Yes. AMF can assist the citrus plants to enhance drought tolerance. See my a review in Scientia Horticulturae, 2013

The physiological responses may be the SOD (Superoxide dismutase) activity of the plants would be declining.

Thanks everybody

The roles of AM fungi in drought tolerance have been well established. AM fungi directory reduce the drought stress through exploration of larg areas, beyond the access of roots. Indirectly, AM fungi change certain physiological parameters in plants. They may increase the accumulation of certain osmolytes in the roots to increase turgor, decrease root membrane permeability. AM fungi may control stomatal conductance to check excess water loss and a number of enzymes are also altered (both increase and decrease) by AM association.

If you want to establish a protocol, then go through that particular site. If there is any wild plant over there, isolate the associated native AM fungi. Multiply them under pot conditions and either make a greenhouse experiment with citrus plant for mechanism evaluation purpose or go directly through that field for application.

One thing I would like to strongly recommend you, to use only native strains (native strains are well adapted to particular stress than non-native)

Here is the link of a research publication. However, this is with reference to salt stress, the materials and methods section will definitely help you in developing protocol.

https://www.researchgate.net/publication/304135167_ARBUSCULAR_MYCORRHIZAL_FUNGI_POTENTIAL_INOCULANTS_FOR_CULTIVATION_OF_AROMATIC_PLANT_VETIVERIA_ZIZANIOIDES_IN_ALKALINE_SOIL

Kind regards.

Article ARBUSCULAR MYCORRHIZAL FUNGI; POTENTIAL INOCULANTS FOR CULTI...

Thank you very much

Here is the abstract of an excellent review : 

Citrus is one of the most widely cultivated fruit crops, whose rhizosphere inhabits a class of beneficial fungi, popularly known as arbuscular mycorrhizal fungi (AMF). Different species of AMF viz., Acaulospora, Entrophospora, Gigaspora, Glomus, Pacispora, Sclerocystis, and Scutellospora have been observed to colonize citrus roots for the formation of arbuscular mycorrhizal (AM) symbiosis, where both the symbiotic partners are mutually benefited (up to 20% of photosynthetic carbohydrates from the host plant is divertedtoward the growth ofAM, in the exchange of water and nutrient uptake from the fungal partner to the host plant). AM symbiosis can usually confer better plant growth, higher nutrient uptake, greater tolerance to abiotic and biotic stresses, and soil structure improvement in the host plant. Meanwhile, AM-inoculated citrus plants have shown greater tolerance to drought stress (DS). Drought stress strongly restricted both the development of non-AM-citrus and the mycorrhizal development of AM-citrus, but AM colonization produced a positive effect on plant growth and photosynthesis, even under DS. This review provides an overview of possible mechanisms involved in DS tolerance through improved water and nutrient uptake (especially P nutrition) using extraradical hyphal growth; effective spatial configuration of root system; elevated concentration of tetramine spermine; osmotic adjustment through non-structural  carbohydrates, K+, Ca2+, and Mg2+, but not proline; scavenging reactive oxygen species through antioxidant enzymes and antioxidants; and glomalin-bound soil structural improvements, besides, some new exciting perspectives including water transport by mycorrhizal hyphae and molecular analysis are suggested.PDF enclosed for further reading ...