We use the distribution of extrasolar planets in circular orbits around stars with surface convective zones detected by ground-based transit searches to constrain how efficiently tides raised by the ...planet are dissipated on the parent star. We parameterize this efficiency as a tidal quality factor (Q sub(*)). We conclude that the population of currently known planets is inconsistent with Q sub(*) < 10 super(7) at the 99% level. Previous studies show that values of Q sub(*) between 10 super(5) and 10 super(7) are required in order to explain the orbital circularization of main-sequence low-mass binary stars in clusters, suggesting that different dissipation mechanisms might be acting in the two cases, most likely due to the very different tidal forcing frequencies relative to the stellar rotation frequency occurring for star-star versus planet-star systems.
Rotation periods are increasingly being used to derive ages for cool single field stars. Such ages are based on an empirical understanding of how cool stars spin down, acquired by constructing ...color-period diagrams (CPDs) for a series of open clusters. Our main aims here are to construct a CPD for M 48, to compare this with other clusters of similar age to check for consistency, and to derive a rotational age for M 48 using gyrochronology. We monitored M 48 photometrically for over 2 months with AIP’s STELLA I 1.2 m telescope and the WiFSIP 4K imager in Tenerife. Light curves with 3 mmag precision for bright (V ~ 14 mag) stars were produced and then analysed to provide rotation periods. A cluster CPD has then been constructed. We report 62 rotation periods for cool stars in M 48. The CPD displays a clear slow/I-sequence of rotating stars, similar to those seen in the 625 Myr-old Hyades and 590 Myr-old Praesepe clusters, and below both, confirming that M 48 is younger. A similar comparison with the 250 Myr-old M 34 cluster shows that M 48 is older and does not possess any fast/C-sequence G or early K stars like those in M 34, although relatively fast rotators do seem to be present among the late-K and M stars. A more detailed comparison of the CPD with rotational evolution models shows that the cluster stars have a mean age of 450 Myr, and its (rotating) stars can be individually dated to ± 117 Myr (26%). Much of this uncertainty stems from intrinsic astrophysical spread in initial periods, and almost all stars are consistent with a single age of 450 Myr. The gyro-age of M 48 as a whole is 450 ± 50 Myr, in agreement with the previously determined isochrone age of 400 ± 100 Myr.
Decoding the mechanisms of plant defense against plant pathogens in a scenario where antagonistic activity and the plant growth-promoting effects of useful organisms intervene simultaneously is a new ...frontier of plant pathology. Here, we demonstrated that (i) two selected strains of
Trichoderma asperellum
and
Trichoderma atroviride
promoted tomato (
Solanum lycopersicum
) growth and reduced the severity of disease caused by the oomycete
Phytophthora nicotianae
and (ii) the genetic patterns of the components of the experimental model system tomato–
Trichoderma
spp.–
P. nicotianae
were differentially expressed. The beneficial effects in both the promotion of the growth of host plant and the biological control of the pathogen by two selected strains of different
Trichoderma
species were tested both
in planta
and
in vitro
. In both respects,
T. atroviride
demonstrated to be more effective than
T. asperellum
. Additionally, the simultaneous transcriptional reprogramming of several plant defense-related genes, pathogen effectors, and mycoparasitism-related genes in tomato,
P. nicotianae
, and
Trichoderma
spp., respectively, was evaluated during the three-component interaction. Results support the hypothesis that
Trichoderma
spp. elicit the expression of plant defense-related genes. As expected, a mycoparasitism-related gene was significantly up-regulated in
Trichoderma
-colonizing tomato plants infected by
P. nicotianae
. Finally, a marked up-regulation of the genes encoding two necrosis-inducing effectors was observed in
P. nicotianae
infecting tomato plants colonized by
Trichoderma
. In conclusion, this study is a contribution toward understanding the genetic pathways related with the ability of
Trichoderma
spp. to counteract the challenge of
P. nicotianae
infections on tomato. Additionally, the experiments revealed the beneficial effects in the tomato growth promotion of a new
T. atroviride
strain and its good antagonistic effectiveness in the biological control of root and crown rot incited by
P. nicotianae
, confirming that
Trichoderma
spp. can be a powerful tool in integrated pest management strategies of
Phytophthora
diseases of horticultural crops.
This study was aimed at testing the integrated use of a natural biostimulant based on seaweed (
) and plant (alfalfa and sugarcane) extracts and reduced dosages of the conventional synthetic ...fungicide Imazalil (IMZ) to manage postharvest rots of orange fruits. The following aspects were investigated: (i) the effectiveness of postharvest treatment with natural biostimulant alone or in mixture with IMZ at a reduced dose against green mold caused by
; (ii) the differential expression of defense genes in orange fruits treated with the natural biostimulant both alone and in combination with a reduced dose of IMZ; (iii) the persistence of the inhibitory activity of both biostimulant and the mixture biostimulant/IMZ against green mold; and (iv) the residue level of fungicide in citrus peel when applied alone or in combination with the biostimulant. Treatments with the chemical plant resistance-inducer potassium phosphite, alone or with a reduced dose of IMZ, were included for comparison. The mixture of natural biostimulant and IMZ at a low dose consistently reduced the incidence and severity of fruit green mold and induced a significant increase of the expression level of β-1,3-glucanase-, peroxidase (PEROX)-, and phenylalanine ammonia-lyase (PAL)-encoding genes in fruit peel, suggesting that the natural biostimulant elicits a long-lasting resistance of citrus fruits to infections by
. Interestingly, the residual concentration of IMZ in fruits treated with the biostimulant/fungicide mixture was significantly lower than that of IMZ in fruits treated only with the fungicide at the same dose and by far below the threshold values set by the European Union. This study laid the foundations for (i) conceiving a practical and more eco-friendly alternative to the conventional postharvest management of green mold of citrus fruits, based almost exclusively on the use of synthetic fungicide IMZ, alone or mixed with potassium phosphite and (ii) providing a better insight into the mechanisms of disease resistance induction by biostimulants.
ABSTRACT
We present models of α Centauri A and B implementing an entropy calibration of the mixing-length parameter αMLT, recently developed and successfully applied to the Sun (Spada et al. 2018, ...ApJ, 869, 135). In this technique the value of αMLT in the 1D stellar evolution code is calibrated to match the adiabatic specific entropy derived from 3D radiation-hydrodynamics simulations of stellar convective envelopes, whose effective temperature, surface gravity, and metallicity are selected consistently along the evolutionary track. The customary treatment of convection in stellar evolution models relies on a constant, solar-calibrated αMLT. There is, however, mounting evidence that this procedure does not reproduce the observed radii of cool stars satisfactorily. For instance, modelling α Cen A and B requires an ad hoc tuning of αMLT to distinct, non-solar values. The entropy-calibrated models of α Cen A and B reproduce their observed radii within $1{{\ \rm per\ cent}}$ (or better) without externally adjusted parameters. The fit is of comparable quality to that of models with freely adjusted αMLT for α Cen B (within 1σ), while it is less satisfactory for α Cen A (within 2.5σ). This level of accuracy is consistent with the intrinsic uncertainties of the method. Our results demonstrate the capability of the entropy calibration method to produce stellar models with radii accurate within $1{{\ \rm per\ cent}}$. This is especially relevant in characterizing exoplanet-host stars and their planetary systems accurately.
The aim of this study was to determine the effectiveness of a Super absorbent polymer (SAP) containing copper (SAP-Cu) in controlling mal secco disease (MSD) of lemon caused by the fungus
Plenodomus ...tracheiphilus
. Super absorbent polymer containing copper was characterized by atomic absorption spectrometry (AAS) and UV-VIS spectroscopy.
In vitro
tests were performed to determine the inhibitory effects of SAP-Cu against the pathogen on both potato-dextrose-agar medium and naturally infected lemon cuttings. Super absorbent polymer was able to absorb up to about 200 and 30 times its weight of ionized water and copper (II) sulfate solution (Cu
2+
ions at the concentration 236 mM), respectively. The distribution of copper released on twigs after 24 h of contact with SAP-Cu was determined by secondary ion mass spectrometry with time-of-flight analyzer (ToF-SIMS). Super absorbent polymer containing copper significantly inhibited the viability of
P. tracheiphilus
in lemon twigs. Overall, the results of this study showed that the SAP could be a suitable carrier of antifungal compounds.
This study identified secondary metabolites produced by
,
, and
in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, ...asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately.
was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18, and 13 were of
,
, and
, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail-injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetin, particularly in the juice of mummified fruits of the Tarocco Lempso cultivar. Moreover, the mycotoxins patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.
Post-harvest fungal diseases of plant products are a serious concern leading to economic losses and health risks. Moreover, the use of synthetic chemical fungicides to prevent these diseases is ...limited due to toxic residues. This study aimed at determining the effective dose of extracts of Trichoderma asperellum IMI393899 (TE1) and Trichoderma atroviride TS (TE2) in inhibiting the contamination by mycotoxigenic fungi on different plant matrices. Extracts were tested on tomatoes contaminated by Fusarium verticillioides and Fusarium graminearum, wheat contaminated by Penicillium verrucosum and maize contaminated by Aspergillus flavus. The efficacy of extracts was evaluated at two time intervals after treatment, 4 and 11 days for tomato, and 10 and 20 days for both wheat and maize. Both extracts showed a significant inhibitory activity on mycotoxigenic pathogens and significantly reduced Log CFU/g compared to the control. Moreover, the extracts reduced mycotoxin production in a dose dependent manner and with a long-lasting effect. The ochratoxin A was reduced by both extracts but only the extract TE2 was effective in reducing aflatoxins, whereas TE1 treatment increased their synthesis.
Phytophthora species pose significant challenges to agricultural and natural ecosystems due to their ecological plasticity and ability to cause diseases of various plant species. Effective control of ...Phytophthora diseases requires integrated approaches that consider specific agronomic practices, environmental factors, and the rationale use of chemicals. In response to the need for eco-friendly alternatives, this study investigated the anti-oomycete potential of a formulation derived from the fermentation of lemon wastes by Lactiplantibacillus plantarum ('bioact-LM'). In vitro assays demonstrated the significant anti-oomycete efficacy of bioact-LM against multiple Phytophthora species, both through direct contact inhibition and the release of volatile organic compounds (VOCs). In vivo assessments on orange and apple fruits further confirmed the effectiveness of bioact-LM in reducing Phytophthora rot severity. These findings suggest bioact-LM is promising as a sustainable alternative to synthetic fungicide for Phytophthora disease management, highlighting the importance of exploring eco-friendly solutions in a scenario of environmental challenges and restriction in the use of conventional chemical control methods.
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•Broad spectrum anti-Phytophthora activity of a lemon peel-based medium fermented by Lactiplantibacillus plantarum (LM).•VOCs released by LM contribute to its anti-Phytophthora activity.•Treatment with LM controls Phytophthora rot in orange and apple fruit.•LM can be exploited as a natural substance to control post-harvest fruit spoilage.
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