Fungal endophytes can improve plant tolerance to abiotic stress conditions. Dark septate endophytes (DSEs) belong to phylogenetically non-related groups of root colonizing fungi among the Ascomycota with high melanin-producing activities. They can be isolated from roots of more than 600 plant species in diverse ecosystems. Still the knowledge about their interaction with host plants and their contribution to stress alleviation is limited. The current work aimed to test the abilities of three DSEs (Periconia macrospinosa, Cadophora sp., Leptodontidium sp.) to alleviate moderate and high salt stress in tomato plants. By including an albino mutant, the role of melanin for the interaction with plants and salt stress alleviation could also be tested. P. macrospinosa and Cadophora sp. improved shoot and root growth 6 weeks after inoculation under moderate and high salt stress conditions. No matter how much salt stress was applied, macroelement (P, N, and C) contents were unaffected by DSE inoculation. The four tested DSE strains successfully colonized the roots of tomato, but the colonization level was clearly reduced in the albino mutant of Leptodontidium sp. Any difference in the effects on plant growth between the Leptodontidium sp. wild type strain and the albino mutant could, however, not be observed. These results show that particular DSEs are able to increase salt tolerance as they promote plant growth specifically under stress condition. Increased plant biomasses combined with stable nutrient contents resulted in higher P uptake in shoots of inoculated plants at moderate and high salt conditions and higher N uptake in the absence of salt stress in all inoculated plants, in P. macrospinosa-inoculated plants at moderate salt condition and in all inoculated plants except the albino mutants at high salt condition. In summary, melanin in DSEs seems to be important for the colonization process, but does not influence growth, nutrient uptake or salt tolerance of plants.

Dark septate endophytes (DSEs) represent a diverse group of root-endophytic fungi that have been isolated from plant roots in many different natural and anthropogenic ecosystems. Melanin is widespread in eukaryotic organisms and possesses various functions such as protecting human skin from UV radiation, affecting the virulence of pathogens, and playing a role in development and physiology of insects. Melanin is a distinctive feature of the cell walls of DSEs and has been thought to protect these fungi from abiotic stress. Melanin in DSEs is assumed to be synthesized via the 1,8-dihydroxynaphthalene (DHN) pathway. Its function in alleviation of salt stress is not yet known. The aims of this study were: (i) investigating the growth responses of three DSEs (Periconia macrospinosa, Cadophora sp., and Leptodontidium sp.) to salt stress, (ii) analyzing melanin production under salt stress and, (iii) testing the role of melanin in salt stress tolerance of DSEs. The study shows that the three DSE species can tolerate high salt concentrations. Melanin content increased in the hyphae of all DSEs at 100 mM salt, but decreased at 500 mM. This was not reflected in the RNA accumulation of the gene encoding scytalone dehydratase which is involved in melanin biosynthesis. The application of tricyclazole, a DHN-melanin biosynthesis inhibitor, did not affect either salt stress tolerance or the accumulation of sodium in the hyphae. In addition, melanin biosynthesis mutants of Leptodontidium sp. did not show decreased growth performance compared to the wild-type, especially not at high salt concentrations. This indicates that DSEs can live under salt stress and withstand these conditions regardless of melanin accumulation.

Endophytic fungi are a significant group of fungi found in various ecosystems, producing significant secondary metabolites with economic applications. The study aims to extract gibberellic acid from endophytic fungi, optimize its production using low-cost agriculture residues, and apply it to plants. Endophytic fungi were isolated from onion leaves, screened for gibberellic acid production, and the highest producer was identified by morphological and molecular tools. The production was optimized using three levels Box–Behnken design, and the hormone was applied to maize seeds at concentrations of 0, 50, and 100 ppm. Fusarium solani, F. oxysporum, F. incarnatum, and F. camptoceras produced gibberellic acid at concentrations from 3.04 to 36.33 mg/l, with the highest production by F. incarnatum-ASU19 (MK387876). The optimal parameters increased the production significantly (R ² 0.9974) to 166.81 mg/l using 20 g/l sugarcane bagasse, 35 °C incubation temperature, and seven days of incubation. Increased gibberellic acid concentrations induced morphological characteristics, chlorophyll, flavonoids, and total antioxidants in maize compared to controls without GA₃ addition. In conclusion, the endophytic fungus Fusarium incarnatum demonstrates significant potential for gibberellic acid production from low-cost agricultural residues. This bioprocess not only promotes a cleaner environment but also enhances plant tolerance to abiotic stress and positively influences agricultural productivity.

Sesame (Sesamum indicum L.), the Queen of oilseeds, is infected with different pathogens, restricting its yield. Fusarium oxysporum f. sp. sesami is the most destructive disease of sesame worldwide, causing economic losses. This work aimed to develop new high-yielding strains, resistant and/or tolerant to Fusarium. Two cycles of pedigree selection were achieved under infection of Fusarium oxysporum f. sp. sesami. Two populations in the F₂ (600 plants each) were used. The selection criteria were five single traits and another three restricted by yield. The restricted selection was better in preserving variability than the single trait selection. The observed genetic gain in percentage from the mid-parent in the F₄-generation was significant for the eight selection criteria. Single trait selection proved to be an effective method for improving the selection criterion, but it caused deleterious effects on the other correlated traits in most cases. The seed yield increased by 30.67% and 20.31% from the better parent in the first and second populations, respectively. The infection% was significantly reduced by 24.04% in the first, and 9.3% in the second, population. The selection index improved seed yield, and its attributes can be recommended.

Fisheries and Aquatic Sciences

Endophytic bacteria enhance plant growth and yield. Sugarcane is a key economic crop in Egypt, yet few studies have examined endophytic bacteria impact on its production. This study aimed to isolate endophytic bacteria from sugarcane roots and stems, screen for indole-3-acetic acid (IAA) production, identify top IAA producer isolates, and optimize yield using Box-Behnken design (BBD). This study is considered as the first paper to use this tool for optimizing IAA production by sugarcane’s endophytes. The salt tolerance of the best performing strain was also investigated. Additionally, the effects of IAA-producing bacteria and their IAA on wheat seed germination were separately evaluated. The results showed that thirty-one endophytic bacterial isolates were isolated from sugarcane ( Saccharum sp., cultivar C 9), from which twelve isolates were IAA producers. Among the positive isolates, strain no. IA47 isolated from sugarcane root demonstrated the highest IAA yield by producing 231.52 ± 0.09 mg/L representing the highest IAA production reported for a sugarcane endophyte. Application of the One-Factor-At-a-Time approach and BBD proved tryptone (5 g/L), tryptophan (0.2 g/L), and incubation temperature (35 °C) as the most critical factors improving IAA production. Bacterial strain IA47 was subjected to molecular analysis and was found to be a member of the family Enterobacteriaceae, closely related to Klebsiella. The strain was deposited in the NCBI database under accession number PX101404. This strain was reported as halotolerant strain that could grow and produce notable high concentration of IAA (13.04 mg/L) when growing in 150 mM NaCl concentration. The plant growth stimulation effect of IA47 on wheat was tested in vitro and showed significant growth promotion, especially for the number of lateral roots, shoot length, and chlorophyll a/b ratio, by bacterial coating treatment. The results of the current study provide a valuable bacterial strain promising to be applied as a biofertilizer for promoting the growth and yield of non-host crops.