Studies on Pythium Leak Rot Disease on Potato Tubers During Storage in Egypt.

Abstract

Pythium leak is a post-harvest disease of potato tubers manifested by a wet, spongy rot that can quickly lead to complete tuber decay.Two isolates of Pythium sp. from Salhia and Ismailia districts were isolated from naturally infected potato tubers. The morphological characters examined were dimensions of oogonia ,oospores , antheridia , hyphal swelling and oospores wall thickness. Oogonia were mostly terminal and the hyphal swelling were mostly intercalary in the two isolates. These morphological characters of Salhia and Ismailia isolates were in accordance with the reference data of Pythium ultimum var, ultimum. . Pathogencity tests of the two P.ultimum isolates of Salhia and Ismailia revealed that Ismailia isolate capable to cause higher incidence of infected tubers and the depth of internal rot was more than that in case of Salhia isolate. Cultivar reactions indicated that Diamant cultivar was the most susceptible to both P.ultimum isolates, however, Maradona and Baraka cultivars were the least susceptible ones. In the same time, Spunta , King Edward, Alpha ,Desiree and Drage showed moderately reactions . The optimum temperature for growth of both isolates of P.ultimumgrowth on PDA was 30 o C . The lowest growth was observed at 5 and 40 o C. Laboratory screening tests with four fungicides indicated that Previcure-N inhibited completely at 150 ppm.Accorrding to the available literature knowledge; this is the first report of infection with leak rot of potato tubers caused by P. ultimum var. ultimum in Egypt.

Feasibility of Volatile Biomarker-Based Detection of Pythium Leak in Postharvest Stored Potato Tubers Using Field Asymmetric Ion Mobility Spectrometry

“…Studies have also reported the recovery potential of infected potato tubers when cooled below 18 °C ( ). El-Marzoky [ 46 ] also observed the lowest growth of P. ultimum isolates on PDA at 5 °C. The leak’s overall infection reduction could be the effect of the exposure of the pathogen to lower air temperature around the tuber shortly after the inoculation [ 17 , 36 ].…”

“…potatogrower.com/). El-Marzoky [46] also observed the lowest growth of P. ultimum isolates on PDA at 5 • C. The leak's overall infection reduction could be the effect of the exposure of the pathogen to lower air temperature around the tuber shortly after the inoculation [17,36]. Storage temperatures below 18.3 • C are also reported as advantageous to limit bruise and remove field heat in typical storage designs to avoid Pythium leak infection [37].…”

Factors affecting the infection by Fusarium oxysporum and F. proliferatum and the progress of garlic clove rot disease during storage

“…Thus, a closely established relationship exists between the presence of the pathogen F. oxysporum and F. proliferatum in the garlic bulb at harvest and the incidence and progress of cloves rot disease in storage. Differences in susceptibility of garlic cultivars to F. oxysporum and F. proliferatum mainly due to genetic factors (Shalaby et al, 2012;Palmero et al, 2013;El-Marzoky, Hanan and Shaban, 2014;Elshahawy et al, 2017;Ignjatov et al, 2018;Jannatun et al, 2020;Filyushin et al, 2021;Anisimova, Olga et al, 2021). In this study, out of storage temperatures affecting the development of cloves rot disease of garlic Balady (the highest susceptible) and Seds 40 (the least susceptible) cultivars after 30, 60, and 90 days of storage, 30 °C was the most affecting ones and gradually increased disease severity index of cloves rot caused by both fungi on stored bulbs of both garlic cultivars after 90 days of storage, followed by 25 °C.…”