White Leaf Disease Research Articles

Identification of grass white leaf disease associated with a ‘Candidatus Phytoplasma asteris’-related phytoplasma strain (16SrI-B and cpn60 I-IIIB) in Mexico

Samples of a wild grass showing white leaf symptoms were collected in 2015 in Veracruz, Mexico around sugarcane plantations. DNA amplification, sequencing and phylogenetic analysis revealed the presence of a ‘Candidatus Phytoplasma asteris’-related strain in the plants that were positive using 16S-based and cpn60 PCR assays. The strain determined to be associated with the grass white leaf disease was identified as a member of the 16SrI-B subgroup and a member of the cpn60 I-IIIB subgroup through in silico RFLP analysis. This is the first report of phytoplasma-infected grass plants associated with white leaf disease in Mexico. The implications of these findings are vital for the management of other plant hosts of the family Poaceae such as sugarcane and corn, and point to weedy grasses as a potential source of phytoplasma inoculum for nearby crop plants.

Molecular detection of ‘Candidatus Phytoplasma australasia’ and ‘Ca. P. cynodontis’ in Iraq

Abstract The association of phytoplasma was investigated in symptomatic tomato (Solanum lycopersicum L.), eggplant (Solanum melongen L.), mallow (Malva spp.) and Bermuda grass (Cynodon dactylon L.) plants exhibiting witches’ broom and white leaf diseases, respectively. Total DNA was extracted from tomato (n=3), eggplant (n=2), mallow (n=2) and Bermuda grass (n=8) samples. Direct polymerase chain reaction (PCR) was performed using P1/P7 primer set, then PCR products were sequenced. Sequences obtained from tomato, eggplant and mallow shared 99% maximum nucleotide identity with phytoplasma belonging to subgroup 16SrII-D, and resulted therefore ‘Candidatus Phytoplasma australasia’-related. Sequences obtained from Bermuda grass showed 100% maximum nucleotide identity to 16SrXIV-A subgroup and were ‘Ca. P. cynodontis’-related. The study presents the first molecular confirmation and sequence data of presence of ‘Ca. P. australasia’ and ‘Ca. P. cynodontis’ in Iraq.

Characterization of Direct Current-Electrical Penetration Graph Waveforms and Correlation With the Probing Behavior of Matsumuratettix hiroglyphicus (Hemiptera: Cicadellidae), the Insect Vector of Sugarcane White Leaf Phytoplasma.

The leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is an important vector of phytoplasma causing white leaf disease in sugarcane. Thus, the aim of our study was to understand and describe the stylet-probing activities of this vector while feeding on sugarcane plants, by using direct current (DC) electrical penetration graph (EPG) monitoring. The EPG signals were classified into six distinct waveforms, according to amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into the host plant tissues (probing). These six EPG waveforms of probing behavior comprise no stylet penetration (NP); stylet pathway through epidermis, mesophyll, and parenchymal cells (waveform A); contact at the bundle sheath layer (waveform B); salivation into phloem sieve elements (waveform C); phloem sap ingestion (waveform D); and short ingestion time of xylem sap (waveform E). The above waveform patterns were correlated with histological data of salivary sheath termini in plant tissue generated from insect stylet tips. The key findings of this study were that M. hiroglyphicus ingests the phloem sap at a relatively higher rate and for longer duration from any other cell type, suggesting that M. hiroglyphicus is mainly a phloem-feeder. Quantitative comparison of probing behavior revealed that females typically probe more frequently and longer in the phloem than males. Thus, females may acquire and inoculate greater amounts of phytoplasma than males, enhancing the efficiency of phytoplasma transmission and potentially exacerbating disease spreading. Overall, our study provides basic information on the probing behavior and transmission mechanism of M. hiroglyphicus.

Effects of Selected Insecticides on Matsumuratettix hiroglyphicus (Matsumura), a Vector of Sugarcane White Leaf Disease, and on Two Natural Enemies of the Sugarcane Stem Borer in Sugarcane Fields

Sugarcane white leaf disease, caused by phytoplasma, is the most severe disease that affects sugar production in Thailand. The major vector of this disease is the leafhopper, Matsumuratettix hiroglyphicus (Matsumura). Although several approaches have been employed for management of this vector, they have not been fully successful in eliminating the disease. In the present study, the efficacy of different insecticides in controlling M. hiroglyphicus was evaluated along with their impact on the natural enemies of sugarcane stem borer, which are commonly released in sugarcane fields in Thailand. The study was performed in fields growing tissue culture-raised sugarcane plantlets. Among the different insecticides tested in greenhouse as well as in field, dinotefuran resulted in high mortality of M. hiroglyphicus and had a long residual effect. The impact of dinotefuran on a natural larval parasitoid, Cotesia flavipes (Cameron), and on an egg parasitoid, Trichogramma confusum Viggiani, was observed to be relatively less, and it disappeared rapidly. Hence, our results suggest that dinotefuran is an effective pesticide for the management of M. hiroglyphicus, a key vector of sugarcane white leaf disease.

Association of ‘Candidatus Phytoplasma cynodontis’ with Bermuda grass white leaf disease and its new hosts in Qassim province, Saudi Arabia

ABSTRACTTypical symptoms of phytoplasma such as whitening of the leaves, shortening of the stolons on Bermuda grass, variegated leaves, yellows, stunting, little leaves and yellows on Giant reed, Cooba and sand olive shrub were observed in Qassim province, Saudi Arabia, during the autumn season of 2015. When tested for phytoplasma by universal primers P1/P7 followed by R16mF2/R16mR2, products of approximately 1400 bp (as expected) were amplified from 16 plants with symptoms but not from symptomless plants. Based on sequencing, phylogenetic analysis and virtual restriction fragment length polymorphism patterns of the 16S rDNA F2nR2 fragments of seven Qassim phytoplasma isolates, bermuda grass isolates 170, 175 and 177, giant reed isolate 180, sand olive isolates 181 and 182 and cooba isolate 185, the associated phytoplasma was identified as a member of ‘Candidatus Phytoplasma cynodontis’ which belong to the 16SrXIV-A subgroup. The 16S rDNA gene sequences of seven Qassim phytoplasma isolates exhibited over 99.2% identity with members of ‘Ca. Phytoplasma cynodontis’ group of phytoplasmas. This is the first report of characterization of ‘Ca. phytoplasma cynodonties’ (16SrXIV) associated with Cynodon dactylon in Saudi Arabia and its new hosts, Dodonaea angustifolia, Arundo donax and Acacia salicia.

Phytoplasma diseases on major crops in Vietnam

The nested-PCR technique was applied to detect and identify phytoplasmas associated with major crops in Vietnam including sugarcane, cassava and longan. Phylogenetic analysis confirmed that phytoplasmas associated with the sugarcane grassy shoot and white leaf diseases belong to the rice yellow dwarf group (16SrXI). In cassava showing witches’ broom symptoms a mixed infection of phytoplasmas related to ‘Candidatus Phytoplasma asteris’ (group 16SrI) and ‘Ca. P. aurantifolia’ (group 16SrII) was detected. In samples showing longan witches’ broom disease three phytoplasmas including ‘Ca. P. aurantifolia’ (group 16SrII), elm yellows (group 16SrV) and “stolbur” (group 16SrXII) were identified.

Analyses of the 16S-23S intergenic region of the phytoplasma causing the sugarcane white leaf disease in Yunnan Province, China

Sugarcane white leaf (SCWL) is an important disease caused by a phytoplasma. In Baoshan, Yunnan, China, SCWL was firstly observed in 2012, and has extended its area of occurrence to 600 hm2 . Up to 52% of the plants may become diseased in a field and even complete loss of cane yield may result in the heavily infected fields, posing a serious threat to Yunnan sugar industry. To ascertain the causal agent of suspected SCWL disease in Yunnan, nested PCR using two sets of phytoplasma primer pairs (MOLX/MLOY and P1/ P2) was used to successfully amplify a genomic region of the 16S ribosomal DNA (16S rDNA) from 36 suspected SCWL samples. On the basis of sequencing, phylogenetic analysis and nucleotide alignments of 17 nested PCR products randomly selected from positive samples, identical fragments of 210bp in length were obtained that could be clustered into the 6Sr group XI (Rice Yellow Dwarf group) and shared 100% identity with the 16S-23S intergenic spacer region (ISR) of a member of this group, the SCWL phytoplasma (GenBank: HQ917068), and 99.52% with Sugarcane grassy shoot phytoplasma, of the same group. These results indicate that the SCWL disease in Baoshan is caused by a phytoplasma of the 6Sr group XI.

Major QTLs Control Resistance to Rice Hoja Blanca Virus and Its VectorTagosodes orizicolus

Rice hoja blanca (white leaf) disease can cause severe yield losses in rice in the Americas. The disease is caused by the rice hoja blanca virus (RHBV), which is transmitted by the planthopper vector Tagosodes orizicolus. Because classical breeding schemes for this disease rely on expensive, time-consuming screenings, there is a need for alternatives such as marker-aided selection. The varieties Fedearroz 2000 and Fedearroz 50, which are resistant to RHBV and to the feeding damage caused by T. orizicolus, were crossed with the susceptible line WC366 to produce segregating F2:3 populations. The F3 families were scored for their resistance level to RHBV and T. orizicolus. The F2:3 lines of both crosses were genotyped using microsatellite markers. One major QTL on the short arm of chromosome 4 was identified for resistance to RHBV in the two populations. Two major QTL on chromosomes 5 and 7 were identified for resistance to T. orizicolus in the Fd2000 × WC366 and Fd50 × WC366 crosses, respectively. This comparative study using two distinct rice populations allowed for a better understanding of how the resistance to RHBV and its vector are controlled genetically. Simple marker-aided breeding schemes based on QTL information can be designed to improve rice germplasm to reduce losses caused by this important disease.

Diagnosis of Sugarcane White Leaf Disease Using the Highly Sensitive DNA Based Voltammetric Electrochemical Determination

A simple and highly sensitive analysis by electrochemical voltammetry has been developed for diagnosis of the most destructive crop disease in Thailand known as sugarcane white leaf (SCWL). Determination of the corresponding DNA interaction has been obtained from the voltammetric signals of electroactive redox methylene blue (MB) by means of cyclic and differential pulse voltammetry. In this study, a chitosan-modified glassy carbon electrode (GCE) was created by self-assembly to produce electrostatic platform for effective immobilization of the DNA. Fabrication of SCWL-DNA hybridization detection system was performed by immobilizing the ssDNA probe as a specific sensor onto chitosan-modified GCE. Hybridization of complementary DNA from the real samples could then be detected by its respective MB signal. This fabricated DNA probe sensor was shown to be capable for discriminative identification among the DNAs from SCWL plants, mosaic virus infected sugarcane and healthy sugarcane plants. Relationship between the specific hybridization signal and DNA target concentration was also observed under optimal condition. The detection limit of 4.709 ng/μl with the regression coefficient (R2) of 0.998 and overall RSD of 2.44% were obtained by response curve fit analysis. The actual SCWL-ssDNA immobilization and hybridizing event were subsequently confirmed by an observation under atomic force microscope. Thus these experiments demonstrate the first successful and effective DNA based voltammetric electrochemical determination for a verification of the specific pathogenic infection within plants from the real epidemic field.

Rapid Spread ofBalclutha rubrostriata(Hemiptera: Cicadellidae) in Texas and Southwestern Louisiana, USA with Notes on its Associated Host Plants

The red streaked leafhopper, Balclutha rubrostriata (Melichar) (Hemiptera: Cicadellidae), is an invasive insect from southeastern Asia that is known to be a vector of the phytoplasma that causes Sugarcane White Leaf Disease (SCWL). Sugarcane is a vital crop for the United States and is being considered as a biofuel source. The purpose of this survey was to determine whether B. rubrostriata has established populations in Texas and Louisiana, USA; and, if established, to estimate its range expansion. The gulf coast region of Texas, east Texas, and 2 southwestern parishes of Louisiana were surveyed for the red streaked leafhopper. Samples of the leafhopper were collected in all Gulf Coast regions and the majority of east Texas counties. However, it was only collected in one Louisiana parish. The leafhopper appears to be closely associated with an invasive grass, King Ranch Bluestem, Bothriochloa ischaemum (L.), throughout much of its present range in the United States, and it is now common along much of the Texas Gulf Coast and is moving into Louisiana.

Candidates for symbiotic control of sugarcane white leaf disease.

The leafhopper Matsumuratettix hiroglyphicus (Matsumura) is the most important vector of a phytoplasma pathogen causing sugarcane white leaf (SCWL) disease. The purpose of this study was to evaluate candidate bacterial symbionts for possible use as vehicles in the control of the disease. 16S rRNA bacterial genes were amplified from whole bodies of M. hiroglyphicus leafhoppers and analyzed by cloning and sequencing. Two dominant groups were found: one belonged to the Betaproteobacteria that did not closely match any sequences in the database and was named bacterium associated with M. hiroglyphicus (BAMH). Another one found to be abundant in this leafhopper is "Candidatus Sulcia muelleri" in the order Bacteroidetes, which was previously reported in the insect members of the Auchenorrhyncha. Most M. hiroglyphicus leafhoppers carry both BAMH and "Ca. Sulcia muelleri." Fluorescent in situ hybridization showed that BAMH and "Ca. Sulcia muelleri" colocalized in the same bacteriomes. BAMH was present in the midgut and ovaries of the leafhopper and was found in all developmental stages, including eggs, nymphs, and adults. Because BAMH appears to be specific for the SCWL vector, we evaluated it as a candidate for symbiotic control of sugarcane white leaf disease.

Dispersal of the leafhoppers Matsumuratettix hiroglyphicus and Yamatotettix flavovittatus (Homoptera: Cicadellidae), vectors of sugarcane white leaf disease

Sugarcane white leaf disease is a serious problem in many Asian Countries. The leafhoppers Matsumuratettix hiroglyphicus (Matsumura) and Yamatotettix flavovittatus Matsumura are the main vectors of sugarcane white leaf disease phytoplasma. Gaining a better understanding of the dispersal behavior of such insect vectors is essential for both disease epidemiology and vector control. The dispersal distances of M. hiroglyphicus and Y. flavovittatus in a sugarcane field were estimated by means of mark–release–recapture experiments. Adult leafhopper vectors collected from the fields were marked using fluorescent dye powder and released at a central release point in a sugarcane field. The marking method did not have a significant effect on the survival or flight activity of the leafhopper vectors. The overall release–recapture rates of M. hiroglyphicus and Y. flavovittatus within 50 m were 10.1 and 13.4 %, respectively. The estimated natural mean dispersal distances for M. hiroglyphicus and Y. flavovittatus were 162.1 and 387.5 m, respectively. Wind appears to be the main factor influencing the leafhopper dispersal direction.

'Candidatus Phytoplasma cynodontis' associated with white leaf disease of golden beard grass (Chrysopogon acicalatus)

A phytoplasma was detected in golden beard grass (Chrysopogon acicalatus) displaying white leaf symptoms near vegetative fields at the Tatkone region in Myanmar, 2011. Based on restriction fragment length polymorphism analysis of PCR-amplified 16S rRNA genes, including the 16S-23S spacer region and part of the 23S rRNA gene, the phytoplasma was identified as a member of the Bermuda grass white leaf phytoplasma (BGWL) group. The golden beard grass white leaf phytoplasma (GBGWL) 16S rRNA gene sequence exhibited over 98.7% similarity with all members of BGWL group phytoplasmas and 99.5% similarity with Thailand Bermuda grass white leaf phytoplasma (AF248961). In addition, the GBGWL phytoplasma was confirmed to be a member of 'Candidatus Phytoplasma cynodontis' by phylogenetic analyses.

Hyparrhenia grass white leaf disease, associated with a 16SrXI phytoplasma, newly reported in Kenya

Hyparrhenia rufa is a thatching grass commonly found throughout the tropics where it also serves as valuable cattle fodder and border grass to prevent soil erosion (Skerman & Riveros, 1990). In June 2010, we observed some H. rufa …

First report of a phytoplasma associated with Bermuda grass white leaf disease in Kenya

Bermuda grass (=Star grass), Cynodon dactylon , is a perennial plant of the family Poaceae that is native to the African Savannah but is now widely distributed over many warm countries of the world (Marcone et al ., 1997). C. dactylon plants…

'CandidatusPhytoplasma cynodontis' (16SrXIV group) affectingOplismenus burmannii(Retz.) P. Beauv. andDigitaria sanguinalis(L.) Scop. in India

A phytoplasma has been detected in Oplismenus burmannii (Retz.) P. Beauv. and Digitaria sanguinalis (L.) Scop. plants with symptoms of chlorotic streaks and white leaf disease in India. By sequence and phylogenetic analyses of polymerase chain reaction-amplified rDNA sequences, the detected phytoplasma was identified as ‘Candidatus Phytoplasma cynodontis’, a member of the 16SrXIV group, and the causal agent of Bermuda grass white leaf disease. This is the first report on the occurrence of ‘Ca. Phytoplasma cynodontis’ in O. burmannii and D. sanguinalis grasses.

First report of a ‘Candidatus Phytoplasma cynodontis’-related strain (group 16SrXIV) associated with white leaf disease of Dichanthium annulatum in India

A phytoplasma has been detected in a formerly undescribed white leaf disease of Dichanthium annulatum (Kleberg’s bluestem) in India. By sequence and phylogenetic analyses of polymerase chain reaction-amplified rDNA sequences, the detected phytoplasma proved to be closely related to Bermuda grass white leaf agent (‘Candidatus Phytoplasma cynodontis’) which is a member of the 16SrXIV group.

Controlling White Leaf Disease (WLD) Incidence of Sugarcane by Heat Therapy

An experiment was conducted to find out the effect of heat therapy on germination and white leaf disease incidence of sugarcane at Sreepur, Gazipur, Bangladesh. Germination was significantly increased in moist hot air treatment (MHAT) treated plot. No white leaf disease was found in MH,AT at 540C for 4 h, 3 h and 2.30 h treated settlings. Similarly, millable cane and cane yield were positively affected by heat therapy. Heat therapy with MHATand hot water treatment (HUT) performed better in increasing sugarcane yield compared to control. Keywords: Moist hot air treatment, hot water treatment, white leaf disease

Molecular identification of ‘Candidatus Phytoplasma cynodontis’ associated with Bermuda grass white leaf disease in India

Molecular identification of ‘<i>Candidatus</i> Phytoplasma cynodontis’ associated with Bermuda grass white leaf disease in India

Transmission of Sugarcane White Leaf Phytoplasma by Yamatotettix flavovittatus, a New Leafhopper Vector

Sugarcane white leaf disease is caused by plant pathogenic phytoplasmas that are transmitted to the plant by the leafhopper Matsumuratettix hiroglyphicus (Matsumura). To determine whether there are other insect vectors that transmit this disease pathogen, leafhopper species in sugarcane, Saccharum officinarum L., fields in northeastern Thailand were monitored by using light traps. Sixty-nine leafhopper species from family Cicadellidae were found. Using nested polymerase chain reaction (PCR) with specific primers, a 210-bp amplified DNA fragment corresponding to phytoplasma associated with sugarcane white leaf disease was detected from 12 species of leafhoppers [Balclutha rubrostriata (Melichar), Balclutha sp., Bhatia olivacea (Melichar), Exitianus indicus Distant, Macrosteles striifrons Anufriew, Matsumuratettix hiroglyphicus (Matsumura), Recilia distincta (Motschulsky), Recilia dorsalis (Motschulsky), Recilia sp., Thaia oryzivora Ghauri, Yamatotettix flavovittatus Matsumura, and Xestocephalus sp.]. The percentage of individual infection with phytoplasma varied from 5% in B. olivacea to 35% in Xestocephalus sp. The most abundant leafhopper species, i.e., E. indicus, Y. flavovittatus, and M. hiroglyphicus were used in transmission tests to determine their vector status for the sugarcane white leaf phytoplasma transmission. Infected insects were reared on healthy plants and specific PCR followed by sequencing of the amplicons was used to determine whether the phytoplasma was transmitted to the plants. The results showed that both Y. flavovittatus and M. hiroglyphicus, but not E. indicus, can transmit sugarcane white leaf phytoplasma to healthy sugarcane plants. The transmission efficiency of M. hiroglyphicus (55%) was higher than that of Y. flavovittatus (45%). We conclude that Y. flavovittatus is a newly discovered vector for sugarcane white leaf disease, in addition to M. hiroglyphicus. These two species peak at different times of the year and therefore complement each other in the transmission of the phytoplasma. Because there are no known alternative host plants for the sugarcane white leaf, management of the disease will necessarily require the control of both Y. flavovittatus and M. hiroglyphicus.