Mycorrhizal infection ameliorates chlorophyll content and nutrient uptake of lettuce exposed to saline irrigation

Salinity is one of the most serious environmental problems influencing crop growth. Today, the use of microorganisms as biofertilizers in agriculture is quite diffused, and good results have been obtained in terms of induction of resistance to biotic and abiotic stresses in crops. The effects of inoculation with a mixture of the mycorrhizal fungi Glomus mosseae, G. intraradices and G. coronatum have been investigated on lettuce (Lactuca sativa L.) cultivated at three different levels of salinity of the irrigation water (0, 1.5 and 3 g NaCl/l) and collected during three subsequent samplings. Dry mass production was significantly enhanced in the inoculated plants collected at the first sampling, and the effect was even more evident at the highest salinity; however, it was not observed at the latest samplings. The chlorophyll content and total foliar area were mostly enhanced by colonization with the mycorrhizal fungi. Moreover, mycorrhization significantly reduced Na and Cl plant uptake, and stimulated the absorption of K and P. The experiment suggests that mycorrhization can be a suitable way to induce salt-stress resistance in horticultural crops, and that it can show its best effects at medium-high salinity levels of the irrigation water.