Background
Agricultural production is often limited by low phosphorus (P) availability. In developing countries, which have limited access to P fertiliser, there is a need to develop plants that are more efficient at low soil P. In fertilised and intensive systems, P-efficient plants are required to minimise inefficient use of P-inputs and to reduce potential for loss of P to the environment.

Plant and microbial strategies to improve the phosphorus efficiency of agriculture

We isolated and examined two endophytic fungi for their potential to secrete phytohormones viz. gibberellins (GAs) and indoleacetic acid (IAA) and mitigate abiotic stresses like salinity and drought. The endophytic fungi Phoma glomerata LWL2 and Penicillium sp. LWL3 significantly promoted the shoot and allied growth attributes of GAs-deficient dwarf mutant Waito-C and Dongjin-beyo rice. Analysis of the pure cultures of these endophytic fungi showed biologically active GAs (GA1, GA3, GA4 and GA7) in various quantities. The cultures of P. glomerata and Penicillium sp. also contained IAA. The culture application and endophytic-association with host-cucumber plants significantly increased the plant biomass and related growth parameters under sodium chloride and polyethylene glycol induced salinity and drought stress as compared to control plants. The endophytic symbiosis resulted in significantly higher assimilation of essential nutrients like potassium, calcium and magnesium as compared to control plants during salinity stress. Endophytic-association reduced the sodium toxicity and promoted the host-benefit ratio in cucumber plants as compared to non-inoculated control plants. The symbiotic-association mitigated stress by compromising the activities of reduced glutathione, catalase, peroxidase and polyphenol oxidase. Under stress conditions, the endophyte-infection significantly modulated stress through down-regulated abscisic acid, altered jasmonic acid, and elevated salicylic acid contents as compared to control. In conclusion, the two endophytes significantly reprogrammed the growth of host plants during stress conditions.

https://www.mdpi.com/1420-3049/17/9/10754/pdf

Endophytic fungi produce gibberellins and indoleacetic acid and promotes host-plant growth during stress.

Endophytic fungi are little known for exogenous secretion of phytohormones and mitigation of salinity stress, which is a major limiting factor for agriculture production worldwide. Current study was designed to isolate phytohormone producing endophytic fungus from the roots of cucumber plant and identify its role in plant growth and stress tolerance under saline conditions. We isolated nine endophytic fungi from the roots of cucumber plant and screened their culture filtrates (CF) on gibberellins (GAs) deficient mutant rice cultivar Waito-C and normal GAs biosynthesis rice cultivar Dongjin-byeo. The CF of a fungal isolate CSH-6H significantly increased the growth of Waito-C and Dongjin-byeo seedlings as compared to control. Analysis of the CF showed presence of GAs (GA1, GA3, GA4, GA8, GA9, GA12, GA20 and GA24) and indole acetic acid. The endophyte CSH-6H was identified as a strain of Paecilomyces formosus LHL10 on the basis of phylogenetic analysis of ITS sequence similarity. Under salinity stress, P. formosus inoculation significantly enhanced cucumber shoot length and allied growth characteristics as compared to non-inoculated control plants. The hypha of P. formosus was also observed in the cortical and pericycle regions of the host-plant roots and was successfully re-isolated using PCR techniques. P. formosus association counteracted the adverse effects of salinity by accumulating proline and antioxidants and maintaining plant water potential. Thus the electrolytic leakage and membrane damage to the cucumber plants was reduced in the association of endophyte. Reduced content of stress responsive abscisic acid suggest lesser stress convened to endophyte-associated plants. On contrary, elevated endogenous GAs (GA3, GA4, GA12 and GA20) contents in endophyte-associated cucumber plants evidenced salinity stress modulation. The results reveal that mutualistic interactions of phytohormones secreting endophytic fungi can ameliorate host plant growth and alleviate adverse effects of salt stress. Such fungal strain could be used for further field trials to improve agricultural productivity under saline conditions.

https://link.springer.com/content/pdf/10.1186%2F1471-2180-12-3.pdf

Endophytic fungal association via gibberellins and indole acetic acid can improve plant growth under abiotic stress: an example of Paecilomyces formosus LHL10

Diversity, regulation, and evolution of the gibberellin biosynthetic pathway in fungi compared to plants and bacteria

Endophytes are microorganisms that live within host plants for at least part of their life and do not cause apparent symptoms of diseases. In general, beneficial endophytes promote host plant growth, increase plant nutrient uptake, inhibit plant pathogen growth, reduce disease severity, and enhance tolerance to environmental stresses. As sustainable and renewable agricultural production (including current biofuel and bioenergy crops) increases in prominence, endophytic microorganisms will play important roles and offer environmentally-friendly methods to increase productivity while reducing chemical inputs. This review discusses various aspects of beneficial fungal and bacterial endophyte interactions with plants, including the physiological and molecular mechanisms by which they benefit plant performance. We also discuss the potential for genetic modification of endophytes with useful genes, which could be used to impart additional traits following inoculation with the genetically engineered endophytes. Finally, we review US-issued patents over the past decade which relate to the use of fungal and bacterial endophytes for plant growth and stress tolerance improvement.

The use of beneficial microbial endophytes for plant biomass and stress tolerance improvement.

Background: Endophytic fungi are known plant symbionts. They produce a variety of beneficial metabolites for plant growth and survival, as well as defend their hosts from attack of certain pathogens. Coastal dunes are nutrient deficient and offer harsh, saline environment for the existing flora and fauna. Endophytic fungi may play an important role in plant survival by enhancing nutrient uptake and producing growth-promoting metabolites such as gibberellins and auxins. We screened roots of Ixeris repenes (L.) A. Gray, a common dune plant, for the isolation of gibberellin secreting endophytic fungi. Results: We isolated 15 endophytic fungi from the roots of Ixeris repenes and screened them for growth promoting secondary metabolites. The fungal isolate IR-3-3 gave maximum plant growth when applied to waito-c rice and Atriplex gemelinii seedlings. Analysis of the culture filtrate of IR-3-3 showed the presence of physiologically active gibberellins, GA 1 , GA 3 , GA 4 and GA 7 (1.95 ng/ml, 3.83 ng/ml, 6.03 ng/ml and 2.35 ng/ml, respectively) along with other physiologically inactive GA5, GA9, GA12, GA15, GA19, GA20 and, GA24. The plant growth promotion and gibberellin producing capacity of IR-3-3 was much higher than the wild type Gibberella fujikuroi, which was taken as control during present study. GA5, a precursor of bioactive GA 3 was reported for the first time in fungi. The fungal isolate IR-3-3 was identified as a new strain of Penicillium citrinum (named as P. citrinum KACC43900) through phylogenetic analysis of 18S rDNA sequence. Conclusion: Isolation of new strain of Penicillium citrinum from the sand dune flora is interesting as information on the presence of Pencillium species in coastal sand dunes is limited. The plant growth promoting ability of this fungal strain may help in conservation and revegetation of the rapidly eroding sand dune flora. Penicillium citrinum is already known for producing mycotoxin citrinin and cellulose digesting enzymes like cellulase and endoglucanase, as well as xylulase. Gibberellins producing ability of this fungus and the discovery about the presence of GA5 will open new aspects of research and investigations.

/pdf/plant-growth-promotion-and-penicillium-citrinum-2az1rypry9.pdf

Plant growth promotion and Penicillium citrinum

Coastal sand-dune plants can survive very effectively with the help of various microbes, especially ecto- and endomycorrihizae. Penicillium citrinum KACC43900 was screened according to growth pro-moting activity on sand-dune plants Calystegia soldanella and Ischaemum anthephoroides. In this study, coastal sand-dune plants were treated with a fungal culture filtrate of endophytic fungus P. citrinum KACC43900 to confirm the promotion of plant growth. C. soldanella and I. anthephoroides were used as representative coastal sand-dune plants, and their shoot length, plant length, and dry weight were analyzed. The shoot lengths of control C. soldanella and I. anthephoroides were 8.60 cm and 8.12 cm, and those of samples treated with fungal culture filtrates of C. soldanella and I. anthephoroides for 20 days were 16.30 cm and 10.56 cm, respectively. The plant lengths of control C. soldanella and I. anthe-phoroides were 14.90 cm and 14.80 cm, and those of samples treated with fungal culture filtrates of C. soldanella and I. anthephoroides for 20 days were 24.06 cm and 17.06 cm, respectively. The dry weight of C. soldanella and I. anthephoroides treated with fungal culture filtrates of C. soldanella and I. anthephor-oides for 20 days were 0.163 g and 0.032 g, respectively. It was shown that the growth of shoots in C. soldanella and I. anthephoroides was promoted, 89.54% and 29.60%, by culture filtrate of P. citrinum KACC43900.Keywords : Penicillium citrinum KACC43900, Calystegia soldanella, Ischaemum anthephoroides, gibberellin, endophytic fungus

http://www.koreascience.or.kr:80/article/JAKO201028455276462.pdf

Byung-Moo Lee

Papers

Plant growth promotion and Penicillium citrinum

Plant Growth Promotion of Calystegia soldanella and Ischaemum anthephoroides by the Strain Penicillium citrinum KACC43900