Background: 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. Results: 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. Conclusion: 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.

We report a noble optical sensing method to diagnose seed abnormalities using optical coherence tomography (OCT). Melon seeds infected with Cucumber green mottle mosaic virus (CGMMV) were scanned by OCT. The cross-sectional sensed area of the abnormal seeds showed an additional subsurface layer under the surface which is not found in normal seeds. The presence of CGMMV in the sample was examined by a blind test (n = 140) and compared by the reverse transcription-polymerase chain reaction. The abnormal layers (n = 40) were quantitatively investigated using A-scan sensing analysis and statistical method. By utilizing 3D OCT image reconstruction, we confirmed the distinctive layers on the whole seeds. These results show that OCT with the proposed data processing method can systemically pick up morphological modification induced by viral infection in seeds, and, furthermore, OCT can play an important role in automatic screening of viral infections in seeds.

Lee DH, et al. Mycobiology. 2011 Sep;39(3):200-205. http://dx.doi.org/10.5941/MYCO.2011.39.3.200

A novel strain, designated KP01^T, belonging to the class Sphingobacteria (phylum Bacteroidetes) was isolated from soil in South Korea and was characterized taxonomically using a polyphasic approach. The strain was found to comprise Gram-negative, aerobic, non-motile, non-spore-forming rods. A phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain belonged to the genus Chitinophaga but was clearly separated from established Chitinophaga species. The 16S rRNA gene sequence similarities between KP01^T and type strains of established Chitinophaga species ranged from 90.3 to 95.7 %. Phenotypic and chemotaxonomic data (major menaquinone, MK-7; major fatty acids, iso-C_15 : 0 and C_16 : 1 ω5c; major hydroxy fatty acid, C_17 : 0 iso 3-OH) supported the affiliation of strain KP01^T with the genus Chitinophaga. Therefore strain KP01^T represents a novel species, for which the name Chitinophaga terrae sp. nov. is proposed. The type strain is KP01^T (=KCTC 12836^T =LMG 24015^T).