Seed Transmission of Three Viruses in Two Pear Rootstock Species Pyrus betulifolia and P. calleryana

Abstract

Viral seed transmission causes the spread of many plant viral diseases. Pyrusbetulifolia and P. calleryana are important rootstock germplasms for pear production in China. This study revealed the widespread infection of apple stem grooving virus (ASGV), apple chlorotic leaf spot virus (ACLSV), and apple stem pitting virus (ASPV) in maternal trees of P. betulifolia and P. calleryana by nested multiplex reverse transcription-polymerase chain reaction (nmRT-PCR) assays. Seeds from eight P. betulifolia and two P. calleryana trees had positive rates of 15.9–73.9%, 0–21.2%, and 40.4% for ASGV, ASPV, and ACLSV, respectively. At the cotyledon and 6–8 true leaf stages, seedlings grown from seeds of infected trees gave positive rates of 5.4% and 9.3% for ASGV, 6.7% and 15.6% for ACLSV, and 0% and 2.7% for ASPV, respectively. Incidence in nursery P. betulifolia seedlings of 10.1%, 5.3%, and 3.5% were determined for ASGV, ACLSV, and ASPV, respectively. The nucleotide sequences of coat protein (CP) and movement protein coding genes of both ASGV and ASPV, and CP gene of ACLSV from maternal trees, seeds, and seedlings were analyzed. Sequence identities and phylogenetic comparison with corresponding sequences from GenBank demonstrated that molecular variation occurred within ASGV, ACLSV, and ASPV isolates, with most sequences determined here had close relationships with reported isolates infecting pear or formed independent clades. This is the first report on the seed transmission and the molecular characteristics of these viruses infecting two rootstock species. These findings provided important evidence in management effort for pear viral diseases.

Viruses of Apple Are Seedborne but Likely Not Vertically Transmitted

“…Similarly to the work of Li et al [ 21 ] on the transmission of ACLSV, ASGV, and ASPV in two pear rootstock species, we found that these three viruses can be detected from the seedcoats of seeds extracted from fruits of infected maternal trees. The rates at which these three viruses were detected in untreated seeds were higher in our experiments (92.7%, 95.9%, and 92.1%, respectively) vs. the rates reported by Li et al [ 21 ] (40.4%, 73.9%, and 21.2%, respectively).…”

“…Similarly to the work of Li et al [ 21 ] on the transmission of ACLSV, ASGV, and ASPV in two pear rootstock species, we found that these three viruses can be detected from the seedcoats of seeds extracted from fruits of infected maternal trees. The rates at which these three viruses were detected in untreated seeds were higher in our experiments (92.7%, 95.9%, and 92.1%, respectively) vs. the rates reported by Li et al [ 21 ] (40.4%, 73.9%, and 21.2%, respectively). These differences may reflect biological differences between the host species studied ( P. betulifolia and P. calleryana vs. M. domestica ), genetic divergence among virus isolates, or differences in the virus detection methodologies employed.…”

“…Pome fruit seeds are therefore typically considered at a low risk for facilitating virus dissemination [ 17 , 18 ]. However, a recent report documented that ACLSV, ASGV, and ASPV are both seedborne and seed transmitted in two pear rootstock species, Pyrus betulifolia and P. calleryana , wherein the three viruses were detected in both seeds and progeny seedlings of infected maternal trees [ 21 ]. These findings demonstrated that ACLSV, ASGV, and ASPV are seedborne in these host species, i.e., they contaminate or infect the seedcoats of the seeds extracted from fruits produced by infected maternal trees; however, it remains unclear whether any of these viruses are present in embryonic tissue in these species.…”

Genetic diversity and phylogenetic relationships of apple chlorotic leaf spot virus isolates from Malus, Pyrus and Prunus hosts in Latvia

“…The natural spread of ACLSV in the field has been reported, but suggested transmission by eudosylaimoid nematodes, aphids (Myzus persicae) or pollen was not confirmed (Mink, 1993;Šutić et al, 1999). Recently, Li et al (2022) demonstrated the presence of ACLSV in seeds from infected P. betulifolia and P. calleryana trees, indicating that the virus can also be transmitted by seeds. Previously, ACLSV has been detected in apple and quince seedlings (Posnette & Cropley, 1964).…”

Spectroscopy Imaging Techniques as In Vivo Analytical Tools to Detect Plant Traits

“…Infections by pathogens are positively connected with economic loss and raise concerns regarding food security. For instance, viral infection in pear plants successfully triggers physiological and biochemical activities [109,110]. Similarly, bacterial attack can also reduce plant productivity, as indicated by lower biochemical and metabolic activities.…”