Investigation was undertaken to screen out the extract of botanicals viz., neem leaf, neem oil, garlic, marsh paper plant, allamanda leaf, wood apple leaf, betel leaf and biological antagonists viz., Trichoderma viride and T. harzianum. Positive control was soil amendment with Provax and negative control with untreated soil. Soil drenching with Provax and untreated soil showed 7.65 and 37.5% wilt of tomato. Wilt incidence varied from 8.5 - 30.81%. Botanicals and biocontrol agents had significant effect on yield of tomato. Provax gave the highest (30.55 t/ha) yield which was statistically identical to garlic extract (29.66 t/ha) and untreated control showed the lowest (20.19 t/ha) yield which was followed by soil drenching with neem leaf extract. Both the biocontrol agents viz., T. harzianum and T. viride as broth and compost significantly reduced wilt incidence of tomato in the field over control.
Aims: Plant growth-promoting rhizobacteria enhance growth by making plant nutrients available to plants under a variety of growing conditions. The study was designed to screen zinc (Zn) solubilizing rhizobacteria and test their colonization ability in the rice rhizosphere.
Place and Duration of Study: The experiments were conducted in the Department of Agricultural Chemistry, Bangladesh Agricultural University, Mymensingh-2202, from January 2019 to July 2019.
Methodology: Initially, thirty-two previously isolated rhizobacteria were used for screening Zn solubilizing ability under a solid medium. Selected rhizobacteria from previous screening were used to quantify Zn solubilization in broth culture and evaluate their root colonization in rice using water agar media in a growth chamber. Early seedling growth was monitored for two weeks, and root-shoot lengths were recorded. Eleven of the tested rhizobacteria responded positively to ZnO-containing media.
Results: The Zn solubilizing index (ZSI) of the positive isolates ranged between 1.08-2.25 after 5 days of incubation. Isolate MQ1 solubilized the highest Zn both in solid medium (ZSI=2.25) and culture broth (solubilized 220.20 ppm Zn). The colonization of bacteria in the root zone was also investigated via bio-primed rice seeds of Binadhan-20. Eight of 11 isolates (MQ1, MQ2, MQ3, MQ4, OSbr5, OSbr6, EC1, and MQL9) showed substantial colonization in the rhizosphere after two weeks. The germination percentage of bio-primed seeds was not increased over the control, however, in most cases, bio-priming boasted early seedling growth. The OSbr5, OSbr6, and MQ6 isolates were superior performers in case of root and shoot growth.
Conclusion: The study identified some Zn solubilizing isolates, revealed their root colonizing ability, and observed early plant growth promotion. These isolates could be used as a potential tool for the Zn biofortification approach in rice.
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