Genetic diversity in seven populations of Nicaraguan teosinte (<Emphasis Type="Italic">Zea nicaraguensis</Emphasis> Iltis et Benz) as estimated by microsatellite variation

Teosintes are the closest relatives to modern maize, Zea mays L. ssp. mays. They are wild grasses with a native distribution area from Mexico to Nicaragua and represent an important genetic resource. However, the genetic diversity of Nicaraguan teosinte (Zea nicaraguensis Iltis et Benz) has not yet been determined. This teosinte species has decreased in the last 25 years and now must be regarded as an endangered species. An analysis of the genetic diversity of Zea nicaraguensis was carried out in a total of 240 individuals from seven populations. Eleven Simple Sequences Repeat (SSR) primer pairs were used. A total of 42 alleles were found, the range of alleles per locus was 2–5 (mean 3.8) and the numbers of genotypes varied between primers. The primer Bnlg 1538 showed the highest value, with 45 genotypes through all populations. The genetic diversity observed (Ho) between all populations varied from 0.51 to 0.63, with an average of 0.563. One of the populations had as many as 40 alleles. Analysis of molecular variance (AMOVA) revealed that most of the variation was within population, at a significantly high level (P < 0.001). Rare alleles were detected in all populations, but unique alleles were only found in four populations. These results are highly relevant when developing conservation strategies and show that preserving populations in their natural habits is highly important.     

Confirmation of the spawning area of the striped marlin, Tetrapturus audax, in the so-called core area of the eastern tropical Pacific off Mexico

We report the presence of striped marlin larvae in coastal waters of the mouth of the Gulf of California, collected during seven oceanographic cruises during 1990 to 1993. From 169 sampled stations, 30 produced a total of 68 larvae of 2.4–30.5 mm total length. Most of the larvae were about 3 mm, indicating a recent spawn. The sea surface temperature at the sampled stations ranged from 19.4°C to 32.0°C, but larvae were caught at stations with temperatures between 27.8°C and 31.5°C. These results clarify the existence of a spawning area of striped marlin in the eastern Pacific, located closer to the coast than previously believed, during several months of the year.     

Antioxidant activity and soluble sugars of African ginger (Siphonochilus aethiopicus) in response to irrigation regimen and nitrogen levels

African ginger (Siphonochilus aethiopicus), as a medicinal plant, is known for its medicinal properties, containing various antioxidant compounds and carbohydrates. Rhizome yield is improved by water regimens and fertilizers applied at plant phenological stages. However, the rhizomatous herb, which is traditionally used for the treatment of asthma, inflammation and malaria has limited information on water and nitrogen requirements for its production. This study assessed the effect of irrigation regimens (30%, 50% and 70% allowable depletion level (ADL) and nitrogen (N) levels (0, 50, 100, 150 and 200?kg?ha^?1) on antioxidant activity and carbohydrates on plant leaf, root and rhizome. The interaction treatment effect of severely stressed (70% ADL) with the N application of 100?kg?ha^?1 had significant effect on leaf phenolic concentration (87.02?±?2.51?mg?g^?1 gallic acid equivalent). Interaction effect of moderately stressed (50% ADL) and severely stressed (70% ADL) treatment with N application rate of 0?kg?ha^?1 had significant effect on plant flavonoids and phenolics in all plant parts. In plant carbohydrates, root had high sucrose content (47.68?±?9.0?mg?g^?1 dry weight) with the application of low N (0?kg?ha^?1) grown under severely stressed treatment. In conclusion, this implies that different S. aethiopicus parts can produce substantial amount of antioxidants and carbohydrates, as exhibited under low N and reduced water supply applied during the phenological cycle.     

长期秸秆还田对白浆土物理性质及水稻产量的影响

【目的】明确长期秸秆还田对白浆土土壤物理性质及水稻产量的影响。【方法】开展秸秆还田长期定位试验。试验设置4个处理,分别为对照(CK),单施秸秆(S),秸秆+化肥(SNPK),单施化肥(NPK)。在2005年后连年处理,并于试验处理前和2010年、2015年试验处理期间调查土壤容重、硬度、孔隙、三相组成以及水稻产量。【结果】白浆土长期秸秆还田有利于水稻产量提高,10年产量平均,秸秆还田配施肥料处理水稻产量比对照和秸秆单独还田处理增产275.70%和133.23%,比单施化肥处理增产14.17%。秸秆还田处理水稻产量在还田第5—10年平均产量比第1—5年有增加趋势;长期秸秆还田可以改善土壤物理性质,降低土壤容重、硬度,还田10年后,秸秆还田配施化肥处理土壤容重低于化肥单施、秸秆单施及对照处理,SNPK处理0—20、20—30 cm土层土壤容重与对照相比分别降低6.34%和10.00%,与还田5年后同类处理相比仍呈下降趋势;秸秆还田配施化肥处理土壤硬度10年后在10、20、30 cm土层与处理前相比分别降低为26.87%、5.68%和4.62%,在20—30 cm土层与对照相比差异显著,还田10年与5年后相比有下降趋势,其他处理变化不明显;还田5年后,秸秆还田配施化肥处理在0—20、20—30、30—40 cm土层土壤固相比例与对照相比分别下降8.82%、8.36%和3.65%,还田10年后分别下降10.87%、10.61%和4.67%,10年后要比5年后下降幅度大,秸秆还田配施化肥比秸秆单施和化肥单施处理下降幅度大;长期秸秆还田可以增加土壤有效孔隙的数量,在处理间和年限间差异极显著,还田10年后,在0—20、20—30、30—40 cm土层秸秆还田配施化肥土壤有效孔隙比对照增加28.86%、63.85%和23.40%,在20—30 cm和30—40 cm土层比化肥单施增加12.55%和62.96%,在0—20、20—30、30—40cm土层比秸秆单施增加19.68%、56.52%和24.46%;与还田5年后相比,土壤有效孔隙度均呈现增加的趋势。【结论】长期秸秆还田可以改善白浆土不良物理性状,降低白浆层的容重、硬度,增加土壤总孔隙度和有效孔隙的比例,提高水稻产量。秸秆还田年限越长改善土壤不良物理性质效果越明显。单独进行秸秆还田改善土壤效果不明显,秸秆还田配施肥料处理效果明显;在不同处理上,秸秆还田配施化肥处理既有改土效果,又可提高水稻产量,而单施化肥和单独秸秆还田均达不到此类效果。     

Ripening-related defense proteins in Annona fruit

In order to obtain a better understanding of the active defense strategy of cherimoya (Annona cherimola Mill.) fruit, hydrolytic and antifungal activity, as well as expression of proteins functionally and immunogenically related to the pathogenesis-related proteins chitinase (PR-Q) and 1,3-β-glucanase (PR-2), were estimated in fruit at different ripening stages. Increase in expression of the 27 kDa constitutive chitinase and the induction of two new proteins, a 26 kDa chitinase and a 51 kDa 1,3-β-glucanase were associated with enhanced in vitro hydrolytic and antifungal activity of the acidic protein extract in ripe fruit. Ripening modified the expression of constitutive basic isoenzymes, with a sharp decrease in both relative accumulation and hydrolytic activity. Likewise, a new basic 33 kDa chitinase was induced in the over-ripe fruit, concomitant with accumulation of a basic constitutive 76 kDa 1,3-β-glucanase. At this stage, the basic protein extract modified in vitro growth inhibition of Botrytis cinerea. Short-term high CO₂ treatment delayed fruit ripening and maintained a similar distribution of activity and isoenzymatic pattern in both protein fractions to that in unripe fruit. These results indicate that the changes in the pattern of defense proteins and hydrolytic activity in cherimoyas appear to be associated with ripening. Moreover, unlike the constitutively expressed isoenzymes, only the transitorily induced chitinases and 1,3-β-glucanases were associated with an active defense-related response.     

Assessment of real-time PCR as a method for determining the presence of <Emphasis Type="Italic">Verticillium dahliae</Emphasis> in different Solanaceae cultivars

Real-time PCR was used to detect and quantify Verticillium dahliae and to assess the susceptibility of four Capsicum annuum cultivars (Luesia, Padrón, SCM331 and PI201234) and the Capsicum chinense cv. C118 to this pathogen. The symptoms which developed after infection included stunting and yellowing, and were more acute in the cv. SCM331, which also suffered defoliation in later stages of the disease and in C118, which suffered severe stunting. Quantification of the pathogen DNA in roots 23 and 34 days post-inoculation (dpi) revealed that there were significantly higher amounts of Verticillium dahliae DNA in C118 than in the other cultivars, followed by SCM331, Padrón and PI201234. The lowest amounts of fungal DNA in roots were found in Luesia. In hypocotyls, the highest amounts of fungal DNA were found in SCM331, while Luesia, Padrón and PI201234 had much lower amounts, and C118 had intermediate levels. When a compatible versus an incompatible system was studied, using the near-isogenic tomato lines LA3030 (susceptible) and LA3038 (resistant to V. dahliae), we were able to detect fungal DNA in both lines. As expected, the fungus/plant DNA ratio was lower in LA3038 than in LA3030 and it decreased with time in LA3038. The amount of Verticillium dahliae DNA in the roots of LA3030 remained constant between days 23 and 34 post-inoculation, but increased 10-fold in collars. Finally, when real-time PCR was applied as a diagnostic method to samples from pepper plants, soil and water collected from farms in northwest Spain, we were able to detect V. dahliae DNA in these samples even when symptoms of the disease were not evident.     

Bioprospection of Microalgae and Cyanobacteria as Biocontrol Agents Against Vibrio campbellii and Their Use in White Shrimp Litopenaeus vannamei Culture

Vibrio spp. are the most common and harmful shrimp pathogenic bacteria; however, microalgae and cyanobacteria have the ability to produce antimicrobial substances against these species. In this study, the organic and aqueous extracts of 28 species of marine microalgae and cyanobacteria were screened against Vibrio campbellii M1. Two of these phytoplankton species with antibacterial activity in aqueous extracts (Dunaliella tertiolecta and Skeletonema costatum) and nontoxic to brine shrimp Artemia franciscana nauplii were used to evaluate their anti‐Vibrio effect when used as green‐water cultures in Vibrio‐challenged white shrimp Litopenaeus vannamei cultures. No differences in mortality of juvenile L. vannamei were observed between treatments tested, suggesting that the pathogenicity of V. campbellii could be related to the growth stage of shrimp. The proximal composition of D. tertiolecta and S. costatum was in the recommended range for penaeid shrimp nutrition, allowing shrimp supplemented with these microalgae to have significantly greater total length and weight than control shrimp. Shrimp supplemented with S. costatum presented the highest values of organic mass (11.48 mg/organism) and growth rate (0.31 mg/d) in comparison to D. tertiolecta. These results indicate that microalgae are not only capable of producing antibacterial compounds against Vibrio but can also help shrimp nutrition.     

Molecular characterization and phylogenetic analysis of Newcastle disease virus isolates from healthy wild birds

Wild waterfowl is considered a natural reservoir of potentially infectious agents and a source of pathogenic viruses like avian paramyxoviruses type 1 (APMV 1). In 1997, commercial poultry in Argentina had reached the status of being free from virulent Newcastle disease virus (NDV) infections. Vaccination and biosecurity measures are actively performed to maintain this preferential sanitary condition. However, the risk of reintroduction of pathogenic viruses is always present. In this context, we conducted a study to describe the status of wild healthy birds in a geographic region relevant for the poultry industry. The presence of anti-NDV antibodies was determined in different species in all areas sampled suggesting previous contact with NDV. Seven ND viruses were isolated and characterized as apathogenic strains by biological and molecular methods. The phylogenetic analysis revealed that the majority of the Argentinian isolates form a subgroup related to viruses of genotype II. The results presented here highlight the importance of maintaining strict biosecurity measures and vaccination programs in poultry industries in order to preserve the virulent NDV-free status for commercial flocks in the country.