要农艺性状进行杂种优势、一般配合力及特殊配合力分析,同时,分析配合力、表型遗传距离以及分子遗传距离用于杂种优势预测的可行性,为甜高粱的种质创新和杂交种选育提供理论参考。【方法】采用不完全双列杂交设计,以8个甜高粱不育系为母本及8个甜高粱恢复系为父本配制64个杂交组合。对亲本及杂交后代进行2年的性状调查,包括：出苗至开花日数、生育期、株高、穗长、茎粗、分蘖、单穗粒重、千粒重、籽粒产量、单株重、生物产量和含糖量。分析不同性状的杂种优势、一般配合力、特殊配合力、表型遗传距离、分子遗传距离以及配合力、遗传距离与杂种优势的相关性。【结果】各性状的中亲优势由强到弱分别为单株重、籽粒产量、单穗粒重、生物产量、株高、穗长、千粒重、茎粗、生育期、至开花日数、分蘖和含糖量,其中,生育期、至开花日数、分蘖和含糖量等性状为负优势。不同性状的中亲优势和超亲优势由强到弱的顺序基本相同。配合力分析表明,每个性状中,不同亲本的一般配合力相差较大,且不同组合的特殊配合力也有很大差异。大多数特殊配合力高的组合,其亲本的一般配合力也较高。杂种优势与配合力和遗传距离的相关性为单株重、籽粒产量、单穗粒重、生物产量、穗长、千粒重、分蘖以及含糖量等性状的杂种优势与其亲本的一般配合力和特殊配合力均为极显著正相关。生育期的杂种优势与特殊配合力为极显著正相关,至开花日数与特殊配合力为显著正相关。亲本间的表型遗传距离为2.86—6.82,分子遗传距离为0.50—0.96。单株重、籽粒产量、单穗粒重、生物产量、株高、穗长、茎粗及含糖量等性状的杂种优势与分子遗传距离的相关性大于表型遗传距离,其中,生物产量、单株重、穗长和茎粗的杂种优势与分子遗传距离为极显著正相关。【结论】所有性状中,与产量相关性状的杂种优势较高,而含糖量和分蘖的杂种优势较低。在杂种优势预测上,利用亲本的配合力可有效预测杂种优势,预测效果优于遗传距离。与表型遗传距离相比,分子遗传距离对杂种优势的预测更有效。     

加工参数对涂抹型再制干酪物理性质和微观结构的影响

加工参数是影响涂抹型再制干酪物性和微观结构的重要因素。通过测定样品的质构性质、融化性、表观黏度和结合微观结构观察，确定加工参数对涂抹型再制干酪的影响。结果表明：剪切速率、加工温度和时间对样品质构指标和融化距离影响显著（P＜0.05），剪切速率由800 r/min升高到1 400 r/min的过程中，硬度、涂抹功和黏着性没有显著升高；适当升高融化温度、延长融化时间会产生更强的乳化性，剪切约2.9 min时样品已呈现乳化状态。确定加工参数为85 ℃、静止预热4 min、800 r/min剪切2.9 min时，     

Thresholds,sensitive stages and genetic variability of finger millet to high temperature stress

Finger millet [Eleusine coracana (L.) Gaertn.] is an important coarse cereal crop grown in the arid and semi‐arid regions and often experiences high temperature (HT) stress. The objectives of this research were (i) to quantify effects of season‐long HT stress on physiological and yield traits, (ii) to identify the developmental stages most sensitive to HT stress and (iii) to quantify the genetic variability for HT stress tolerance in finger millet. Research was conducted in controlled environment conditions. HT stress decreased the chlorophyll index, photosystem II activity, grain yield and harvest index. Maximum decrease in number of seeds per panicle and grain yield per plant was observed when stress was imposed during booting, panicle emergence or flowering stages. Maximum genotypic variation was explained by panicle width and number of seeds per panicle at optimum temperature (OT) and grain yield per plant at HT and number of seeds at HT. Based on the stress response and grain yield, tolerant or susceptible genotypes were identified. Finger millet is sensitive to HT stress during reproductive stages, and there was genotypic variability among the finger millet genotypes for number of seeds per panicle and grain yield under HT, which can be exploited to enhance stress tolerance.     

Effect of Bacillus cereus as a water or feed additive on the gut microbiota and immunological parameters of Nile tilapia

We evaluated the effects of Bacillus cereus, as an additive in water and feed, on the gut microbiota and immunological parameters of Nile tilapia (Oreochromis niloticus) fingerlings. Experiments were performed in tanks and net cages respectively. Experiment 1: Tilapia were housed in tanks for 42 days, and B. cereus was added to the water at 1.0 × 10⁴ cfu mL^?1 (Treatment 1) and 1.0 ×10⁵ cfu mL^?1 (Treatment 2) weekly. For the control, no probiotic was added. Experiment 2: Tilapia were housed in cages for 42 days, and the feed was supplemented with B. cereus at 1.0 × 10⁷ cfu g^?1 (Treatment 1) and 1.0 × 10⁸ cfu g^?1 (Treatment 2) weekly. For the control, no probiotic was added. Each treatment contained three replicates, with 50 male tilapias per replicate. The fish from the probiotic treatments in both tank and cage experiments had significantly higher serum lysozyme and peroxidase activities than the control. In the cage experiment, alkaline phosphatase and total superoxide dismutase activities in tilapia were significantly higher in probiotic treatments compared with the control. The results of polymerase chain reaction‐denaturing gradient gel electrophoresis showed that B. cereus supplementation in the feed and water affected the autochthonous gut bacteria community of tilapia and stimulated various potentially beneficial bacteria. Therefore, B. cereus, as a water or feed additive, could enhance the immune status and affect the gut microbiota of tilapia. Bacillus cereus was more effective as a feed supplement rather than a water additive for enhancing the immune status of tilapia.     

用线粒体D-loop和Cyt b基因序列分析拉氏(鲮)3个群体的遗传结构和遗传分化

用线粒体DNA的D-loop和Cytb基因序列分析方法研究了吉林延吉、敦化和辽宁法台3个区域的29尾拉氏鱼岁Phoxinus lagowskii Dybowsky的遗传多样性.经PCR扩增和测序,获得了783～785bp D-loop和818bpCyt b的同源序列.两者多态性遗传参数统计显示,29尾个体分别存在47(D-loop)和89(Cyt b)个变异位点,分别检测出15 (D-loop)和1l(Cyt b)个单倍型,总群体单倍型(Hd)分别为0.8966 (D-loop)和0.8990(Cyt b),核苷酸多样性指数(Px)分别为0.0246(D-loop)和0.0498 (Cyt b),平均核苷酸差异数(K)分别为19.2857(D-loop)和40.7365(Cytb).分子方差分析(AMOVA)结果表明,79.02％(D-loop)和81.69％(Cyt b)变异来自群体间,20.98％(D-loop)和18.31％(Cyt b)来自群体内.单倍型呈明显的地理差异,分成2个分支,一个以延吉群体为主,一个以法台群体为主.拉氏(鲮)的遗传多样性水平较高,群体间遗传分化明显.该结果可为拉氏(鲮)的种质资源保护提供参考.     

养殖大鳞鲃发病死亡F_3个体的微卫星标记分析

采用24个已报道的多态微卫星标记对天津市天祥水产有限责任公司养殖的大鳞鲃Barbus capito F_2亲本及F_3成活和病发死亡个体进行基因分型,结果有8个标记无多态,13个标记用以分析本研究群体的遗传多样性、亲缘关系及遗传结构。遗传参数分析显示,13个标记在87个大鳞鲃个体中分别检测到2~7个等位基因,平均等位基因数(4.27~4.53)极显著高于平均有效等位基因数(3.09~3.22)(P0.01);观察杂合度(0.58~0.64)整体低于期望杂合度(0.64~0.65),多态位点比例明显下降(8/24),表明大鳞鲃F2及F_3个体的纯合度增加,遗传多样性下降。聚类分析显示,F2亲本与成活子代亲缘关系更近,聚在一起;而死亡子代单独聚为1支。遗传结构分析显示,亲本与子代清晰地划分成两大类群,多数亲本与多数成活个体归为第一类群(划分概率为51.8%~97.7%),少数亲本与多数死亡个体归为第二类群(划分概率为52.9%~98.4%),这与亲缘关系分析的结果一致,表明少数亲本是F_3死亡个体遗传组成的直接贡献者。本研究初步认定,由于几个亲本的近亲交配,子代基因组纯合度增加,遗传多样性下降,抗逆性下降,这可能是F_3出现不明缘由病发死亡的主要原因之一。     

华南6水系与澜沧江-湄公河攀鲈线粒体ND2基因的遗传多样性分析

测定了中国华南6水系及澜沧江(云南勐腊)-湄公河流域(柬埔寨洞里萨湖)的125尾攀鲈(Anabas testudineus)线粒体部分ND2基因1 010 bp序列,分析发现39个变异位点和12个单倍型,总遗传多样性较低(h=0.369,π=0.003 8),推测可能经历过严重的瓶颈效应;中国攀鲈群体遗传多样性更低(h=0.282,π=0.000 4),处于边缘区的中国攀鲈群体是造成低遗传多样性的主要原因。在单倍型网络图中柬埔寨和中国攀鲈各自聚类,具有明显地理结构和谱系结构,推测地质运动和气候变化导致基因交流受阻所致。核苷酸错配图和中性检验表明中国群体经历过种群扩张,时间约为(5.94~4.13)万年前。华南水系群体间基因交流通畅,不存在明显分化;但与云南澜沧江群体间分化大而显著(FST=0.775,P0.01),AMOVA分析显示变异主要来自组群间(77.41%),推测二者分化时间约为(4.0~2.8)万年前,云南群体受末次冰期的影响,基因交流受阻而出现分化。中国群体和柬埔寨群体可作为2个管理单位进行保护;就中国群体而言,韩江水系群体遗传多样性最高,建议优先保护;澜沧江与华南水系间群体分化显著且遗传多样性极低,建议对澜沧江水系群体进行保护,以避免种质资源灭绝。     

Probiotic efficiency of Bacillus sp. in Labeo rohita challenged by Aeromonas hydrophila: assessment of stress profile,haemato‐biochemical parameters and immune responses

Fish are always susceptible to a wide variety of deadly pathogens which cause a huge loss in aquaculture industries. In this investigation, we have demonstrated the in vivo probiotic efficiency of Bacillus sp. MVF1 (GenBank Acc. No. KP256503) in Labeo rohita challenged with pathogenic strain of Aeromonas hydrophila (MTCC 1739). To check the probiotic potential of the selected bacterial strain, fish were divided into four groups: control, D1, D2 and D3. A total of 100 days (70 days probiotic feeding + 71th day sampling and 28 days challenged test + 29th day sampling) of feeding trial was conducted. To establish the probiotic potential of Bacillus sp. MVF1, certain haematological parameters (haemoglobin, total erythrocyte and leucocyte count), serum biochemical parameters (total protein, albumin and globulin), immune parameters (serum lysozyme and total IgM levels) and hepatic stress profile (malondialdehyde production, superoxide dismutase and catalase activity) have been measured. Our results demonstrated that red blood cell number, white blood cell number and haemoglobin content were much higher in D2 group fish compared to other groups and control fish. Similarly, total protein contents, albumin concentration, globulin concentration, lysozyme activity and IgM production were also recorded to be highest in D2 group fish. This finding clearly indicated the probiotic potential of Bacillus sp. MVF1 in L. rohita. Furthermore, our results also demonstrated that 1 × 10⁷ CFU g^?1 feed (D2) provides better immunity compared to 1 × 10⁵ (D1) and 1 × 10⁹ (D3). Due to beneficial effects, the bacterium Bacillus sp. MVF1 might be useful in aquaculture industries to reduce the disease susceptibility.