Scientific Journals of INIA (Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria)
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Nile tilapia fingerling cultivated in a low-salinity biofloc system at different stocking densities
Get PDFA 42-day trial was conducted to evaluate the effects of a low-salinity biofloc system with different stocking densities on water quality and zootechnical performance of Nile tilapia fingerlings (10 g/L). Four treatments were tested at different densities: 500 fish/m³, 750 fish/m³, 1,000 fish/m³ and 1,250 fish/m³, all in triplicate. Fingerlings of Oreochromis niloticus (initial mean weight of 1.17 ± 0.05 g) were stocked in twelve experimental black-plastic tanks (40 L) with no water exchange during the experimental period. Molasses was added daily to the system at 30% of the amount of feed, and fish were given four daily rations of a formulated feed composed of 36% crude protein and 9% lipids. Water quality variables (dissolved oxygen, pH, salinity, TAN, NO2, NO3 and PO43) did not demonstrate significant differences between the treatments. However, significant influences (α ≤ 0.05) of the stocking densities were observed for total suspended solids, settleable solids, final weight, yield, and protein efficiency ratio. The results showed survival over 96%, final weight values between 12 and 18 g, yield between 9.49 and 15.27 kg/m3, water consumption of 52 to 101 L/kg fish, and total time of settling chambers between 238 and 305 h/kg fish. These results indicate a negative effect of stocking density on final weight, survival, alkalinity, NO2, PO43 and water consumption, and a positive effect on yield in Nile tilapia fingerling culture (1-20 g) in a low-salinity biofloc system with densities up to 1000 fish/m³
Characterization of the antifungal activity of three rhizobacterial strains against Rhizoctonia solani
Get PDF In this study, three rhizobacterial strains were characterized by their ability to inhibit Rhizoctonia solani and tested in chili (Capsicum annuum L.) seedlings. Strains A46 and P61 were identified as Pseudomonas tolaasii, and S108 as Rhanella aquatilis. In the dual culture tests, all the strains inhibited the radial growth of R. solani. None of the three strains produced chitinases or volatile compounds, but they were found to produce siderophores. However, this last characteristic was not responsible for the rhizobacterial inhibitory effect on the growth of R. solani, other bacterial metabolites were possibly involved. The bacterial filtrates added to the potato dextrose agar medium (PDA) in a 3:7 ratio had significant antifungal activity, being the filtrate from strain S108 the one that showed the highest effect, with 56% fungal inhibition. The co-culture of strain A46 with the phytopathogenic fungi in potato dextrose broth (PDB) increased the antifungal activity of the rhizobacterial filtrate. The application of the rhizobacterial strains to Serrano chili decreased the R. solani-related mortality rate in seedlings; particularly, S108 had the greatest effect, which was similar to the fungicide effect. This study showed that the S108 strain has potential as a biofungicide to control R. solani in chili seedlings
Effect of heat shock on the germination of seeds of the species Acacia senegal L. and Acacia seyal Del. from sub-Saharan Africa (Ethiopia).
Get PDFAim of the study: Understanding post-fire germination of tree species in arid and semi-arid zones of sub-Saharan Africa.Area of study: Ethiopian Acacia senegal L. and Acacia seyal Del. forests.Material and methods: Seeds were subjected to heat shocks at combinations of four temperatures (60º, 90º, 120º and 150ºC) and three exposure times (1, 5 and 10 minutes). A control was also included, resulting in a total of thirteen treatments. After the application of the heat shocks, the viability of no germinated seeds was assessed after immersion in a Tetrazolium solution. A mixed and a logistic model were used to analyse the influence of heat shock on germination.Main results: Results showed that germination depended on the species, the heat shock treatment and their interaction. Both species showed similar germination results at temperatures below 90ºC in all exposure times, however, germination in Acacia senegal was statistically higher in most of the heat shocks. On the other hand, germination probability decreased in both species, when the exposure time increased, although with a different behaviour. In 1 minute of time of exposure, the germination probability was higher than 60% in the two species throughout the temperature range. However, at 5 minutes of time and temperature smaller than 90°C, the probability of germination was higher than 70% in A. senegal and 50% in A. seyal. Although germination in both species was impacted by the different heat shocks, non-germinated seeds were viable.Research highlights: This paper showed, according to these results, that heat shock would negatively influence the regeneration of both species, and especially for A. seyal.Key words: germination, Acacia, heat shock, logistic model
Assessing site productivity based on national forest inventory data and its dependence on site conditions for spruce dominated forests in Germany
Get PDFAim of study: (i) To estimate site productivity based on German national forest inventory (NFI) data using above-ground wood biomass increment (ΔB) of the stand and (ii) to develop a model that explains site productivity quantified by ΔB in dependence on climate and soil conditions as well as stand characteristics for Norway spruce (Picea abies (L.) Karst.).Area of study: Germany, which ranges from the North Sea to the Bavarian Alps in the south encompassing lowlands in the north, uplands in central Germany and low mountain ranges mainly in southern Germany.Material and methods: Biomass increment of the stand between the 2nd and 3rd NFI was calculated as measure for site productivity. Generalized additive models were fitted to explain biomass increment in dependence on stand age, stand density and environmental variables.Main results: Great part of the variation in biomass increment was due to differences in stand age and stand density. Mean annual temperature and summer precipitation, temperature seasonality, base saturation, C/N ratio and soil texture explained further variation. External validation of the model using data from experimental plots showed good model performance.Research highlights: The study outlines both the potential as well as the restrictions in using biomass increment as a measure for site productivity and as response variable in statistical site-productivity models: biomass increment of the stand is a comprehensive measure of site potential as it incorporates both height and basal area increment as well as stem number. However, it entails the difficulty of how to deal with the influence of management on stand density.Keywords: Site index; site potential; biomass increment; statistical model; climate
Identification, pathogenicity and distribution of the causal agents of dieback in avocado orchards in Spain
Get PDFAn increased incidence of dieback from branches in several avocado orchards in southern Spain was observed in 2014. Surveys were conducted from May to October 2014, sampling the affected branches to isolate the causal agents. A total of 68 fungal isolates, recovered from ten avocado orchards, were identified, by morphological characterisation and DNA sequencing, as belonging to the genera: Neofusicoccum parvum (50%), Colletotrichum gloeosporioides (17.6%), Neofusicoccum luteum (16.2%), Neofusicoccum australe (13.2%), Neofusicoccum mediterraneum (1.5%) and Lasiodiplodia theobromae (1.5%). A decreasing level of virulence in artificial inoculations on avocado plants was observed in N. parvum, N. luteum, N. mediterraneum, N. australe, C. gloeosporioides and L. theobromae, there were significant differences among N. parvum and the rest of species of this genus, and significant differences were only observed between N. luteum and C. gloeosporioides. The geographical distribution of N. parvum and N. Luteum covers different areas, while C. gloeosporioides and N. australe are located only in the areas around Benamocarra and Vélez-Málaga (southern Spain), while N. mediterraneum and L. theobromae appear only occasionally. This is the first study of avocado branch cankers in Spain which identifies the causal agents and establishes their pathogenicity groups, with N. parvum as the most important causal agent of avocado dieback in this area
Winter biodisinfestation with Brassica green manure is a promising management strategy for Phytophthora capsici control of protected pepper crops in humid temperate climate regions of northern Spain
Get PDFPhytophthora capsici causes root and crown rot of protected pepper (Capsicum annuum L.) crops in the Basque Country (northern Spain), a humid temperate climate area. The objective was to determine the effect of winter biofumigation and plastic cover (biodisinfestation) with Sinapis alba L. (cultivar 'Ludique') fresh green manure on the survival of introduced P. capsici inoculum (oospores) in a greenhouse soil. After autumn-winter Brassica cover crop soil incorporation in February, oospores remained at 15 and 30 cm depth for four weeks´ time exposure in two consecutive years, 2009 and 2010. Oospores viability was estimated with a plasmolysis method and infectivity with a potted pepper bioassay. Viability was significantly higher in biodisinfestated oospores than in the non-treated control in both years (81% and 21% relative increase in 2009 and 2010, respectively) and significantly higher at 30 cm depth than at 15 cm in 2009 (24% relative increase). Conversely, biodisinfestation significantly delayed disease incidence progression until the first half of infectivity bioassays in both years compared to the non-treated soils (83% and 75% relative decrease of dead plants in 2009 and 2010 respectively). The low soil temperatures could explain the low oospore survival reduction and suggest that the suppressiveness expressed in the infectivity bioassay was related with an increase of microbial activity in the biodisinfestation treatment. We conclude that winter biodisinfestation with fresh Brassica green manure is a promising management strategy for Phytophthora root rot control of protected peppers crops in regions of humid temperate climate such us northern Spain
X-ray computerized tomography for characterization of pick-up destruction and pick-up parameter optimization of tomato root lumps
Get PDFThis study was aimed to find the causes of pick-up destruction of tomato root lumps using X-ray microcomputed tomography, and to identify the pick-up parameters of low root lump destruction. The roots and pores were reconstructed three-dimensionally and analyzed quantitatively. It was found that the roots acted winding and wraping the root lumps and thus preventing the substrate from loosening. The major causes for root lump destruction were pore aggregation and crack formation. The apex and circumference of pick-up pins were areas where root lumps were prone to fracture and breakage, respectively. Lacunarities of these two areas were used as index to quantify the root lump destruction. Single-factor analysis of variance was conducted with pick-up pin shape (circular, flat), diameter (2, 2.5, 3 mm) and initial pick-up angle (18°, 21°, 24°) as the test factors and then the effects of these three factors on root lump destruction were studied. It was found the lacunarities at the fracturable area and breakable area both increased with the rise of pick-up pin diameter and decreased with the rise of initial pick-up angle. At the same pick-up conditions, lacunarities with the use of flat pins always surpassed that of circular pins. When circular pick-up pins with diameter of 2 mm and initial pick-up angle of 24° were used, the destruction rate of root lumps (6.63%) was smaller than under other test conditions. The optimized pick-up parameters can be used to guide gripper design and to improve the working performance of automatic transplanters
Leaf cuticular wax content is involved in cotton leaf curl virus disease resistance in cotton (Gossypium hirsutum L.)
Get PDFCotton leaf curl virus disease (CLCuVD) limits cotton production in many cotton growing countries of the world, including Pakistan. In the past, efforts were made to combat this disease by different approaches. Cuticular wax is reported to confer resistance to plants against various biotic and abiotic stresses. Present study was designed to assess the role of cuticular wax content (WC) to resist CLCuVD infestation. The WC of 42 cotton genotypes, originating from various countries (Pakistan, USA, China, etc.), was quantified during two culture periods (2015 & 2016). Cotton germplasm was also scored for % disease index (%DI), seed cotton yield (SCY), number of bolls/plant (NB), and plant height (PHt) for the same culture periods. Significant negative correlation between WC and %DI was found during the two years of experimentation. WC was found positively correlated with SCY and NB. Six cotton genotypes (A-7233, B-557, A-162, BLANCO-3363, CIM-473, and SLH-2010-11) did not show any signs of CLCuVD infestation during both 2015 and 2016. These cotton genotypes contained relatively higher WC. The results from analysis of variance (ANOVA) demonstrated that there were significant differences among genotypes for %DI, WC, SCY, NB, and PHt. These results indicated that WC was involved in resisting CLCuVD and it also had positive effect on plant growth and yield potential. On the basis of these findings, it was concluded that cuticular wax could be used as an indirect criterion for distinguishing and selecting resistant/susceptible cotton genotypes
Short communication: Use of a new form of protected sodium butyrate to control Salmonella infection in fattening pigs
Get PDFA field trial on a commercial pig farm was carried out to assess the efficacy of the addition in the diet of fattening pigs of a new form of sodium butyrate protected with a sodium salt of coconut fatty acid distillate (3 kg/ton of feed) to control Salmonella spp. infection. Around 50 pigs were assigned to treatment group and 50 kept as controls. During the fattening period pigs were monthly sampled (serum and feces), and after slaughter fecal and mesenteric lymph nodes samples were collected. No differences in the proportion of shedders were observed between the sodium butyrate and the control groups, but a significant reduction in the number of infected pigs (61% vs. 4%; p<0.01) and in the median ELISA Optical Density percentage values (55.9% vs. 19.4%; p<0.01) at slaughter was observed in pigs under treatment compared to the controls. In addition, an overall significant association between seropositivity and Salmonella shedding and infection was detected. Results from this study add more evidences on the positive effect of butyrate on the control of pig salmonellosis
Heterogeneity, transient and persistent technical efficiency of Polish crop farms
Get PDFAccounting for heterogeneity in the measurement of farm efficiency is crucial to avoid biases related to climate and soil quality diversity in a given area. Therefore, this paper investigates the level of technical efficiency (TE) of Polish crop farms based on several stochastic frontier panel data models with different approaches to the measurement of unobserved heterogeneity, short- and long- run inefficiency. In our study, we show that ignoring farm heterogeneity can lead to underestimation of the level of TE in conventional stochastic frontier panel data models. Moreover, we have found empirically that not accounting for heterogeneity in the Generalized True Random Effects model may lead to incorrect estimates of persistent TE. The obtained results for Polish crop farms indicate that the level of transient TE (0.81) is lower than the level of persistent TE (0.88). This result suggests that Polish farms may have, for example, problems with adopting new technologies and poor managerial skills