Mycorrizas have huge role in imparting the mycorrhized plants with required physiological preparedness to withstand against any abiotic stress including salinity..
The results of experiments has shown positive effects of some salt tolerant micorrhiza on crop growth under salinity conditions, as good papers presented by my collegues here.
Salinity tolerance of different strains of micorrhiza are different, just as it is different among crops. Thus, not all micorrhiza has positive effects under saline conditions, except salt tolerant ones.
The main reason that micorrhiza has positive effects on crop growth under saline conditions, is that usually they are more salt tolerant than the host plant or crop. Thus they are able to abosorb more water and or nutrients and stimulants and provide them to the host crop. So, we can see their positive effects on crops.
Kindly follow the link below https://www.researchgate.net/profile/Arvind_Singh56/post/what_is_the_role_of_mycorrhiza_to_increase_the_plant_tolerance_to_salinity/attachment/5a4b23b7b53d2f0bba483cbe/AS:578236711424000@1514873783235/download/1_SaltstressAMFMiransari.pdf