The role of duration of various varying heat-treatment durations on the germination of oil palm seeds is well documented. We investigated the effects of different heat-treatment durations on germination and seedling growth of 10 oil palm progenies. Batches of 250 oil palm seeds from each progeny were heat-treated at a temperature of 39° C ± 1° C for 60, 80, 100 and 120 days, to break dormancy. Seedling growth parameters measured included rate of leaf production, leaf area and relative leaf area growth rate, rate of leaf elongation, and diameter of base of seedlings stem. Germination rates for 60, 80, 100, and 120 days combined were highest for progenies A5240 and A5221 (> 80 %) but very low (< 5%) for progenies A5228 and A5268. Progenies A5240, A5291, A5234 and A5221 were found to be the most outstanding progenies in terms of germination. Prolonged heat-treatment resulted in reduced germination and less vigorous seedling growth. Heat-treatment of 60 days gave the best seedling growth performance and seedling growth was adversely affected when heat-treatment exceeded 100 days. The study indicated that heat-treatment duration of 60 days and not 80 days was effective for breaking dormancy of the oil palm seeds and successful seedling growth. This study shows that oil palm seeds germination can be obtained successfully within a short period (60 days) of heat-treatment compared to the current 80 days application by PAMOL Plantation Ltd. Lobe estate. These results could provide significant solutions to the numerous demands of oil palm seeds by local farmers.

Abstract. Tambunan VB, Apriyanto A, Ajambang W, Etta CE, Sahari B, Buchori D, Hidayat P. 2020. Molecular identification and population genetic study of Elaeidobius kamerunicus Faust. (Coleoptera: Curculionidae) from Indonesia, Malaysia and Cameroon based on mitochondrial gene. Biodiversitas 21: 3263-3270. Oil palm pollinating weevil Elaeidobius kamerunicus is a very important insect pollinator in oil palm plantation. However, there is still lack of information about molecular identification and population genetic study in this species. The purpose of this study was to explore the effectiveness of oil palm pollinating weevil identification using mitochondrial DNA of COI gene and to assess its genetic variation between different locations and countries. We sequenced the DNA barcode of 36 individuals of this species using the mtDNA Cytochrome Oxidase I (COI) gene to explore their genetic variation, identity and phylogenetic relationship. The COI gene sequences generated from this study were successful in identifying E. kamerunicus. Phylogenetic analysis also revealed 3 well-supported monophyletic haplogroups of E. kamerunicus population. In addition, genetic differentiation analysis revealed that most populations from Indonesia were different from Malaysian and Cameroonian populations indicating that there was a genetic variation between the population samples from these countries. The overall E. kamerunicus used in this study were geographically structured in two regions; outside Indonesia region (Cameroon and Malaysia) and Indonesia region. These results demonstrate the feasibility of using COI gene sequence for molecular identification and population genetic study of E. kamerunicus species.

The large grove-forming tropical tree Microberlinia bisulcata (Fabaceae) is demonstrably a mast fruiter, and it is ectomycorrhizal. The Korup forest site in Cameroon has one short pronounced dry season; the soils are sandy and very low in P and K availability. Nutrients are largely recycled through a distinctive soil surface mat of fine roots and hyphae. Pods mature over the longer wet season after leaf exchange and flowering in the dry one. Reproductive allocation is considerable. To test the nutrient resource limitation hypothesis, phenological recordings between 1989 and 2017 were matched with climate variables, and analyzed using logistic time-series regression. Masting happened mostly on 2- or 3-year cycles. A strong predictor was mean daily rainfall in the dry season: low in the current year of masting and high in the year prior. Less strongly predictive was the increase in dry season radiation between prior and mast years. Masting events showed no relationship to annual stem increment, nor with local plantation yields. Later, the normally heavy mastings became moderate after two attacks by caterpillars. Collated studies of fallen leaf nutrient concentrations showed that P increased markedly, K rose and fell, but N and Mg changed little, in the inter-mast interval. P and K were likely being accumulated and stored, and then triggered masting events when internal thresholds were crossed. The drier season prior to masting enabled a rise in C, and the wetter season the year before, with higher soil moisture, enabled better acquisition and uptake of nutrients by roots and mycorrhizas. The main storage of P may be in bark and branches, that for K on soil organic-colloids. A rooting-fruiting trade-off in C allocated over a minimal 2-year cycle is implied. Hypothesized is that synchrony among masting trees may be achieved, in part, by an equilibration of P across the mycorrhizal network and possibly root grafts. The long-term driver appears to be the inherent year-to-year stochasticity of dry-season rainfall, realization of which leads to an important refinement of the hypothesis. Life history strategy linked to nutrient resource dynamics provides a plausible mechanistic explanation for the masting events observed.