Specialized 16SrX phytoplasmas induce diverse morphological and physiological changes in their respective fruit crops

Area of Science:

• Plant pathology
• Phytopathology
• Plant physiology

Background:

• Phytoplasma infections in apple, peach, and pear trees exhibit varying disease severity despite belonging to the same 16SrX group.
• Apple trees tolerate phytoplasma infections for decades, while peach and pear trees succumb within years.

Purpose of the Study:

• To investigate phytoplasma-induced morphological and physiological changes in apple, peach, and pear.
• To compare these changes with non-infected plants to understand differential host tolerance.

Main Methods:

• Analysis of vascular system morphology, phloem sap physiology, and leaf phytohormones in infected and non-infected trees.
• Comparative study across Malus domestica (apple), Prunus persica (peach), and Pyrus communis (pear).

Main Results:

• Apple trees showed reduced leaf and vascular area, impacting phloem mass flow, unlike peach and pear.
• Pear trees exhibited increased phloem mass flow and altered sap characteristics.
• Callose deposition increased in pear and peach but not apple; phytohormone levels rose in apple and peach, but not pear.

Conclusions:

• Reduced vascular area and sap flow in apple trees are linked to their long-term survival and tolerance to phytoplasma.
• Phytohormone-mediated defenses may play a role in host tolerance to phytoplasma infections.