Plant Growth Promoting rhizobacteria-Induced Systemic Resistance Against ToLCV Disease in Tomato (Lycopersicon esculentum Mill.)
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Date
2012
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UAS Dharwad
Abstract
Fifty rhizobacterial isolates were screened against ToLCV disease in tomato.
Based on the disease severity control, ten isolates were selected for further studies.
The presence of ToLCV in affected leaves was confirmed by both transmission
electron microscopy and sequencing of viral coat protein specific gene. The
mechanism of virus control was elucidated. All the isolates induced systemic
resistance in tomato plants. These plants also showed the highest reduction in the
insect population. The green house experiment revealed Pseudomonas 206(4) as the
most promising isolate. Semi quantitative PCR analysis revealed lower viral load
accumulation in the plants inoculated with Pseudomonas 206(4). The plants
inoculated with this isolate also recorded maximum plant height, total biomass,
chlorophyll content and fruit yield over the diseased control. Based on biocontrol
potential and plant growth promotion, three efficient isolates were further evaluated in
combination with chitosan both under glasshouse and field conditions. The
rhizobacterial consortia + chitosan emerged as the best treatment in disease severity
control, plant growth promotion as well as in increasing the yield both under
glasshouse and field conditions in two consecutive seasons. The histopathological
studies revealed more anatomical destruction in diseased plants as compared to
rhizobacteria + chitosan treated plants. The root colonization ability of the most
efficient PGPR strain 206(4) was assessed by SEM, which indicated that the roots
inoculated with this isolate in combination with chitosan showed higher population
than the isolate without chitosan. The subcellular changes due to ToLCV and
rhizobacterial+chitosan inoculation, as studied by TEM , revealed complete loss of
subcellular architecture in diseased cells and the cells appeared somewhat closer to
normal cells in the treated leaves. Thus, the rhizobacterial consortia and chitosan,
significantly reduced ToLCV-induced symptom severity and yield losses, and can be
recommended as a component of integrated disease management systems.