Effect of rhizobial nod factors (lipo­chitooligosaccharide) on seedling growth of blackgram under salt stress

Abstract

A study was carried out to examine the performance of blackgram seedlings under varying levels of salinity and to ascertain the remedial effect of lipo chitooligosaccharide (LCO) against salinity stress. Higher germination percentage, root and shoot length, vigour index and salt tolerance index and lower phytotoxicity of roots and shoots (0) were observed in control (no salinity) treatment irrespective of priming. Salinity negatively influenced the seedling growth and as the salinity increased the seedling growth characters were drastically reduced. The nod factor treated blackgram seedlings had relatively higher germination percentage , root and shoot length, vigour index and salt tolerance index and lower phytotoxicity of roots and shoots. Seed priming with nod factor was found to have significant effect on eliminating the effects of salinity.Key words: Lipo chitooligosaccharide, Nod factors, Phytotoxicity, Priming, Salt tolerance index, Salinity.Agricultural productivity is adversely affected by salinity in many arid and semi-arid regions. Globally, 800 million hectares is adversely affected by salinity especially in the areas of irrigated agriculture (FAO, 2012). It causes reduction in the cultivated land size every year and in India 8.1 million hectares of land is salt affected.Salinity reduces the yield of pulses by more than 50 per cent (Bray et al., 2000). Major obstacles to the growth and productivity of widely cultivated greengram, blackgram and cowpea in arid and semiarid regions are the everincreasing salinity and sodicity of soils and the scarcity of good quality irrigation water (Alqurainy, 2007).Seed germination is very sensitive to salinity. Salinity hinders the seedling establishment by accelerating the osmotic potential. Seeds may be more sensitive to stresses than mature plants because of exposure to the dynamic environment close to the soil surface. Dash and Panda (2001) reported decrease in germination percentage, root length, shoot length and fresh mass with an increase in NaCl concentration and at 3 per cent NaCl concentration there was no emergence of root. Udhaya Nandhini et al. (2015) reported that, salt stress decreased germination percentage and reduced seedling growth in maize.Attempts have been made to alleviate the negative effects of salt stress during germination through priming with lipo-chitooligosaccharides (nod factors). Rhizobial bacteria from the family Rhizobiaceae (i.e., rhizobia) affect fundamental processes in plants by producing signal molecules, lipo-chitooligosaccharides (LCOs), during nitrogen fixing symbiosis. These compounds, known as nodulation factors (nod factors), are complex, with activity at concentrations as low as picomolar (Spaink, 1994).It has been shown that LCOs can stimulate several physiological responses in non-host plants including cell division (Egertsdotter and Von Arnod, 1998). Application of nod factors to seeds of legumes and non-legumes stimulates germination, seedling emergence, plant growth and yield in crop and horticultural plan...

Rhizobium-Linked Nutritional and Phytochemical Changes Under Multitrophic Functional Contexts in Sustainable Food Systems

“…Leguminous root exudates contain flavonoids that are the main allelochemical attractants for Rhizobium symbiosis (Hassan and Mathesius, 2012;Makoi and Ndakidemi, 2012). On the other side, Rhizobium secretes lipo-chitooligosaccharide compounds known as Nod factors that induce root nodulation in leguminous host plants (D'haeze and Holsters, 2002;Nandhini et al, 2018). Besides flavonoids, legumes also produce strigolactone allelochemicals that enhance Rhizobium activities on host roots (Peláez-Vico et al, 2016;McAdam et al, 2017), while stimulating the germination of arbuscular mycorrhizal fungi that facilitate phosphorus acquisition for improved nitrogen fixation (Püschel et al, 2017;Kafle et al, 2019).…”

Nod factors improve the nitrogen content and rhizobial diversity of faba bean and alter soil dehydrogenase, protease, and acid phosphomonoesterase activities

“…The beneficial effects of NF application on roots, plant physiology, growth, and yields were observed under some stressful conditions such as low pH and temperature as well as water and salt stress (Duzan et al, 2004;Prudent et al, 2016;Nandhini et al, 2017). The positive effects of NF on pea growth and symbiotic activity were noted in compacted soils (Siczek et al, 2013).…”

Microbial Derived Compounds Are a Promising Approach to Mitigating Salinity Stress in Agricultural Crops

“…Lipochitooligosaccharide is a signal molecule produced by rhizobia to communicate with its host plant. The same molecule, isolated from Bradyrhizobium japonicum has been reported to enhance plant growth under saline conditions (Gautam et al, 2016;Subramanian et al, 2016;Nandhini and Somasundaram, 2018). Soybean seeds treated with LCO upregulated proteins essential for salt stress tolerance (Subramanian et al, 2016).…”