Rhizosphere fungus Penicillium chrysogenum promotes growth and induces defence‐related genes and downy mildew disease resistance in pearl millet

Abstract

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.

Exogenous Trehalose Treatment Enhances the Activities of Defense-Related Enzymes and Triggers Resistance against Downy Mildew Disease of Pearl Millet

“…Seed treatment is an effective and economical way of controlling pearl millet downy mildew disease because pearl millet is mainly grown in low-input rain-fed agricultural system in which farmers cannot afford expensive and repeated control measures (Thakur et al, 2004; Zarafi et al, 2004; Murali et al, 2013). In recent years, increasing evidence has indicated that trehalose and its derivatives have the capacity to act as signal molecules that can induce plant resistance against various types of stress (Lunn et al, 2014; Mostofa et al, 2015).…”

“…Treated seeds were subjected to a germination assay as described by Sudisha et al (2010). Seedling vigor of 7-day-old seedlings was examined according to Murali et al (2013). Both the seed germination and seedling vigor experiments were conducted with four replicates of 25 seeds per treatment, and were repeated twice.…”

“…Downy mildew disease caused by the oomycete Sclerospora graminicola is one of the most destructive diseases in pearl millet ( Pennisetum glaucum ), which affects its yield, and as a consequence income of resource-poor farmers (Nutsugah et al, 2002). The classical control of this disease is mainly dependent on host resistance genotypes and fungicides (Jogaiah et al, 2007; Murali et al, 2013). However, because S. graminicola occupies distinct physiological and phylogenetic niche, most of the disease control measures have failed to obtain a durable downy mildew disease resistance (Jogaiah et al, 2014).…”

“…A number of such inducers have been tested against pearl millet downy mildew disease, including oligosaccharides supplemented with mannitol, N -acetylchitooligosaccharides, β-aminobutyric acid, and 3,5-dichloroanthranilic acid (Sharathchandra et al, 2004; Nandini et al, 2013; Shailasree and Melvin, 2015; Lavanya and Amruthesh, 2016). However, previous attempts with various classes of inducing agents have resulted in identification of only a few bioagents for durable downy mildew disease resistance (Jogaiah et al, 2010; Raj et al, 2012; Murali et al, 2013). Thus, the present situation demands a constant and concerted effort in order to create a panel of effective inducers of downy mildew disease resistance in pearl millet.…”

Isolation of phosphate solubilizing fungi from rhizosphere soil and its effect on seed growth parameters of different crop plants

“…Similarly, A. niger and P. italicum solubilize tri-calcium phosphate (TCP) and improve the growth of soyabean in TCP amended soil [24]. Likewise, seeds treated with T. harzianum in sunflower [25] and Penicillium chrysogenum and P. oxalicum in pearl millet [13,26] which were isolated from the rhizosphere soil offered enhanced seed germination and seedling vigour over the control.…”