Journal of Oil Palm Research (Special Issue - April 2006), p. 24-36
CHARACTERIZATION OF PARAMETERS FOR THE DEVELOPMENT OF AN EARLY SCREENING TEST FOR BASAL STEM ROT TOLERENCE IN OIL PALM PROGENIES
Basal stem rot (BSR) of oil palm (Elaeis guineensis Jacq.) is caused by Ganoderma boninense, and is one of the most commercially devastating diseases in Southeast Asia. So far, cultural practices, combined to some extent with biological control, have been considered as the best approach for controlling the disease. However, in recent years, sources of genetic resistance and susceptibility have been identified in field trials, leading to the consideration of a genetic approach as an integrated component in controlling the disease. To develop this approach, an early screening test at the nursery or pre-nursery stage is needed, based on artificial inoculation and correlated with field observations. The success of nursery seedling artificial inoculation relies on a set of parameters such as defining the inoculum potential like the aggressiveness of G. boninenseisolates, the incubation period of pre-infected rubberwood blocks (RWB), the ratio between the size of pre-infected RWBs and the volume of soil for infection, and the quality of nursery or pre-nursery shade as pre-disposing factors. When this set of parameters was optimized, disease symptoms were observed three months after the inoculation of germinated seeds. This avoided the transfer of seedlings from the pre-nursery to the main nursery, minimized transplanting shock and root damage, and also reduced the time taken for the screening test and the nursery area required. This early inoculation enabled the discrimination of isolates according to their aggressiveness, expressed by the quantification of external and internal disease symptoms and by using a standardized scoring scale. Development of this method will lead to the selection of isolates to be used in screening for resistance or tolerance to BSR. Preliminary results seemed to show that it was possible to distinguish the degree of susceptibility of progenies inoculated artificially at the germinated seed stage or when transferred to polybags. A good correlation was obtained between those two stages, suggesting that the level of resistance was conserved irrespective of the physiological stage used for screening in the nursery. However, it is important to bear in mind that these results need to be confirmed and correlated with field observations under natural infection conditions.KEYWORDS:
* CIRAD UPR28, TA 80/01, Avenue Agropolis, F34398 Montpellier cedex 5, France.
** PT PP London Sumatra Indonesia Tbk, Bah Lias Research Station,
Jl. Jend. A. Yani No. 2, P. O. Box 1154, Medan 20111, Indonesia.
+ PT Socfin Indonesia,
Jl. K.L. Yos Sudarso No. 106,
P. O. Box 1254,
Medan 20115, Indonesia.