What’s Left of the Pear Tree After the Fire Blight Outbreak? An Urgent Need for Germplasm Preservation

The pear Pyrus communis crop has been safe from any threat against the fire blight disease. The surprising destruction of the national plantations recorded since 2013, led specialists to give reasonable explanations: pear fruit growers had never experienced such a problem. The north of Tunisia hosts the majority of commercial pear orchards with up to 75% of harvested areas. Fifteen commercially grown varieties were inventoried. The majority (10) are European or American. After the fire blight outbreak, approximately 65% of pear crop areas were lost. All genotypes were sensitive to the disease. However, the response of the tree to Erwinia amylovora differs from one cultivar to another. “Alexandrine” was the most susceptible cultivar, while “Williams” was the most tolerant one. Time and duration of blossom seem crucial to make a decision about which cultivar to choose for one specific area. Local varieties, with their precocious flower set, could escape firing blight disease if removing the last wave of blossom. Grafting pear scion on other than BA29 rootstock (OHF333) may be promising. The use of organic fertilizer enriched by seaweed extract and microorganisms, starting from the early growth period promotes the natural defense and regenerative forces of the plant against bacterial virulence. Ex-situ conservation of pear resources is highly recommended to make easier access to plant material, systematic safeguard, and gene pool dissemination. In this case, it will be necessary to proceed to the sanitation of young plants starting in-vitro and continuing in the nursery.