First Report of Lasiodiplodia theobromae, L. pseudotheobromae, and Diplodia seriata Causing Bot Canker and Gummosis of Nectarines in Turkey


Endes A. , Kayım M., Eskalen A.

Plant Disease, vol.100, no.11, pp.2321, 2016 (Journal Indexed in SCI Expanded)

  • Publication Type: Article / Case Report
  • Volume: 100 Issue: 11
  • Publication Date: 2016
  • Doi Number: 10.1094/pdis-01-16-0036-pdn
  • Title of Journal : Plant Disease
  • Page Numbers: pp.2321

Abstract

In 2013, dieback symptoms were observed in young nectarine (Prunus persica) trees in Adana Province, Turkey. Symptoms included shoot-dieback, gummosis, and sunken necrotic bark lesions, which progressed into the trunk and resulted in the death of large sections of the trees. Three different fungi were isolated on potato dextrose agar amended with 0.01% tetracycline (PDA-tet) from symptomatic tissue (5 to 10 mm2). The morphological characteristics of isolates resembled those in the Botryosphaeriaceae family (Phillips et al. 2013). The rDNA internal transcribed spacer (ITS) (White et al. 1990) and β-tubulin (BT) (Glass and Donaldson 1995) loci were amplified using primer pairs. The DNA sequences of four isolates (CU9, CU10, CU12, CU13) were identical (GenBank nos. 100% to GQ469915 for ITS and 100% to DQ458859 for BT) as Lasiodiplodia theobromae. The sequences of four isolates of L. theobromae were deposited in GenBank (KF494364, KF494365, KF494367, and KF494368 for ITS and KF515961, KF515962, KF515964, and KF515965 for β-tubulin, respectively). Colonies of L. theobromae on PDA-tet were initially white, but became dark gray mycelium with age. The mycelium produced black pycnidia with conidia. The conidia were unicellular, ellipsoid with a rounded apex and a flat base, and became dark brown with age. They were 1-septate with a longitudinally striated apperance and averaged 24.2 ± 0.2 × 13.3 ± 0.1 µm (n = 50). The sequence of one isolate (CU15) was identical as L. pseudotheobromae (identity 100% to JX914479 and 100% to EU673111 for ITS and β-tubulin, respectively). The sequences of one isolate of L. pseudotheobromae were deposited in GenBank (KF494370 and KF515967 for ITS and β-tubulin, respectively). The colony of Lpseudotheobromae is more aerial than the colony of L. theobromae, but had the same color and similar morphological characteristics as the conidia. The conidia averaged 24.0 ± 0.3 × 14.1 ± 0.2 µm (n = 50). Results identified two isolates (CU14 and CU16) as Diplodia seriata (identity of 100% to KC527828 and 100% to DQ458856 for ITS and β-tubulin, respectively). The sequences of two isolates of D. seriata were deposited in GenBank (KF494369, KF494371 for ITS and KF515966, KF515968 for β-tubulin). Colonies of D. seriata on PDA-tet were gray-brown with dense aerial mycelium producing brown cylindroid to ellipsoid conidia, which were rounded at both ends and averaged 21.8 ± 0.2 × 9.3 ± 0.1 µm (n = 50). Pathogenicity tests were conducted with all three fungi on 1-year-old stem cutting (15 cm length) from healthy nectarine trees of cv. Francoise. Five cutting shoots were used for each isolate. One wound per shoot was made in the middle of stem cuttings using a 4-mm diameter cork borer and the wounded surfaces were inoculated with 4-mm diameter mycelial plugs of each isolate grown on PDA. Control shoots were inoculated with sterile PDA plugs. Inoculated shoots were incubated at 25°C for 2 weeks. Lesions similar to those on the original infected shoots were observed on all inoculated cutting shoots 15 days after inoculation, whereas control cutting shoots did not develop any disease symptoms. Inoculated fungi were reisolated from all cuttings to fulfill Koch’s postulates. L. pseudotheobromae previously has not been reported as a causal agent of trunk disease of fruit trees. To our knowledge, this is the first report of L. theobromaeL. pseudotheobromae, and D. seriata associated with nectarine dieback in Turkey.