Presence and seed transmission of phytoplasmas in tomato fields in Italy

Tomatoes are the second most consumed vegetable, quite often severely affected by phytoplasma-associated diseases worldwide. The identification and confirmation that the phytoplasmas associated with the disease in Southern Italy are also transmitted through seeds was achieved. DNA extractions from mother plants collected in 2020 and 2021 and the seedlings from these plants, tested at different times, allowed the detection of phytoplasmas in both mother plants and seedlings grown under an insect-proof greenhouse. Phytoplasmas enclosed in groups 16SrX-B (‘Candidatus Phytoplasma prunorum’) and 16SrV-A (‘Ca. P. ulmi’) were identified in 2020 samples, and the same phytoplasma groups were identified in the seedlings. Phytoplasmas enclosed in groups 16SrI and 16SrXII were identified in mother plants collected in 2021 and were also identified in the seedlings. Moreover, a difference in germination percentage was observed. The 16SrXII-A group phytoplasmas detected in the mother plants and were identified as variants St5 for the stamp gene, tuf-b1 for the tuf gene and Vm44 for the vmp1 gene. This research is a significant confirmation of previous laboratory results on transmission of phytoplasmas through seeds from several diseased plant species. The epidemiological role of phytoplasma seed transmission is an essential knowledge for efficient management strategy planning for a seed production aimed at reducing the impact of phytoplasma-associated diseases in horticultural relevant crops such as tomatoes.