Rhizosphere fungus Penicillium chrysogenum promotes growth and induces defence-related genes and downy mildew disease resistance in pearl millet.
Susceptible pearl millet seeds (cv 7042S) were treated with the plant growth promoting fungus Penicillium chrysogenum (PenC-JSB9) at 1 × 10(8) spores·ml(-1) to examine mRNA expression profiles of five defence responsive genes and test its ability to induce resistance to downy mildew caused by Sclerospora graminicola. PenC-JSB9 treatment at 1 × 10(8) CFU·ml(-1) for 6 h significantly enhanced seed germination (9.8- 89%), root length (4.08% to 5.1 cm), shoot length (18.9% to 7.77 cm) and reduced disease incidence (28%) in comparison with untreated controls. In planta colonisation of PenC-JSB9 showed that all three root segments (0-6 cm) and soil dilutions incubated on PDA produced extensive mycelial growth, however colonisation frequency of PenC-JSB9 was significantly higher in soil than in root segments. Spatiotemporal studies revealed that induction of resistance was triggered as early as 24 h and a minimum 2-3 days was optimal for total resistance to build up between inducer treatment and challenge inoculation in both experiments. In Northern blot analysis, transcript accumulation of resistant and PenC-JSB9 induced susceptible cultivars showed higher basal levels of defence gene expression than non-pretreated susceptible controls. Transcript accumulation in resistant seedlings challenge-inoculated with the pathogen showed maximum expression of CHS (3.5-fold increase) and Pr-1a (threefold increase) at 24 and 12 h, respectively. While PenC-JSB9 pretreated susceptible seedlings challenge-inoculated showed rapid and enhanced expression of LOX and POX at 48 h and for CHT at 24 h, whereas non-pretreated susceptible seedlings after pathogen inoculation showed weak expression of hybridised defence genes. Enhanced activation of defence genes by PenC-JSB9 suggests its role in elevated resistance against S. graminicola.
Applied Plant Pathology Laboratory, Department of Studies in Botany, University of Mysore, Manasagangotri, Mysore, India.
M
M
Murali
J
J
Sudisha
K N
KN
Amruthesh
S-I
SI
Ito
H S
HS
Shetty
D060467:Disease Resistance; D017343:Genes, Plant / Q000235:genetics; D009868:Oomycetes / Q000502:physiology*; D010408:Penicillium chrysogenum / Q000502:physiology*; D031782:Pennisetum / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000382:microbiology*; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000382:microbiology; D012333:RNA, Messenger / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D058441:Rhizosphere; D036226:Seedlings / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000382:microbiology; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000276:immunology / Q000382:microbiology; D013997:Time Factors
D012333:RNA, Messenger; D018749:RNA, Plant