Grape root cell features related to phylloxera resistance and changes of anatomy and endogenous hormones during nodosity and tuberosity formation

Abstract

Background and Aims: Cell wall anatomical and chemical components of different phylloxera resistant grapevine roots were examined. Changes in anatomy and endogenous hormone levels were tested during phylloxera-induced nodosity and tuberosity formation. Methods and Results: Tertiary roots of 3–5 mm diameter from 4-year-old grapevines with different phylloxera resistance ratings were collected in September to examine cellular anatomy and endogenous hormones in nodosities and tuberosities. Grapevine roots with reported high phylloxera resistance had more periderm cell layers, smaller parenchyma cells, and higher lignin, cellulose and pectin contents. 140 Ruggeri periderm cell wall thickened and accumulated more polyphenolic materials after phylloxera infestation. Nodosity cells distal to the insect feeding site and tuberosity cells near the feeding site showed increased cell division and enlargement. Tuberosity cells were oriented parallel to the phylloxera stylet. Endogenous hormone levels increased during nodosity formation, with zeatin and gibberellic acid continually increasing and kinetin, indole acetic acid and abscisic acid initially increasing but later decreasing. Root dehydrogenase activity was 4.85 times higher than that of uninfested controls. Conclusions: Cell features of phylloxera-resistant Vitis species were likely physically restrictive for phylloxera feeding. Periderm cell changes of phylloxera-resistant rootstock 140 Ruggeri infested by phylloxera prevented phylloxera infestation. Cell changes during susceptible cultivars' nodosity and tuberosity formation were beneficial for phylloxera feeding, and endogenous hormone changes during phylloxera infestation may have affected nodosity formation. Significance of the Study: A high content of cell wall chemical components could potentially be an initial, convenient assessment index in phylloxera resistance breeding. This paper revealed that endogenous hormones affected nodosity formation.