Yellow Virus Research Articles

AN AFRICAN PERSPECTIVE ON TOSPOVIRUSES

Tospoviruses, an emerging group of plant viruses, infect food crops and ornamental plants causing billions of dollars in losses worldwide. There are at least 28 Tospovirus species worldwide, most of which are found in tropical and subtropical environments. Despite having a largely tropical climate, Africa has only five reported species namely: Tomato spotted wilt virus (TSWV), Groundnut ringspot virus (GRSV), Impatiens necrotic spot virus (INSV), Tomato yellow ring virus (TYRV) and Iris yellow spot virus (IYSV). The low tospovirus diversity on the continent is mainly due to lack of surveys. Most Tospovirus species have only been reported in the last twenty-five years, yet no surveys have been done in most African countries. Most African countries lack institutional and infrastructural capacities to carry out virology research. This article reviews the characteristics and control of tospoviruses, with a bias towards those found in Africa.

FIRST REPORT OF ONION YELLOW DWARF VIRUS INFECTING

Onion (Allium cepa L., family Liliaceae) is one of the most important vegetable crops worldwide. Among all onion diseases, yellow dwarf disease caused by Onion yellow dwarf virus (OYDV) causes significant yield losses (Conci et al., 2003). OYDV (genus Potyvirus, family Potyviridae) is transmitted by aphids in a non-persistent manner and has a host range limited to Allium species and Narcissus. In July 2015, onions with irregular yellow striping, downward leaf curling, and plant stunting were observed in the Tungurahua province of Ecuador. Symptomatic (n=10) and healthy onion samples were screened by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) with OYDV polyclonal antibodies (Agdia, USA). All symptomatic onion samples reacted positively to OYDV antibodies in DAS-ELISA. Total RNA was isolated from a single plant with Triazol (Sigma, USA) and used in RT-PCR to amplify a DNA fragment of ca. 350 bp with universal primers designed in the potyviral NIb domain (Zheng et al., 2008). The amplicon was sequenced and the sequence (329 bp, GenBank accession No. KT590400) was analysed by BLAST and compared with the corresponding sequence of OYDV isolates from different countries. The partial NIb gene sequence of isolate OYDV-Ecuador showed a 91.1% and 98.1% maximum identity at the nucleotide and amino acid levels with isolates from Germany ((JX433020) and Italy (KF623533), respectively. A phylogenetic tree constructed with MEGA version 4.1 showed that the OYDV isolate from Ecuador was closely related to isolates from Germany, Italy, Argentina (JX433019) and USA (NC005029), all forming one cluster, whereas isolates from India (FR873734), Poland (KF862691), Japan (AB000474), Egypt (KT225546) and South Korea (AY390253) formed a separate cluster. To the best of our knowledge, this is the first report of OYDV on onion in Ecuador.

FIRST REPORT OF ONION YELLOW DWARF VIRUS IN GARLIC FROM NIGERIA

Garlic (Allium sativum L.) is one of the most important culinary herbs in the world. Several viruses belonging to genera Potyvirus, Carlavirus, and Allexivirus are known to infect garlic (Dijk, 1994; Walkey and Antill, 1989). This study was undertaken to investigate the status of viral infection in Nigerian garlic. Ten garlic bulbs showing mild to severe mosaic symptoms each were collected in March of 2015 from two fields in Kano and Sokoto region of Nigeria. Direct antigen coated (DAC)-ELISA was performed with antisera to Onion yellow dwarf virus (OYDV) (Bioreba, Reinach, Switzerland). All the samples were positive for OYDV. To confirm the presence of OYDV, reverse transcription (RT)-PCR was performed using primers published earlier (Majumder and Baranwal, 2014) and total RNA extracted from 100 mg of leaves with the RNeasy Plant Mini kit (Qiagen, Germany) according to the manufacturer’s instructions. Expected amplicons of ca. 320 bp for OYDV were obtained from all the samples tested, indicating infection by OYDV. Direct sequencing of the PCR products produced 276 bp long nucleotide sequences with 87% identity with sequence of an OYDV isolate from leek in Vietnam (GenBank accession No. DQ925454.1). Sequence obtained from the Nigerian isolate was deposited in GenBank under accession number KU854388. To our knowledge, this is the first report of OYDV in garlic from Nigeria.

Obtaining advanced generations from Solanum peruvianum PI 126944 in the genetic background of S. lycopersicum by immature seed culture

The accession Solanum peruvianum PI 126944 has been reported as resistant to different biotic and abiotic stresses. In previous works of the group, advanced generations were derived from two interspecific hybrids, including up to pseudo-F6 generations and backcrosses to the cultivated species of some of the pseudo-Fn generations. Moreover, resistance to Tomato yellow leaf curl virus (TYLCV) and Tomato spotted wilt virus (TSWV) was confirmed in some of the plant materials obtained. Here we describe the development of some advanced backcross generations between the cultivated tomato and S. peruvianum. Three backcross assays were carried out. In the first assay, 16 plants belonging to pseudo-F4, pseudo-F5 and pseudo-F6 generations were backcrossed as male parents to cultivated tomato. Immature seeds from the 408 fruits obtained were platted and 77 plants were regenerated. A total of 21 descendants obtained in the first assay were backcrossed as male parents in the second assay, which allowed the obtaining of 599 fruits and regeneration of 365 plants. The 19 male parents used in the third assay were obtained either in the first or in the second one. Seventeen of them were obtained in the first assay and two in the second. A total of 339 plants were regenerated from 519 fruits. A high number of the plants obtained in these assays has been acclimated. Some plants set fruits with viable seeds.

Pyramiding Ty-1/Ty-3 and Ty-2 in tomato hybrids dramatically inhibits symptom expression and accumulation of tomato yellow leaf curl disease inducing viruses

Tomato yellow leaf curl disease is a major constraint for tomato production worldwide and availability of new resistant materials is of great importance for breeding programmes. A phenotypic survey was undertaken to evaluate the level of resistance to the main tomato yellow leaf curl disease-inducing viruses Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus, in several commercial tomato cultivars, never characterised before. Seven weeks post inoculation, two cultivars resulted in high resistant phenotypes to both begomoviruses, and four were tolerant to at least one of them. In the two highly resistant hybrids (SJ12, RFT112), symptoms were completely absent and viral DNA was from 102 to 105 fold lower than in susceptible plants. Molecular marker analysis revealed that these genotypes harbour the resistant genes Ty-1/Ty-3 and Ty-2. Given their high resistance, they can be considered good candidates for cultivation and breeding in areas where incidence of TYLCD is very elevated.

Genetic Diversity of Tomato (<i>Solanum lycopersicum</i> L.) Begomovirus in Togo

Geminiviruses, in particular the members of the genus Begomovirus , are considered to be a major phytosanitary problem for tomato crops production in the world. They are responsible for yield losses of up to 20% to 100%. Regrettably, Togo is not spared from this situation. This work aims to show the genetic diversity of the begomoviruses affecting tomato crops production in Togo and their relationship with other begomoviruses. To achieve these objectives, 307 samples of tomato leaves and wild plant species with typical virus symptoms were collected in the Maritime, Plateaus, Central, Kara and Savannah regions and submitted to PCR analysis. The results revealed the presence of begomovirus in 25.40% of the analyzed samples. The PCR products obtained were submitted to direct sequencing. Phylogenetic analysis of sequences of DNA-A different regions of begomovirus identified in this work with that of other begomoviruses showed a nucleotide identity of 96% respectively for Tomato leaf curl Togo virus-Fontem, Tomato Leaf Curl Togo Virus , Ageratum leaf curl Cameroon Alphasatellite; 98% respectively to Tomato leaf curl Nigeria virus , Ageratum leaf curl Cameroon virus , Tomato leaf curl Cameroon virus-Fontem, Ageratum leaf curl Cameroon virus and 99% respectively to Tomato leaf curl Kumasi virus , Pepper yellow vein Mali virus Bazegahot and Pepper yellow vein Mali virus-Ouaga. These results suggest a high degree of genetic diversity of tomato begomoviruses identified in Togo.

Pathogenic Variation and Occurrence of Multiple Resistance-Breaking <i>Rice yellow mottle virus</i> Strains in Tanzania

Rice yellow mottle virus (RYMV) is a major biotic constraint for rice production in Africa. The resistance-breaking ability of Tanzanian RYMV strains and phylotypes (S4lm (Tz526), S4lv (Tz516), S4ug (Tz508), S5 (Tz429, Tz445), S6c (Tz486) and S6w (Tz539)) were tested by inoculating rice cultivars with RYMV1 resistant alleles (Gigante (rymv1-2), Tog12387 (rymv1-3), Tog5681 (rymv1-3), Tog5438 (rymv1-4), Tog5672 (rymv1-4+rymv2) and Tog5674 (rymv 1-5)) in a screen house. The results revealed multiple resistance-breaking strains and phylotypes on resistant cultivars Gigante, Tog12387, Tog5438 and Tog5681. However, the resistance breakdown was highly variable depending on the strain used, and disease severity ranged from 11% - 75.3%. The virulence potential of RYMV phylotype S4lm (Tz526) was similar to phylotype S6w (Tz539). The impact of strains and phylotypes on yield and its components in rice cultivars revealed highly significant differences (P ≤ 0.001). The lowest percent plant height reduction (2.8%), number of tillers per plant (2.5%), 1000 grain weight (2.7%), spikelet sterility (3.5%) and yield (5%) was recorded in rice cultivar Gigante inoculated with RYMV phylotype S6c (Tz486). Phylotype S6c (Tz486) despite being less virulent compared to other strains, its virus titer in rice cultivar Gigante (1.833) was higher than S5 (Tz429, Tz445) inoculated on Tog5674 (0.171, 0.207) and S6w (Tz539) inoculated on Tog5681 (0.283). The resistant-breaking strain S5 (Tz445) multiplied in resistant rice cultivar Tog5674 without inducing visible symptoms but showed positive reaction to ELISA with low virus titer. The strain S5 overcame wide range of resistant alleles including rymv1-2, rymv1-3, rymv1-4 and rymv1-5 resistance, with exception of rymv1-4 + rymv2. The current results gave a new perspective for future identification of resistance-breaking mutations through sequencing of the RYMV genome in infected rice cultivars and mutagenesis of an infectious viral clone useful for future RYMV resistant breeding programs.

トルコギキョウに発生したトマト黄化葉巻ウイルス・マイルド系統の配列解析

トルコギキョウに発生したトマト黄化葉巻ウイルス・マイルド系統の配列解析

Assessment of Genetic diversity and Principle component Analysis among Bhendi Yellow Vein Mosaic Virus resistant Okra Genotypes

Assessment of Genetic diversity and Principle component Analysis among Bhendi Yellow Vein Mosaic Virus resistant Okra Genotypes

First Report of Alternanthera yellow vein virus From Eclipta prostrata in Pakistan

First Report of <i>Alternanthera yellow vein virus</i> From <i>Eclipta prostrata</i> in Pakistan

&lt;i&gt;Imperata yellow mottle virus&lt;/i&gt;: An Emerging Threat to Maize, Sorghum and Pearl Millet in Burkina Faso

Imperata yellow mottle caused by Imperata yellow mottle virus (IYMV) of the genus Sobemovirus was first characterized on Imperata cylindrical and Zea mays in Burkina Faso. The disease has been reported in several localities of the country but its ecology and epidemiology are poorly known. In particular, only I. cylindrical and maize have been reported within IYMV host range. The aim of this study was to investigate the experimental host range of the virus. Mechanical inoculation of a mixture of four IYMV isolates to 18 plant species, including four crops (maize, rice, sorghum and pearl millet) and 14 wild grasses showed clear mottle symptoms in maize, sorghum and pearl millet and two wild grass species (Setaria verticillata and Rottboellia exaltata). Symptom development was confirmed by Enzyme-linked immunosorbent assay and reverse transcription–polymerase chain reaction (RT-PCR). Infection of crop species by IYMV depended on cultivars tested. Therefore, proportions of positive cultivars were 16/36 in maize, 4/10 in sorghum and 4/9 in pearl millet, respectively. Studies on virus-host interactions using individual virus isolates showed two pathogenic patterns. Three out of the four isolates tested infected all plant species and cultivars. In contrast, the fourth IYMV isolate could infect only one maize cultivar. These results expand the previously known host range of IYMV from two to five species, indicating a narrow host range. Among the new characterized host species, sorghum and pearl millet are important cereal crops. Therefore, Imperata yellow motte disease is a potential threat for the cereal crop production and its ecology and epidemiology should be thoroughly investigated.

Amaranthus sp. and Eleusine indica are natural hosts of Iris yellow spot virus in Zimbabwe

<i>Amaranthus</i> sp. and <i>Eleusine indica</i> are natural hosts of <i>Iris yellow spot virus</i> in Zimbabwe

Genetic diversity of Croton Yellow Vein Mosaic Virus and betasatellites associated with yellow vein mosaic disease of Sida acuta in India

Genetic diversity of Croton Yellow Vein Mosaic Virus and betasatellites associated with yellow vein mosaic disease of Sida acuta in India

토마토품종의 토마토황화잎말림바이러스병에 대한 저항성 평가

토마토품종의 토마토황화잎말림바이러스병에 대한 저항성 평가

MOLECULAR CHARACTERIZATION AND IDENTIFICATION OF GARLIC VIRUS D ASSOCIATED WITH GARLIC IN INDIA

Garlic virus D (GarV-D) was detected in garlic plants exhibiting yellow stripes, dwarfing and mosaic symptoms, by reverse transcription-polymerase chain reaction (RT-PCR). These plants were co-infected with Onion yellow dwarf virus (OYDV). Amplicons of ca. 750 bp and ca. 450 bp from infected plants were cloned and sequenced. By BLASTn analysis, virus under study (GenBank Accession No. KP862055) shared highest 88% nucleotide (nt) identity with GarV-D (HQ681944) from Iran in a region corresponding to coat protein (CP) and nucleic acid binding protein (NABP), whereas 450 bp sequence (KR045605) in a region corresponding to partial CP shared highest 91% nt similarity with GarV-D (KF550407) from Australia. The sequence (KP862055) shared 78-87.7% nt and 82.1-91.2% amino acid (aa) identity with previously reported isolates of GarV-D from different parts of world. To our knowledge this is first report of GarV-D occurring naturally on garlic from India.

First Report of Iris yellow spot virus Infecting Green Onion (Allium fistulosum) in the United States

First Report of <i>Iris yellow spot virus</i> Infecting Green Onion (<i>Allium fistulosum</i>) in the United States

Pepper huasteco yellow vein virus Associated to Sweet Pepper Disease in Sinaloa, Mexico

<i>Pepper huasteco yellow vein virus</i> Associated to Sweet Pepper Disease in Sinaloa, Mexico

Coat protein and movement protein based characterization of Lima bean yellow mosaic virus disease in Karnataka (India)

Yellow mosaic disease caused by a Begomovirus has become an important production constraint in lima bean cultivation in Karnataka. The begomovirus causes Lima bean Yellow Mosaic Virus (LYMV), was characterized by sequencing the CP and MP genes. Distinct viral gene specific PCR product corresponding to CP and MP gene ~1000 bp and ~900 bp was obtained. The PCR product were sequenced and compared with the reference Begomoviruses sequences from the NCBI blast database. LYMV (GKVK isolate) shared highest nucleotide identity (98%) with Horsegram yellow mosaic virus (HgYMV) of French bean isolate (Accession No. AM932425.1). Phylogenetic analysis of CP and MP gene sequences of LYMV-GKVK isolate showed that LYMV-GKVK clustered with isolates of HgYMV Horsegram and French bean isolates of Tamil Nadu, Srilanka, Karnataka. Based on Nucleotide Identity begomovirus infecting lima bean at Bangalore is to be considered as strain of HgYMV. The disease was also successfully transmitted to French bean and Horsegram when experimentally transmitted using whitefly vector. Therefore, the begomovirus causing yellow mosaic disease of lima bean is considered as strain of HgYMV. Lima bean is infected by Mungbean Yellow Mosaic India Virus (MYMIV) according to earlier reports whereas our study the reports the infection of HgYMV on Lima bean from Karnataka. Thus it is concluded that Lima bean is infected by both MYMIV and HgYMV in different geographical locations.

First Report of Sugarcane yellow leaf virus Infecting Grain Sorghum (Sorghum bicolor) in the United States

First Report of <i>Sugarcane yellow leaf virus</i> Infecting Grain Sorghum (<i>Sorghum bicolor</i>) in the United States

TOMATO YELLOW LEAF CURL YUNNAN VIRUS, A NEW BEGOMOVIRUS SPECIES ASSOCIATED WITH TOMATO YELLOW LEAF CURL DISEASE IN CHINA

Yellow leaf curl disease was observed in tomato (Solanum lycopersicum) plants in Yunnan Province, China. Analysis of the full-length viral DNA isolated from an infected tomato plant indicated that the viral genome contained 2759 nucleotides (nt) and had the typical genome structure of begomoviruses. Further analysis of the viral sequence showed that it shared the highest nt sequence identity (86.0%) with Tomato yellow leaf curl Vietnam virus (TYLCVNV) previously identified in Vietnam. The virus is therefore a new Begomovirus species for which the name Tomato yellow leaf curl Yunnan virus (TYLCYnV) has been proposed. The betasatellite was also obtained and showed the highest nt sequence identity (70.1%) with Tomato yellow leaf curl China betasatellite (TYLCCNB).