Phytopythium vexans Associated with Apple and Pear Decline in the Saïss Plain of Morocco

Abstract

An extensive survey conducted in the Saïss plain of Morocco during the 2017–2018 growing season revealed that 35 out of 50 apple and pear orchards were infested with a pathogen that causes the decline disease. Morphological and phylogenetic tree analyses using the cox II gene allowed us to identify the pathogen as Phytopythium vexans. Interestingly, no Phytophthora and Pythium species were isolated. The occurrence and prevalence of the disease varied between locations; the most infested locations were Meknes (100%), Imouzzer (83%), and Sefrou (80%). To fulfill Koch’s postulate, a greenhouse pathogenicity test was performed on the stem and collar of one-year-old healthy seedlings of apple rootstock M115. Symptoms similar to those observed in the field were reproduced in less than 4 months post-inoculation with root rot disease severity ranging from 70 to 100%. The survey results evidenced that apple rootstocks, soil type, and irrigation procedure may contribute significantly to the occurrence of the disease. The disease was most prevalent in drip water irrigation and sandy-clay soil on wild apple rootstock. Accordingly, a rational drip advanced watering system and good sanitation practices could eliminate water stagnation and help prevent the onset of this disease. It was concluded that Pp. vexans occurrence may be strongly influenced by irrigation mode and type of soil. Therefore, the obtained findings of this study could help to better understand the recurrence of this disease and to develop a reliable integrated strategy for its management.

Characterization of Phytopythium Species Involved in the Establishment and Development of Kiwifruit Vine Decline Syndrome

“…In this work, we demonstrated for the first time the pathogenicity of P. litorale on kiwifruit plants and P. helicoides was reported for the first time on kiwifruit plants in Italy. P. litorale , P. helicoides and P. vexans were previously reported as pathogenic on other hosts, such as on Platanus orientalis [ 37 ], Rhododendron pulchrum [ 38 ], on citrus, apple, and pear [ 39 ], and on almond [ 40 ]. Moreover, P. helicoides was already reported as agent of root and collar rot on kiwifruit in China [ 41 ].…”

First report of a Canadian isolate of Phytopythium vexans causing root rot disease on apple and peach under laboratory conditions

“…The fruit baiting technique described by Jabiri et al. (2021) was used. Pear fruit were disinfected with 70% ethanol for 30 seconds and rinsed three times with sterile water.…”

“…Phytopythium vexans was reported as a pathogen causing root and crown rot and decline on fruit trees and woody ornamentals including apple, avocado, citrus, durian, ginkgo, flowering cherry, grapevine, kiwi, pear and red maple in the Canary Islands, China, Italy, Morocco, South Africa, Tunisia, Turkey, Vietnam and the USA (Benfradj et al., 2017; Baysal‐Gurel et al., 2021; Jabiri et al., 2021; Zhou et al., 2022). To the best of our knowledge, this is the first report of a Canadian isolate of P. vexans causing disease in apple and peach under laboratory conditions in Ontario.…”

The Hidden World within Plants

“…Indeed, many of them are harmful, with deleterious effects on their hosts. Four papers in this Special Issue describe pathogen interactions (bacteria, fungi, oomycetes and parasitic nematodes) with various plants [ 7 , 8 , 9 , 10 ]. The work of Havrlentová et al [ 7 ] reported the consequences of artificial Fusarium infection on the quality of oat grain ( Avena sativa ).…”

“…Factual observations made by the group of Lahlali [ 8 ] in the Saïss plain of Morocco during the 2017–2018 growing season reported several marked symptoms on apple and pear trees characteristic of the apple and pear decline diseases. After collection of 50 samples from five different locations in the areas of Fez-Meknes, the causal agent of the disease symptoms observed was an oomycete and not related to an infection by Phytophthora or Pythium species.…”