The Titer of Citrus Yellow Vein Clearing Virus is Positively Associated with the Severity of Symptoms in Infected Citrus Seedlings

Citrus yellow vein clearing virus is a new member of the genus Mandarivirus in the family Alphaflexiviridae. Citrus yellow vein clearing virus (CYVCV) is the causal agent of citrus yellow vein clearing disease and is widely distributed in Pakistan, India, Turkey, and China. CYVCV is transmitted from citrus to citrus by Dialeurodes citri, grafting, and contaminated knife blades, threatening citrus production. In this study, four infectious full-length cDNA clones of CYVCV (namely AY112, AY132, AY212, and AY221) derived from CYVCV isolate AY were obtained through yeast homologous recombination and inoculated to ‘Eureka’ lemon (Citrus limon Burm. f.) by Agrobacterium-mediated vacuum infiltration. Pathogenicity analysis indicated that the clones AY212 and AY221 caused more severe symptoms than AY112 and AY132. Northern blot and quantitative reverse transcription PCR (qRT-PCR) analyses showed that the titers of virulent clones (AY212 and AY221) were significantly higher than those of attenuated clones (AY112 and AY132) in the infected ‘Eureka’ lemon (Citrus limon Burm. f.) seedlings. Subsequent comparative studies of viral infectivity, accumulation, and symptoms induced by AY221 in nine citrus cultivars indicated that (i) the infectivity of AY221 varied from 25% to 100% among different cultivars; (ii) ‘Oota’ ponkan (C. reticulata L.) showed the lowest infection rate with mild symptoms, which might be a useful resource for CYVCY-resistance genes; (iii) CYVCV titer was positively associated with the symptom development in infected citrus seedlings. In general, this report revealed the biological properties of CYVCV, thus laying a foundation for further investigation of pathogenic mechanisms in this virus.

The Whitefly Dialeurodes citri: A New Pest on Citrus in Tunisia?

Whiteflies invaded citrus orchards in Tunisia in the 90’s. Two species: Aleurothixus floccosus and Parabemisia myricae have been recorded successively infesting citrus and causing severe damage in Cap-Bon (North-East of Tunisia). These pests were first controlled by several insecticidal applications but with a relative efficiency. Then two biological control programs have been deployed completing the action of native natural enemies especially for P. myricae. The result was a very satisfactory control of both whitefly species, to a point that they almost disappeared from orchards for about 30 years. In 2017, a third whitefly species, identified as Dialeurodes citri, was observed during a prospection in citrus orchards in Takelsa region (Cap-Bon). It was a common species in Algeria, but never caused damage in Tunisia. In 2020, D. citri was found again with very high population densities in the regions of Menzel Bou Zelfa (Cap-Bon) and Tunis. These observations confirmed its change of status and spread in Tunisia. The main morphological and biological traits to distinguish between D. citri and the other two whitefly species, already recorded in Tunisia, were described and first observations on its infestation were reported. Some recommendations to manage this new pest are given.

Populasyon değişimş Antalya ili turunçgillerinde zararlı Turunçgil Pamuklu Beyazsineği Aleurothrixus floccosus maskell ve Turunçgil Beyazsineği Dialeurodes citri (ashmead) (Hemiptera: Aleyrodidae) ile bazı doğal düşmanlarının populasyon gelişmeleri

Bu çalışmada iki beyazsinek türü (Aleurotrhrixus floccosus ve Dialeurodes citri) ile bazı doğal düşmanlarının (Chilocorus bipustulatus, Oenopia conglobata, Chrysoperla carnea, Cales noacki ve Encarsia lahorensis) populasyon değişimleri 2012 ve 2013 yıllarında Gıda, Tarım ve Hayvancılık Bakanlığı’na bağlı, BATEM (Batı Akdeniz Tarımsal Araştırma Enstitüsü)’in mandarin, altıntop, washington portakal, yafa portakal ve limon bahçelerinde incelenmiştir. Örneklemelerde beyazsinek nimflerinin populasyon değişimini belirlemek için iki farklı örnekleme metodu kullanılmıştır. Yaprak örneklemeleriyle sürdürülen bu metodlar rastgele örnekleme ve yönlendirilmiş örnekleme yöntemleridir. Çok az yaprak üstünde kümülatif bir dağılım gösterdiği için A. floccosus’da yönlendirilmiş örnekleme yöntemi kullanılmıştır. Nispeten daha çok yaprak üstünde ve rasgele bir dağılım gösterdiği için D. citri için rastgele örnekleme yöntemi kullanılmıştır. Bunlara ilaveten sarı yapışkan tuzaklar kullanarak ergin populasyon yoğunlukları belirlenmiştir. İlk ergin uçuşlarının mart sonu- nisan ayının ilk haftasında görüldüğü D. citri ve A. floccosus’un haziran ayında populasyon yoğunluğunun arttığı görülmüştür. Aynı şekilde zararlıların nisan ayında yumurta bırakmaya başladığı ve eylül ayına kadar yumurta bırakmaya devam ettiği, kışı nimf veya pupa döneminde geçirdiği saptanmıştır.

HARM OF SUITING CITRUS CROPS PEST

The article discusses the harm, biology and morphology of sucking pests of citrus crops. Citrus whitefly on citrus, in case of early settlement and high density, yield can be reduced up to 30%. It can give up to 3-4 generations. In the conditions of the Bukhara and Khorezm regions of Uzbekistan, citrus whitefly (Dialeurodes citri.) Can develop, which is distinguished by its smaller size and yellowish color.Citrus aphids One of the most common and dangerous pests of lemons and tangerines is aphids. It most often affects the plant during the period of active growth of young shoots, settling on them and quickly sucking juice from them. By this, it slows down its development; one can also observe that the leaves of citrus dry and fall, and young growth dries out

An assessment of population fluctuations of a hemipteran citrus pest in the northeast of Algeria: A case study from Guelma region

<p>In this study, which takes place in the northeast of Algeria at the region of Guelma between January 2016 and June 2017, we were able to follow the spatio-temporal evolution of the main hemipteran pests in an orchard of citrus (orange variety). This monitoring showed the presence of 12 hemipteran species, their appearance in the orchard is closely linked to the sap flow. The most abundant species was <em>Aleurothrixus floccosus</em>. The number of the other species that found was very small or absent in most of the time. We also noted that <em>Aonidiella aurantii</em> and <em>Chrysomphalus dictyospermi</em> had a preference to develop in the center of the tree while the other species found, which are: <em>Dialeurodes citri, Aphis gossypii</em>, <em>Aphis spiraecola</em>, <em>Lepidosaphes beckii, Parlatoria ziziphi, Saissetia olea, Coccus hesperidum</em>, <em>Coccus pseudomagnoliarum</em> and <em>Icerya purchasi</em>, were found in the sunniest parts of the tree.<br /><strong> </strong></p>

Identification of Dialeurodes citri as a Vector of Citrus yellow vein clearing virus in China

In 2009, a new citrus viral disease caused by Citrus yellow vein clearing virus (CYVCV) was first discovered in China and now CYVCV is widely distributed in the field. CYVCV is transmissible by grafting and is spread by aphids from lemon to bean, and from bean to bean. However, until now, no vector has been shown to transmit CYVCV from citrus to citrus. In this study, after a 24-h acquisition access period (AAP), CYVCV was tested for in Dialeurodes citri (Ashmead), Panonychus citri McGregor, and Aphis citricidus (Kirkaldy) by quantitative RT-PCR. After an AAP of 48 h, groups of adults of D. citri, P. citri, and A. citricidus were given a 48 h inoculation access period on cultivar Daidai sour orange seedlings. Three, 6, and 12 months post-transmission by D. citri, CYVCV was detected in the receptor plants, and the mean incidence of infected trees was 31.9, 39.1, and 39.1%, respectively. CYVCV was not transmitted to citrus by P. citri or A. citricidus. This is the first report of the ability of D. citri to transmit CYVCV from infected to healthy citrus under laboratory conditions.