studies on the interaction of non rhizobial endophytic yeast and rhizobia in root nodules of blackgram colonization signal molecules nodulation plant growth and drought tolerance

Abstract

newline Legume-Rhizobium symbiosis is more complex mutualistic phenomenon. The present newlinestudy explores endophytic yeast in the nodule that assists Rhizobium sp. in multifarious newlineways of plant growth promotion (PGP), nodulation, plant protection, and drought newlinetolerance. Nowadays, soil yeasts have received much attention due to its potential plant newlinegrowth promoting activities and sugar production. Besides their biological significance, newlineinvestigation on endophytic yeast are scanty. In this context, the present study aimed to newlineevaluate the effect of nodule Rhizobium sp. VRE1 and non- rhizobial endophytic (NRE) newlineyeast, C. tropicalis VYW1 and its co-inoculum on blackgram plants. Biochemical test newlineand plant growth-promoting traits revealed the importance NRE yeast in colonization of newlinerhizobia in the nodules. Concerning PGP attributes, the co-inoculants exhibited higher newlinenitrogen fixing efficiency (426.22 n moles of ethylene produced h-1mg-1 of protein) and newlinemaximum IAA production with and without tryptophan (98.31 and 34.32 mg g-1 newline), newlinerespectively, and gibberellic acid (8.6 µg mL-1) newline. Similarly, co-inoculum showed higher newlineP and Zn nutrient solubilization (98 mg mL-1 newlineand 7.20 ppm) and the strains also possess newlinesiderophore, ammonia, HCN production, and catalase activity. The in vitro antagonistic newlineactivity showed an inhibition percentage of 40.5% against Rhizoctonia solani. To localize newlinethe yeast colonization in nodules, NRE yeast VYW1 was tagged with red fluorescent newlineprotein marker using CIp10 integrated pUSB001 vector, and it produced fluorescence newlineemission (gt104 newline). The root colonization study showed endogenous colonization of newlineinoculant populations ranged from 2.78 to 5.86 Log10 CFU g-1 newline. The relative fluorescence newlineintensity emitted by the nodule extract of tagged VRE1GFP and VYW1RFP strains reached newlinea higher threshold level of 103 newline-105 newlineand 104 newline-105, respectively. Additionally, their presence newlinein the nodule was authenticated by Scanning electron microscopy and Confocal scanning newlineelectron microscopy. Furthermore, the p