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Many studies have described the potential of root organ culture (ROC) to study the biology of arbuscular mycorrhizal (AM) fungi. The dual in vitro cultivation of AM fungi and ROC permits the establishment of the mycorrhizal symbiosis and the completion of fungal life cycle by producing new and infective propagules. However, some differences in AM fungal development are evident when growing in synthetic medium versus pot microcosms or in nature. We aimed to develop a new in vitro method that allows the study of AM symbiosis in a more natural environment, but under controlled conditions. This new culture method combines an artificial growth medium and differently sterilized soil samples for the cultivation of the AM fungal species Rhizophagus intraradices and Rhizophagus aggregatus. An extensive extraradical mycelia network and abundant viable spores, with similar morphological characteristics to those obtained under pot cultures developed under this in vitro soil-based cultivation system. Formation of sporocarp-like structures by R. aggregatus was also detected for the first time using this method. [ABSTRACT FROM AUTHOR]

To our knowledge, there are no studies on the interactive effects of inoculation with arbuscular mycorrhizal fungi and cytokinin addition to plants under drought stress. We investigated the potential protective effect of arbuscular mycorrhizae on pomegranate plants, combined with exogenous cytokinin addition, under two contrasting soil water availability regimes. Our results showed that exogenous cytokinin addition enhances plant biomass, shoot to root ratio and water content, as well as increasing the anthocyanin content. However, a combination of AM fungal inoculation and cytokinin addition did not result in a synergistic protective effect against water stress. Plants were equally well protected against this stress by cytokinin spraying alone. The improvement of pomegranate growth was due mainly to exogenous cytokinin addition. Photosynthesis was promoted both by mycorrhizal inoculation alone and by exogenous cytokinin addition. The main protection against oxidative stress caused by drought was via enhanced accumulation of anthocyanins when the plants were sprayed with cytokinins. When cytokinins were used, the photosynthesis apparatus was also protected. [ABSTRACT FROM AUTHOR]