The ongoing expansion of oil palm plantations in the humid tropics, especially in Southeast Asia, is generating considerable concern and debate. Amid industry and environmental campaigners' claims, it can be hard to perceive reality. Is oil palm a valuable route to sustainable development or a costly road to environmental ruin? Inevitably, any answer depends on many choices. But do decision makers have the information they require to avoid pitfalls and make the best decisions? This review examines what we know and what we don't know about oil palm developments. Our sources include academic publications and ‘grey' literature, along with expert consultations. Some facts are indisputable: among these are that oil palm is highly productive and commercially profitable at large scales, and that palm oil demand is rising. Implementing oil palm developments involves many tradeoffs. Oil palm's considerable profitability offers wealth and development where wealth and development are needed—but also threatens traditional livelihoods. It offers a route out of poverty, while also making people vulnerable to exploitation, misinformation and market instabilities. It threatens rich biological diversity—while also offering the finance needed to protect forest. It offers a renewable source of fuel, but also threatens to increase global carbon emissions. We remain uncertain of the full implications of current choices. How can local, regional and international benefits be increased while costs are minimised? While much important information is available, it is often open to question or hard to generalise. We conclude this review with a list of pressing questions requiring further investigation. Credible, unbiased research on these issues will move the discussion and practice forward.

/pdf/the-impacts-and-opportunities-of-oil-palm-in-southeast-asia-1gon2jniml.pdf

The impacts and opportunities of oil palm in Southeast Asia: What do we know and what do we need to know?

https://cyberleninka.org/article/n/868784.pdf

Yield gaps in oil palm: A quantitative review of contributing factors

African oil palm has the highest productivity amongst cultivated oleaginous crops. Species can constitute a single crop capable to fulfill the growing global demand for vegetable oils, which is estimated to reach 240 million tons by 2050. Two types of vegetable oil are extracted from the palm fruit on commercial scale. The crude palm oil and kernel palm oil have different fatty acid profiles, which increases versatility of the crop in industrial applications. Plantations of the current varieties have economic life-span around 25-30 years and produce fruits around the year. Thus, predictable annual palm oil supply enables marketing plans and adjustments in line with the economic forecasts. Oil palm cultivation is one of the most profitable land uses in the humid tropics. Oil palm fruits are the richest plant source of pro-vitamin A and vitamin E. Hence, crop both alleviates poverty, and could provide a simple practical solution to eliminate global pro-vitamin A deficiency. Oil palm is a perennial, evergreen tree adapted to cultivation in biodiversity rich equatorial land areas. The growing demand for the palm oil threatens the future of the rain forests and has a large negative impact on biodiversity. Plant science faces three major challenges to make oil palm the key element of building the future sustainable world. The global average yield of 3.5 tons of oil per hectare (t) should be raised to the full yield potential estimated at 11-18t. The tree architecture must be changed to lower labor intensity and improve mechanization of the harvest. Oil composition should be tailored to the evolving needs of the food, oleochemical and fuel industries. The release of the oil palm reference genome sequence in 2013 was the key step toward this goal. The molecular bases of agronomically important traits can be and are beginning to be understood at the single base pair resolution, enabling gene-centered breeding and engineering of this remarkable crop.

/pdf/oil-palm-natural-diversity-and-the-potential-for-yield-4wso1csw7j.pdf

Oil palm natural diversity and the potential for yield improvement

The oil palm, an economically important tree, has been one of the world’s major sources of edible oil and a significant precursor of biodiesel fuel. Unfortunately, it now faces the threat of a devastating disease. Many researchers have identified Ganoderma boninense as the major pathogen that affects the oil palm tree and eventually kills it. But identification of the pathogen is just the first step. No single method has yet been able to halt the continuing spread of the disease. This paper discusses the modes of infection and transmission of Ganoderma boninense and suggests techniques for its early detection. Additionally, the paper proposes some possible ways of controlling the disease. Such measures, if implemented, could contribute significantly to the sustainability of the palm oil industry in South East Asia.

/pdf/detection-and-control-of-ganoderma-boninense-strategies-and-3x6bu656cs.pdf

Detection and control of Ganoderma boninense: strategies and perspectives

Reproducible infection of intact roots of oil palm (Elaeis guineensis) with Ganoderma boninense, the cause of basal stem rot, showed penetration followed by rapid longitudinal progression of hyphae and colonization of the lower stem (bole) Light and transmission electron microscopy showed invasion of the root cortex, with no evidence of selective progression through the vascular system or lacunae In newly colonized tissue the fungus behaved as a hemibiotroph, with numerous, wide, intracellular hyphae occupying entire host cells that possessed intact cell walls and contained discernible cytoplasm and organelles In the bole this phase coincided with a complete depletion of previously abundant starch grains in advance of invasion Subsequently, in the roots and colonized stem base, widespread necrotrophic, enzymatic attack of all layers of the host cell walls occurred Hyphae were intra- and intercellular and intramural and associated host cell wall degradation was often at a distance from hyphae, resulting in cavities within cell walls A third developmental stage was the formation of an extensive, melanized, tough mycelium or pseudo-sclerotium which surrounded roots and comprised many very thick-walled cells encasing more typical thin-walled hyphae Macroscopic observation of and isolation from the bole of randomly felled, commercial palms provided confirmatory evidence that multiple infections originated in the roots before spreading into the base of long-established palms

https://bsppjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3059.2009.02100.x

Basal stem rot of oil palm (Elaeis guineensis); mode of root infection and lower stem invasion by Ganoderma boninense.

Ganoderma boninense causes severe losses to oil palm in South East Asia. The disease typically manifests itself as basal stem rot, but there remains controversy over the route of infection and source of inoculum. Using isolates differing in aggressiveness, infection via roots was confirmed; it was also shown that large inoculum provided as Ganoderma-infested palm- or rubber-wood blocks (12 × 6 × 6 cm) is necessary for soil infection of seedlings after 6–8 months. Smaller blocks (3 × 3 × 3 cm) produced rapid (≤ 3 months) infection of roots and lower stem when physically attached to roots. Therefore fragmentation of infested palm wood from a felled, mature plantation before subsequent replanting may provide inoculum. Failure of G. boninense to grow through non-sterile soil or organic debris from frond bases, suggests it is a poor competitor and that roots must contact inoculum directly. Severe disease occurred after 8 months on inoculated seedlings under shade, but not on seedlings exposed to sun. Soil temperatures in sunlight frequently rose above 40°C and reached 45°C, whereas in shade they never exceeded 32°C. Ganoderma boninense is probably inhibited in exposed soil since optimal growth in vitro was 25–30°C, and there was no recovery from 45°C. Soil temperature may explain why symptoms often first appear in mature plantations when canopy formation creates shade. Infection is not peculiar to senescing palms but can occur throughout the growth cycle.

Effects of inoculum potential, shading and soil temperature on root infection of oil palm seedlings by the basal stem rot pathogen Ganoderma boninense

Basidiospores are implicated in the distribution and genetic diversity of Ganoderma boninense, cause of basal stem rot (BSR) and upper stem rot (USR) of oil palm (Elaeis guineensis). Measurement of aerial basidiospores within plantations in Sumatra showed continuous and high production over 24 h (range c. 2–11 000 spores m−3) with maximum release during early evening. Basidiospores applied to cut surfaces of fronds, peduncles and stems germinated in situ. Equivalent, extensive wounds are created during plantation harvesting and management and represent potential sites for formation of infective heterokaryons following mating of haploid basidiospore germlings. Use of spore-sized micro-beads showed that basidiospores could be pulled up to 10 cm into severed xylem vessels, where they are relatively protected from dehydration, UV irradiation and competing microflora. Diversity of isolates from five locations on two plantations was assessed by RAMS fingerprinting. Isolates from within individual palms with USR were identical and represent single infections, but different USR infections had unique band patterns and revealed separate infections. Some BSR-affected trees contained more than one isolate, and thus had multiple infections. There was one example of adjacent BSR palms with the same isolate, indicating vegetative spread, but there were no identical genets from BSR infections and adjacent fallen palms. Isolate diversity was as great within a plantation as between plantations. It is evident that basidiospores play a major role in spread and genetic variability of G. boninense. Evidence for direct basidiospore infection via cut fronds, indirectly through roots via colonized debris and less frequently, infection by vegetative, clonal spread is considered.

/pdf/ganoderma-boninense-basidiospores-in-oil-palm-plantations-2hb7wc763o.pdf

Ganoderma boninense basidiospores in oil palm plantations: evaluation of their possible role in stem rots of Elaeis guineensis

This review addresses some key current issues concerning Ganoderma boninense, causal agent of basal stem rot (BSR) and upper stem rot (USR), as a continuing limiting factor in palm oil production. Spread and infection can occur through roots, yet genetic evidence shows considerable isolate diversity and reveals the major input of airborne basidiospores to spread and infection. This has implications for control measures, screening for resistance and choice and deployment of resistance. Where infective heterokaryotic mycelium resulting from spore matings establishes or infects is not understood, because Ganoderma is a weak saprophytic competitor in soil and palm debris. Spores do germinate on cut fronds (and on other wounded surfaces, as revealed by cryo-scanning electron microscopy) and are pulled into xylem vessels under negative tension and may colonise from that protected niche. Improved screening for resistance by attaching small inoculum to roots, along with shading seedlings to mimic canopy cover are described. Pathogenicity mechanisms of G. boninense revealed by light and transmission electron microscopy involves an initial biotrophic phase in root cortex and lower stem, rapid starch depletion then extensive, simultaneous host cell wall breakdown by its array of lignases and polysaccharidases. Suggestions for future research are outlined.

Ganoderma boninense in oil palm plantations: current thinking on epidemiology, resistance and pathology.

Diseases caused by Ganoderma boninense are considered the greatest threat to sustainable palm oil production in SE Asia but the host-pathogen interaction has not been fully investigated at the cellular level. The pathogen growing from colonised blocks as small as 3cm could successfully infect oil palm seedlings provided the inoculum was attached to the roots. Reproducible infection of roots with an aggressive isolate GMR3 showed penetration and infection of intact roots, followed by rapid progression throughout the root and then colonization of the lower stem (bole). Transmission electron microscopy showed invasion of the root cortex, with no evidence of selective progression through the vascular system or lacunae. In newly colonised tissue, the fungus appeared as a hemibiotroph, with numerous large hyphae occupying entire cells. In the bole, this led to a complete depletion of previously abundant starch grains. Subsequently, in the roots and colonized bole widespread, necrotrophic, enzymatic attack of all layers of the host cell walls occurred. A third developmental stage was the formation of an extensive, melanized, tough mycelium or pseudo-sclerotium which surrounded roots and comprised many very thick-walled cells. Macroscopic observation of the bole of randomly felled, commercial palms provided confirmatory evidence that multiple infections originated in the roots before spreading into the palm base. The pathogen did not grow well in soil (except when sterilised) and is therefore unlikely to spread from palm to palm by mycelial extension. It is likely to remain in debris to avoid competition from natural soil microflora. The field implications of these studies is discussed.

R. W. Rees

Papers

Basal stem rot of oil palm (Elaeis guineensis); mode of root infection and lower stem invasion by Ganoderma boninense.

Effects of inoculum potential, shading and soil temperature on root infection of oil palm seedlings by the basal stem rot pathogen Ganoderma boninense

Ganoderma boninense basidiospores in oil palm plantations: evaluation of their possible role in stem rots of Elaeis guineensis

Ganoderma boninense in oil palm plantations: current thinking on epidemiology, resistance and pathology.

Some Latest R&D on Ganoderma Diseases in Oil Palm