Naslov
First Report on Phytoplasmas infecting wild apples and wild pears in Croatia

Autori
Ježić, Marin ; Poljak, Igor ; Idžojtić, Marilena ; Liber, Zlatko ; Ćurković-Perica, Mirna

Izvornik
Plant disease (0191-2917) 100 (2016), 1; 207-207

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, vijest, znanstveni

Ključne riječi
Malus sylvestris; phytoplasma; Pyrus pyraster

Sažetak
Wild apple (Malus sylvestris /L./ Mill.) and wild pear (Pyrus pyraster /L./ Burgsd.) are direct ancestors of modern apple (M. domestica Borkh.) and pear (P. communis L.) cultivars grown and utilized for human consumption. These endangered species are native to central, western and southern Europe. They occur in a scattered distribution pattern as single individuals or in small groups. In late summer of 2012 and 2013, leaves of 140 wild pear and 61 wild apple trees from ten locations across Croatia were collected and tested for presence of phytoplasma DNA. Disease symptoms (yellowing leaves) were observed on nine apple and five pear trees that were sampled. Leaf veins were excised for total DNA extraction using CTAB containing extraction buffer as described in Šeruga et al. (2003) and amplification of phytoplasma 16S rRNA gene by using generic primers P1/P7 in a direct PCR assay followed by a nested PCR using primer pair R16F2n/R2 (Gundersen and Lee 1996). DNA isolation and PCR were performed twice with phytoplasma DNA extracts from infected in vitro grown Catharatnus roseus plants as positive controls as well as appropriate negative controls (DNA extracts from healthy plants and water control). Amplicons from consistently positive samples (~1, 2 kb) were subjected to (I) restriction fragment length polymorphism (RFLP) using restriction endonucleases AluI, KpnI and MseI, and to (II) reamplification of the phytoplasma DNA using original extracts with P1/P7 direct, followed with R16F2n/R2 nested primer pairs, purification using PCR purification kit (Qiagen), and sequencing. Sequences produced that way were searched for in the NCBI database using BLAST tool and identified. In total, phytoplasma DNA was detected in four wild pears (two of them being completely asymptomatic) and two wild apple samples from three different locations in Croatia. Their 16S rDNA sequences (NCBI accessions KP006694-KP006699) and RFLP patterns indicated the following affiliations: phytoplasmas from two wild pear trees and one wild apple tree from Moslavačka Gora (MOS_P13: KP006695, MOS_P5: KP006696 and MOS_M4: KP006698) belonged to Apple proliferation group (SrX) (100% identity with KJ676480 for example) ; phytoplasmas from one wild pear tree from Brinje (BR_P18: KP006694) and one from Moslavačka gora (MOS_P14: KP006697) belonged to Aster yellows group (SrI) (100% identity with KP662136 for example) and phytoplasma from one wild apple tree sampled in Vinkovci (VK_M4: KP006699) belonged to X–disease group (SrIII) (99% identity with KC283217 for example). This is the first report of wild apple infected with SrIII group phytoplasma, and third accidental finding of a phytoplasma belonging to this group in Croatia (Ježić et al. 2013). Phytoplasmas belonging to SrI and SrX groups were previously reported in Croatia on fruit trees grown in orchards (Križanac et al. 2010). Our findings confirm the presence of phytoplasmas belonging to these three groups (SrI, SrIII and SrX) in new hosts - wild apples and pears. The results imply that these phytoplasmas might infect a number of yet unknown hosts that either do not show any symptoms or show weak, uncharacteristic symptoms. Furthermore, they might pose a threat to commercially grown pears and apples.

Izvorni jezik
Engleski

Znanstvena područja
Biologija, Šumarstvo

POVEZANOST RADA