Bean yellow disorder virus: Parameters of transmission by Bemisia tabaci and host plant range

Abstract Bean yellow disorder virus (BnYDV) was recently identified as the first crinivirus (family Closteroviridae) that infects members of the family Leguminosae. It was first observed during the autumn of 2003, causing heavy losses in French bean (Phaseolus vulgaris L.) grown commercially in Spain. The virus is transmitted by the sweetpotato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) Q‐biotype, and disease symptoms resemble nutritional disorders consisting of interveinal mottling and yellowing in leaves, combined with stiffness or brittleness, and are typically produced on the middle to lower parts of the plant. Transmission experiments showed that 50% and 100% of B. tabaci adults acquired the virus after a feeding period of 3 and 7 h, respectively. Viruliferous whiteflies infected 66% and 100% of P. vulgaris plants after a feeding period of 12 and 24 h, respectively. The transmission efficiency of single whiteflies was 37% and persistence of BnYDV in the vector lasted up to 2 weeks with a half‐life of 9 days. BnYDV was transmitted to P. vulgaris, Pisum sativum L., Lens culinaris Medik., and Vicia faba L., but not to Vigna unguiculata L., Glycine max (L.) Merr., Cicer arietum L., and to crop species belonging to families of the Solanaceae and Cucurbitaceae. No virus was detected in field samples collected from 30 different species from Boraginaceae, Asteraceae, Geraniaceae, Lamiaceae, Leguminosae, Malvaceae, Scrophulariaceae, Thymelaeaceae and Verbenaceae. The restricted host range and efficient management of crops regarding whitefly infestation may be key elements in the control of BnYDV.     

Raspberry viruses affect the behavior and performance of Amphorophora agathonica in single and mixed infections

Pathogens may alter their hosts, which consequently increases transmission efficiency by vectors. We examined the effects of Raspberry leaf mottle virus [RLMV; Closterovirus (Closteroviridae)] and Raspberry latent virus [RpLV; Reovirus (Reoviridae)], alone and in a co‐infection in raspberry, Rubus idaeus L. (Rosaceae) cv. Meeker, on the behavior and performance of its vector, Amphorophora agathonica Hottes (Hemiptera: Aphididae). Longevity was increased in aphids feeding on all infected‐plant treatments compared with healthy plants, but aphid fecundity only increased in the co‐infection treatment. In a two‐way choice study between infected and healthy plants, aphids showed no difference in preference between plants after 30 min of exposure. After 24 h, aphids significantly preferred to settle on plants infected with RLMV over healthy, but healthy plants over plants infected with RpLV. There were no differences in settling preferences between healthy and co‐infected plants. An electrical penetration graph study showed no differences in aphid feeding behavior on plants infected with RLMV and RLMV+RpLV when compared with healthy controls. Our results are consistent with past findings that infected plant's impact vector performance and behavior, but also highlight the need to further investigate greater virus diversity and effects of mixed infections.     

Further Evidence for Limited Genetic Diversity among East African Isolates of Sweet potato chlorotic stunt virus

In Africa, the crinivirus Sweet potato chlorotic stunt virus (SPCSV) exists in two serologically and genetically distinct strains, geographically distinguished as a West African (SPCSV_WA) and an East African (SPCSV_EA) strain. To obtain a better understanding of the genetic diversity among SPCSV_EA isolates, the major coat protein (CP) and heat shock protein 70 homologue (Hsp70h) gene sequences of 24 further isolates of SPCSV_EA were determined and compared. SPCSV_EA diversity was also examined using available monoclonal antibodies (mAbs) to SPCSV_EA but there was no apparent coincidence between CP and partial Hsp70h gene nucleotide sequences and the subdivision of SPCSV_EA isolates by the mAbs into two serotypes, suggesting this latter may not be of great biological significance. The nucleotide (nt) sequences of isolates of SPCSV_EA displayed a high degree of conservation and the only variation observed consisted of a few base exchanges. Pairwise alignments of CP nucleotide sequences revealed differences of <4% between SPCSV_EA isolates. Comparisons with published SPCSV sequences confirmed a more distant relationship (up to 34.6% nt; 12% amino acid divergence) between the Hsp70h sequences of isolates of SPCSV_EA and SPCSV_WA and indicated that SPCSV_EA in East and Southern Africa is the more homogeneous than SPCSV_WA isolates from West Africa, North and South America, which were up to 12.4% nt divergent among themselves.