Application of mycorrhizae to ornamental horticultural crops: lisianthus (Eustoma grandiflorum) as a test case

Ornamental crops are high-cash crops, grown under greenhouse conditions in semi-arid regions in Israel where a reduction in the native population of arbuscular mycorrhizal fungi (AMF) is expected due to routine soil disinfection. The application of AMF inoculum to the soil has been shown to be effective at improving plant growth and enhancing plant resilience to abiotic and biotic stresses. One of our aims is to introduce mycorrhizal application to ornamental crops, and a test case is presented here for two cultivars of lisianthus (Eustoma grandiflorum), one of the major ornamental crops grown in Israel. Several different methods of AMF application and their effects on growth, yield and vase life were examined in lisianthus grown in two different semi-arid locations in southern Israel. AMF enhanced lisianthus growth and yield, especially when introduced to the growth medium during seeding and to the pit hole during planting. Significantly enhanced growth and yield parameters included flowering stem length (58 ± 0.7 and 65.1 ± 0.7 cm for control and AMF treated, respectively) and number of flowering stems per square meter (73 ± 9 and 106 ± 6 for control and AMF treated, respectively); positive but non-significant effects were recorded on stem weight, number of flowers per stem and vase life of cut flowers. Yield enhancement was recorded under both low and regular phosphorus conditions. Although not significant, higher resilience against two pathogenic fungi was also recorded following AMF inoculation (23 ± 13 and 41 ± 10 surviving plants for control and AMF treated, respectively). Hence, AMF is suggested to be a useful growth amendment for promotion of lisianthus commercial production, and may potentially be applied to additional ornamental crops.