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The present study aimed to characterize the potential plant growth-promoting rhizobacteria (PGPR) based on biochemical tests based on eight bacterial isolates, and to identify potential PGPR based on the 16S rRNA sequencing molecular method. Eight potential PGPR strains (UPMC1166, UPMC1168, UPMC1254, UPMC1376, UPMC1389, UPMC1393, UPMC703 and UPMC704) isolated from the soils in the oil palm (Elaeis guineensis) estates across Malaysia were selected because of their most PGPR activities. They were screened for nitrogen fixation, phosphate and potassium solubilization, and production of indole-3-acetic acid (IAA). All isolates showed the ability to grow between pH 2 to 9 and survive from 2 to 15% (w/v) of the salt medium. Among the isolated PGPRs, four PGPRs (UPMC1166, UPMC1168, UPMC1254 and UPMC1389) showed the ability to fix nitrogen and had the potential to produce IAA. Furthermore, two PGPRs (UPMC1393 and UPMC1376) demonstrated the ability to solubilize phosphate, while three PGPRs (UPMC703, UPMC704, and UPMC1393) showed the ability to solubilize potassium. Therefore, all the above eight PGPR isolates can benefit the oil palm cultivation industry. The molecular identification based on 16S rRNA gene sequence revealed that UPMC1166 was identified as Bacillus methylotrophicus; UPMC1168 as B. siamensis; UPMC1254 as B. subtilis; UPMC1389 as B. albus; UPMC1376 as Lactobacillus plantarum; UPMC1393 as B. marisflavi; UPMC703 as Burkhoderiaanthina and UPMC704 as B. metallica. These novel strains can be further investigated for their viability and effectiveness for bio-organic fertilizer production and application in the immature stage of oil palm growth.

The oil palm (OP) Elaeis guineensis is a robust feeder of nutrients and necessitates the adjustment and adequate allocation of nutrients for optimum growth and yields. Therefore, information on leaf nutrient concentrations during the immature stage is essential for maximal OP yield at the mature stage. Currently, in Malaysia, fertilizer by the standard practice application (Treatment 1; T1) is considered a cost-effective fertilization practice in terms of fertilization cost and the overall cost per palm oil tree per hectare. However, there is an idea to further reduce the costs of fertilizers and labour per hectare to make it more cost-effective. Therefore, the present study aims to develop a novel biochemical fertilizer by testing the Universiti Putra Malaysia (UPM) biochemical fertilizer (Treatment 2; T2) in the immature OP. Since the use of T1 has been well established in Malaysia, the present study is to compare the leaflets’ nutrient levels (nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), and boron (B)) and vegetative parameters (frond length (FL), frond number of leaves (FNL), frond width (FW), frond thickness (FT), chlorophyll index (CI), and the canopy of immature OP by using T2 to compare with those in T1. This study was conducted 6 to 48 months after planting (MAP) at the Telang OP plantation, Kuala Lipis (Pahang), from January 2015 to December 2018. Based on the chemical levels of the pre-treatment soil samples collected at the weeded circle area in January 2015 in the two depths (0–15 cm and 15–30 cm), there was no significant difference (p > 0.05) in all 11 chemical parameters (pH, total N, organic carbon (Org C), total P, available P (Av P), cation exchange capacity (CEC), exchangeable K, (Ex K), exchangeable Ca (Ex Ca), exchangeable Mg (Ex Mg), exchangeable aluminium (Ex Al) and B between T1 and T2. This indicated that the chemical levels in the OP soils in both T1 and T2 would not be significant factors when T1 and T2 were applied. All six leaflets’ nutrient levels showed at least ‘Optimum’ or ‘Excessive’ compared to the established guideline using T1 and T2. Overall, there was no significant (p > 0.05) difference in all the above six leaflets’ nutrient levels and six vegetative parameters between T1 and T2 based on the t-Test, multiple linear stepwise regression analysis, and correlation analysis. These results suggested that rates of T1 and T2 applied in this study are enough to provide the amount of nutrients needed to support the OP vegetative growth during the immature period. The estimated cost savings for the combination of T2 fertilizers per hectare (RM 1113.43 or 250 USD) and reduction of the number of rounds (RM 133.85; or 30 USD) of T2 fertilizer application would give a sum of total cost savings of at least RM 1247.25 (280 USD) per hectare. If only based on the T2 fertilizer per hectare, the economic benefit of the total cost saving is estimated to be at least 10.6%. In summary, this study recommends the utilization of T2 as a novel, cost-effective, and alternative biochemical fertilizer treatment for better management of immature OP plantations in Malaysia.

Latex production from Hevea brasiliensis rubber tree is the second most important commodity in Malaysia, but this industry is threatened by the white root rot disease (WRD) caused by Rigidoporus microporus that leads to considerable latex yield loss and tree death. This study aimed to characterize and compare the virulence of five R. microporus isolates obtained from infected rubber trees located at different states in Malaysia. These isolates were subjected to morphological and molecular characterization for species confirmation and pathogenicity test for the determination of virulence level. BLAST search showed that the ITS sequences of all the pathogen isolates were 99% identical to R. microporus isolate SEG (accession number: MG199553) from Malaysia. The pathogenicity test of R. microporus isolates conducted in a nursery with 24 seedlings per isolate showed that isolate RL21 from Sarawak has developed the most severe above- and below-ground symptoms of WRD on the rubber clone RRIM600 as host. Six months after being infected with R. microporus, RL21 was evaluated with the highest average of disease severity index of 80.52% for above- and below-ground symptoms, followed by RL22 (68.65%), RL20 (66.04%), RL26 (54.38%), and RL25 (43.13%). The in vitro growth condition tests showed that isolate RL21 of R. microporus has optimum growth at 25–30 °C, with the preference of weakly acidic to neutral environments (pH 6–7). This study revealed that different virulence levels are possessed among different R. microporus isolates even though they were isolated from the same host species under the same climate region. Taken together, field evaluation through visual observation and laboratory assays have led to screening of the most virulent isolate. Determination of the most virulent isolate in the present study is vital and shall be taken into consideration for the selection of suitable pathogen isolate in the development of more effective control measures in combating tenacious R. microporus.