First Report of Cucurbit yellow stunting disorder virus in California and Arizona, in association with Cucurbit leaf crumple virus and Squash leaf curl virus.

Authors: KUO, YEN-WEN - UNIV. CALIFORNIA, DAVIS; ROJAS, M - UNIV. CALIFORNIA, DAVIS; GILBERTSON, R - UNIV. CALIFORNIA, DAVIS; Wintermantel, William - Bill

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2006
Publication Date: 3/1/2007
Citation: Kuo, Y., Rojas, M.R., Gilbertson, R.L., Wintermantel, W.M. 2007. First Report of Cucurbit yellow stunting disorder virus in California and Arizona, in association with Cucurbit leaf crumple virus and Squash leaf curl virus. Plant Disease. V. 91. pg. 330.

Interpretive Summary: In August and September of 2006, melon plants (Cucumis melo L.) near Niland in California’s Imperial Valley and near Yuma, Arizona began exhibiting interveinal chlorosis and leaf mottling and spotting symptoms resembling those resulting from infection by viruses of the genus Crinivirus, family Closteroviridae. Some plants also exhibited leaf crumpling and curling, symptoms characteristic of begomovirus (genus Begomovirus, family Geminiviridae) infection. Leaves of plants had large populations of silverleaf whitefly (Bemisia tabaci biotype B), a known vector of begomoviruses and numerous criniviruses. Leaf samples were collected from 4 representative plants from California and 13 plants from 3 separate fields in Arizona. Total RNA was extracted and subjected to both reverse transcription polymerase chain reaction (RT-PCR) and DNA sequencing. The 500-nucleotide RT-PCR fragment, from 4 plants from California and 5 plants from Arizona, was 94-99% identical to CYSDV isolates from Texas (AY242077) and Spain (AJ537493), respectively. Subsequent RT-PCR analysis of RNA from these 9 plants, with primers specific to two other genes of CYSDV, was used to confirm virus identity. The expected fragments, 202- and 175-nucleotides, respectively, were amplified from all 9 samples, but not from healthy controls. DNA extracts also were prepared from these 9 melon samples from California and Arizona, and PCR assays were conducted for the begomoviruses Cucurbit leaf crumple virus (CuLCrV) and Squash leaf curl virus (SLCV). The 4 plants from California showed crumpling, curling and yellowing symptoms; all were infected with SLCV and one with CuLCrV, indicating begomovirus and crinivirus co-infection. The five plants from Arizona showed mostly yellowing symptoms, and SLCV infection was detected in one of these plants. Because all three viruses are transmitted by B. tabaci, co-infection of CYSDV and begomoviruses may become a common occurrence now that both viruses are established in the desert vegetable production regions of California and Arizona. Impact of such co-infections on cucurbit production remains to be determined, as these viruses have never been known to occur together before. The virus causes economic losses worldwide for cucurbit production.

Technical Abstract: In August and September of 2006, melon plants (Cucumis melo L.) near Niland in California’s Imperial Valley and near Yuma, Arizona began exhibiting interveinal chlorosis and leaf mottling and spotting symptoms resembling those resulting from infection by viruses of the genus Crinivirus, family Closteroviridae (3). Some plants also exhibited leaf crumpling and curling, symptoms characteristic of begomovirus (genus Begomovirus, family Geminiviridae) infection. Leaves of plants had large populations of silverleaf whitefly (Bemisia tabaci biotype B), a known vector of begomoviruses and numerous criniviruses. Leaf samples were collected from 4 representative plants from California and 13 plants from 3 separate fields in Arizona. Total RNA was extracted and subjected to reverse transcription polymerase chain reaction (RT-PCR) using degenerate primers specific to the conserved polymerase region of a diverse group of criniviruses (2). The expected 500-nucleotide RT-PCR product was amplified exclusively from RNA obtained from all of the symptomatic melons, whereas no fragment was obtained from RNA extracted from leaves of virus-free melons. The 500-nucleotide fragment, from 4 plants from California and 5 plants from Arizona, was 94-99% identical to CYSDV isolates from Texas (AY242077) and Spain (AJ537493), respectively. Subsequent RT-PCR analysis of RNA from these 9 plants, with primers specific to the capsid protein and HSP70h genes of CYSDV, was used to confirm virus identity. The expected fragments, 202- and 175-nucleotides, respectively, were amplified from all 9 samples, but not from healthy controls. DNA extracts also were prepared from these 9 melon samples from California and Arizona, and PCR assays were conducted for the begomoviruses Cucurbit leaf crumple virus (CuLCrV) and Squash leaf curl virus (SLCV). The 4 plants from California showed crumpling, curling and yellowing symptoms; all were infected with SLCV and one with CuLCrV, indicating begomovirus and crinivirus co-infection. The five plants from Arizona showed mostly yellowing symptoms, and SLCV infection was detected in one of these plants. Because all three viruses are transmitted by B. tabaci, co-infection of CYSDV and begomoviruses may become a common occurrence now that both viruses are established in the desert vegetable production regions of California and Arizona. Impact of such co-infections on cucurbit production remains to be determined, as these viruses have never been known to occur together before. The virus causes economic losses worldwide for cucurbit production.