Colonization and Performance of Diazotroph Endophytic Bacteria on Palm Oil (Elaeis guineensis Jacq L.) Leaves

Abstract

Excessive and continous use of inorganic fertilizer can lead to negative impact on the environtment qualities, therefore microbial biochemical approaches which are more friendly need to be considered. The absorption of nitrogen elements has been widely known through the roots and then transported to the leaves before chlorophyll performing the works on the photosynthesis process. However, the discovery of many diazotroph endophytic bacteria in the leaves suggests that nitrogen is not only supplied through the soil but it can be fixed by the diazotroph endophytic bacteria through the leaves. This study aims to evaluate the colonization and performance of the diazotroph endophytic bacteria on palm oil leaves. A total of 42 isolates of endophytic bacteria isolated by Mardiah (2014) were selected based on their ability to fix nitrogen qualitatively on nitrogen free medium and quantitatively based on Nessler reagent. One of the selected isolates with the highest nitrogen fixation capability is KSD2. The sequencing results showed that KSD2 isolate is closely related to Bacillus cereus. Colonization and performance evaluation of Bacillus cereus on palm oil seedlings were performed at 0, 2, and 4 weeks after inoculation. Treatments included Co (control / untreated), Ta (inoculation via soil), and Da (inoculation via leaves) with 7 replications. Data were evaluated using SPSS program with Univariate Analysis of Variance (significance level >95%). The colonization of Bacillus cereus was evaluated with PCR method approach using a specific primer (BCFomp1 / BCRomp1). PCR results showed that Bacillus cereus successfully colonized palm oil leaves as evidenced by the target sequences of 575 bp long.