Disease survey, identification and pathogenicity of root fungi in forest plantations of peninsular Malaysia
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Date
2010
Authors
Ahmad, Mohd Farid
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Abstract
Root-diseases were the main thrust of this study as they have the potential to cause
high tree mortality in forest plantations. Moreover, there is very little information on
the incidence of root disease in forest plantations of Peninsular Malaysia. The main
objectives of this study were to determine the most common root disease in forest
plantations and to identify their causal organisms. In this study, root disease surveys
were conducted in monoculture Jati (Tectona grandis), Akasia (Acacia mangium),
Sentang (Azadirachta excels) plantations as well as rubber tree (Hevea brasiliensis)
interplanted with Sentang plantations in Peninsular Malaysia. The results revealed
that root disease occurred in 14 out of 33 plantations surveyed. Three major root
diseases were often found, these were white root, brown root and red root disease.
Morphological studies conducted on 14 isolates collected from surveyed sites
identified five isolates as Rigidoporus microporus, eight as Phellinus noxius and one
as R. vinctus. Based on PCR amplification of ribosomal DNA-ITS regions, RVIN02
paired with universal primer ITS4 successfully discriminated isolates FRIM142 and
FRIM143 previously identified as R vinctus. Similarly, specific primer combinations
PNOX02/ITS4 and RLIG02/ITS4 were sensitive and specific in amplifying DNA of
all isolates morphologically identified asP. noxius and R microporus respectively.
Pathogenicity tests confirmed that R microporus and P. noxius were the causal
organisms of white root and brown root disease, respectively. Pathogenicity studies
also revealed that R. microporus was most aggressive in killing rubber tree (86.67%)
followed by Sentang (80%), Akasia (13.33%) and Jati (6.67%), respectively. P.
noxius was most aggressive in killing rubber tree (80%) followed by Sentang
(53.33%) and Jati (33.33%) and least aggressive against Akasia (13.33%). The
highest disease severity index (DSI) was found on rubber tree inoculated with R
microporus followed by rubber tree inoculated with P. noxius, Sentang inoculated
with R. microporus, Jati inoculated with P. noxius and Sentang inoculated with P.
noxius respectively. The ANOVA revealed that effect of the pathogens in DSI
between hosts was significant throughout the experiment except for Akasia
(p=0.092). During pathogenesis, both R. microporus and P. noxius could penetrate
Sentang seedling roots in the absence of wounding. Penetration and colonization of
root cells by R. microporus hyphae were faster than that by P. noxius. However,
degradation of cell walls by P. noxius was more rapid and serious compared to R.
microporus. From this study, it is therefore concluded that the most common and
destructive root disease fungi found in forest plantations in Peninsular Malaysia are
R. microporus and P. noxi