Morphological and Physiological Responses of Sugarcane toLeifsonia xylisubsp.xyliInfection

Abstract

Ratoon stunt, caused by the bacterium Leifsonia xyli subsp. xyli, is one of the major sugarcane diseases worldwide. The objectives of this study were to determine the variation in morphology and DNA sequence of L. xyli subsp. xyli strains isolated in China, to compare the changes that occurred in vascular ultrastructure and levels of endogenous hormone abscisic acid (ABA), auxins (indoleacetic acid [IAA]), and gibberellic acids (GA3) in sugarcane stalks. Experiments were also conducted with two sugarcane varieties, ‘ROC22’ and ‘Badila’, in the greenhouse to understand the cytological and physiological mechanisms of L. xyli subsp. xyli–induced growth stunting. There were three treatments in the experiments: (i) healthy plants (L. xyli subsp. xyli–free plants), (ii) infected plants (L. xyli subsp. xyli–infected seedcanes treated with hot water, and (iii) infected plants (healthy seedcanes dipped in L. xyli subsp. xyli cell culture). The results showed that sequence coverage of a locally isolated strain, LxxGXBZ01, was 99.99%, and the average nucleotide identity between LxxGXBZ01 and the other well-characterized Brazilian isolate LxxCTCB07 was 93.61%. LxxGXBZ01 occurred in different sizes and shapes in xylem vessels of infected plants. In comparison with healthy stalks, the secondary walls of the vessel element in L. xyli subsp. xyli–infected stalks were degraded with uneven wall thickness, deformities, sticky substances, and electron-dense substances accumulated inside the cells. Compared with the healthy and hot-water treatments, the contents of IAA and GA3 were significantly lower, while that of ABA was significantly higher in the L. xyli subsp. xyli–infected stalks. The information obtained in this study will expand our understanding of ratoon stunt etiology and cytological and physiological bases of the disease manifestation.

The physiological characteristics and associated gene expression of sugar cane inoculated with Leifsonia xyli subsp. xyli

“…We used the Lxx strain GXBZ01 (accession number LFYU00000000) in this study, isolated and cultured from the sugar cane variety Badila. Bacteria were cultured in a modified M‐SC medium (Brumbley, Petrasovits, Birch, & Taylor, ), as described in our earlier publications (Zhang et al., , ).…”

“…xyli ( Lxx ) (Davis, Gillaspie, Harris, & Lawson, ) and is an important disease globally because it is responsible for substantial crop yield losses (Comstock, ; Grisham, ; Li et al., ; Young et al., ). Infection affects not just the ratoon crop, but also impacts plant yields (Chen et al., ; Comstock, ; Steindl & Hughes, ; Zhang et al., , ).…”

“…The last of these treatments, seedcane thermotherapy and equipment disinfection, have only limited efficacy, however, and cannot be used to completely eradicate Lxx (Carvalho et al., ). At the same time, meristem tissue culture consumes both time and resources (Zhang et al., ).…”

“…Previous studies in this area have mainly focused on culturing the Lxx pathogen, as well as detection methods and control technique; earlier work has not addressed the interactions between the pathogen and host or their associated molecular mechanisms. The Lxx pathogen extracts nutrients from plants after infection before destroying structures, changing host metabolism and further influencing growth and development (Kao & Damann, ; Zhang et al., ). Thus, interactions between the host plant and pathogen as well as their mutual recognition are key factors in the development of disease resistance (Lamb, Lawton, Dron, & Dixon, ).…”

“…Thus, interactions between the host plant and pathogen as well as their mutual recognition are key factors in the development of disease resistance (Lamb, Lawton, Dron, & Dixon, ). Previous work has shown that sugar cane growth, ultrastructure, endogenous hormones and photosynthetic characteristics are all adversely affected by ratoon stunt infection (Chen et al., ; Zhang et al., , ).…”