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

Abstract

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.

In vitro growth of Ganoderma boninense isolates on novel palm extract medium and virulence on oil palm (Elaeis guineensis) seedlings

“…Isolation of Ganoderma tissues from the fresh basidiocarps was performed by using Ganodermaselective medium (GSM) (Ariffin et al, 2000 andSeman, 1991). Procedures and components required for preparing the Ganoderma-selective medium was outlined by Ariffin and Seman (1991) and Rees et al, (2007). After isolation of Ganoderma mycelia, pure cultures were maintained on malt extract agar (MEA) (Difco) in petri dishes prior to in-vitro growth, DNA extraction and inoculum preparations.…”

“…Khairudin et al, (1991) reported 100% success in infecting oil palm by wrapping bare roots of seedlings over rubber wood blocks (RWB) (6 x 6 x 12 cm or 432 cm 3 ) pre-inoculated with Ganoderma boninense. In Indonesia, inoculating seedlings using oil palm and rubber wood blocks in a range of sizes (Rees et al, 2007) as the substrates had been reported. However, Ganodermainoculated RWB still remains the most effective option for artificial inoculation of Ganoderma spp.…”

“…to screen for Ganoderma tolerance and to study various control measures in the nursery (Breton et al, 2006 andNur Ain Izzati andAbdullah, 2008). Common RWB sizes used to inoculate with Ganoderma fungal mycelia and recorded to be effective in infecting oil palm seedlings were 3 x 3 x 3, 6 x 6 x 6, 6 x 3 x 3, 5 x 5 x 15 and 6 x 6 x 12 cm 3 (Rees et al, 2007 andSariah et al, 1994).…”

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

“…In some areas, specific diseases are known to reduce yields. The most notable is the bracket fungus Ganoderma, which commonly causes basal stem rot in Asian plantations (Paterson 2007;Rees et al 2007;Anonymous 2008b). There is no cure and infection is lethal to oil palm trees.…”

In Vitro Management of Ganoderma Basal Stem Rot Disease on Oil Palm Using Wild Basidiomycetes Fruiting on the Ground after Rainfall

“…Many control methods have been adopted for management of BSR such as mechanical and chemical treatments, plus cultural practices but still have not proved satisfactory to control the disease due to the fact that G. boninense had various resting stages (melanised mycelium, basidiospores and pseudosclerotia) [33]. Thus, reference [33] and [26] suggested that alternative control approaches to overcome the Ganoderma problem were focused on the use of biocontrol agents and planting resistant materials.…”