Harnessing abiotic elicitors to bolster plant's resistance against bacterial pathogens

Bacterial pathogens have been of considerable interest in the field of plant pathology as they are known to cause serious constraints in crop production once infected. When environmental conditions favor disease development, the well-known bacterial pathogens including Pseudomonas syringae, Ralstonia spp., and Xanthomonas spp. exert severe harmful impacts across a variety of crop plants. The bacterial pathogens are known to infect plant tissues' extracellular spaces and release virulence factors directly into the cytosol or apoplast of the host plant. In this context, developing long-lasting and effective methods for controlling bacterial infections becomes essential for maintaining sustainable agricultural production. However, conventional methods such as copper-based bactericides and antibiotics are often proven to be ineffective and also adversely affect human health and the environment. Therefore, the immense challenges offered by bacterial diseases in global agriculture have encouraged interest in developing environment-friendly and sustainable alternatives for chemical pesticides. Abiotic elicitors are chemicals with non-biological origins that activate plant defense mechanisms and can potentially help in agriculture and crop protection. Numerous abiotic elicitors have shown impressive effectiveness in boosting plant defenses against bacterial infections, employing multiple mechanisms of induced resistance in various crops. The present review explores the rapidly developing field of abiotic elicitors and discusses their role in strengthening plant defenses through induction of resistance, understanding their role in boosting plant immunity, and highlighting both the potential benefits and current challenges to strengthen global food security

Comparative analysis of activities of vital defence enzymes during induction of resistance in pearl millet against downy mildew

Pearl millet Pennisetum glaucum (L.) R. Br. has the seventh largest annual production in the world giving it significant economic importance. Although generally well adapted to the growing conditions in arid and semi-arid regions, major constraints to yields are susceptibility to downy mildew disease caused by the oomycete Sclerospora graminicola (Sacc.) Schroet. Induction of resistance against downy mildew disease of pearl millet has been well established using various biotic and abiotic inducers. The present study demonstrated the comparative analysis of the involvement of the important defence enzymes like β-1,3-Glucanase, chitinase, phenylalanine ammonia-lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO) and lipoxygenase (LOX) during induced systemic resistance (ISR) mediated by inducers like Benzo(1,2,3)-thiadiazole-7-carbothionic acid-S-methyl ester (BTH), Beta amino butyric acid (BABA), Chitosan and Cerebroside against pearl millet downy mildew disease. Native-PAGE showed six POX isozymes in all categories of uninoculated pearl millet seedlings and maximum intensity of bands was noticed in resistant seedlings. After inoculation in Cerebroside-treated seedlings, there were seven isoforms, POX-4 was not present in any other seedlings. Native-PAGE analysis showed the presence of five PPO isozymes in all categories of uninoculated pearl millet seedlings and after inoculation seven isoforms of PPO-7 were noticed, and the intensity of banding was more in resistant and Cerebroside-treated seedlings. The isoforms PPO-3 were present as an extra band after inoculation in all seedlings. Isoform PPO-7, though found in all seedlings, was very prominent in Chitosan- and Cerebroside-treated seedlings. β-1,3-Glucanase Native-PAGE analysis showed the presence of only one isozyme in all categories of uninoculated/inoculated pearl millet seedlings. Glu-1 isozyme was very prominent in all seedlings including resistant and susceptible seedlings. Among the induced resistant seedlings, highest intensity was observed in Cerebroside-treated seedlings. Native-PAGE analysis showed the presence of three LOX isozymes in all categories of uninoculated pearl millet seedlings, and the intensity of banding pattern was very low in BTH-treated seedlings. LOX-1 and LOX-2 were very prominent in resistant, Chitosan- and Cerebroside-treated seedlings. Upon inoculation, one extra band, LOX-3, was exclusively noticed in Cerebroside-treated seedlings. In inoculated seedlings, LOX-1, LOX-2 and LOX-4 were very prominent in Chitosan Cerebroside-treated seedlings compared to other seedlings