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This study aimed to verify the effect of Plant Growth-Promoting Rhizobacteria (PGPR) and humic acid amendment with different N-fertilizer rates on sweet potato. The results showed that inoculation of UPMRB9 in combination with 50% fertilizer-N produced significantly higher dry matter (DM) in leaves, storage, and fibrous roots, and in the whole plant. Similar trends were observed for nitrogen use efficiency (NUE), in which 75% N+UPMB10 and 50% N+UPMRB9 treatments significantly produced higher efficiency by 44.89% and 40%, respectively. In addition, the highest OD of β-carotene, 0.71 and 0.68 mg g-1, were observed in 50% N+UPMRB9 and 75% N+UPMB10, respectively. Sweet potato plants obtained greater NUE and N uptake when lower rates of N were used with the microbial inoculations. These findings show the ability of PGPR-HA to fix nitrogen and thereby increase N availability of soils, reducing the need to provide mineral nitrogen to crops. Thus, applying biofertilizer containing PGPR amended with humic acid could be a sustainable approach to improving the NUE and total N concentration of sweet potato plants. Higher N use efficiency will lead to savings in the amount of N fertilizer needed, thus reducing costs and promoting an eco-friendly approach at the same time. [ABSTRACT FROM AUTHOR]

Basal stem rot of oil palms (OPs) is caused by Ganoderma boninense, a white-rot fungus. Root tissues are the primary route for G. boninense penetration and subsequent pathogenesis on OPs. Little is known on the host lignin biochemistry and selectivity for G. boninense degradation. Oil palm genotypes with different defense responses to G. boninense (highly tolerant, intermediately tolerant, and susceptible) were assessed for root lignin biochemistry (lignin content and composition), plant functional traits (height, fresh weight, girth), chlorophyll content, and root elemental nutrient content. One-year-old seedlings and five-year-old trees were screened for root thioglycolic acid lignin (TGA) content, lignin composition, and elemental nutrient depositions, while plant functional traits were evaluated in the one-year-old seedlings only. The TGA lignin in all the oil palm seedlings and trees ranged from 6.37 to 23.72 pM µg−1, whereas the nitrobenzene oxidation products showed a syringyl (S)-to-guaiacyl (G) ratios of 0.18–0.48. Tolerant genotypes showed significantly lower lignin content compared to the intermediately tolerant and susceptible genotypes. Likewise, the S/G ratio was higher in genotypes with lower lignin content. The depositions of root Fe, Si, Ti, S, and Cu were significantly different among the oil palm genotypes with the susceptible genotypes showing greater content than the tolerant genotypes.

Plant growth-promoting rhizobacteria (PGPR) is a soil bacterium that positively impacts soil and crops. These microbes invade plant roots, promote plant growth, and improve crop yield production. Bacillus subtilis is a type of PGPR with a short shelf-life due to its structural and cellular components, with a non-producing resistance structure (spores). Therefore, optimum formulations must be developed to prolong the bacterial shelflife by adding humic acid (HA) as an amendment that could benefit the microbes by providing shelter and carbon sources for bacteria. Thus, a study was undertaken to develop a biofertilizer formulation from locally isolated PGPR, using HA as an amendment. Four doses of HA (0, 0.01, 0.05, and 0.1%) were added to tryptic soy broth (TSB) media and inoculated with B. subtilis (UPMB10), Bacillus tequilensis (UPMRB9) and the combination of both strains. The shelf-life was recorded, and viable cells count and optical density were used to determine the bacterial population and growth trend at monthly intervals and endospores detection using the malachite green staining method. After 12 months of incubation, TSB amended with 0.1% HA recorded the highest bacterial population significantly with inoculation of UPMRB9, followed by mixed strains and UPMB10 at 1.8x107 CFUmL-1, 2.8x107 CFUmL-1and 8.9x106 CFUmL-1, respectively. Results showed that a higher concentration of HA has successfully prolonged the bacterial shelf-life with minimal cell loss. Thus, this study has shown that the optimum concentration of humic acid can extend the bacterial shelf-life and improve the quality of a biofertilizer. [ABSTRACT FROM AUTHOR]

Aims: This study was designed to examine the enzyme activity of selected virulent isolates of Ganoderma boninense against oil palm. In a separate in vitro assessment, the effect of macronutrients on the mycelial growth of four selected Ganoderma spp. was also tested. Methodology and results: The study involved a comparison of ligninolytic enzymes; lignin peroxidase (LiP), manganese peroxidase (MnP) and laccase (Lac) profiling of eight isolates of G. boninense, categorized into three levels of aggressiveness, with two control isolates (G. boninense PER71 and G. tornatum NPG1) using solid-state fermentation (SSF). The Principal Component Analysis (PCA) revealed that the isolates had a significant production of ligninolytic enzymes on day 80. The most aggressive isolate, ET61 had the highest Lac production. As for the macronutrient test, mycelial growth for all the Ganoderma spp. was highly affected by potassium (K). Conclusion, significance and impact of study: The findings of this study elucidated the characteristics of G. boninense in relation to enzyme production for the degradation of oil palm lignin and the identification of essential nutrients involved in the survival and growth of Ganoderma spp. The study provides vital information on the pathogenic characteristics of G. boninense isolates involved in biomass degradation along with the role of nutrient on the growth of Ganoderma spp. that may influence basal stem rot (BSR) management in the field. [ABSTRACT FROM AUTHOR]

Ganoderma boninense, a phytopathogenic white rot fungus had sought minimal genetic characterizations despite huge biotechnological poten­tials. Thus, efficient collection of fruiting body, basidiospore and protoplast of G. boninense is described. Matured basidiocarp raised under the glasshouse conditions yielded a total of 8.3 × 104 basidiospores/ml using the low speed centrifugation technique. Mycelium aged 3-day-old treated under an incubation period of 3 h in lysing enzyme from Trichoderma harzianum (10 mg/ml) suspended in osmotic stabilizer (0.6 M potassium chloride and 20 mM dipotassium phosphate buffer) yielded the highest number of viable protoplasts (8.9 × 106 single colonies) among all possible combinations tested (regeneration media, age of mycelium, osmotic stabilizer, digestive enzyme and incubation period).