Yellow Leaf Syndrome Research Articles

Ampelopsis grossedentata Represents a New Host of the 16SrI Group of Phytoplasma Associated with Yellow Leaf Symptoms in China.

Ampelopsis grossedentata, commonly known as "Vine Tea" and well-recognized for its rich flavonoid content, is mainly distributed in the southern regions of the Yangtze River basin in China. These regions include Hunan, Hubei, Jiangxi, and Guizhou provinces. Vine Tea is mainly consumed as an herbal tea and has garnered attention for its reported health benefits, including antioxidant, anti-inflammatory, anti-tumor, anti-diabetic, and neuroprotective properties. It has been used to alleviate coughs and sore throats (Zhang et al., 2021; Wang et al., 2017; Gao et al., 2009). In the Zhangjiajie region of Hunan province alone, the Vine Tea planting area reached 7,670.5 hectares and produced commercial goods worth 1.417 billion RMB in 2022. In May 2021, leaf margins and veins fading to yellowing mottling, and crumpling of leaf blades in the shape of a boat symptoms were found in ~16% of Vine Tea plants in the Sanjiakuan Township, Yongding District, Zhangjiajie region (29°15'E, 110°30' N) (Figure 1a, b, c). (Figure 1a, b, c). Phytoplasma-like microbial cells (small oval shaped bacterial cells, around 1000 nm in size) were observed in sieve tube cells in the phloem of diseased leaves using transmission electron microscopy. No such cell was observed in the phloem of healthy leaves (Figure 2a, b). To investigate the potential association between phytoplasma and the observed symptoms of the diseased plants, total DNA was isolated from ten diseasedeaves and compared with ten healthy leaves from the same field using SteadyPure Plant Genomic DNA Extraction Kit. The isolated DNAs were analyzed first in a direct PCR using universal phytoplasma primer pair R16mF2/R16mR1 targeting the 16S rRNA gene (Gundersen and Lee 1996) and specific pair rpF1/rpR1 (Lee et al. 1998) targeting the DNA fragment encoding partial ribosomal proteins (rp) L22 (complete) and S3 and S19 (partial). The initial amplified products were used as templates and further amplified by nested PCR respectively with primer pair R16F2n/R16R2 for the 16S rRNA gene (Lee et al. 1998) and the rpF2/rpR2 primer pair for the rp gene (Martini et al. 2007). No amplification was obtained with DNA from healthy leaf samples using any of the four primer pairs. The amplified fragments from diseased leaves by nested PCR were cloned and sequenced (Qingke Biotech, China). The obtained sequences have been deposited in GenBank with accession numbers OR282806 for the 16S rRNA gene and GenBank OR353012 for the rp gene. BLASTn analysis revealed that the partial 16S rRNA gene sequence in our sample shared 99.4% nucleotide sequence identity with 'Candidatus Phytoplasma sp.' (MW364378) and 'Peony yellows phytoplasma' (KY814723) of the 16SrI group. Similarly, our rp gene sequence shared 99.6% nucleotide identity with the rpI group of phytoplasma such as the 'Balsamine virescence phytoplasma' (JN572890) and 'Paulownia witches'-broom phytoplasma' (HM146079). Phylogenetic analysis of the 16S rRNA and rp sequences using MEGA version 7.0 revealed that the phytoplasma strain associated with A. grossedentata yellow leaf syndrome in our study site belonged to the 16SrI (Candidatus Phytoplasma asteris) group of phytoplasma (Figure 3a, b). Using the interactive online phytoplasma classification tool iPhyClassifier (Zhao et al., 2009), virtual restriction fragment length polymorphism (RFLP) analysis of the 16S rRNA gene sequences showed our strain having a distinct RFLP map but was closest to that of the onion yellow phytoplasma 16SrI-B subgroup (GenBank accession number: AP006628), with a similarity coefficient of 0.94 (Figure 4a, b). To confirm phytoplasma transmission, healthy plants were inoculated with three scions of infected plants of A. grossedentata. After 16 days, the new leaves of the inoculated A. grossedentata showed yellow leaf symptoms (Figure 5a, b, c), akin to the symptoms originally observed in the field, and the outer contour of the leaf margin appeared chlorotic. After 26 days, primer pairs R16mF2/R16R1 and R16F2n/R16R2 were used for nested PCR detection of phytoplasma in symptomatic A. grossedentata leaves. Phytoplasma was detected in the first and second leaves of symptomatic branches and leaves while negative control showed no amplification. Sequencing of the amplified fragments showed 100% nucleotide identity to the strain from the grafting source. Our results indicated that the pathogen and the disease can be transmitted by tissue grafting, consistent with the biological characteristics of phytoplasma, and further confirmed that the phytoplasma was the pathogen of yellow leaf syndrome of A. grossedentata. Toour knowledge, this is the first report of phytoplasma of group 16SrI affecting A. grossedentata.

Registration of ‘CP 13‐4474’ sugarcane for sand soils

Abstract‘CP 13‐4474’ (Reg. no. CV‐209, PI 700305) sugarcane cultivar (a complex hybrid of Saccharum spp.) was released to growers in June 2021 for cultivating on sand soils in Florida after a decade‐long advancement through cooperative research conducted by the USDA‐ARS, the Florida Sugar Cane League Inc., and the University of Florida. It originated from a poly‐cross at Canal Point (CP). The Florida Sugarcane Variety Committee released CP 13‐4474 due to its high sugar yields, sucrose content on sand soils, and acceptable disease resistance. CP 13‐4774 has demonstrated resistance to brown rust (caused by Puccinia melanocephala H. & P. Sydow), orange rust (caused by Puccinia kuehnii E.J. Butler), mosaic (caused by Sugarcane mosaic virus strain E), and ratoon stunt (caused by Leifsonia xyli subsp. xyli Evtushenko et al.) and moderate resistance to smut [caused by Sporisorium scitamineum (Syd.) M. Piepenbr. et al.], leaf scald (caused by Xanthomonas albilineans Ashby, Dowson), and yellow leaf syndrome (caused by Sugarcane yellow leaf virus). In late‐stage yield trials, CP 13‐4474 sugar yields were 9.4% greater than that of the check variety ‘CL 88‐4730’, while sucrose yields did not differ significantly from the reference check ‘CP 96‐1252’. CP 13‐4474 displayed superior resistance to both brown and orange rusts and produced more commercial recoverable sucrose than all three tested reference checks over the same harvest trials. With its demonstrated resistance to diseases and elevated sugar production capacity, CP 13‐4474 is expected to positively influence both sugarcane production and crop sustainability in Florida.

A survey of causal agents associated with sugarcane yellowing in Northeast Brazil

The etiological agents of the yellow leaf syndrome (YLS) are the Sugarcane yellow leaf virus (ScYLV), and phytoplasmas of different groups. Due to a lack of knowledge on the occurrence of YLS and the importance of sugarcane to Brazil, the aims of this study were to assess the occurrence and distribution of the pathogens associated with YLS in sugarcane cultivation areas in three states of Northeast Brazil. For this purpose, 101 sugarcane samples with symptoms of YLS were collected in 2018 crop cycle. ScYLV and a new phytoplasma were detected by RT-PCR and nested PCR, respectively. The identity of virus- and phytoplasma-positive samples was confirmed by Sanger sequencing, and these sequences were used in subsequent phylogenetic studies. Both pathogens were present in all sampled regions. ScYLV and the phytoplasma were detected in 40.4% and 62.2% of the samples, respectively. Mixed infections were found in 33.5% of the samples. Phylogenetic analysis showed that the ScYLV isolates identified were most closely related to ScYLV genotypes REU, PER, HAW, CHN2 and BRA. The phytoplasma 16S rDNA gene nucleotide sequences shared 99.0% identity with sequences of the 16SrVII phytoplasmas from Argentina and Brazil. This is the first report of the presence of a member of the 16SrVII phytoplasma group in association with sugarcane leaf yellowing in the world. These findings are important to raise awareness among sugarcane producers on the impact of pathogens causing YLS in Northeast Brazil.

Occurrence of sugarcane yellow leaf virus in southern Punjab

Sugarcane Yellow Leaf disease was first recognized as Yellow Leaf Syndrome during the 1980s in Hawaii. Later it was reportedly associated with yield losses of 25% or more in the cultivar SP 71-6163 in Brazil. In Pakistan occurrence of the disease was neglected up to a specific period of time by agricultural extension worker and growers due to low level of losses. Secondly the disease was attributed to nitrogen deficiency factor commonly as indicated by agricultural extension workers. However when disease spread in many parts of the south Punjab beyond the economic threshold level, research workers chalked out a program for the comprehensive survey. The data was recorded on basis of total number of leaf showing symptoms on individual clone as well in the whole field. Visual observation was taken into consideration for the assessment percentage of the disease in the most places, where the disease occurs in patches. The disease has been noted in the central Punjab also. It is concluded that losses due to disease ranged from 10% to 75%

Sugarcane Yellow Leaf Disease

Sugarcane Yellow Leaf disease was first recognized as Yellow Leaf Syndrome during the 1980s in Hawaii. Later it was reportedly associated with yield losses of 25% or more in the cultivar SP 71-6163 in Brazil. Subsequently the virus sugarcane Yellow Leaf Virus (SCYLV) was discovered to be associated with the disease. Yellow leaf has been found in numerous countries of the world. However, somewhat confusedly, another disease, “leaf yellows”, has been found in other areas. Although it has similar symptoms, it is caused by a phytoplasm rather than a virus. To date, this phytoplasm pathogen has not been identified on sugarcane in Florida. This document is SS-AGR-256, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. This publication is also a part of the Florida Sugarcane Handbook, an electronic publication of the Agronomy Department. Original publication date: September 2005.

Genetic transformation with untranslatable coat protein gene of sugarcane yellow leaf virus reduces virus titers in sugarcane

Sugarcane yellow leaf syndrome, characterized by a yellowing of the leaf midrib followed by leaf necrosis and growth suppression, is caused by sugarcane yellow leaf virus (SCYLV). We produced SCYLV-resistant transgenic sugarcane from a susceptible cultivar (H62-4671) and determined the amount of virus present following inoculation. The transgenic plants were produced through biolistic bombardment of cell cultures with an untranslatable coat protein gene. Presence of the transgene in regenerated plants was confirmed using PCR and Southern blot analysis. The transgenic lines were inoculated by viruliferous aphids and the level of SCYLV in the plants was determined. Six out of nine transgenic lines had at least 10(3)-fold lower virus titer than the non-transformed, susceptible parent line. This resistance level, as measured by virus titer and symptom development, was similar to that of a resistant cultivar (H78-4153). The selected SCYLV-resistant transgenic sugarcane lines will be available for integration of the resistance gene into other commercial cultivars and for quantification of viral effects on yield.

Detection of a 16SrXII phytoplasma associated with sugarcane yellow leaf syndrome in India

Phytoplasma strain was detected in leaves of sugarcane in India exhibiting symptoms of yellowing of midribs. A phytoplasma characteristic 1.2 kb rDNA PCR product was amplified from DNAs of all diseased samples but not in healthy sugarcane plants tested using phytoplasma universal primer pairs P1/P7 and f5U/r3U. Restriction fragment length polymorphism (RFLP) analysis of amplified 16S rDNA indicated that diseased sugarcane was infected by phytoplasma. The 16S rDNA sequence of the Indian sugarcane yellow leaf phytoplasma (SCYLP) showed the closest identity (99%) to that of SCYLP in Cuba identified as Macroptilium lathyroides (AY725233), which belongs to 16SrXII (Stolbur group). This is the first record of the detection of SCYLP, and identification of the 16SrXII group of phytoplasma associated with yellow leaf syndrome (YLS) in India.

Molecular Identification and Phylogenetic Analysis of a Group 16SrI‐B Phytoplasma Associated with Sugarcane Yellow Leaf Syndrome in Brazil

AbstractYellow leaf syndrome was a serious problem in the beginning of the 1990s in Brazil, when yield losses were estimated to be around 50%. The disease is currently endemic, but it is considered potentially important. Previous studies have revealed only the presence of a luteovirus associated with the disease in Brazil. We report that a phytoplasma of 16SrI‐B is also associated with this disease. This is the first demonstration of the presence of a group 16SrI‐B phytoplasma in association with sugarcane yellow leaf in Brazil.

Sugarcane yellow leaf phytoplasma associated for the first time with sugarcane yellow leaf syndrome in India

Sugarcane yellow leaf phytoplasma associated for the first time with sugarcane yellow leaf syndrome in India

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.

Movement of aphid‐transmitted Sugarcane yellow leaf virus (ScYLV) within and between sugarcane plants

Sugarcane yellow leaf virus (ScYLV) is distributed worldwide and has been shown to be the cause of the disease sugarcane yellow leaf syndrome (YLS). This study was an investigation of the transmission and spread of ScYLV in Hawaii. Several aphids are known to transmit the virus, but investigation of infestation and transmission efficiency showed Melanaphis sacchari to be the only vector important for field spread of the disease. The initial multiplication of ScYLV in a virus‐free plant occurred exclusively in very young sink tissues. When a single leaf was inoculated on a plant, that leaf and all older leaves remained virus‐free, based on tissue‐blot immunoassay, whereas meristems and all subsequently formed new leaves became infected. Therefore, only after those leaves which had already developed before inoculation had been shed, did the complete plant contain ScYLV. Spread of the viral infection to neighbouring plants in the plantation fields via aphids was relatively slow and in the range of a few metres per year. No indication of long‐distance transfer could be seen. This indicates that it may be possible to produce and use virus‐free seed cane for planting of high‐yielding but YLS‐susceptible cultivars.

Transmission of a sugarcane yellow leaf phytoplasma by the delphacid planthopper Saccharosydne saccharivora, a new vector of sugarcane yellow leaf syndrome

During surveys of sugarcane fields in western and central Cuba from December 2001 to March 2003, the delphacid planthopper Saccharosydne saccharivora was the most prevalent of the Auchenorrhyncha fauna surveyed. Individuals of S. saccharivora collected tested positive for the sugarcane yellow leaf phytoplasma (SCYLP). Saccharosydne saccharivora were reared in cages and used for experimental transmission studies of SCYLP. The S. saccharivora were given acquisition‐access feeds of 72 h on SCYLP‐infected canes collected from the field followed by an inoculation‐access period of 15 days on healthy sugarcane seedlings. Symptoms of yellow leaf syndrome developed on 24 out of 36 plants, 7–12 months postinoculation. None of the 36 healthy seedlings that were inoculated with S. saccharivora fed on phytoplasma‐free sugarcane developed symptoms. All phytoplasma‐positive sugarcane and S. saccharivora samples showed identical RFLP patterns and had 99·89% similarity in their 16S/23S spacer‐region sequences, but only 92·6–93·6% similarity with other phytoplasmas. Sequences were deposited with GenBank [accession numbers: AY725237 (S. saccharivora) and AY257548 (sugarcane)]. Phylogenetic analysis suggested that the phytoplasmas from sugarcane and S. saccharivora are putative members of a new 16Sr phytoplasma group. This is the first report of vector transmission of a phytoplasma associated with sugarcane yellow leaf syndrome and the first time that S. saccharivora has been shown to vector a phytoplasma.

Detection of sugarcane yellow leaf virus, the causal agent of yellow leaf syndrome in sugarcane by DAS-ELISA

DAS-ELISA studies were conducted on detection of sugarcane yellow leaf virus (SCYLV) causing yellow leaf syndrome (YLS) of sugarcane in leaf and juice antigens. Among the two types of antigen sources used for the virus detection, juice antigen showed high titre for the virus as compared to leaf antigen. Assay with juice samples recorded more number of varieties positive to the virus. Further DAS-ELISA studies revealed that plants raised from disease-infected planting materials recorded high titre for SCYLV as compared to those raised from symptom-free seed canes. Similarly, assaying SCYLV titre in plant and ratoon crop in the field showed that SCYLV infection was partial in plant crop and in the subsequent ratoon crop, all the samples were positive to the virus. ELISA studies also indicated that 33 of 41 cane varieties showing YLS were positive to the virus.

Yellow leaf syndrome modifies the composition of sugarcane juices in polysaccharides, phenols and polyamines

Some ultrastructural changes can be observed in diseased Saccharum officinarum L. (cv. Cuba 120-78) plants with visual symptoms of yellow leaf syndrome (YLS), used to discriminate between healthy and diseased plants. Abaxial epidermis of diseased leaves shows a large amount of adhered superficial bodies, which partially occluded some stomata. Bundle sheath cells surrounding the bottom of phloem of diseased leaves are separated from the conducting tissues by a large layer of an amorphous matrix similar to wax. Debris of the end wall can be observed in large xylem vessels. Sometimes, spherical bodies similar to phytoplasma can be observed in the intercellular spaces of bundle sheath cells. These particles have never been observed in healthy plants. YLS was also associated to an increase of the concentration of reducing sugars, glucose index, and glycoproteins recovered in juices whereas the amount of sucrose decreases. Sugarcane juices obtained from both healthy and YLS-affected Cuba 120-78 cultivars of sugarcane contained putrescine (PUT), cadaverine (CAD), spermidine and spermine (SPM) as free and macromolecules-conjugated compounds. Only CAD and SPM appeared as acid-soluble conjugates to small molecules whereas PUT and CAD are the major polyamines (PAs) conjugated to macromolecules, mainly to high molecular mass glycoproteins. The disease was associated to an increase in total PA fraction. Arginase and ornithine decarboxylase activities, responsible for the synthesis of PUT, were higher in YLS juices than in those obtained from healthy plants. CAD and SPM presumably conjugated mostly to chlorogenic, syringic and ferulic acids in juices from YLS plants.

Sugarcane yellow leaf virus and sugarcane yellows phytoplasma: elimination by tissue culture

Yellow leaf syndrome (YLS) is a recently reported disease of sugarcane, characterized by yellowing of the leaves. Two pathogens: a virus, Sugarcane yellow leaf virus (SCYLV); and a phytoplasma, sugarcane yellows phytoplasma (SCYP), are associated with the disease. The use of tissue culture was investigated as a means to eliminate both SCYLV and SCYP from exotic varieties undergoing quarantine in Mauritius. Of 43 varieties in quarantine, 28 were infected with SCYLV and 19 with SCYP when checked by RT–PCR and nested PCR, respectively. Seventeen varieties were coinfected with both pathogens. Thirty infected varieties were induced to form callus in vitro using leaf rolls as explants. After two subcultures, 19 varieties were successfully regenerated and tested for SCYLV and SCYP. No pathogen could be detected in any regenerated plantlets. All the regenerated plants remained free from both SCYLV and SCYP over a period of 1 year in the glasshouse, confirming that the pathogens had been eliminated by tissue culture.

Phytoplasma diseases of sugarcane

Sugarcane is severely affected by yellows and decline diseases of phytoplasmal etiology. These diseases which are of considerable economic importance, cause similar symptoms but differ in the identity of the associated phytoplasmas, vectorship and geographic distribution. Sugarcane white leaf (SCWL) and sugarcane grassy shoot (SCGS) occur only in the south-east Asian region and not in other sugarcane growing areas of the world. Both are caused by a single phytoplasma type that is a member of the SCWL group and appears to infect only sugarcane. However, SCWL and SCGS phytoplasmas are closely related organisms and could be differentiated by RFLP analysis of rDNA using suitable restriction endonucleases. Sugarcane yellow leaf syndrome (SCYLS) disease has been reported from several African countries, Cuba and Australia, and is associated with distinctly different phytoplasmas which are not specific pathogens. They include members of the X-disease, faba bean phyllody, aster yellows, SCWL, LfWB and CirP groups which are known to infect a wide range of wild and cultivated plants and have a low insect vector specificity. Ramu stunt disease of sugarcane (SCRS) is known to occur in Papua New Guinea. This disease is associated with a SCWL-related phytoplasma and is presumed to be naturally spread by the leafhopper Eumetopina flavipes. Sugarcane green grassy shoot (SCGGS) is a newly discovered phytoplasmal disease of sugarcane in Thailand.

Improved detection of Sugarcaneyellowleafvirus using a real-time fluorescent (TaqMan) RT-PCR assay

Yellow leaf syndrome (YLS) of sugarcane has been associated with Sugarcane yellow leaf virus (ScYLV) and has been reported from most sugarcane growing countries around the world. As sugarcane is vegetatively propagated, it is important to use effective and sensitive detection methods to screen new propagating material. Virus detection in symptomatic tissue is currently achieved using enzyme linked immunosorbent assay (ELISA), tissue blot immunoassay (TBIA) or a conventional RT-PCR based assay. This paper reports the development of an improved assay based on multiplex real-time fluorescent RT-PCR. The new assay is 100-fold more sensitive than conventional RT-PCR, and incorporates a novel ‘RNA specific’ internal positive control (based around the intron of the caffeic acid 3- o-methyltransferase gene) to guard against false negative results. The paper also describes the comparison of eight RNA extraction methods for sugarcane tissue giving a number of alternatives for different laboratory situations. The sensitivity of this assay has allowed the detection of ScYLV in many samples that were thought to be healthy following conventional testing (RT-PCR, ELISA or TBIA). The detection of ScYLV using this TaqMan assay can be applied to the production of ScYLV-free plants and prevents its spread through the propagation material.

Current situation of Tomato yellow leaf curl virus in Portugal

The name Tomato yellow leaf curl virus (TYLCV) has been applied to a group of virus species of the genus Begomovirus in the family Geminiviridae that cause a similar tomato disease worldwide. In 1995, TYLCV was first reported in Algarve (southern Portugal) as responsible for an epidemic outbreak of a severe tomato disease. Molecular data have shown that this Portuguese TYLCV isolate was distinct from those previously reported in Europe, as it belonged to the TYLCV‐Israel species1. Since then, TYLCV epidemics have occurred annually, being a limiting factor mainly for autumn/winter glasshouse tomato crops. In 1998, TYLCV was also found associated with the emergence of a novel disease of Phaseolus vulgaris in Algarve. The affected bean plants were severely stunted and gave no marketable yield. However, the disease occurs only sporadically, even in conditions of high TYLCV infection pressure. Recently, Tomato chlorosis virus (ToCV), a whitefly‐transmitted bipartite closterovirus (genus Crinivirus, family Closteroviridae), was found associated with an unusual tomato yellow leaf syndrome, in single or mixed infection with TYLCV. The impact of this new pathosystem on tomato production has yet to be determined. Surveys are in progress in mixed cropping systems infested with whiteflies. So far, TYLCV and ToCV diseases are limited to the Algarve region.

Report of Sugarcane yellow leaf virus in Ecuador, Guatemala, and Nicaragua.

In 1998, sugarcane plants with symptoms similar to yellow leaf syndrome were observed in Ecuador, Guatemala, and Nicaragua. These plants showed yellowing of the central portion of the third to sixth leaves on the abaxial surface from the youngest expanding spindle leaf. Intense yellowing and necrosis of the leaf tip and the central portion of the leaf blade near the midrib occurred in severe cases. A tissue blot immunoassay was used to detect Sugarcane yellow leaf virus (SCYLV) in the midrib of the top visible dewlap leaf (2) using an antiserum specific to a Florida isolate of SCYLV (1). Since the virus can be detected in asymptomatic plants, leaf samples were collected from both symptomatic and asymptomatic plants. Symptom expression was most intense in plants at maturity that were under stress. Cut ends of leaf samples were imprinted on nitrocellulose membranes in the country of origin, and control samples of healthy and SCYLV-infected leaves were imprinted in Florida on each membrane prior to serological processing. The results from the following locations and cultivars, and the ratio of SCYLV-positive samples over the total samples is indicated: Milagro, Ecuador, PR 70-2085 (11/24) and PR 76-3385 (48/63) in 1999; Escuintla, Guatemala, CP 57-603 (1/10), CP 73-1547 (0/10), CP 72-2086 (120/308), PR 75-2002 (8/11), PR 78-294 (10/10), and PR 87-2080 (13/13) in both 2000 and 2001; Tipitapa, Nicaragua, L 68-40 (21/70) in 1998; and Chinandega, Nicaragua, CP 72-2086 (30/30) and CP 74-2005 (13/45) in 2000. CP 72-2086 is a major commercial cultivar in Central American countries and was infected in both Guatemala and Nicaragua. SCYLV was detected in 9 of 10 cultivars sampled. An exception was noticed in CP 73-1547 in Guatemala where none of the 10 plants tested were infected; however this cultivar has a high incidence of SCYLV in Florida. Only 1 of 10 samples of CP 57-603 was SCYLV positive in Guatemala; however, this cultivar has a low incidence of infection in Florida and is considered more resistant than the other CP cultivars sampled. To our knowledge, this is the first report SCYLV in Ecuador, Guatemala, and Nicaragua.

Elimination of Sugarcane yellow leaf virus from infected sugarcane plants by meristem tip culture visualized by tissue blot immunoassay

Sugarcane yellow leaf virus (SCYLV), a member of the Luteoviridae, is implicated in the sugarcane disease known as yellow leaf syndrome (YLS), which is characterized by yellowing of the leaf midrib followed by leaf necrosis and possible growth suppression. YLS is distributed worldwide and susceptible cultivars are commonly infected with SCYLV. However, not all cultivars infected with SCYLV show symptoms of YLS and some cultivars that show symptoms do so sporadically. Since it is difficult to obtain virus‐free plants of susceptible cultivars, it has not been possible to study the factors involved in SCYLV infection nor the effects of infection on plant growth and yield. A tissue blot immunoassay was used to visualize in vivo presence of the virus so that virus‐infected and virus‐free plants could be distinguished. Meristem tip cultures were used to produce virus‐free plantings of six SCYLV‐susceptible sugarcane cultivars. Nearly all of the regenerated sugarcane lines remained virus‐free over a period of up to 4 years, whether grown in isolated fields or in the glasshouse. Experimental re‐infection of the virus‐free plants by viruliferous aphids demonstrated that meristem tip culture did not affect susceptibility of sugarcane to SCYLV. Improved diagnosis and production of virus‐free plants of SCYLV‐susceptible cultivars will facilitate research to quantify the effect of the virus on yield and to analyse the processes involved in disease development.