Plant growth promoting bacteria associated with corm ofCrocus sativusduring three growth stages

Abstract

Corm, being a unit of reproduction and storage, plays an indispensable role in the life cycle of Crocus sativus (saffron). This study deals with the screening of bacteria isolated from cormosphere (area surrounding the corm sheath) of C. sativus during three growth stages for biofertilizer and biocontrol property. Out of 1000 protease producing bacteria isolated from the cormosphere (soil adhering corm sheath in analogy to rhizosphere), three plant growth promoting (PGP) Bacilli namely Bacillus thuringiensis DC1, B. megaterium VC3 and B. amyloliquefaciens DC8 were selected based on multiple and maximum PGP traits along with corm rot pathogen antagonism. To evaluate in vivo efficacy of the consortia, pot trials were conducted and a significant increase in number and length of both, shoot and root were observed. Further, the disease incidence in test corms was reduced by threefold as compared to control and the number of daughter corms produced in pot trials was also increased. Since corm is a unit of reproduction/propagation, increase in its number is of major significance. This is the first report on isolation and characterization of Plant growth promoting bacteria from any cormosphere.

Field evaluation of PGP Bacillus sp. strain D5 native to Crocus sativus, in traditional and non traditional areas, and mining of PGP genes from its genome

“…Bacillus subtilis EA-CB0575 from banana rhizosphere increased the total dry weight (root + shoot) of banana plant by 34.60% under green house conditions 67 . In the present study, the increase in root-shoot length and number attributed to the production of phytoharmone IAA, phosphate solubilization and siderophore production by Bar D5 making inslouble nutrients present in soil, available to plant and increase in cormlets production could be due to starch hydrolysis and IAA production by Bacillus strain 28 . The starch hydrolysis in saffron corm helps the floral, vegetative buds and roots to differentiate during dormancy.…”

“…Bar D5 based bio-formulation was also found to be better than previously reported three different bio-formulations by our group on the basis of pot assay evaluation Table 5. Earlier bio-formulations were (i) bacterial consortia comprising of (Chryseobacterium elymi WRF4, Pseudomonas tremae WRF2, Acetinobacteria calcoaceticus WRF1, Bacillus aryabhattai WRF5, Pseudomonas kilonensis WRF3 and Pseudomonas koreensis WRF6A 26 (ii) Bacillus amyloliquefaciens W2 8 and (iii) bacilli consortia comprising of Bacillus thurinniensis DC1, Bacillus megaterium VC3 and Bacillus amyloliquefaciens DC8 28 . Previously, reported Bacillus aryabhattai strains associated with saffron rhizosphere 26 and cormosphere 28 are from saffron fields in Kashmir.…”

“…Earlier bio-formulations were (i) bacterial consortia comprising of (Chryseobacterium elymi WRF4, Pseudomonas tremae WRF2, Acetinobacteria calcoaceticus WRF1, Bacillus aryabhattai WRF5, Pseudomonas kilonensis WRF3 and Pseudomonas koreensis WRF6A 26 (ii) Bacillus amyloliquefaciens W2 8 and (iii) bacilli consortia comprising of Bacillus thurinniensis DC1, Bacillus megaterium VC3 and Bacillus amyloliquefaciens DC8 28 . Previously, reported Bacillus aryabhattai strains associated with saffron rhizosphere 26 and cormosphere 28 are from saffron fields in Kashmir. The one being reported in present study has been isolated from cormosphere of saffron plant grown in Kishtwar region Bacillus and Pseudomonas are used pre-dominantly as PGP and biological control agents, for both direct as well as indirect mechanism of plant growth promotion 50 .…”

“…A total of 30 corms were primed with Bar D5 bio-formulation (10 8 CFU ml −1 ) and 30 corms were treated with only talc and CMC to serve as control 26 . The corms (control as well as treated) were planted in steam-sterilized sand: soil mixture (1:1 w/w) inoculated with Fusarium oxysporum R1 spores (10 12 spores ml −1 , 5 × 10 10 spores gm −1 of soil) in pots, so as to evaluate disease incidence 28 . Pots were incubated in plant growth chamber, under 16 h of light and 8 h of dark cycle at 26 ± 2 °C with 80% relative humidity for 40 days, and were irrigated after every 3 days.…”

Microbiome Fingerprint as Biomarker for Geographical Origin and Heredity in Crocus sativus: A Feasibility Study

“…This explains the dominance of Proteobacteria, Actinobacteria, and Bacteroidetes in the cormosphere, which are among the most dominant phyla in the soil and maybe getting transferred from the soil, just like in rhizosphere (Miyashita, 2015;Fierer, 2017;Compant et al, 2019). To our knowledge, cormosphere microbiome has not been studied in any other plant, except for saffron reported previously by our group (Ambardar and Vakhlu, 2013;Ambardar, 2014;Ambardar et al, 2014Ambardar et al, , 2016Kour et al, 2018) from Kashmir, India (Chamkhi et al, 2018), and from Taliouine, Morocco. Previous reports by our group have also confirmed the dominance of Proteobacteria in Kashmir saffron rhizosphere and cormosphere, even though the method used was cultivation dependent and 16S targeted metagenome sequencing was different than the methods used in the present study (Ambardar and Vakhlu, 2013;Ambardar et al, 2014) (Supplementary Material 1).…”