Kushawaha Akhilesh Kumar, Rabindran Ramalingam, Dasgupta Indranil
1Department of Plant Molecular Biology, University of Delhi, South Campus, Benito Juarez Road, New Delhi, 110021 India.
2Center for Plant Breeding and Genetics, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641003 India.
Virusdisease. 2018 Mar;29(1):61-67. doi: 10.1007/s13337-018-0432-x. Epub 2018 Feb 1.
Cassava mosaic disease is a widespread disease of cassava in south Asia and the African continent. In India, CMD is known to be caused by two single-stranded DNA viruses (geminiviruses), Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosdaic virus (SLCMV). Previously, the diversity of ICMV and SLCMV in India has been studied using PCR, a sequence-dependent method. To have a more in-depth study of the variability of the above viruses and to detect any novel geminiviruses associated with CMD, sequence-independent amplification using rolling circle amplification (RCA)-based methods were used. CMD affected cassava plants were sampled across eighty locations in nine districts of the southern Indian state of Tamil Nadu. Twelve complete sequence of coat protein genes of the resident geminiviruses, comprising 256 amino acid residues were generated from the above samples, which indicated changes at only six positions. RCA followed by RFLP of the 80 samples indicated that most samples (47) contained only SLCMV, followed by 8, which were infected jointly with ICMV and SLCMV. In 11 samples, the pattern did not match the expected patterns from either of the two viruses and hence, were variants. Sequence analysis of an average of 700 nucleotides from 31 RCA-generated fragments of the variants indicated identities of 97-99% with the sequence of a previously reported infectious clone of SLCMV. The evidence suggests low levels of genetic variability in the begomoviruses infecting cassava, mainly in the form of scattered single nucleotide changes.
木薯花叶病是南亚和非洲大陆木薯的一种广泛传播的病害。在印度,已知木薯花叶病由两种单链DNA病毒(双生病毒)引起,即印度木薯花叶病毒(ICMV)和斯里兰卡木薯花叶病毒(SLCMV)。此前,已使用依赖序列的PCR方法对印度的ICMV和SLCMV多样性进行了研究。为了更深入地研究上述病毒的变异性,并检测与木薯花叶病相关的任何新型双生病毒,采用了基于滚环扩增(RCA)的不依赖序列的扩增方法。在印度南部泰米尔纳德邦九个区的80个地点采集了受木薯花叶病影响的木薯植株样本。从上述样本中获得了12个常住双生病毒外壳蛋白基因的完整序列,包含256个氨基酸残基,结果表明仅在六个位置发生了变化。对80个样本进行RCA后再进行RFLP分析表明,大多数样本(47个)仅含有SLCMV,其次是8个样本同时感染了ICMV和SLCMV。在11个样本中,其模式与两种病毒中任何一种的预期模式均不匹配,因此为变异体。对变异体的31个RCA生成片段平均700个核苷酸进行序列分析,结果表明与先前报道的SLCMV感染性克隆序列的同一性为97 - 99%。证据表明,感染木薯的菜豆金色花叶病毒属病毒的遗传变异性较低,主要表现为分散的单核苷酸变化形式。