Fusarium spp. suppress germination and parasitic establishment of bean and hemp broomrapes

Thirty-nine Fusarium isolates were obtained from newly emerged infected bean broomrape (Orobanche crenata) and hemp broomrape (O. ramosa) collected from infested fields of faba bean (Vicia faba) and tomato (Lycopersicon esculentum) respectively, in two governorates located south of Giza, Egypt. All Fusarium isolates were identified to species level and the effect of their culture filtrates on the germination of seeds from the two Orobanche species was tested in vitro. The inhibition of seed germination differed between the tested Fusarium isolates, depending on the plant part from which they were isolated, with isolates from the shoots of Orobanche inhibiting seed germination more than isolates from the inflorescences. The culture filtrates of Fusarium species from O. crenata were more toxic to the seeds of both Orobanche species than the Fusarium filtrates from O. ramosa. Seeds of O. crenata were more resistant to Fusarium culture filtrates than seeds of O. ramosa. The highest inhibition of Orobanche seed germination was achieved by six Fusarium isolates, one of which was identified as F. oxysporum, one as F. equiseti, whilst the other four were all F. compactum. Aqueous mixtures of mycelia and conidia of all the Fusarium isolates were directly sprayed on O. ramosa tubercles attached to the roots of tomato plants grown in transparent plastic bags, and were also used to infest soil in pots seeded with both faba bean and O. crenata. Two of the four F. compactum isolates (22 and 29) were significantly more pathogenic against O. crenata and O. ramosa, respectively, than the other Fusarium isolates tested in the pots and plastic bags. The study clearly shows the potential of biocontrol agents originating in one Orobanche sp. (e.g. O. crenata) to control another Orobanche sp. (e.g. O. ramosa), as many Fusarium isolates deriving from O. crenata were found to be more pathogenic to O. ramosa seeds than the isolates from O. ramosa themselves. This may widen the host range of these fungal pathogens, with the use of isolates from one Orobanche species effective against other species as well

The 1-aminocyclopropane-1-carboxylic acid deaminase-producing Streptomyces violaceoruber UAE1 can provide protection from sudden decline syndrome on date palm

In the United Arab Emirates (UAE), sudden decline syndrome (SDS) is one of the major fungal diseases caused by Fusarium solani affecting date palm plantations. To minimize the impact of the causal agent of SDS on date palm, native actinobacterial strains isolated from rhizosphere soils of healthy date palm plants were characterized according to their antifungal activities against F. solani DSM 106836 (Fs). Based on their in vitro abilities, two promising biocontrol agents (BCAs), namely Streptomyces tendae UAE1 (St) andStreptomyces violaceoruber UAE1 (Sv), were selected for the production of antifungal compounds and cell wall degrading enzymes (CWDEs), albeit their variations in synthesizing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD). Although both isolates showed antagonism when applied 7 days before the pathogen in the greenhouse experiments, the ACCD-producing Sv was relatively superior in its efficacy against SDS over the non-ACCD-producing St. This was evident from the symptoms of SDS in diseased date palm seedlings which were greatly reduced by Sv compared to St. On a scale of 5.0, the estimated disease severity indices in Fs-diseased seedlings were significantly (P < 0.05) reduced from 4.8 to 1.5 and 0.5 by St and Sv, respectively. Thus, the number of conidia of Fs recovered from plants pre-treated with both BCAs was comparable, but significantly (P < 0.05) reduced compared to plants without any BCA treatment. In addition, a significant (P < 0.05) decrease in ACC levels of both the root and shoot tissues was detected inSv + Fs seedlings to almost similar levels of healthy seedlings. However, in planta ACC levels highly increased in seedlings grown in soils infested with the pathogen alone or amended with St prior to F. solani infestation (St + Fs). This suggests a major role of ACCD production in relieving the stress of date palm seedlings infected with F. solani, thus supporting the integrated preventive disease management programs against this pathogen. This is the first report of effective rhizosphere actinobacterial BCAs to provide protection against SDS on date palm, and to help increase agricultural productivity in a more sustainable manner in the UAE and the other arid regions

Impact of Folic Acid in Modulating Antioxidant Activity, Osmoprotectants, Anatomical Responses, and Photosynthetic Efficiency of Plectranthus amboinicus Under Salinity Conditions

Salinity is a major threat to the sustainability of agricultural production systems. Salt stress has unfavorable implications on various plant physio-morphological and biochemical reactions, causing osmotic and ionic stress. Exogenously applied folic acid (FA) may at least provide one mechanism to evade the injurious stress effects of saline irrigation water on Plectranthus amboinicus. In this regard, two pot trials were performed during the 2018–2019 and 2019–2020 seasons in an open greenhouse of an experimental farm (29°17'N; 30°53'E) in Fayoum, Egypt. We tested four levels of saline irrigation water (SW): 34, 68, and 102 mM NaCl, plus tap water as the control = 0), combined with FA at three concentrations (25 and 50 μM, plus spray with distilled water as the control = 0). The growth parameters, biochemistry, physiology, elemental leaf status, essential oil content, and anatomical responses were assessed. Salt markedly reduced photosynthetic productivity [Fv/Fm and performance index (PI)], total chlorophyll [soil plant analysis development (SPAD)], and leaf osmoprotectant compounds, i.e., total soluble sugars (TSS), free amino acids, proline, and total phenolics, thus hampering P. amboinicus growth and essential oil yield. However, the addition of FA as a foliar spray to P. amboinicus irrigated with saline water induced increases in Fv/Fm, SPAD, and PI. These were linked with enriched stem anatomical structures, leaf osmoprotectant compounds, and enhanced leaf enzymatic activity, e.g., superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, glutathione, ascorbic acid, and antioxidant content. Under salt stress, supplementation of 25 and 50 μM FA increased the growth and production of essential oil by 27.8 and 55.6%, respectively, compared with no applied FA. The highest growth characteristics and elemental leaf contents were obtained when P. amboinicus was irrigated with 0 mM saline water and treated foliarly with 50 μM of FA compared with non-treated plants. Overall, these data showed that foliar spraying with FA reduces the impact of salt stress on P. amboinicus irrigated with saline water

Genome-Wide identification and expression analysis of metal tolerance protein gene family in Medicago truncatula under a broad range of heavy metal stress

Metal tolerance proteins (MTPs) encompass plant membrane divalent cation transporters to specifically participate in heavy metal stress resistance and mineral acquisition. However, the molecular behaviors and biological functions of this family in Medicago truncatula are scarcely known. A total of 12 potential MTP candidate genes in the M. truncatula genome were successfully identified and analyzed for a phylogenetic relationship, chromosomal distributions, gene structures, docking analysis, gene ontology, and previous gene expression. M. truncatula MTPs (MtMTPs) were further classified into three major cation diffusion facilitator (CDFs) groups: Mn-CDFs, Zn-CDFs, and Fe/Zn-CDFs. The structural analysis of MtMTPs displayed high gene similarity within the same group where all of them have cation_efflux domain or ZT_dimer. Cis-acting element analysis suggested that various abiotic stresses and phytohormones could induce the most MtMTP gene transcripts. Among all MTPs, PF16916 is the specific domain, whereas GLY, ILE, LEU, MET, ALA, SER, THR, VAL, ASN, and PHE amino acids were predicted to be the binding residues in the ligand-binding site of all these proteins. RNA-seq and gene ontology analysis revealed the significant role of MTP genes in the growth and development of M. truncatula. MtMTP genes displayed differential responses in plant leaves, stems, and roots under five divalent heavy metals (Cd2+, Co2+, Mn2+, Zn2+, and Fe2+). Ten, seven, and nine MtMTPs responded to at least one metal ion treatment in the leaves, stems, and roots, respectively. Additionally, MtMTP1.1, MtMTP1.2, and MtMTP4 exhibited the highest expression responses in most heavy metal treatments. Our results presented a standpoint on the evolution of MTPs in M. truncatula. Overall, our study provides a novel insight into the evolution of the MTP gene family in M. truncatula and paves the way for additional functional characterization of this gene family

Soil application of effective microorganisms and nitrogen alleviates salt stress in hot pepper (Capsicum annum L.) plants

The application of effective microorganisms (EMs) and/or nitrogen (N) have a stimulating effect on plants against abiotic stress conditions. The aim of the present study was to determine the impact of the co-application of EMs and N on growth, physio-biochemical attributes, anatomical structures, nutrients acquisition, capsaicin, protein, and osmoprotectant contents, as well as the antioxidative defense system of hot pepper (Capsicum annum L.) plants. In the field trials, EMs were not applied (EMs-) or applied (EMs+) along with three N rates of 120, 150, and 180 kg unit N ha-1 (designated as N120, N150, and N180, respectively) to hot pepper plants grown in saline soils (9.6 dS m-1). The application of EMs and/or high N levels attenuated the salt-induced damages to hot pepper growth and yield. The application of EMs+ with either N150 or N180 increased the number, average weight and yield of fruits by 14.4 or 17.0%, 20.8 or 20.8% and 28.4 or 27.5%, respectively, compared to hot pepper plants treated with the recommended dose (EMs- × N150). When EMs+ was individually applied or combined with either N150 or N180, increased accumulation of capsaicin were observed by 16.7 or 20.8%, protein by 12.5 or 16.7%, proline by 19.0 or 14.3%, and total soluble sugars by 3.7 or 7.4%, respectively, in comparison with those treated with the integrative EMs- × N150. In addition, the non-enzymatic contents (ascorbate, and glutathione) and enzymatic activities (catalase, superoxide dismutase, and glutathione reductase) of the antioxidant defense systems significantly increased in hot pepper plants treated with EMs+ alone or combined with N150 or N180 under salt stress conditions. Higher accumulation of nutrients (N, P, K+, and Ca2+) along with reduced Na+ acquisition was also evidenced in response to EMs+ or/and high N levels. Most anatomical features of stems and leaves recovered in hot pepper plants grown in saline soils and supplied with EMs+ and N. The application of EMs and N is undoubtedly opening new sustainable approaches toward enhancing abiotic stress tolerance in crops (e.g. hot pepper)

Influence of elemental sulfur on nutrient uptake, yield and quality of cucumber grown in sandy calcareous soil

Abstract This study was carried out to investigate the effect of elemental sulfur (S 0 ) and sulfur oxidizing bacteria (Paracoccus versutus) on nutrient uptake, yield and quality of cucumber grown in sandy calcareous soils. Both elemental sulfur powder (S 0 P) and pellets of sulfur powder-Tiger 90 (S 0 T) were applied at rates of 0, 1, 5 and 10 t/ha at Al Hamraneya. On the contrary, S 0 P was used at rates of 0, 1, 5 and 10 t/ha combined with or without Paracoccus versutus (Pv) at Al Kuwaitat, United Arab Emirates (UAE). Higher concentrations of N, P, S, Mn and Zn in leaves and yield of cucumber at both locations were obtained with application of S 0 at rates of 5 and 10 t/ha. Total soluble sugar (TSS) content and vitamin C was higher with the application of S 0 at rates of 5 and 10 t/ha. Application of Pv individually or with varying levels of S 0 P had no positive effect on nutrients uptake, yield and quality of cucumber. A positive correlation was observed between shelf life and vitamin C. At Al Hamraneya S 0 P performed better than S 0 T. The results reveal that application of S 0 P at the rate of 5 t/ha in sandy calcareous soils can enhance the nutrients uptake ability, increase yield and superior quality of cucumber at both locations in UAE

<I>Fusarium </I>spp. suppress germination and parasitic establishment of bean and hemp broomrapes

Thirty-nine Fusarium isolates were obtained from newly emerged infected bean broomrape (Orobanche crenata) and hemp broomrape (O. ramosa) collected from infested fields of faba bean (Vicia faba) and tomato (Lycopersicon esculentum) respectively, in two governorates located south of Giza, Egypt. All Fusarium isolates were identified to species level and the effect of their culture filtrates on the germination of seeds from the two Orobanche species was tested in vitro. The inhibition of seed germination differed between the tested Fusarium isolates, depending on the plant part from which they were isolated, with isolates from the shoots of Orobanche inhibiting seed germination more than isolates from the inflorescences. The culture filtrates of Fusarium species from O. crenata were more toxic to the seeds of both Orobanche species than the Fusarium filtrates from O. ramosa. Seeds of O. crenata were more resistant to Fusarium culture filtrates than seeds of O. ramosa. The highest inhibition of Orobanche seed germination was achieved by six Fusarium isolates, one of which was identified as F. oxysporum, one as F. equiseti, whilst the other four were all F. compactum. Aqueous mixtures of mycelia and conidia of all the Fusarium isolates were directly sprayed on O. ramosa tubercles attached to the roots of tomato plants grown in transparent plastic bags, and were also used to infest soil in pots seeded with both faba bean and O. crenata. Two of the four F. compactum isolates (22 and 29) were significantly more pathogenic against O. crenata and O. ramosa, respectively, than the other Fusarium isolates tested in the pots and plastic bags. The study clearly shows the potential of biocontrol agents originating in one Orobanche sp. (e.g. O. crenata) to control another Orobanche sp. (e.g. O. ramosa), as many Fusarium isolates deriving from O. crenata were found to be more pathogenic to O. ramosa seeds than the isolates from O. ramosa themselves. This may widen the host range of these fungal pathogens, with the use of isolates from one Orobanche species effective against other species as well

Biological Control of Mango Dieback Disease Caused by Lasiodiplodia theobromae Using Streptomycete and Non-streptomycete Actinobacteria in the United Arab Emirates

Dieback caused by the fungus Lasiodiplodia theobromae is an important disease on mango plantations in the United Arab Emirates (UAE). In this study, 53 actinobacterial isolates were obtained from mango rhizosphere soil in the UAE, of which 35 (66%) were classified as streptomycetes (SA) and 18 (34%) as non-streptomycetes (NSA). Among these isolates, 19 (12 SA and 7 NSA) showed antagonistic activities against L. theobromae associated with either the production of diffusible antifungal metabolites, extracellular cell-wall-degrading enzymes (CWDEs), or both. Using a “novel” mango fruit bioassay, all isolates were screened in vivo for their abilities to reduce lesion severity on fruits inoculated with L. theobromae. Three isolates, two belonging to Streptomyces and one to Micromonospora spp., showed the strongest inhibitory effect against this pathogen in vitro and were therefore selected for tests on mango seedlings. Our results revealed that the antifungal action of S. samsunensis UAE1 was related to antibiosis, and the production of CWDEs (i.e., chitinase) and siderophores; whilst S. cavourensis UAE1 and M. tulbaghiae UAE1 were considered to be associated with antibiotic- and CWDE-production, respectively. Pre-inoculation in greenhouse experiments with the most promising actinobacterial isolates resulted in very high levels of disease protection in mango seedlings subsequently inoculated with the pathogen. This was evident by the dramatic reduction in the estimated disease severity indices of the mango dieback of individual biocontrol agent (BCA) applications compared with the pathogen alone, confirming their potential in the management of mango dieback disease. L. theobromae-infected mango seedlings treated with S. samsunensis showed significantly reduced number of defoliated leaves and conidia counts of L. theobromae by 2- and 4-fold, respectively, in comparison to the other two BCA applications. This indicates that the synergistic antifungal effects of S. samsunensis using multiple modes of action retarded the in planta invasion of L. theobromae. This is the first report of BCA effects against L. theobromae on mango seedlings by microbial antagonists. It is also the first report of actinobacteria naturally existing in the soils of the UAE or elsewhere that show the ability to suppress the mango dieback disease