Bean golden yellow mosaic virus from Chiapas, Mexico: Characterization, pseudorecombination with other bean-infecting geminiviruses and germ plasm screening

The complete nucleotide (nt) sequences of the cloned DNA-A (2644 nts) and D NA-B (2609 nts) components of Bean golden yellow mosaic virus (BGYMV-MX) fr om Chiapas, Mexico were determined. The genome organization of BGYMV-MX is similar to that of other Western Hemisphere bipartite geminiviruses (genus Begomovirus). Infectivity of the cloned BGYMV-MX DNA components in common b ean (Phaseolus vulgaris) plants was demonstrated by particle bombardment an d agroinoculation. BGYMV-MX was identified as a BGYMV (previously type II B GMV) isolate based on sequence analyses, sap-transmissibility, and pseudore combination experiments with other bean-infecting begomo-viruses. On the ba sis of differences in the DNA-B hypervariable region, symptom phenotype, an d properties of infectious pseudorecombinants, BGYMV-MX may represent a dis tinct strain of BGYMV. Pseudorecombination experiments further established that BGYMV symptom determinants mapped to DNA-B, and that BGYMV-MX was most closely related to BGYMV from Guatemala. A Tomato leaf crumple virus (TLCr V) DNA-A/BGYMV-MX DNA-B pseudorecombinant was infectious in bean, establish ing that a viable reassortant can be formed between begomovirus species fro m different phylogenetic clusters. Bean germ plasm representing the two maj or gene pools (Andean and Mesoamerican) was screened for response to BGYMV- MX with three methods of inoculation: sap-inoculation, particle bombardment , and agroinoculation. Andean germ plasm was very susceptible and similar r esults were obtained with all three methods, whereas Mesoamerican germ plas m showed resistance to BGYMV-MX, particularly with agroinoculation.