Transmissibility of citrus yellow vein clearing virus by three dominant citrus aphids

Document Type : Research Paper

Authors

• Reza Maghsoudi ¹
• Saeid Nassrollahnejad ²
• Sirous Aghajanzadeh ³
• Seyed Mehdi Bani Hashemian ³

¹ Department of Plant Protection, Gorgan University of Agricultural Sciences and Natural Resources, Golestan, Iran

² Department of Plant Protection, Gorgan University of Agricultural Sciences and Natural Resources, Golestan, Iran.

³ Citrus and Subtropical Fruits Research Center, Horticultural Sciences Research Institute, Agricultural Research, Education and Extension Organization, Ramsar, Iran

Abstract

Keywords

• Aphid
• Eureka lemon
• Persian lime
• Virus

20.1001.1.20084781.1402.54.1.7.7

Extended Abstract

Introduction

   Citrus yellow vein clearing disease (CYVCD) was first observed on lemons (Citrus limon (L.) and sour oranges (C. aurantium L.) from Pakistan (Catara et al., 1993). It was also reported in lemon from Turkey (Onelge, 2002), India (Alshami et al., 2003), China (Chen et al., 2014), and Iran (Bani Hashemian and Aghajanzadeh, 2017). CYVCD reduces yield in Eureka lemon (C. limon) from 50-80% (Alshami et al., 2003; Zhou et al., 2017; Liu et al., 2019) and fruit quality is also reduced in China (Onelge et al., 2011a; Li et al., 2017; Zhang et al., 2018).

    The results of the research showed rapid spreading of CYVCV in the citrus orchards. CYVCV is an aphid-transmissible virus (Onelge et al., 2011a; Afloukou et al., 2021). Aphis spiraecola, A. gossypii, and Toxoptera aurantii (Hemiptera: Aphididae) are the predominant aphids in citrus orchards of the north of Iran (Aghajanzadeh et al., 1997; Alavi and Rezvani, 2007). Here, the potential transmissibility of CYVCV by these aphids was studied.

Materials and Methods

    Eureka lemon seedlings were used as receiver plants. A characterized isolate of CYVCV (Isolate LIE, GenBank accession number: KX902487) collected from an infected Persian lime tree in the north of Iran (Bani Hashemian and Aghajanzadeh, 2017) was graft-inoculated with bark patches onto several sour orange seedlings to create virus donor plants.

    The Transmission of CYVCV by A. spiraecola, A. gossypii, and Toxoptera aurantii was conducted in two experiments. The virus-donor plants were fed by virus-free aphids for 24 24-hour acquisition access period (AAP). Thirty adult aphids were placed on young flushes of each 30 lemon seedling receptor plants, and given 24- and 48-hour inoculation access period (IAP), separately. After inoculation, the receptor plants were treated with insecticide and maintained in an isolated insect-proof greenhouse at 22 ± 3 °C. 30 virus-free Eureka lemon seedlings were considered as the negative control.

    The appearance of CYVCV symptoms on the leaves of the donor plants and the inoculated receptor lemon seedlings was monitored and compared with non-inoculated control plants 6 months after the IAP in the experiments. The number of these plants was counted.

    Six months after inoculation, the presence of CYVCV in the symptomatic donor and receiver plants was confirmed by a two-step Reverse Transcription Polymerase chain reaction (RT-PCR) using a specific primer pair of the virus coat protein gene (Chen et al. 2015), following the extraction of the total RNA of the new flashes of seedling samples by SDS-Potassium acetate method (Bani Hashemian and Aghajanzadeh, 2017).

    To calculate the transmission efficiency, the number of approved infected plants by symptom evaluation and molecular test was divided by the total number of inoculated plants.

RESULTS and Discussion

   Six months after inoculation, the infected plants were counted. Then their infection was confirmed by a two-step RT-PCR test. The results of the first test showed that 6 months’ post-inoculation, the mean transmission rate of CYVCV by A. spiraecola, A. gossypii, and T. aurantii was 16.67%, 13.33%, and 26.67%, respectively, for 24h AAP/24h IAP. The mean transmission rate was 23.33%, 20%, and 33.33% for 24h AAP/48h IAP, respectively. By increasing the inoculation access period of aphids on virus-infected plants from 24 h to 48 h, the transmission rate increased. In the second test, all three species of aphids with an unknown AAP were collected on infected Persian lime trees in the orchard, under natural conditions and allowed to feed for 24 and 48 hours on Eureka lemon in the greenhouse. It was found that the tested aphids were capable of transmitting this virus. One of the important factors in the spread of viral disease is the presence of vectors in citrus orchards. The transmission of viruses by aphids has always been one of the most important ways, so the transmission of CYVCV by A. spiraecola from China (Zhang et al., 2018) and A. gossypii from Turkey (Afloukou et al., 2021) has been reported. Since the 3 species of studied aphids in this research are dominant aphids in citrus orchards (Aghajanzadeh et al., 1997; Alavi and Rezvani, 2007) and the presence of these aphids in virus-infected areas can be the reason for the virus transmission by these aphids.

Conclusion

    The present study confirmed that the virus is transmitted from Persian lime to Eureka lemon by dominant citrus aphids (A. spiraecola, A. gossypii, and T. aurantia) under controlled conditions. Future studies need to obtain more information concerning different aspects of CYVCV and its vectors to integrate pest management programs for vector control.