Detection of the phytoplasma associated with yellow leaf syndrome of sugarcane
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Reference (Identifier)
MRR-18-00081
Title
Detection of the phytoplasma associated with yellow leaf syndrome of sugarcane
Broad Theme Classification
3. Agricultural and Veterinary Sciences
Second Level Classification
3.5 Other Agricultural Sciences
Country Specific Sectors
28. Other
Date Published
1 April 2002
Abstract
In the 1960s a new symptom known as yellow wilt was observed in sugar cane in Tanzania. These symptoms were then found to be widespread in Central and East Africa. (Ricaud, 1968; Rogers, 1970). No pathogen was at that time associated with yellow wilt. Several years later yellow leaf syndrome (YLS) which has similar symptoms as yellow wilt of sugar cane was described in Hawaii (Schenck, 1990; Schenck and Hu, 1991). YLS is characterized by the yellowing of the midrib. The colour gradually extends to the leaf blade and is sometimes accompanied by a shortening of the upper internodes, producing a fan-like appearance. Thereafter YLS was reported in 34 countries (Lockhart and Cronjé, 2000). The syndrome was found to be transmitted by vegetative propagation (Schenck, 1990) suggesting that a pathogen was involved. Subsequently, a new luteovirus- Sugarcane yellow leaf virus (SCYLV)- was found to be associated with YLS in several countries. Furthermore Cronjé et al. (1996, 1998) during their search for the SCYLV, found electron microscopic evidence for phloem-inhabiting phytoplasma-like bodies. Phytoplasmas, previously known as mycoplasma-like organisms (MLOs) were first discovered in the late 1960s by Doi et al. (1967) as wall-less microbes in electron micrographs of mulberry tissue affected by the âyellowsâ disease, mulberry dwarf. They were called âmycoplasma-like organismsâ (MLOs) because of their morphological similarity to the wall-less mollicutes mycoplasmas, known to cause numerous disorders of human and animals. Recent evidence showing that MLOs are only distantly related to animal mycoplasma led to their designation as âphytoplasmaâ a name that reflects their primary plant hosts (Sears and Kirkpatrick, 1994). Phytoplasmas have been found to be associated with diseases of several hundred plant species (McCoy et al., 1989; Kollar et al., 1990). Cronje et al. (1998) presented evidence of phytoplasmas in sugar cane with symptoms of YLS based on PCR amplification of the 16S rDNA of the organism, RFLP analysis of the PCR products, scanning electron microscopy and transmission studies. These authors further distinguished two groups of the phytoplasma (which they named Sugarcane yellows phytoplasma - SCYP I and SCYP II), present in both YLS symptomatic and asymptomatic field grown sugar cane. They also found poor association between the presence of SCYLV and YLS in field grown sugar cane varieties in eight African countries and 12 countries outside Africa. In Thailand two important sugar cane diseases, sugar cane white leaf (SCWL) and sugar cane grassy shoot (SCGS), are caused by phytoplasma (Wongkaew et al., 1997). Analysis of the RFLP pattern and of the PCR product of the 16S rRNA and the sequence data of the spacer region between the 16S rRNA and the tRNA (Ile) showed that the SCWL and the SCGS diseases are caused by two different phytoplasmas. On the other hand sequences obtained from the intergenic spacer region between the 16S and the 23S rDNA genes of the ScYP I and ScYP II confirmed the identity of the phytoplasma as belonging to the Western X and SCWL phytoplasma groups (Cronje et al., 1998). In Mauritius no phytoplasma disease was recorded in sugar cane until recently. YLS was first observed in 1994 on variety CP 721210 imported from Florida, USA. Symptoms were also observed in local varieties a few months later. The presence of SCYLV was confirmed in 1996 and that of the phytoplasma in 1997. This study was undertaken to investigate the distribution of the two pathogens associated with YLS, particularly the phytoplasma for which the incidence was unknown in Mauritius. The phytoplasma was detected by polymerase chain reaction (PCR) and the virus by reverse transcriptase PCR (RT-PCR). An attempt was made to relate symptoms to the presence of either or both pathogens. Strain variation in the phytoplasma was studied using PCR and RFLP analysis of the phytoplasma 16S rDNA and PCR products were cloned and sequenced using an ABI 310 DNA analyser. Tissue culture techniques were investigated to free diseased material from YLS.
Keywords
Yellow Leaf Syndrome,Yellow Wilt,Sugarcane
Publisher
Mauritius Research Council
Content Classification
Report
Funding Agency(ies)
Mauritius Research Council
Date Uploaded
1 November 2018