Methyl jasmonate (MJ) (10-7, 10-6 and 10-5 M) and Salicylic Acid (SA) (1 mM, 5 mM and 10 mM) were injected into wheat ear heads of a Karnal Bunt (KB) susceptible (HD 2329) and a resistant (WH 283) genotype at boot leaf stage, 24 h before (pretreatment) and 24 h after (posttreatment) inoculations with Karnal bunt pathogen. Karnal bunt incidence was quite high (28.35%) in susceptible genotype HD 2329 under conditions of artificial infection. Pre/ posttreatment of ear heads with methyl jasmonate or salicylic acid reduced the disease development in this genotype. To study the effect of pre/posttreatments of methyl jasmonate and salicylic acid in vitro conditions, 15, 18 and 21-day-old embryos of both the genotypes were co-cultured with N. indica in petri plates. Application of methyl jasmonate was not only effective in early induction of Inhibition Zone (IZ) (i.e., in 15-day-old embryos) but significantly increased the percentage of inhibition zone forming embryos and also the diameter of inhibition zone in co-culturing. Both pre and posttreatments of inoculated ear heads of WH 283 genotype with salicylic acid could induce inhibition zone formation in co-culturing of pathogen and embryos at 18 Days After Pollination (DAP). Five mM solution of salicylic acid was the most effective for inducing higher frequency of inhibition zone formation, but 10 mM solution of salicylic acid was the most effective for bigger size of inhibition zone in coculturing at 21 days after pollination. Thus, both methyl jasmonate and salicylic acid were able to induce resistance both in vivo and in vitro conditions in the present experiment. However, to see the feasibility of using these chemicals at larger scale, spraying on developing ear-heads is yet to be observed.

Jasmonic acid and derivatives, collectively called jasmonates (JAs), have emerged as important signals in the regulation of plant responses to pathogenic and beneficial microorganisms. The complex interplay of JAs with the alarm signals like salicylic acid (SA) provides plants with a regulatory potential that shapes the ultimate outcome of the plant-microbe interaction. The production of these signals varies greatly in quantity, composition and timing, and results in the activation of differential sets of defenserelated genes that eventually determine the nature of the defense response against the attacker encountered (Reymond and Farmer 1998; Rojo et al., 2003; Van Oosten et al., 2004). Although the role of JAs in plant defense against insects and during wounding has been well documented, the importance of JAs in the defense against pathogenic microorganisms has only been envisaged in the last decade. In the present investigation, effects of exogenous applications of Methyl Jasmonate (MJ) and SA on Karnal bunt resistance in wheat were studied in vitro and in vivo conditions.

Karnal bunt, caused by Neovossia indica (Mitra) Mundkur, is one of the most important diseases of wheat. It was first detected in India and was subsequently found in Mexico, Nepal, Pakistan, Iran, Afghanistan and USA (Babadoost, 2000). The pathogen being quite resistant to physical and chemical treatment, easily spreads to new areas, calling for stringent quarantine measures locally and globally (Gill et al., 1993, Rush et al., 2005). Implementation of the zero-tolerance quarantine for Karnal bunt pathogen adversely affected wheat trade globally. Presently, India has a great potential to export wheat, but this means rigid quality specification of international trade. Most of the countries require phytosanitary declarations that the wheat is produced in regions where Karnal bunt is not known to occur. The disease has wide occurrence and infects most of the cultivated varieties. Therefore, finding some easy, timesaving means of producing Karnal bunt-free grains will offer us some of the new opportunities to trade more and contribute to national growth and better economy.

Genetics & Evolution Journal, CEL-I Endonuclease, Heterozygous Mutants, Homozygous Mutants, Biological Processes, Plant Mutants, Solanum Lycopersicon, Microcentrifuge Tubes, Homozygous Plants, Plant Genes, Cross Pollination, Heteroduplex Formation.