Identification and Evaluation of the Growth Promotion of Endophytic Bacteria on in vitro Potato Plants.

<b>Background and Objective:</b> Isolation and investigation of plant growth promoting bacteria on potato plants can provide significant information for the application of beneficial bacteria in potato production. This study aims to isolate and characterize endophytic bacteria isolated from potato roots. In addition, the potential application of endophytes in promoting potato growth under <i>in vitro</i> conditions was also investigated. <b>Materials and Methods:</b> The roots from 15 healthy potato plants were excised and surface sterilized by NaOCl and finally rinsed by sterilized water. The confirmed surface-sterilized roots were then aseptically cut into small fragments and spread onto the isolation media, followed by incubation at 27°C for up to 3 days. Six isolates that showed differences in colony morphology were selected for further investigation. All isolates were screened for IAA production, nitrogen fixation, and phosphate solubilization. <b>Results:</b> Five of the isolates were identified as <i>Bacillus</i> and isolate 30 was identified as <i>Paenibacillus alvei</i>. All isolates exhibited good IAA production. While Iso-27 had no nitrogen fixation activity, Iso-28 showed the highest level of nitrogen fixation activity (3.59 mg L¹), four isolates (Iso-9, Iso-10, Iso-11, Iso-28) could solubilize phosphate, ranging from 49.64 g L¹ to 67.98 mg L¹. After being inoculated with <i>in vitro</i> potato plants, isolates 9, 10, 28, 30, improved the stalk length, root number, fresh mass and dried mass of the potato plants. <b>Conclusion:</b> The four isolates can potentially be applied in <i>in vitro</i> potato culture.

Insecticidal and Feeding Deterrent Effects of Kaempferia galanga L. and Amomum subulatum on Pieris rapae L. Larva.

<b>Background and Objective:</b> <i>Pieris rapae</i> L., is one of the most widespread and destructive pests of cruciferous plants. At present, synthetic chemical insecticide is still the main approach to control this pest despite several disadvantages to human health and the wildlife environment as well as biological resistance. To search for plants having insecticidal activity, the biological effects of two medicinal plants <i>Kaempferia galanga</i> L. and <i>Amomum subulatum </i>on <i>Pieris rapae</i> L., were investigated. <b>Materials and Methods:</b> The methanol extracts of dry rhizomes and fruits of <i>Kaempferia galanga</i> L. and <i>Amomum subulatum </i>were used to determine the mortality, feeding and oviposition deterrence of larvae and adult of <i>Pieris rapae</i> L. <b>Results:</b> <i>Kaempferia galanga</i> L. and <i>Amomum subulatum</i> exhibited insecticidal activity against <i>Pieris rapae</i> L., with LC₅₀ values of 2.11 and 11.80% (w/v), respectively. In the antifeedant test, <i>Kaempferia galanga</i> L., extract showed no significant difference with the control at the low concentration (0.5 and 1%). Whereas, with a concentration of 0.5%, <i>Amomum subulatum</i> extract demonstrated a high antifeedant effect on <i>Pieris rapae</i> L., larvae. In addition, plants treated with these two extracts reduced eggs laid by <i>Pieris rapae</i> L., in field conditions showing the oviposition deterrent properties. <b>Conclusion:</b> These results indicated that <i>Kaempferia galanga</i> L. and <i>Amomum subulatum </i>extracts have insecticidal substances against <i>Pieris rapae </i>L., which can be used for developing effective pesticides or/and oviposition deterrents for integrated pest management.