Yellow Leaf Disease Research Articles

Diagnosis of Sugarcane yellow leaf virus in asymptomatic sugarcane by RT-PCR

Sugarcane yellow leaf virus (SCYLV) that causes yellow leaf disease (YLD) in sugarcane belongs to Polerovirus. The disease expression is commonly observed during 6 to 8 months stages of the crop and there is a need to diagnose the disease before the symptom appearance. We have standardized RT-PCR technique with a new set of primers to detect SCYLV in sugarcane in pre-symptomatic stages of YLD. During presymptomatic stage 33 of the 44 varieties studied tested positive to SCYLV in RT-PCR. During eighth month stage all the 44 varieties have shown characteristic disease symptoms and except one all of them tested positive to the virus in RT-PCR. The two RT-PCR assays performed separately during pre- and post-symptom expression stages in 44 varieties clearly revealed that most of the varieties have detectable level of the virus in asymptomatic stage. Expression of disease symptoms and presence of the virus in all the varieties except one very clearly indicated the severe virus infection in the tested varieties. The studies also proved the diagnostic efficiency of the new set of primers to detect SCYLV in asymptomatic plants.

Simultaneous detection and identification of four sugarcane viruses by one-step RT-PCR

Sugarcane mosaic disease (SMD) caused by the Sugarcane mosaic virus (SCMV), Sorghum mosaic virus (SrMV) and Sugarcane streak mosaic virus (SCSMV) and sugarcane yellow leaf disease (SYLD) caused by the Sugarcane yellow leaf virus (SCYLV) are the two most prevalent and economically important viral diseases of sugarcane. In this study, a one-step quadruplex reverse transcription (RT)-PCR method that employed virus-specific primers was developed for the simultaneous detection and differentiation of SCMV, SrMV, SCSMV and SCYLV. Several sets of primers for each target virus were evaluated for their sensitivity and specificity by simplex and quadruplex RT-PCR. The optimum primer combinations and concentrations, RT temperature and time, and PCR annealing temperature and extension time were determined for the quadruplex RT-PCR. The assay was then validated using sugarcane samples affected with SMD and/or SYLD collected from sugarcane breeding fields and farmers’ fields in southern China.

Identification of three genotypes of sugarcane yellow leaf virus causing yellow leaf disease from India and their molecular characterization

Sugarcane yellow leaf virus (SCYLV) that causes yellow leaf disease (YLD) in sugarcane (recently reported in India) belongs to Polerovirus. Detailed studies were conducted to characterize the virus based on partial open reading frames (ORFs) 1 and 2 and complete ORFs 3 and 4 sequences in their genome. Reverse-transcriptase polymerase chain reaction (RT-PCR) was performed on 48 sugarcane leaf samples to detect the virus using a specific set of primers. Of the 48 samples, 36 samples (field samples with and without foliar symptoms) including 10 meristem culture derived plants were found to be positive to SCYLV infection. Additionally, an aphid colony collected from symptomatic sugarcane in the field was also found to be SCYLV positive. The amplicons from 22 samples were cloned, sequenced and acronymed as SCYLV-CB isolates. The nucleotide (nt) and amino acid (aa) sequence comparison showed a significant variation between SCYLV-CB and the database sequences at nt (3.7-5.1%) and aa (3.2-5.3%) sequence level in the CP coding region. However, the database sequences comprising isolates of three reported genotypes, viz., BRA, PER and REU, were observed with least nt and aa sequence dissimilarities (0.0-1.6%). The phylogenetic analyses of the overlapping ORFs (ORF 3 and ORF 4) of SCYLV encoding CP and MP determined in this study and additional sequences of 26 other isolates including an Indian isolate (SCYLV-IND) available from GenBank were distributed in four phylogenetic clusters. The SCYLV-CB isolates from this study lineated in two clusters (C1 and C2) and all the other isolates from the worldwide locations into another two clusters (C3 and C4). The sequence variation of the isolates in this study with the database isolates, even in the least variable region of the SCYLV genome, showed that the population existing in India is significantly different from rest of the world. Further, comparison of partial sequences encoding for ORFs 1 and 2 revealed that YLD in sugarcane in India is caused by at least three genotypes, viz., CUB, IND and BRA-PER, of which a majority of the samples were found infected with Cuban genotype (CUB) and lesser by IND and BRA-PER genotypes. The genotype IND was identified as a new genotype from this study, and this was found to have significant variation with the reported genotypes.

Symptom expression of yellow leaf disease in sugarcane cultivars with different degrees of infection by Sugarcane yellow leaf virus

Sugarcane yellow leaf virus (ScYLV) is present in many sugarcane growing areas of the world. It is suspected to cause yellow leaf disease (formerly called YLS, yellow leaf syndrome) of sugarcane. This study investigated symptom expression in a selection of cultivars classified into three groups; ScYLV‐susceptible/infected, ScYLV‐resistant and intermediately infected cultivars grown in plantation fields in the islands of Hawaii. Incidence of yellow leaf symptoms was correlated, though not tightly, to the presence of ScYLV. The correlation is based on two factors: (i) only ScYLV‐infected cultivars (from both susceptible and intermediate groups) showed severe symptom expression, and (ii) ScYLV‐infected plants had four times higher symptom incidence than virus‐free plants of the same cultivar. The yellow leaf symptom expression fluctuated, peaking at 200, 350, 500 and 600 days after planting. These symptom peaks were correlated with an increase of ScYLV content in the intermediately infected group of cultivars. No nutritional, environmental or field factor could be identified which clearly influenced symptom expression. It is speculated that the symptom expression is elicited by assimilate backup in the stalks and that the fluctuation of symptom expression is caused by the growth rhythm of mature sugarcane stalks.

‘Candidatus Phytoplasma graminis' and ‘Candidatus Phytoplasma caricae’, two novel phytoplasmas associated with diseases of sugarcane, weeds and papaya in Cuba

During 2003, surveys of sugarcane yellow leaf disease and papaya bunchy top-like disease were carried out on plantations in Havana province, Cuba, to determine the roles of weeds and Auchenorrhyncha insects in the epidemiology of these diseases. More than 250 plant and insect samples were collected and indexed by using a nested PCR for phytoplasma 16S rDNA with the generic primer pairs P1/P7 and R16F2n/R16R2. The PCR products were further characterized by restriction fragment length polymorphism using HaeIII, AluI, Sau3AI, Tru9I, HhaI, HpaII and TaqI endonucleases, giving patterns that distinguished them from those of the other reference phytoplasmas analysed. Phylogenetic analysis of 16S rRNA gene sequences identified the phytoplasmas present in sugarcane (Saccharum officinarum L.), Cynodon dactylon L., Conyza canadensis L. Cronq., Sorghum halepense L. Pers., Macroptilium lathyroides L. Urb., Saccharosydne saccharivora (Westwood) and Cedusa spp., and those in papaya (Carica papaya L.) and Empoasca papayae, as two novel provisional phytoplasma species. We propose that these phytoplasmas should be given Candidatus status, as 'Candidatus Phytoplasma graminis' and 'Candidatus Phytoplasma caricae', respectively.

Association of a Monopartite Begomovirus with Yellow Mosaic Disease of Pumpkin (Cucurbita maxima) in India.

Pumpkin (Cucurbita maxima) is an economically important vegetable crop of the family Cucurbitaceae. Yellow mosaic in C. maxima was observed in and around Lucknow, India, during the winter season of 1999-2000. High populations of whiteflies (Bemisia tabaci) were associated with diseased plants. Whiteflies were allowed to feed on diseased C. maxima plants and placed on healthy C. maxima seedlings. Symptoms of yellow mosaic disease were successfully reproduced in the seedlings. These results suggested a possible involvement of a geminivirus with the disease. Total DNA was extracted from infected and uninfected C. maxima seedlings by the CTAB method. DNA samples were used as templates in polymerase chain reaction (PCR) using degenerate primers A (5'-TAATATTACCKGWKGVCCSC-3') and B (5'-TGGACYTTRCAWGGBCCT TCACA-3'), which have been designed to amplify a region of about 500 to 600 nt from DNA-A of a majority of begomoviruses (1). The PCR products obtained were analyzed on a 1.5% agarose gel. The major amplicon obtained from the DNA of infected plants was about 550 bp as expected from these primers. However, no such amplicon was observed in DNA samples from uninfected plants. The amplicon obtained from PCR was cloned in a suitable cloning vector. Three separate clones were sequenced and the corrected sequence data (GenBank Accession No. AF381977) was compared with the corresponding sequences of other known geminiviruses. The highest identity (88%) was with a strain of monopartite Tomato leaf curl virus (TLCV) from southern India (GenBank Accession No. U38239). The first 34 nucleotides showed significant identity (91% and 97%, respectively) with Althea rosea enation mosaic virus (GenBank Accession No. AF014881) and TLCV strain D2 reported from Australia (GenBank Accession No. AF084006), both of which are monopartite begomoviruses. These results establish the provisional identity of the pathogen causing yellow mosaic disease on pumpkin in India as a closely related strain of the monopartite TLCV. The yellow leaf disease of muskmelon in Thailand and watermelon leaf curl disease in Pakistan also were recently reported to be caused by an Indian strain of TLCV (2,3). However, to our knowledge this is the first report of detection of a monopartite geminvirus causing yellow mosaic disease on pumpkin in India.

Yellow Leaf Disease of Muskmelon from Thailand Caused by Tomato leaf curl virus.

Muskmelon (Cucumis melo L. var. reliculatus) plants exhibiting a yellow leaf disease have been observed in central Thailand since 1993. The pathogen is transmitted to muskmelon by the whitefly, Bemisia tabaci Genn. Based on leaf yellowing symptoms and whitefly transmission, infection by a geminivirus was suspected. Five naturally infected musk-melon plants showing leaf yellowing were collected from a field at Kam-phaengsaen, Nakorn Pathom, Thailand, in 1996. Virus cultures were maintained in muskmelon plants in a screenhouse. Inoculations were done with B. tabaci, and leaf symptoms were the same as symptoms in the field. Geminivirus DNA associated with yellow leaf disease of musk-melon was amplified by polymerase chain reaction with geminivirus-specific degenerate primers (2) that anneal within the rep (replication-associated protein) and cp (coat protein) genes (2). Fragments of 1.2 kb were amplified and cloned from affected muskmelon plants. The insert of three independent clones was sequenced, and identical 32-base stem loop regions were found, including the conserved nonanucleotide sequence TAATATTAC present in all geminiviruses. The iterative sequence GGCGTC also was found in the intergenic region (IR; 434 bp) of the amplified fragments (1). The B component was not found from the total length of the restriction fragment sizes of dsDNA isolated from infected muskmelon. The nucleotide sequences of IR and V1 (precoat open reading frame) were compared with 28 well-studied whitefly-transmitted geminiviruses and revealed ≍97% sequence similarity with DNA A of Tomato leaf curl virus (genus Geminivirus) from India (ToLCV-In2; GenBank Accession no. u15016) (1). The iterative sequence GGCGTC in the IR also was identical to ToLCV-In2. These results establish the provisional identity of the virus causing melon yellow leaf disease as ToLCV or closely related strains.

Association of ‘Candidatus Phytoplasma australiense’ with green petal and lethal yellows diseases in strawberry

The identity of phytoplasmas detected in strawberry plants with green petal (SGP) and lethal yellows (SLY) diseases was determined by RFLP analysis of the 16S rRNA gene and adjacent spacer region (SR). RFLP and sequence comparisons indicated that the phytoplasmas associated with SGP and SLY were indistinguishable and were most closely related to ‘Candidatus Phytoplasma australiense’, the phytoplasma associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases. This taxon lies within the aster yellows strain cluster. Primers based on the phytoplasma tuf gene, which amplify only members of the AY strain cluster, amplified a DNA product from the SGP and SLY phytoplasmas. Primers deduced from the 16S rRNA/SR of P. australiense that amplify only members of this taxon amplified rDNA sequences from the SGP and SLY phytoplasmas. Primers that selectively amplify members of the faba bean phyllody (FBP) phytoplasma group, the most commonly occurring phytoplasma group in Australia, did not amplify rDNA from the SGP and SLY phytoplasmas.

Yellow Leaf Disease of Cantaloupe and Wax Gourd from Thailand Caused by Tomato leaf curl virus.

Cantaloupe (Cucumis melo var. reliculatus) and wax gourd (Benincasa hispida Cogn.) plants showing a yellow leaf disease have been observed in central Thailand since 1993. The disease has been transmitted to cantaloupe and wax gourd plants by grafting and whiteflies (Bemisia tabaci Genn.) (K. Kittipakorn, unpublished data). Because of the leaf yellowing symptoms and transmission by whiteflies, a geminivirus was suspected. Three naturally infected cantaloupe and four naturally infected wax gourd plants showing leaf yellowing were collected from fields at Kamphaengsaen, Nakorn Pathom, Thailand. Virus cultures were maintained in cantaloupe and wax gourd plants. Inoculations were done with a whitefly vector. Symptoms in cantaloupe and wax gourd plants were the same as those observed in the field. Virus DNA associated with yellow leaf disease of cantaloupe and wax gourd plants was amplified by polymerase chain reaction with geminivirus-specific degenerate primers, described by Rojas et al. (2), that anneal within the AC1 open reading frame (ORF; replication associated protein gene) and the AV1 ORF (coat protein gene) of bipartite geminiviruses and the C1 and V2 ORFs of monopartite geminiviruses (2). Fragments (1.2 kbp) were amplified and cloned from affected cantaloupe and wax gourd plants. Three independent clones were sequenced and analyzed, and identical 32-base stem loop regions were found in the amplified fragments from both isolates, including the conserved nonanucleotide sequence TAATATTAC, which is present in all geminiviruses. The iterative sequence GGCGTC also was found in the intergenic region (IR) (434 bp) of the amplified fragments from both isolates. The B component could not be detected. The nucleotide sequences of the IR and V1 were compared with 28 well-studied whitefly-transmitted geminiviruses and revealed ≈96% sequence identity with DNA A of Tomato leaf curl virus of the genus Geminivirus from India (ToLCV-In 2) (1) for both isolates. The iterative sequence GGCGTC in the IR also was identical to the sequence in ToLCV-In 2. These results establish the provisional identity of the pathogen causing yellow leaf disease on cantaloupe and wax gourds in Thailand as ToLCV or closely related strains.

Tomato leaf curl geminivirus associated with cantaloupe yellow leaf disease in Thailand

Geminivirus associated with yellow leaf disease of cantaloupe plants was detected using polymerase chain reaction (PCR) with geminivirus-specific degenerate primers which anneal within the AC1 ORF (replication initiator protein gene) and the AV1 ORF (coat protein gene). A DNA fragment of 1.2 kbp was amplified, cloned and sequenced. The 32-base stem loop region was found in the amplified fragment. This included the conserved nonanucleotide sequence TAATATTAC present in all geminiviruses. The nucleotide sequence of the intergenic region (IR) was compared with 28 whitefly-transmitted geminiviruses. The geminivirus associated with yellow leaf disease of cantaloupe plants showed 96.2% sequence identity with DNA A of tomato leaf curl geminivirus from India (ToLCV-In2). These data suggest that cantaloupe yellow leaf disease was caused by ToLCV.

Yellow Leaf Disease of Muskmelon from Thailand Caused by Tomato leaf curl virus

Muskmelon (Cucumis melo L. var. reliculatus) plants exhibiting a yellow leaf disease have been observed in central Thailand since 1993. The pathogen is transmitted to muskmelon by the whitefly, Bemisia tabaci Genn. Based on leaf yellowing symptoms and whitefly transmission, infection by a geminivirus was suspected. Posted 17 August 2000.

First Report of Sugarcane Yellow Leaf Virus in the French West Indies.

Unusually severe leaf yellowing symptoms, similar to those described for yellow leaf syndrome (1), have been observed in several sugarcane clones in Guadeloupe since 1994, and since 1997 in Martinique. Leaf samples exhibiting various types of yellowing were taken from five different sugarcane clones, and analyzed by immunosorbent electron microscopy. Spherical particles, 24 to 28 nm in diameter and characteristic of luteoviruses, were found in two of five samples. The two infected samples showed yellowing on the underside of the midrib and one had a pinkish coloration on the upper side. The presence of sugarcane yellow leaf virus (ScYLV), the causal agent of sugarcane yellow leaf disease, was confirmed by reverse transcription-polymerase chain reaction (2) in these two samples and in 36 of 184 sugarcane clones bred in Guadeloupe and sent to Cirad's quarantine station in Montpellier, France. Following these observations, surveys were undertaken with a tissue blot enzyme immunoassay to analyze the distribution of ScYLV in sugarcane clones in the French West Indies. The midrib base of the first visible dewlap leaf was used to detect the presence of the virus in the phloem. In a first survey, clones of various origins worldwide were taken from germplasm collections. Two to three leaf samples per clone were analyzed from 78 clones in a collection in Guadeloupe and from 36 in a collection in Mar-tinique. Fifty of the 114 clones were infected by ScYLV, and ScYLV was detected in 21 of the 32 clones exhibiting severe leaf yellowing (score 3 or higher on a 1 to 5 scale). In a second survey, 19 leaf samples were taken from each of 53 clones from plants produced by Cirad's breeding program in Guadeloupe. The virus was detected in at least one sample for 25 of these 53 clones. ScYLV incidence in commercial fields was tested in Martinique in the variety B5992, which constitutes 57% of the cultivated area. Twenty leaves from different stools were sampled in six different fields, five of which had ScYLV-infected plants. The percentage of virus-infected stalks ranged from 0 to 90% whereas the percentage of stalks showing symptoms ranged from 50 to 100%. ScYLV appears widespread in the French West Indies, perhaps because a vector (Melanaphis sacchari) exists in Martinique and Guadeloupe. However, ScYLV was not found in all symptomatic plants, indicating that even if this luteovirus is a causal agent of leaf yellowing in the French West Indies, there may be other causal agents as well.

Phormium Yellow Leaf Phytoplasma Is Associated with Strawberry Lethal Yellows Disease in New Zealand

A yellows disease of strawberry plants was identified in propagation beds in New Zealand. Affected plants were flatter to the ground, showed purpling of older leaves, reduced leaf size, yellowing of younger leaves, and sometimes plant death. A phytoplasma was observed in the phloem of affected plants. The 16S rRNA gene of the phytoplasma was amplified by polymerase chain reaction from symptomatic plants and from one asymptomatic plant, but not from 36 other asymptomatic plants. Nucleotide sequence analysis of the 16S rRNA gene showed that the phytoplasma is closely related or identical to the phytoplasma associated with the yellow leaf disease of New Zealand flax (Phormium tenax).

Detection of phormium yellow leaf phytoplasma in New Zealand flax (Phormium tenax) using nested PCRs

A reliable diagnostic method was developed for use in studying the relationship between phormium yellow leaf disease of New Zealand flax (Phormium tenax) and its associated phytoplasma (phormium yellow leaf phytoplasma: PYL). Diagnosis involved a nested PCR (polymerase chain reaction) technique targeting the 16S rRNA gene. DNA was extracted from woody rhizome tissues of NZ flax plants using CTAB and a high salt precipitation step. This method effectively eliminated polysaccharides, gum‐like material and other compounds inhibitory to PCRs that occur at high concentrations in diseased NZ flax rhizomes. PCR competence of each DNA preparation from both healthy and yellow leaf diseased plants was assessed using the general prokaryotic 16S rRNA gene primers, Gd1/Berg54. These primers amplified DNA from both diseased and healthy plants. PYL 16S rDNA sequences were not detected consistently following amplification by PCR (35 cycles) using the ‘universal’ phytoplasma‐specific primer pairs R16F2/R16R2 or P1/P6. By contrast, PYL was consistently detected in diseased, but not healthy, NZ flax plants, following nested PCR of the products of the above three primer pairs. Nested PCRs involve the primers NGF/NGR, which were designed to hybridize with all phytoplasmas for which published sequences were available. The most sensitive level of detection by nested PCR was achieved using primers R16F2/R16R2, rather than primers P1/P6 or Gd1/Berg54, for the primary amplification step. The consistent association found in this study between yellow leaf disease and PYL further substantiates this phytoplasma as the causal agent. PCR products of the expected size were also amplified by nested PCR using the primers R16F2/R16R2 followed by NGF/NGR from C. roseus tissues infected with five other phytoplasmas representing three distinct phytoplasma groups. Therefore nested PCRs with these pairs of primers should be useful for detecting other phytoplasmas, in particular those occurring at low concentrations or in recalcitrant tissues.

'Candidatus Phytoplasma australiense' is the phytoplasma associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases

Sequence comparisons and phylogenetic analysis of the 16S rRNA genes and the 16S/23S spacer regions of the phytoplasmas associated with Australian grapevine yellows, papaya dieback and Phormium yellow leaf diseases revealed minimal nucleotide differences between them resulting in the formation of a monophyletic group. Therefore, along with Australian grapevine yellows, the phytoplasmas associated with Phormium yellow leaf and papaya dieback should also be considered as ‘Candidatus Phytoplasma australiense’.

Sugarcane Yellow Leaf Disease in Brazil: Evidence of Association with a Luteovirus.

Evidence of the viral etiology of sugarcane yellow leaf disease (SCYLD), occurring in southeast Brazil, was obtained by light and electron microscopy combined with serology. Light microscopy using epifluorescence illumination showed an abnormal yellow-green fluorescing material in the phloem of SCYLD-affected plants that was rarely observed in control plants. Immunolocalization in tissue-printed (or -blotted) nitrocellulose membranes, using barley yellow dwarf virus (BYDV) serotype PAV antiserum, showed a weak but clearly positive reaction in the phloem. Isometric viruslike particles of 24 to 26 nm in diameter were found by electron microscopy both in situ and in partially purified preparations. Examination of thin sections showed that phloem companion cells contained viruslike particles and presented cytological changes apparently related to the development of virus infection. Partially purified preparations produced UV absorption spectra typical of a nucleoprotein, with high absorbance at 260 nm, as expected for isometric virus particles. Virus particles were observed in extracts and partially purified preparations using immunosorbent electron microscopy with BYDV-PAV antiserum. Plate-trapped antigen enzyme-linked immunosorbent assays with the same antiserum indicate a weak serological relationship between BYDV-PAV and SCYLD-associated virus.

Notes on the Genus Ceriospora in India

In November 1975, an ascomycete on the leaves of cardamum, Elettaria cardamomum (L.) Maton (Zingiberaceae), was collected at Cherambane, Coorg district, where the average rainfall is ca. 5,000 mm per yr. This fungus belongs to the genus Ceriospora Niessl (Pyrenomycetes, Sphaeriales, Amphisphaeriaceae), erected by Niessl in 1876. Ceriospora dubyi Niessl, on Humulus lupulus L. Cannabinaceae), is the type species. Ainsworth (1971) incorrectly limited the distribution of the genus to temperate regions; three species have been described on different genera of Palmae from South Europe and North Africa, South India, and Australia (Miiller and von Arx, 1962). Four species have been reported from India: Ceriospora arecae Menon, found on the leaflets of Areca catechu L. (Palmae) affected by yellow leaf disease (Menon, 1959; Muller and von Arx, 1962); C. lantanae Tilak & Kale on Lantana camara L. (Verbenaceae) (Tilak and Kale, 1967); C. prinsepiae Ramachandra Rao on dead stems of Prinsepia utilis Royle (Rosaceae) (Ramachandra Rao, 1971); and C. acaciae Kale & Kale, on dead stems of Acacia leucophloea Willd. (Leguminosae) (Kale and Kale, 1972). The measurements given by Muller and von Arx (1962) for C. arecae are much larger than those in Menon's (1959) original description (perithecia 100-140 ,m in diam, versus 46-70 width x 52-70 um height; asci 72-80 x 12-14 tm versus 30-58 x 4.6-6 pm; and ascospores 23-28 x 5-6 Mam versus 12-24 x 3-4 um). Menon does not mention whether asci are bitunicate or unitunicate. Miiller and von Arx (1962) retain this species in Ceriospora, indicating that they consider the asci unitunicate.

Mycoplasma like organisms associated with yellow leaf disease of Areca catechu L.

Mycoplasma like organisms (MLO) were found in the young sieve elements of arecanut palms declining with yellow leaf disease in Kerala and Karnataka States of India. The organisms resembled those MLO found in coconut palms affected with lethal yellowing in Florida and Africa.

Some experiments on the yellow leaf disease of turfgrass

Some experiments on the yellow leaf disease of turfgrass

A mycoplasma-like organism associated with Phormium yellow leaf disease

Summary The phloem elements of Phormium tenax plants showing symptoms of yellow leaf disease in the field contain mycoplasma-like organisms. These appear to be confined to the phloem and are more numerous in rhizome phloem than in the roots or leaves. No mycoplasma-like organisms were found in healthy plants. Morphologically similar organisms were found in organs of most individuals of the plant hopper Oliarus atkinsoni collected from diseased plants in the field. The mycoplasma-like organisms were observed most frequently in the cells of the gut wall. Attempts to transmit yellow leaf disease with extracts containing the organisms were unsuccessful, as were attempts to culture them in vitro. No virus-like particles were seen in thin sections of cells from diseased plants.