Occurrence of cucumber mosaic virus within tomato seed lots

Tomato (Solanum lycopersicum L.) is an important crop whose fruit is widely consumed globally. However, its yield is affected by cucumber mosaic virus (CMV) and can cause total crop failure. The virus is mainly transmitted by aphid vectors, but data on its spread via seeds are limited. Thus, the occurrence of CMV within tomato seed lots obtained from different sources was investigated. Seven tomato accessions and varieties were collected from five sources and evaluated for seed transmission of CMV. One hundred seeds each were sown in a plastic tray, and germination rates were recorded. The incidence and severity of virus symptoms were observed at 3, 6, and 9 weeks after sowing (WAS), while leaves were tested for CMV using antigen-coated plate enzyme-linked immunosorbent assay (ACP-ELISA). The germination percentage ranged from 60% in accession 'V4' to 92% in 'UC-82B'. Infection rates were 100%, 71.74%, 70.31%, 45.90%, and 8.33% in 'Roma-VF', 'UC-82B', 'NG/AA/SQ/09/053', 'V2', and 'V4', respectively. 'Kerewa' and 'Alausa-Long' exhibited zero infection rates and tested negative for CMV using ACP-ELISA. Eighty percent of test plants became symptomatic at 6 and 9 WAS, although accession 'NG/AA/SQ/09/053' tested positive for CMV despite showing no symptoms. Tomato seeds from commercial stores, research institutes, and farmers' fields tested positive for CMV, while seeds from the market were negative at 9 WAS. The results from this study confirm the transmissibility of CMV through seeds in tomatoes, although the rate of seed transmission is cultivar dependent

Chromogenic detection of yam mosaic virus by closed-tube reverse transcription loop-mediated isothermal amplification (CT-RT-LAMP)

A closed-tube reverse transcription loop-mediated isothermal amplification (CT-RT-LAMP) assay was developed for the detection of yam mosaic virus (YMV, genus Potyvirus) infecting yam (Dioscorea spp.). The assay uses a set of six oligonucleotide primers targeting the YMV coat protein region, and the amplification products in YMV-positive samples are visualized by chromogenic detection with SYBR Green I dye. The CT-RT-LAMP assay detected YMV in leaf and tuber tissues of infected plants. The assay is 100 times more sensitive in detecting YMV than standard RT-PCR, while maintaining the same specificity

Investigation on seed transmission of cucumber mosaic virus in cowpea

Cowpea breeding lines were infected with cucumber mosaic virus (CMV) by mechanical inoculation to investigate seed transmission rates for this virus. Transmission rates ranging from 0% to 6% were scored by symptom assessment. However, when cowpeas grown from seeds of infected mother plants were tested by ELISA, up to 30% of the plants were infected with CMV. Evaluating ELISA for CMV detection in cowpea revealed that virus concentration was highest in flowers and lowest in primary leaves. To compare the capacity of ELISA for CMV detection, the serological test was compared with RT-PCR; ELISA proved sensitive and reliable for detection of CMV in infected tissue. For seed analysis, a non-destructive assay for CMV detection based on tissue blotting of hypocotyls tissue was developed. RÉSUMÉ Des varietés sélectionnées du niebé étaient infectées par inoculation mécanique avec le virus de la mosaíque de concombre (CMV) afin d'étudier la transmission par semence de ce virus. Les taux de transmission de l'ordre de 0 % à 6 % étaient enregistrés après l'évaluation des symptômes. Cependant, lorsque les plantes de niébé issues de semences provenant des parents infectés ont été testéés par ELISA, jusqu'á 30 % des plantes étaient infectées par le CMV. L'évaluation de L'ELISA pour la détection du CMV chez le niébé a révélé que la concentration du virus était la plus élevée dans les fleurs et le plus faible dans les feuilles primaires. Afin d'évaluer la capacité d'ELISA de détecter CMV, le test sérologique était comparé á la RT-PCR, où l'ELISA s'est montré sensible et fiable pour la détection du CMV dans des tissus infectés. Pour l'analyse de semence, une méthode non-destructive de détection de CMV basée sur le blotting de tissus d'hypocotyle était développé. (Af Crop Science and Production: 2001 9(4): 677-684

Effect of Detopping on Disease Incidence and Symptom Severity of African Cassava Mosaic Virus Disease (ACMD) on Some Newly Developed Cassava Cultivars from Landraces Introgression

Twenty-five cassava genotypes were exposed to natural infection by African cassava mosaic disease (ACMD) in plots at the International Institute of Tropical Agriculture (IITA), Ibadan (forest-savanna transition zone), Nigeria. The effect of removing the shoot tips (detopping) of cassava plants on disease incidence and symptom severity was assessed fortnightly for 14 weeks, starting 8 weeks after planting (WAP). There were highly significant differences (P < 0.01) in disease incidence (DI) and symptom severity (ISS) among clones throughout the period of observation, indicating different levels of resistance to infection. Detopping produced a significant effect on disease incidence in clones 91/02322, 91/02324, 91/02327 and 92/0427. It also had a significant effect on symptom severity of clones 92/0342, M94/0177 and TMS 4(2) 1425. The interaction between the treatment (TRT) and clone was highly significant (P < 0.01) for DI and ISS throughout the period of observation, an indication that there are differential responses of the clones to detopping. Cassava genotypes M94/0121 and Isu were observed to be highly resistant and highly susceptible respectively to the disease, while plants of genotypes 82/00058 and 91/02322 showed moderate susceptibility. None of the genotypes was immune to the disease. There was also a highly significant and positive correlation between DI and ISS in both detopped and undetopped plants. A conclusion from this study is that removal of shoot tips from moderately resistant cassava clones for consumption should be discouraged as it increases the severity of ACMD infection in the regenerating shoots of these clones

Effects of cassava genotype, climate, and the Bemisia tabaci vector population on the development of African cassava mosaic geminivirus (ACMV)

A survey was carried out in the 1996/97 and 1997/98 growing seasons on a field planted in three replicates with five clones of cassava at the International Institute of Tropical Agriculture, Ibadan, located in a transition forest, to determine the effects of cassava genotype and climate on the development of African cassava mosaic geminivirus (ACMV) and changes in the Bemisia tabaci population. Cassava genotype, climate and their interactions have significan