First Report on the Association of a 16SrII-A Phytoplasma with Sesame (Sesamum indicum) Exhibiting Abnormal Stem Curling and Phyllody in Taiwan

Abstract

Sesame (Sesamum indicum L.), an annual plant, is grown as an oilseed crop and the seeds are used in bakery products in Taiwan. In June 2013, plants exhibiting symptoms including phyllody and abnormal stem curling were observed in sesame fields in Pitou Township, Changhua County, Taiwan. Incidence of infected plants was estimated to be greater than 90% within a single field. Phytoplasmas associated with sesame exhibiting phyllody, witches'-broom, or virescence have been classified as strains of 16SrI-B in Myanmar (GenBank Accession No. AB558132), 16SrII-A in Thailand (JN006075), 16SrII-D in Oman (EU072505) and India (KF429486), 16SrIV-C in Iran (JF508515), and 16SrVI-A (KF156894) and 16SrIX (KC139791) in Turkey (1). Three symptomatic and four asymptomatic plants were uprooted and transplanted in a greenhouse for further study. Transmission electron microscopy (TEM) revealed clusters of phytoplasma cells ranging from 300 to 800 nm in diameter only in phloem sieve elements of stems of three symptomatic and two asymptomatic plants. Comparable tissues from two other symptomless plants were devoid of phytoplasma cells. Total DNA was extracted with a modified CTAB method (2) from plant tissues (100 mg each) including stem, leaf, petiole, and root from the same plants used for TEM work. Analyses by a nested PCR using universal primer pairs P1/P7 (5′-AAGAGTTTGATCCTGGCTCAGGATT/5′-CGTCCTTCATCGGCTCTT) followed by R16F2n/R16R2 (5′-GAAACGACTGCTAAGACTGG/5′-TGACGGGCGGTGTGTACAAACCCCG) were performed to detect putative phytoplasma DNA (3). Each primer pair amplified a single PCR product of either 1.8 or 1.2 kb, respectively, only from the three symptomatic and two asymptomatic plant tissues that had phytoplasma cells in their sieve elements. It is likely that these two asymptomatic plants were in the early stage of infection before symptoms became noticeable. The nested PCR products (1.2 kb) amplified from the symptomatic plants were cloned separately and sequenced (GenBank Accession Nos. KF923391, KF923392, and KF923393). BLAST analysis of the sequences revealed that they shared 99.2% sequence identity with strains reported from India and Thailand (KF429486 and JN006075), which were classified to the 16SrII-D and 16SrII-A subgroups, respectively. Moreover, iPhyClassifier software (4) was used to perform sequence comparison and generate a virtual restriction fragment length polymorphism (RFLP) profile. The 16S rDNA sequences shared 99.4% identity with that of the ‘Candidatus Phytoplasma australasiae’ (Y10097) and the RFLP patterns were identical to that of the 16SrII-A subgroup, indicating the Taiwanese strain is a ‘Ca. P. australasiae’-related strain. To our knowledge, this is the first report of a 16SrII-A subgroup phytoplasma causing phyllody and abnormal stem curling on sesame in Taiwan. The occurrence of phytoplasma on sesame could have direct implications for the cultivation of this economically important oilseed plant and the bakery industry in Taiwan. References: (1) M. Catal et al. Plant Dis. 97:835, 2013. (2) T. M. Fulton et al. Plant Mol. Biol. Rep. 13:207, 1995. (3) D. E. Gundersen and I. M. Lee. Phytopathol. Mediterr. 35:144, 1996. (4) Y. Zhao et al. Int. J. Syst. Evol. Microbiol. 59:2582, 2009.

Association of two groups of phytoplasma with various symptoms in some wooden and herbaceous plants

“…Sesame plants affected by phytoplasma showed symptoms of floral virescence, phyllody, stem fasciation, shortened internodes and cracking of seed capsules (Figure j). Sesame phyllody has been reported to be caused by different groups of phytoplasma, that is group 16SrI in India (Khan, Raj, & Snehi, ), Myanmar (Win, Back, & Jung, ) and South Korea (Lee et al., ); group 16SrII in India (Pamei & Makandar, ), Iran (Esmailzadeh‐Hosseini, Mirzaie, Jafari‐Nodooshan, & Rahimian, ), Oman (Al‐Sakeiti, Al‐Subhi, Al‐Saady, & Deadman, ), Pakistan (Akhtar et al., ), Taiwann (Tseng, Deng, Chang, Huang, & Jan, ), Thailand (Martini et al., ) and Turkey (Ikten et al., ); group 16SrVI in Turkey (Sertkaya, Martini, Musetti, & Osler, ); group 16SrIX in Iran (Salehi, Heydarnejad, & Izadpanah, ) and Turkey (Catal, Ikten, Yol, Ustun, & Uzun, ); and subgroup 16SrIX–C in Turkey (Ikten et al., ).…”

“…in India (Pamei & Makandar, 2016) 2009), Taiwann (Tseng, Deng, Chang, Huang, & Jan, 2014), Thailand and Turkey (Ikten et al, 2014); group 16SrVI…”

Current Research Trends and Prospects for Yield and Quality Improvement in Sesame, an Important Oilseed Crop

“…Symptoms associated with phyllody disease in sesame include phyllody (floral parts replaced with leafy structures), flower virescence (abnormal development of green pigmentation), witches' broom, shoot tip fasciation, vivipary (seeds or embryos begin to develop before being detached from the parent), and cracking of seed capsules. Phyllody disease has also been reported in the Asian and African countries, including Burkina Faso, Ethiopia, and India (Madhupriya et al, 2015;Rao et al, 2015), Iraq, Israel, Mexico, and Myanmar (Win et al, 2010), Nigeria, Oman, Pakistan, Sudan, and Taiwan (Tseng et al, 2014), Tanzania, Thailand, and Turkey (Catal et al, 2013), and Venezuela and Uganda (Singh et al, 2007). Several diagnostic methods, including Dienes stains and TEM techniques, can detect phytoplasma bodies in phloem sieve tissues; however, PCR-based assays are more reliable for identifying phytoplasmas associated with the disease (Rao et al, 2015).…”

The Distribution of Phytoplasmas in South and East Asia: An Emerging Threat to Grapevine Cultivation

“…A few studies also suggest the presence of phytoplasma associated with AY and PnWB in Taiwan on different cultivated crops as Hibiscus sabdariffa and Sesamum indicum (Tseng et al, 2014a; Tseng et al, 2014b).…”