Abstract
In this research, the biosynthetic and biocontrol potential of endophytic yeast to improve the growth and development of tobacco has been elucidated. Three yeast strains were enriched and isolated from different plant tissues. Partial sequence analysis of ITS5-5.8-ITS4 region of the nuclear ribosomal DNA with universal primers identified YD5, YE1, and YSW1 as Saccharomyces cerevisiae (S. cerevisiae), Zygosaccharomyces bailii (Z. bailii), and Saccharomyces kudriavzevii (S. kudriavzevii), respectively. When cultivated in a medium supplemented with 0.1% L-tryptophan, isolated yeast strains produced indole-3-acetic acid (IAA). The capacities of those strains to improve the mobility of phosphorus and synthesize siderophores has been proven. Their antimicrobial activities against several Solanaceae plant pathogenic fungi (Alternaria solani pathovar. tobacco, Rhizoctonia solani, and Fusarium solani pathovar. phaseoli) were determined. S. cerevisiae YD5, Z. bailii YE1, and S. kudriavzevii YSW1 inhibited the growth of all tested pathogens. Yeast strains were tested for endophytic colonization of tobacco by two different inoculation methods: soil drench (SD) and leaf spraying (LS). To establish colonization in the various tissues of tested tobacco (Nicotiana tabaccum L.) plants, samples were taken on the seventh, fourteenth, and twenty-first days after treatment (DAT), and explants were inoculated on yeast malt agar (YMA). Both techniques of inoculation showed a high frequency of colonization from 83.33% to 100%. To determine the effectiveness of the microbial endophytes, their effect on some physiological processes in the plant were analyzed, such as photosynthesis, stomatal conductivity, and transpiration intensity. The effect of single and double treatment with yeast inoculum on the development and biochemical parameters of tobacco was reported. Plants have the ability of structural and functional adaptation to stress effects of different natures. All treated plants had a higher content of photosynthetic pigments compared to the control. Photosynthesis is probably more intense, and growth stimulation has been observed. The chlorophyll a/b ratio remained similar, and the total chlorophyll/carotenoid ratio slightly increased as a result of elevated chlorophyll levels. The most significant stimulating effect was recorded in tobacco plants treated by foliar spraying with Z. bailii YE1 and S. cerevisiae YD5. In contrast, S. kudriavzevii YSW1 had a better effect when applied as a soil drench. Thus, S. cerevisiae YD5, Z. bailii YE1, and S. kudriavzevii YSW1 have a high potential to be used as a biocontrol agents in organic agriculture.
Highlights
In recent years, increasing attention has been paid to organic farming, which has become a priority in agriculture worldwide
The present study aims to evaluate the effect of three endophytic yeast strains on tobacco plants physiology and development to demonstrate PGP activity and their possible application in organic farming
YD5 was identified as S. cerevisiae, YE1 as Z. bailii, and YSW1 S. kudriavzevii, respectively
Summary
In recent years, increasing attention has been paid to organic farming, which has become a priority in agriculture worldwide. The importance of the soil rhizosphere enrichment with beneficial microorganisms to boost the conditions of root nutrition has led to the appliance of microbial fertilizers [1]. They show significant advantages over artificial synthetic fertilizers, namely, they synthesize physiologically active substances (vitamins, auxins, etc.) and provide them to the plant, increase the productivity of photosynthesis, enhance enzymatic processes in plants and improve water regime, induce the activity of other soil microorganisms, act as antagonists of phytopathogenic microorganisms, and increase the protective functions of plants [2–4]. There have been an increased number of studies concerning the isolation of endophytic yeasts that stimulate plant growth [18]. Chitin-containing pathogens such as Fusarium solani, Rhizoctonia solani, and Alternaria solani induce damage to tobacco such as root and stem rot and leave brown spots [25]
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