Characterization and Pathogenicity ofPythium-Like Species Associated with Root and Collar Rot of Kiwifruit in Turkey

Abstract

During the period of June to October in 2018, a widespread decline was observed on kiwifruit vines in the vineyards located in Altınordu, Fatsa, and Perşembe districts of Ordu province. The symptoms were associated with reddish-brown rots expanding from the root to the collar with sparse off-color foliage. Based on the percentage of the total infected samples across 18 vineyards, the most common oomycete species were Globisporangium intermedium (37.1%), Phytopythium vexans (34.3%), G. sylvaticum (14.3%), G. heterothallicum (11.4%), and Pythium dissotocum (2.9%). The morphological identification of isolates was confirmed based on partial DNA sequences containing the nuclear rDNA internal transcribed spacer region (rDNA ITS) and the mitochondrial cytochrome c oxidase subunit II (coxII) gene. The optimum growth temperature and the optimum pH of 5 species ranged from 22.98 to 28.25°C and 5.67 to 8.51, respectively. Pathogenicity tests on the seedlings of kiwifruit cv. Hayward revealed significant differences in virulence among isolates. Phytopythium vexans and G. sylvaticum isolates caused severe root and collar rot resulting in seedling death, while G. heterothallicum and G. intermedium isolates had relatively lower virulence. All Globisporangium spp. and P. vexans isolates significantly decreased plant growth parameters (plant height, shoot and root dry weights and root length); however, P. dissotocum caused very mild symptoms and did not affect these parameters of growth. To our knowledge, this is the first study reporting G. sylvaticum, G. heterothallicum, and G. intermedium causing root and collar rot on kiwifruit not only in Turkey but also in the world.

Genetic diversity of Actinidia spp. shapes the oomycete pattern associated with Kiwifruit Vine Decline Syndrome (KVDS)

“…(clade 7, Phytophthora sojae ), has already been reported in the literature on Actinidia spp. in sites affected by KVDS in Italy and Turkey 4 , 27 . There is also a record of the association of Phytophthora.…”

“…On this basis, the genetics of the host can shape the plant-pathobiome structure; in fact, Escudero-Martinez and co-workers 20 found that the plant endosphere has the potential to attract or filter the microbes inhabiting the rhizosphere. Thus, the aforementioned observations indicate that microbes are selectively chosen from within the root in response to multiple signals from the plant 21 – 23 , where in the context of KVDS, the pathogens follow the same trend, especially for the most studied (i.e., oomycetes) 24 – 27 .…”

Soil, rhizosphere, and root microbiome in kiwifruit vine decline, an emerging multifactorial disease

“…Phytopythium spp. have also been reported more broadly as root rot causal agents on kiwifruit in different countries, like China ( Wang et al, 2015 ), Turkey ( Türkkan et al, 2022 ), and Japan ( Shimizu et al, 2005 ). Phytophthora has also been isolated and identified as a kiwi root rot pathogen with symptoms similar to KVDS in France ( Baudry et al, 1991 ) and Turkey ( Akilli et al, 2011 ; Kurbetli and Ozan, 2013 ).…”

In vitro application of Eruca vesicaria subsp. sativa leaf extracts and associated metabolites reduces the growth of Oomycota species involved in Kiwifruit Vine Decline Syndrome

“…In Italy, the area planted with kiwifruit is currently 25,000 ha (repository http://dati.istat.it ). Recently, a new and complex disease called Kiwifruit Vine Decline Syndrome (KVDS), has appeared in different kiwifruit growing regions, being reported initially in Italy and then in other countries ( Donati et al., 2020 ; Türkkan et al., 2022 ). This has led to significant yield and economic losses in Italy, estimated to be around €300,000,000 in 2020 ( Tacconi et al., 2019 ).…”

“…KVDS epidemiological traits are still under investigation, and at present there are no effective methods of control to stop the disease quickly spreading worldwide ( Savian et al., 2022 ; Türkkan et al., 2022 ; Mian et al, 2022c ), although some experience exists ( Mian et al., 2023) . Biofumigation for controlling soilborne pests is an indispensable practice for achieving consistent crop quality and yields during the commercial production of many vegetable and high value crops with mainly narrow rotation systems ( Yu et al., 2019 ).…”