ELISA to detect proteolysis of ultrahigh-temperature milk upon storage

Casein proteolysis can occur in milk during storage leading to its gelation. The two main proteolytic systems suspected to be involved are the plasmin and the proteases produced by psychrotrophic bacteria. The latter have been shown to cleave kappa-casein at the Phe105-Met106 bond. Although several techniques allow the determination of plasmin in milk, few rapid and easy-to-perform analytical techniques are available to check for bacterial proteolytic activity. This study presents the development of an inhibition ELISA allowing for the quantification of the kappa-casein intact at the Phe105-Met106 bond. It uses a monoclonal antibody specifically directed against this peptide bond that binds to the protein as long as the molecule's cleavage site is intact but not when it is cleaved. This simple technique allows for the rapid analysis of more than 20 samples within 3 h. Applied to commercial milks, this assay allowed for the detection of unstable milk.     

High colonization by native arbuscular mycorrhizal fungi (AMF) of rubber trees in small-holder plantations on low fertility soils in North East Thailand

Rubber tree is a very important crop in Thailand, representing an essential source of income for farmers. In the past two decades, rubber tree plantations have been greatly expanding in unfavorable areas, where climate conditions are difficult and soil fertility is very poor. To optimize latex yields, mineral fertilizers have been widely used. A better understanding of the roles of the biological compartment in soil fertility is essential to determine alternative management practices to sustain soil fertility and optimize latex yields. Arbuscular mycorrhizal fungi (AMF) are widely recognized as beneficial for plants, mainly through their role in improving plant nutrient uptake. The objective of this study was to assess the AMF populations in rubber tree plantations and the impact of both soil characteristics and plantation age on these communities. Our results showed that all rubber trees were highly colonized, regardless of the soil structure and nutrient contents. AMF colonization was not affected by the age of the trees, suggesting that maintaining the symbiosis is likely to be beneficial at all stages. A better understanding and management of the microbial communities would contribute to maintaining or restoring soil fertility, leading to a better tree growth and optimized latex yield.     

Cacao-fruit tree intercropping effects on cocoa yield, plant vigour and light interception in Côte d’Ivoire

A major challenge for cocoa producers in Côte d’Ivoire is to seek alternative shade trees or crop associations to adapt their planting devices and techniques to the shortage of forests. The recent tendency developed by farmers is to plant simplified orchards combining cacao and fruit trees. An on-farm trial was set up in a 5-year-old cocoa farm to compare a cacao monocrop planted at densities of 1,115 trees ha^?1 with cacao intercropped with orange or avocado trees, both at 44 trees ha^?1. Observations were done on incident light received by the cacao, vigour, growth and cocoa yields. On average, the cacaos received 100 % light in the monocrop, 89.6 % under orange trees and 80.6 % of incident light under avocado trees. They yielded 64.0 pods tree^?1 year^?1 in the monocrop (equivalent to 2.54 kg dry cocoa beans tree^?1), 30.3 pods tree^?1 when combined with orange trees and 28.3 pods tree^?1 with avocado trees. The two combinations allowed cocoa yields equivalent to those observed in the region (0.58 kg dry cocoa beans tree^?1). Vigour and yield were very highly correlated with the incident light received. Both the yield and the incident light are a logistic function of the planting distance from the shade tree. The inflexion point of the logistic functions corresponds to the minimum planting distance between the cacao and the intercropped fruit trees. On this basis, we suggest that the cacaos should not be planted closer than 6.50 ± 0.2 m to the orange or avocado trees.     

Establishment of an in vitro plant regeneration protocol for Casuarina cunninghamiana Miq. via indirect organogenesis

An in vitro plant regeneration protocol via indirect organogenesis from morphogenetic callus was established for Casuarina cunninghamiana Miq. Effects of plant growth regulator NAA (naphthaleneacetic acid) and BAP (6-benzylaminopurine), sucrose and AgNO₃ on callus induction, adventitious bud differentiation and shoot development were examined. Explants used were epicotyl fragments from 45-day-old seedlings. The largest callus (4.29 mm in diameter) was obtained after 1 month on a basic culture medium consisting of Murashige and Skoog ? macro- and full strength micro- elements, Nitsch and Nitsch vitamins, supplemented with 0.54 μM NAA, 3.30 μM BAP, and 30 g L⁻¹ sucrose. The calli were subcultured in the same medium above for 2 months. They were then cultured for another 2 months for adventitious bud differentiation and shoot development. The highest mean adventitious bud differentiation, number of shoots formed per callus and number of shoots ≥2 cm long per callus (47.50%, 27.38 and 4.75, respectively) were achieved on the above medium modified with NAA at 0.27 μM and supplemented with AgNO₃ 1 mg L⁻¹. Shoots were successfully rooted without plant growth regulator and the rooted plantlets survived and grew normally. This protocol for in vitro plant regeneration provides a tool not only for vegetative propagation but also for plant genetic transformation and gene function studies of C. cunninghamiana.     

Diversity of water use efficiency among Quercus robur genotypes: contribution of related leaf traits

? Previously, a large intra-specific diversity and a tight genetic control have been shown for Δ¹³C (carbon isotope discrimination) in a pedunculate oak (Quercus robur L.) family, which is an estimator for intrinsic water use efficiency (W _i), a complex trait defined as the ratio of net CO₂ assimilation rate (A) to stomatal conductance for water vapour (g _s ).

? In the present study, twelve genotypes with extreme phenotypic values of Δ¹³C were selected within this family to (i) asses the stability of genotype differences across contrasting environments and for different measures W _i; (ii) quantify the relationship between Δ¹³C and W_i within this family; (iii) identify which leaf traits drive the diversity in W _i observed in this family.

? Genetic variability of Δ¹³C and W _i was largely independent from different temporal integration scales and their correlation was found to be strong (R ² = 88% for leaf sugars) within this family.

? Weak correlations between measures of W _i with estimators of photosynthetic capacity, suggest a minor role of the latter in the diversity of W _i.

? However, the tight correlation between g _s and Δ¹³C as well as W _i, and the related genotypic variation in stomatal density, suggest that the genotypic diversity in W _i within this pedunculate oak family might be due to differences in g _s .

     

Effects of single and dual inoculation with selected microsymbionts (rhizobia and arbuscular mycorrhizal fungi) on field growth and nitrogen fixation of <Emphasis Type="Italic">Calliandra calothyrsus</Emphasis> Meissn

Our study aimed to assess the effect of dual inoculation with the selected Rhizobium strain KWN35 and the arbuscular mycorrhizal isolate BEG 176 (Glomus etunicatum) on the growth of Calliandra calothyrsus cultivated under irrigation in the field in Senegal (Dakar) over a period of 24 months. Although plants inoculated with both microsymbionts grew better (height and root collar diameter) than plants from three other inoculation treatments (control, single inoculation with KWN35 or BEG 176), these results were not statistically different except at 1 and 5 months after field transplantation. KWN35 was present in a relatively high percentage of nodules harvested from plants inoculated with this rhizobial strain either alone or with mycorrhiza (approximately 60% and 40% 1 and 2 years after field transplantation respectively). The percentage of mycorrhizal root infections was around 60% in the inoculated plants after 12 months with significantly higher N, P and K foliar contents of trees compared with the non-inoculated controls. However, as for nodulation, by 24 months after transplantation, there were no significant differences between treatments. We conclude that field inoculation of C. calothyrsus with Rhizobium strain KWN35 and arbuscular mycorrhizal isolate BEG 176 did not have a long-lasting effect on the growth of trees, even when a majority of nodules were occupied by the inoculated rhizobia and the roots infected by the mycorrhiza. Several reasons can be postulated for these results, such as a possible effect of soil fertility on the efficiency of the nodules.     

Impact of successive drought and re-watering cycles on growth and specific leaf area of two Populus x canadensis (Moench) clones, 'Dorskamp' and 'Luisa_Avanzo'

Responses to successive drought and re-watering cycles (1-3 cycles) were compared in greenhouse-grown cuttings of Populus x canadensis (Moench) clones, 'Luisa_ Avanzo' and 'Dorskamp.' Total leaf number increment rate, duration of leaf expansion, total and individual leaf area expansion rates and stomatal conductance were recorded periodically during the experiment. Soil water content (SWC) and predawn leaf water potential (Psi(WP)) were measured four times during each drought cycle. In parallel, relative leaf water content (RWC) and specific leaf area (SLA) were estimated on leaves collected from the top to bottom of each cutting. Under well-watered conditions, 'Luisa_Avanzo' and 'Dorskamp' differed in their patterns of leaf area expansion. Although duration of leaf expansion was similar between clones, 'Luisa_ Avanzo' exhibited higher total leaf number increment rates and individual leaf area increases than 'Dorskamp.' As a result, 'Luisa_Avanzo' cuttings reached larger individual and total leaf areas than 'Dorskamp.' 'Dorskamp' leaves had lower SLA than 'Luisa_Avanzo' leaves. In response to successive drought cycles, both clones underwent decreases in total leaf number increment rates and in total leaf area expansion rates, but both whole-plant and individual leaf areas were drastically reduced only in 'Luisa_Avanzo.' 'Dorskamp' maintained a constant leaf area as a result of an increase in the duration of leaf expansion during drought and a significant stimulation of individual leaf area expansion rate and total leaf number increment rate in response to re-watering. Drought caused a greater decrease in SLA in 'Luisa_Avanzo' than in 'Dorskamp.' Expanded leaves of 'Dorskamp' were constitutively dense or thick, or both, whereas leaves of 'Luisa_Avanzo' became dense or thick, or both, only in response to drought. In both clones, re-watering caused partial recovery of SLA to control values. Our data confirm previous field and greenhouse observations that 'Dorskamp' is more tolerant to successive drought and re-watering cycles than 'Luisa_Avanzo.' We conclude that this difference is mainly attributable to the plasticity of 'Dorskamp' after re-watering, rather than to clonal differences in drought responses.     

An AHP Assessment Of Barriers in Adopting Sustainable Forest Management Practices in The Context Of Carbon Emission Reductions in Cameroon

ABSTRACT

As the role of forests in climate change mitigation is explicitly recognized in the Paris Agreement, the need to enhance the adoption of Sustainable Forest Management (SFM) practices is crucial. Therefore, this paper aims at identifying and evaluating barriers in adopting SFM practices in the context of forest carbon emission reductions. A total of 15 barriers in adopting SFM practices are listed through literature and expert inputs. Using Cameroon as a case study, the listed barriers are then evaluated by experts to determine their relative importance using the Analytical Hierarchy Process (AHP) method. According to our findings, the ‘Regulatory and Legislative frameworks’ barrier category was attributed to the highest importance among other categories, in adopting SFM practices in the forestry sector. ‘Inadequate political will and incentive to enforce regulations’ appears to be the major obstacle in adopting SFM practices in Cameroon. As carbon emission reduction initiatives are being developed, there is need to move from broad to concrete suggestions that will overcome these barriers. However, proper diagnosis is necessary in order to target barriers with the right incentives and enabling conditions that will support carbon programs and projects to deliver effective emission reductions.     

Influence of the extent of hemoglobin hydrolysis on the digestive absorption of heme iron. An in vitro study

This study was designed to assess the interactions of heme with peptides produced by enzyme hydrolysis of hemoglobin, and their relationship with heme iron absorption. Bovine hemoglobin was hydrolyzed by pepsin or by subtilisin, which differ in their hydrolysis processes. The hydrolysis rate ranged from 0 (native hemoglobin) to 15%. Heme solubility and heme-peptides interactions were compared to iron absorption by the Ussing chamber model, at intestinal pH (7.5). Increasing hemoglobin hydrolysis enhanced iron absorption; the highest value was reached between 8 and 11% hydrolysis, whatever the enzyme used. Comparing the products of hydrolysis of the two enzymes showed that heme iron absorption depends not only on its solubility, but relies mainly on the balance between the strength of heme-peptides and the polymerization rate of heme.