Genetic diversity of apricot revealed by a set of SSR markers from linkage group G1

Eight polymorphic simple sequence repeat (SSR) markers located in the G1 linkage group of apricot (Prunus armeniaca L.) were previously developed and evaluated in a small set of cultivars. Those primers were used for studying variability in 77 apricot cultivars belonging to five different geographical groups, such as Chinese, Asian (Irano-Caucasian and Central Asian), North American, Mediterranean and Western European as well as Middle European cultivars. Six of the markers were polymorphic and revealed a total of 71 alleles ranging from 5 (aprigms11) to 20 (aprigms1) alleles per locus with a mean value of 11.83 alleles per locus. In conclusion, the SSR loci located in the G1 linkage group show a level of polymorphism which is similar to loci dispersed throughout the entire genome. The total number of alleles and the number of unique alleles were the highest in Chinese apricots and the lowest in Middle European cultivars. Heterozygosity also showed a decrease from Asia and China to Middle Europe. No association could have been observed between any SSR markers tested and plum pox virus (PPV) resistant phenotype of cultivars. PPV resistant cultivars did not form a separate clade on the dendrogram obtained by UPGMA cluster analysis. Middle European and Chinese cultivars formed separate clusters while other genotypes formed smaller multiple sub-groups or scattered among different clusters. Our results support previous hypotheses on the origin of PPV resistance in North American apricots. The allele data was also presented in a form that allowed the easy observation of allele frequencies in each geographical group at each locus. Using this data field, differences and similarities between cultivar groups can be easily assessed. The analysis demonstrated the links between the North American and Mediterranean apricot germplasm and confirmed that the Chinese and Eastern European cultivars are distantly related.     

Channels and ditches as the last shelter for freshwater mussels: the case of Margaritifera auricularia and other naiads inhabiting the mid Ebro River Basin,Spain

• 1. Freshwater mussels or naiads are generally considered to thrive in river habitats, provided the ecological conditions are good. The presence of populations of these bivalves in artificial channels and ditches with natural bottoms has only scarcely been reported. The aim of this paper was to present the idea that these ‘channel’ and ‘ditch’ habitats could in fact be a sanctuary for naiads.
• 2. Approximately 80 km of several of these waterways fed by the mid Ebro River were sampled in Spain to monitor their naiad populations. Observations indicate that these habitats harbour substantial colonies of freshwater mussels (including two populations of adult specimens of the endangered species Margaritifera auricularia), much more so than the corresponding river.
• 3. The authors wish to alert conservation authorities and freshwater mussel experts to the extreme fragility and importance of this kind of habitat for the long‐term conservation of these imperilled molluscs.

Copyright © 2008 John Wiley & Sons, Ltd.     

Nutritional value of Pavlova spp. (Prymnesiophyceae) for spat of the Cortez oyster Crassostrea corteziensis during late-nursery culturing at the hatchery

Three Pavlova species were evaluated for their nutritional value as diets for growth and survival of the Cortez oyster Crassostrea corteziensis spat during late‐nursery cultivation at a hatchery. Microalgae were provided as monospecific diets (Pavlova salina, P. sp. C50 and P. sp. C53) and in binary combinations of diets 1+2, 1+3 and 2+3 at 80–90 × 10³ cells mL^?1 for 21 days. Juveniles experienced high survival rates and grew well with all dietary treatments, but binary diets yielded greater survival and growth of spat. From the three binary treatments, Diet 6 (P. sp. C50 and P. sp. C53) promoted significantly (P<0.001) fastest growth of juveniles in shell height (0.19 mm day^?1), shell length (0.14 mm day^?1), total wet weight (0.04 g day^?1) and dry weight of meat biomass (0.024 g day^?1). For all shell dimensions, the lowest growth rates occurred with Diets 2 (P. sp. C56 alone) and 3 (P. sp. C50 alone). These results highlight the importance of testing microalgal diets for bivalve spat rather than just relying on published nutritional values.     

Simulation of transpiration, drainage, N uptake, nitrate leaching, and N uptake concentration in tomato grown in open substrate

Free-drainage or “open” substrate system used for vegetable production in greenhouses is associated with appreciable NO₃⁻ leaching losses and drainage volumes. Simulation models of crop N uptake, N leaching, water use and drainage of crops in these systems will be useful for crop and water resource management, and environmental assessment. This work (i) modified the TOMGRO model to simulate N uptake for tomato grown in greenhouses in SE Spain, (ii) modified the PrHo model to simulate transpiration of tomato grown in substrate and (iii) developed an aggregated model combining TOMGRO and PrHo to calculate N uptake concentrations and drainage NO₃⁻ concentration. The component models simulate NO₃⁻-N leached by subtracting simulated N uptake from measured applied N, and drainage by subtracting simulated transpiration from measured irrigation. Three tomato crops grown sequentially in free-draining rock wool in a plastic greenhouse were used for calibration and validation. Measured daily transpiration was determined by the water balance method from daily measurements of irrigation and drainage. Measured N uptake was determined by N balance, using data of volumes and of concentrations of NO₃⁻ and NH₄⁺ in applied nutrient solution and drainage. Accuracy of the two modified component models and aggregated model was assessed by comparing simulated to measured values using linear regression analysis, comparison of slope and intercept values of regression equations, and root mean squared error (RMSE) values. For the three crops, the modified TOMGRO provided accurate simulations of cumulative crop N uptake, (RMSE = 6.4, 1.9 and 2.6% of total N uptake) and NO₃⁻-N leached (RMSE = 11.0, 10.3, and 6.1% of total NO₃⁻-N leached). The modified PrHo provided accurate simulation of cumulative transpiration (RMSE = 4.3, 1.7 and 2.4% of total transpiration) and cumulative drainage (RMSE = 13.8, 6.9, 7.4% of total drainage). For the four cumulative parameters, slopes and intercepts of the linear regressions were mostly not statistically significant (P < 0.05) from one and zero, respectively, and coefficient of determination (r²) values were 0.96-0.98. Simulated values of total drainage volumes for the three crops were +21, +1 and −13% of measured total drainage volumes. The aggregated TOMGRO-PrHo model generally provided accurate simulation of crop N uptake concentration after 30-40 days of transplanting, with an average RMSE of approximately 2 mmol L⁻¹. Simulated values of average NO₃⁻ concentration in drainage, obtained with the aggregated model, were −7, +18 and +31% of measured values.     

Growth,absorption and assimilation efficiency by mature cuttlefish (<Emphasis Type="Italic">Sepia officinalis</Emphasis>) fed with alternative and artificial diets

The effects of feeding three natural frozen diets, grass shrimp (Palaemonetes sp.), crayfish (Procambarus clarkii) and fish (Sardina pilchardus) and two semi-humid artificial diets (based on fish powder) to mature cuttlefish, Sepia officinalis, were analysed. Growth and feeding rates (GR and FR, % BW day⁻¹), food conversions (FC, %), and total protein and lipid composition of the diets were determined. Digestive gland to body weight ratio and absorption efficiency were calculated for each diet. Cuttlefish fed shrimp and crayfish grew larger (1.5 and 1.1% BW day⁻¹, respectively) compared to the other diets. Shrimp promoted the highest FC, followed by crayfish, and sardine. The highest FR was obtained for cuttlefish fed crayfish (8.4% BW day⁻¹). Although both artificial diets were accepted, none produced growth. A positive correlation (r = 0.96) between cuttlefish ingestion rate and digestive gland weight was obtained. Some cannibalism occurred among cuttlefish fed the artificial diets during the last week of the experiment. According to the results obtained, P. clarkii could be used as an alternative prey to shrimp for rearing adult mature (>50 g) S. officinalis.     

小麦面粉白度与色泽因子配合力及相关分析

为探讨面粉白度与色泽相关因子的遗传特性及相互关系,选择11个在面粉白度等性状方面具有不同特点的小麦品种作亲本,按5×6不完全双列杂交设计组配杂交组合,对30个F₁杂种和11个亲本的面粉白度与色泽相关因子进行了分析。结果表明,面粉白度、黄色素含量、多酚氧化酶活性在亲本表型值与其一般配合力效应值间存在显著的正相关。在亲本表型值间和一般配合力效应值间,面粉白度与黄色素含量均呈显著负相关,与多酚氧化酶活性间无显著相关性。面粉白度、黄色素含量和多酚氧化酶活性的广义遗传力和狭义遗传力都较高,主要受基因加性效应影响,适合在早代进行选择。德麦3号、济麦22号和济麦20号都能较好地降低后代的黄色素含量和多酚氧化酶活性,是小麦白度育种中较适宜选择的亲本。在优质中强筋小麦育种中,不应过分追求面粉的白度和亮度,但可通过对低多酚氧化酶活性和低黄色素含量的选择,培育面粉色泽优良的小麦新品种。     

六倍体小黑麦株高形成中内源激素含量的变化

为了解六倍体小黑麦株高形成与内源激素的关系,以六个不同株高的六倍体小黑麦品种（系）为材料,对小黑麦在株高形成时期叶片中内源激素含量的动态变化进行了分析。结果表明,矮秆小黑麦品种的ABA、ZR和GA含量在所调查时期均显著高于高秆品种,而IAA含量在生长后期则显著低于高秆品种。同时高秆小黑麦中IAA/ABA、GA/ABA与（IAA＋GA）/ABA的比值均高于矮秆小黑麦,但ZR/IAA、ZR/ABA比值的变化趋势则与IAA、GA含量的变化趋势相反。可见不同株高类型的小黑麦在株高形成过程中内源激素具有显著差异。     

灌水对黄淮海冬小麦叶片光合特性的影响

为了解灌水对黄淮海地区冬小麦光合特性的影响,以周麦18、豫农202、豫麦49、郑麦366、矮抗58等5个黄淮海主栽冬小麦品种为材料,比较和分析了越冬水、越冬水+拔节水、越冬水+拔节水+灌浆水3个不同灌水处理下冬小麦开花后叶面积指数、旗叶叶绿素含量、光合参数及水分利用效率的特点。结果表明,随灌水次数减少,小麦灌浆期叶片光合功能衰退加快,叶面积指数和叶绿素含量下降,旗叶净光合速率、气孔导度和蒸腾速率减小,胞间二氧化碳浓度增加,光合作用受非气孔因素的限制增大,同时叶片水分利用效率增加。在不同灌水条件下,矮抗58和郑麦366叶片水分利用效率均较高,而周麦18、豫麦49和豫农202叶片水分利用效率均较低。     

Enhanced kernel set promoted by synchronous pollination determines a tradeoff between kernel number and kernel weight in temperate maize hybrids

Maize (Zea mays L.) grain yield is strongly related to the number of harvested kernels, where kernel number can be increased by synchronously pollinating silks rather than allowing them to be progressively pollinated as they naturally appear from the husks. However, there is scarce evidence on how this practice affects kernel weight (KW) and plant grain yield (PGY), and no report exists on its effects when combined with treatments aimed to reduce apical dominance, like male sterility and detasseling. Field experiments were conducted in two growing seasons (Exp₁ and Exp₂) using two hybrids, cropped at contrasting stand densities (3 and 9 plants per m²) and including (i) male-fertile and male-sterile versions, (ii) tasseled and detasseled plants, and (iii) natural (NP) and synchronous pollination (SP; pollen added manually to ears bagged 5 days after initial silking) systems. Tassel growth of sterile and fertile versions was also evaluated in a separate experiment (Exp₃). Detasseling increased the number of ears per plant reaching silking (P < 0.001) of NP plants, but this beneficial effect of reduced apical dominance did not improve kernel number per plant (KNP) or PGY. Similarly, the early arrest of anther growth in male-sterile plants had no clear benefit on KNP. In contrast, KNP was enhanced by synchronous pollination (range between −13% and +71%; average of +15.4% in Exp₁ and +3.9% in Exp₂). However, this pollination system promoted a decreased in KW (range between −30% and +4%; average of −11.8% in Exp₁ and −7.8 in Exp₂) such that the treatment had no effect on PGY (range between −19% and +37%; average of +1% in Exp₁ and −4% in Exp₂). Because plant growth rate around flowering was not different between pollination treatments, assimilate availability per kernel was reduced from ovary fertilization onwards in synchronously pollinated plants when compared to open pollinated plants. This explains the reduced KW when increasing KNP by synchronous pollination. In summary, none of the imposed treatments allowed grain yield to be increased at the plant level.     

Design and validation of a RT‐qPCR procedure for diagnosis and quantification of most types of infectious pancreatic necrosis virus using a single pair of degenerated primers

Infectious pancreatic necrosis virus (IPNV) is an important virus which affects the salmonid aquaculture industry worldwide; therefore, it is important to develop rapid and reliable methods of diagnosis to detect the disease at early stages. Nowadays, RT‐qPCR is replacing other methods because it provides additional information on the viral load, which is important to have a better understanding of the virus replication level and of the stage of the infection and its risk level. The main problem stems from the high diversity of this virus, which can compromise the reliability of the diagnosis. In this study, we have designed an RT‐qPCR procedure for diagnosis and quantification of IPNV based on a single pair of primers targeted to segment B. The procedure has been validated, in vitro and in vivo, testing two different types of standards against seven reference strains and 23 field isolates from different types. The procedure is reliable for the detection of any type, with a detection limit of 31 TCID₅₀ mL^?1, 50 pfu mL^?1 or 66 RNA copies mL^?1, depending on the standard. All the standard curves showed high reliability (R² > 0.95). The results support the high reliability of this new procedure for the diagnosis and quantification of IPNV.