Incidence, Molecular Detection, and Partial Nucleotide Sequencing of Some Viruses Causing Fig Mosaic Disease (FMD) on Fig Plants in Egypt

Abstract

Fig mosaic disease (FMD) is a viral disease that poses a significant danger to Egypt's fig-producing economy. During the two growing seasons 2017 and 2018, fig leaves and fruits displaying a variety of symptoms linked with fig mosaic disease (FMD) were collected and differentiated from the most famous fig-growing governorates in Egypt, Mersa Matruh, Ismailia, and Giza. Symptomatic samples were tested for the presence of fig mosaic virus (FMV), fig leaf mottle-associated virus 1 (FLMaV-1), fig leaf mottle-associated virus 2 (FLMaV-2), fig mild mottle-associated virus (FMMaV), fig latent virus 1 (FLV-1), fig fleck-associated virus (FFkaV), and fig cryptic virus (FCV) using reverse transcription-polymerase chain reaction (RT-PCR) with specific primers. Three viruses were detected in mixed infections and showed positive results. FMV was detected with infection rate 49% followed by FLMaV-2 with infection rate 21.8% and FLMaV-1 with infection rate 10.9%, respectively, whereas all tested samples were negative for the other viruses. According to the sequence and phylogenetic analysis, the Egyptian FMV isolate was closely related to other FMV isolates, particularly the Argentina ones (Acc. No. KP796424), with 99% identity. While FLMaV-1 showed more than 98% identity with reference isolate FLMaV-1 (Acc. No. LN873219), on the other hand, the isolate of FLMaV-2 showed 100% identity with reference FLMaV-2 isolate (Acc. No. FJ473383) based on phylogenetic analysis. Because fig output in Egypt is expanding, our findings suggest that greater attention should be paid to improving the phytosanitary condition of fig trees in Egypt.

Figure 1

Governorates of Egypt from which several fig varieties were sampled.

Figure 2

Fig mosaic disease symptoms on leaves and fruits observed in orchards from three governorates in Egypt, revealing a wide range of foliar discoloration and malformation (a) healthy, (b) mosaic, (c) chlorotic ringspot, (d) deformation, (e) chlorosis, (f) mottling, (g) chlorotic blotching, (h) chlorotic blistering, (i) vein clearing, (j) yellowing, (k) vein feathering, (l) yellow ringspots, (m) necrotic ringspot, and (n) deformation.

Figure 3

Incidence of FMV, FLMaV-1, FLMaV-2, FMMaV, FFkaV, FLV-1, and FCV infections using RT-PCR assays in samples from three Egyptian governorates and distinct fig varieties.

Figure 4

(a) RT-PCR amplification of fig mosaic virus (FMV) in fig samples as demonstrated by gel electrophoresis analysis. M: DNA marker ladder weight 100 bp, lanes (1–15): different symptomatic fig samples, lane 16: positive control, and lane 17: healthy fig sample used as a negative control. (b) Gel electrophoresis demonstrating RT-PCR amplification of fig leaf mottle-associated virus 1 (FLMaV-1) in fig samples. M: DNA marker ladder weight 100 bp, lanes (1–14): different symptomatic fig samples, lane 15: positive control, and lane 16: healthy fig sample used as a negative control. (c) Gel electrophoresis demonstrating RT-PCR amplification of fig leaf mottle-associated virus 2 (FLMaV-2) in fig samples. M: DNA marker ladder weight 100 bp, lanes (1–14): different symptomatic fig samples, lane 15: positive control, and lane 16: healthy fig sample used as a negative control.

Figure 5

Phylogenetic trees for the Egyptian isolate of FMV, FLMaV-1, and FLMaV-2 based on nucleotide sequences analysis using the maximum-likelihood method compared to other sequences in GenBank. Numbers above branches represent percentages of bootstrap values (1000 replicates), and accession numbers of viral sequences are reported within parentheses. (a) For the Egyptian isolate of FMV, the genetic relationship between the RdRp gene for RNA-dependent RNA polymerase and other isolates in GenBank is shown. (b) The genetic relationship between the Egyptian isolate of FLMaV-1's HSP70 gene for RNA-dependent RNA polymerase and other isolates in GenBank. (c) Phylogenetic analysis based on nucleotide sequences revealing the genetic relationship between the Egyptian isolate of FLMaV-2's HSP70 gene for RNA-dependent RNA polymerase and other isolates in GenBank. The bar represents 0.05 changes per site.