Salt tolerance in the genus Lolium (ryegrass) during germination and growth

Abstract

Two studies were undertaken, one to evaluate the degree of genotypic variation for salt tolerance within the Lolium (ryegrass) genus, and the other to compare the responses of three representative ryegrass species (Wimmera (L. rigidum), Italian (L. muttiforum) and perennial (L. perenne) ryegrass) with those of two known salt-tolerant grasses, tall wheat grass (Elytrigia pontica) and saltmarsh grass (Puccinellia ciliafa). Both germination and growth responses to increasing concentrations of NaCl were assessed under controlled environment conditions: seeds were germinated in petri dishes, and plants were grown in pots containing coarse river sand. In the first study, significant intra- and inter-specific variation for salt tolerance was demonstrated, particularly during germination. However, there was no apparent adaptation for salt tolerance in field collected accessions from saline sites. In the second study, all species were shown to be relatively insensitive to NaCl up to 200 mol m-3 during germination, but higher concentrations were tolerated only by saltmarsh grass, tall wheat grass and Italian ryegrass. Only the latter two grasses maintained their high tolerance during vegetative growth, whereas the ryegrasses were moderately tolerant. It was clear from both studies that relative salt tolerance ranking differed for germination and growth phases. Shoot concentrations of Na, Cl and K did not relate to the degree of salt tolerance.