NO-TILL PROVIDES THE OPPORTUNITY TO MANAGE UNDERGROUND INTERACTIONS BETWEEN ARBUSCULAR MYCORRHIZAL FUNGI, WEEDS AND CROP PLANTS UNDER MEDITERRANEAN CONDITIONS

Early colonization of crop roots by arbuscular mycorrhiza (AM) is considered beneficial but its importance likely depends on the possible stresses faced by the host plant. Manganese toxicity is one such stress that AM can alleviate. Colonization initiated by extraradical mycelium (ERM) is faster than other sources of inoculum. No-till creates the possibility of encouraging inoculation via this source. At seeding time the ERM available for colonizing plants under no-till would have developed in association with previous crops or those weeds that germinated after the first autumn rain. However, the long, hot and dry summer under Mediterranean conditions might reduce the effectiveness of the ERM to colonize the new crop. The hypothesis that an intact ERM developed by weeds can affect the earlier AM colonization of wheat and alleviate Mn toxicity was tested in a pot experiment. Two mycotrophic (Ornithopus compressus L., Lolium rigidum Gaudin), and one non-mycotrophic (Silene galica L) weed species were grown for 7 weeks before being controlled with Glyphosate (the ERM remaining intact) or by mechanical disturbance (which also disrupted the ERM). Wheat was then planted and allowed to grow for 21 days. AM colonization, plant dry weight and shoot nutrient content were evaluated for both weeds and wheat. When an intact mycelium was present at the seeding of wheat (treatments with Ornithopus compressus and Lolium rigidum controlled by Glyphosate) there was a threefold increase in the AM colonization rate and growth of the crop compared with results for all the other treatments. The enhanced growth of wheat was associated with an alleviation of Mn toxicity, consistent with the hypothesis. However, there was a significant difference of the wheat growth after Ornithopus and Lolium (1.9 times), suggesting functional diversity within mycotrophic weeds and crops

Automated quantitative analysis of MCC-IMS spectra

Ion Mobility Spectrometry coupled with Multi Capillary Columns (MCC -IMS) is a fast analytical technique working at atmospheric pressure with high sensitivity and selectivity making it suitable for the analysis of complex biological matrices. MCC-IMS analysis generates its information through a 3D spectrum with peaks, corresponding to each of the substances detected, providing quantitative and qualitative information. Sometimes peaks of different substances overlap, making the quantification of substances present in the biological matrices a difficult process. In the present work we use peaks of isoprene and acetone as a model for this problem. These two volatile organic compounds (VOCs) that when detected by MCC-IMS produce two overlapping peaks. In this work it’s proposed an algorithm to identify and quantify these two peaks. This algorithm uses image processing techniques to treat the spectra and to detect the position of the peaks, and then fits the data to a custom model in order to separate the peaks. Once the peaks are separated it calculates the contribution of each peak to the data

Rhizobia of chickpea from southern Portugal: symbiotic efficiency and genetic diversity

Abstract: Aims: In order to evaluate differences between chickpea rhizobial populations from three geographical areas in southern Portugal (Beja, Elvas and Evora), isolates from the three regions were obtained and analysed. Methods and Results: The genetic characterization of the isolates was done by plasmid profiles and restriction analysis of the nif H gene. Symbiotic efficiency of the isolates was also determined. Relationships between geographical origin, symbiotic efficiency and molecular characteristics were established. Beja soil revealed a larger rhizobia population as well as the presence of some of the isolates with higher symbiotic efficiency values. Isolates with a single plasmid showed a significantly higher symbiotic efficiency. Conclusions: Genetic and phenotypic differences were detected between the natural rhizobial populations from the three locations

Practical exploitation of mycorrhizal fungi in agricultural systems

Improving the sustainability of agricultural systems requires a more efficacious use of soil resources. Mycorrhizas are known to contribute to host plant P acquisition and protection against both biotic and abiotic stresses, such as soil-borne diseases and toxic metal ions. However, practical exploitation of the mutualistic relationship is rarely considered in agricultural systems, allegedly owing to the cost of inoculation and the requirement for timely colonisation. To overcome these limitations, the presence of an extensive extraradical mycelium (ERM) from indigenous arbuscular mycorrhizal fungi (AMF) could be used as the preferential source for colonisation of a crop plant. Colonisation of crop roots starting from an intact ERM takes place faster and generally forms a more effective mycorrhizal association than when initiated from other propagules such as spores and root fragments. We report on the ability of an intact ERM developed by indigenous AMF population on mycotrophic plants (Developers) to significantly improve the AMF colonisation of wheat, subterranean clover and maize allowing for a better performance of the crop. This mechanism allowed the protection of wheat and subterranean clover from excessive Mn concentration in the shoots or in the roots, as in the case of the clover, leading to a greater growth of the crop (2.7 and 4.7 times respectively). Using the same strategy to promote the AMF colonisation of maize, the crop was able to exhibit high levels of colonization, even up to 45 kg P.ha-1 of applied P, and the plants took advantage in terms of P use efficiency. Our results indicate that the use of intact ERM as preferential AMF propagule is a valid strategy to increase the role of this symbiosis under marginal or more intensive cropping systems, through simple adaptations to both crop rotations and tillage practices

Mesorhizobium ciceri LMS-1 expressing an exogenous 1-aminocyclopropane-1-carboxylate (ACC) deaminase increases its nodulation abilities and chickpea plant resistance to soil constraints

Aims: Our goal was to understand the symbiotic behaviour of a Mesorhizobium strain expressing an exogenous 1-aminocyclopropane-1-carboxylate (ACC) deaminase, which was used as an inoculant of chickpea (Cicer arietinum) plants growing in soil. Methods and Results: Mesorhizobium ciceri LMS-1 (pRKACC) was tested for its plant growth promotion abilities on two chickpea cultivars (ELMO and CHK3226) growing in nonsterilized soil that displayed biotic and abiotic constraints to plant growth. When compared to its wild-type form, the M. ciceri LMS-1 (pRKACC) strain showed an increased nodulation performance of c. 125 and 180% and increased nodule weight of c. 45 and 147% in chickpea cultivars ELMO and CHK3226, respectively. Mesorhizobium ciceri LMS-1 (pRKACC) was also able to augment the total biomass of both chickpea plant cultivars by c. 45% and to reduce chickpea root rot disease susceptibility. Conclusions: The results obtained indicate that the production of ACC deaminase under free living conditions by Mesorhizobium strains increases the nodulation, plant growth abilities and biocontrol potential of these strains. Significance and Impact of the Study: This is the first study regarding the use of a transformed rhizobial strain expressing an exogenous ACC deaminase in different plant cultivars growing in soil. Hence, obtaining Mesorhizobium strains with high ACC deaminase activity is a matter of extreme importance for the development of inoculants for field applications

Enhanced chickpea growth-promotion ability of a Mesorhizobium strain expressing an exogenous ACC deaminase gene

Aims The main goal of the study reported herein was to assess the nodulation performance of a Mesorhizobium strain transformed with an exogenous ACC deaminase gene (acdS), and its subsequent ability to increase chickpea plant growth under normal and waterlogged conditions. Methods The Mesorhizobium ciceri strain LMS-1 was transformed with the acdS gene of Pseudomonas putida UW4 by triparental conjugation using plasmid pRKACC. A plant growth assay was conducted to verify the plant growth promotion ability of the LMS-1 (pRKACC) transformed strain under normal and waterlogging conditions. Bacterial ACC deaminase and nitrogenase activity was measured. Results By expressing the exogenous acdS gene, the transformed strain LMS-1 showed a 127% increased ability to nodulate chickpea and a 125% promotion of the growth of chickpea compared to the wild-type strain, under normal conditions. Plants inoculated with the LMS-1 wild-type strain showed a higher nodule number under waterlogging stress than under control conditions, suggesting that waterlogging increases nodulation in chickpea. No significant relationship was found between ACC deaminase and nitrogenase activity. Conclusions The results obtained in this study show that the use of rhizobial strains with improved ACC deaminase activity might be very important for developing microbial inocula for agricultural purposes

Intact extraradical mycelium - a strategy for arbuscular mycorrhizal fungi in agricultural systems.

Arbuscular mycorrhiza are known to contribute to host plant P acquisition and protection against both biotic and abiotic stresses. However the practical exploitation of this mutualistic relationship is rarely considered in agricultural systems, allegedly owing to the cost of inoculation and the requirement for timely colonisation. AMF colonisation starting from an intact extra-radical mycelium (ERM) takes place faster than when initiated from other AMF propagules. We report on the ability of an intact ERM developed by indigenous AMF population on mycotrophic plants (developers) to significantly improve the subsequent AMF colonisation of wheat, subterranean clover and maize. This mechanism allowed the protection of wheat and subterranean clover from excessive Mn, leading to a greater growth of the crop (2.7 and 4.7 times, respectively). Using the same strategy to promote the AMF colonisation of maize, the crop was able to exhibit high levels of colonisation, even up to 45 kg of P per ha of applied P, and the plants took advantage in terms of P use efficiency. Our results indicate that the use of intact ERM as preferential source of AMF inoculum is a valid strategy to increase the role of this symbiosis under marginal or more intensive cropping systems. This strategy can easily be implemented in cropping systems through simple adaptations to both crop rotation and tillage practices

Comparison of chickpea rhizobia isolates from diverse Portuguese natural populations based on symbiotic effectiveness and DNA fingerprint

Abstract: Aims: To test the hypothesis that differences in chickpea yields obtained in four distinct Portuguese regions (Beja, Elvas-Casas Velhas , Elvas-Estacao Nacional de Melhoramento de Plantas (ENMP) and Evora) could be due to variation between the natural rhizobia populations. Methods and Results: Estimation of the size of the different rhizobial populations showed that Elvas-ENMP population was the largest one. Elvas-ENMP population also revealed a higher proportion of isolates carrying more than one plasmid. Assessment of genetic diversity of the native rhizobia populations by a DNA fingerprinting PCR method, here designated as DAPD (Direct Amplified Polymorphic DNA), showed a higher degree of variation in Elvas-ENMP and Beja populations. The symbiotic effectiveness (SE) of 39 isolates was determined and ranged 13-34%. Statistical analysis showed that SE was negatively correlated with plasmid number of the isolate. Conclusions: The largest indigenous rhizobia population was found in Elvas-ENMP. DAPD pattern and plasmid profile analysis both suggested a higher genetic diversity among the populations of Elvas-ENMP and Beja. No relationship was found between SE of the isolates and their origin site. Significance and Impact of Study: The large native population, rather than the symbiotic performance of individual rhizobia, could contribute to the higher chickpea yields obtained in Elvas-ENMP

Molecular detection of Leishmania spp. in dogs and a cat from Doha, Qatar

Research Areas: Parasitology ;Tropical MedicineBackground: Canine and feline leishmanioses are increasingly reported worldwide and represent a threat to both animal and human health. Despite their relevance, data about leishmanioses in companion animals in the east-central part of the Arabian Peninsula are unavailable. Therefore, we investigated the occurrence of Leishmania spp. in dogs and cats from Qatar. Methods: From March 2016 to May 2018, 199 pets (120 dogs and 79 cats) living in Doha or its outskirts were included in this study. From each animal a blood sample was collected and tested for Leishmania spp. by quantitative real-time PCR. Results: Out of the 199 animals, four (2.0%) were positive for Leishmania spp., including three dogs (2.5%) and one cat (1.3%). Conclusions: All positive animals were born in Qatar and had not travelled overseas, suggesting that infection was locally acquired. Considering the occurrence of Leishmania spp. and its potential impact on the health of animals and humans, it is crucial to increase scientific knowledge in order to plan screening and regular prophylaxis against sand fly vectors to reduce the risk of infection.info:eu-repo/semantics/publishedVersio