Studies on fungi associated with tomato fruits and effectiveness of some commercial fungicides against three pathogens

Abstract

Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994, Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes, Alternaria alternata, Rhizopus stolonifer and A. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory against A. alternata, A. niger and R. stolonifer. At 10 and 100 micrograms ml-1, neither of the fungicide caused a noticeable inhibition of Alternaria rot. At 1000 micrograms ml-1 benlate, rovral and sumisclex completely prevented Alternaria and Aspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused by A. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 micrograms ml-1). Sodium hypochlorite has good curative properties against fruit rots especially those caused by A. alternata and A. niger.

Antagonistic effect of two isolates ofTrichoderma harzianumagainst postharvest pathogens of tomato (Lycopersicon esculentum)

“…Our results of postharvest pathogens isolated from tomato fruits are consistent with the previously reported studies (Abdel-Mallek et al 1995;Wade et al 2003;Fajola 2006), whereas, most of fungal isolated pathogens were around the same fungi of these investigations. In our investigation, the results of the pathogenicity tests showed that Rhizopus sp.…”

Inhibitory Effects of Na-Hypochlorite and Heating on the Mycobiota Associated with Fruits or Juice of Passion (Passiflora edulisSims) in Uganda

“…In this respect, the use of Na-hypochlorite has been proved to be effective for the control of passion fruit rot-development caused by fungal species most commonly encountered from passion fruits (Ismail, 2001). Also, Na-hypochlorite is reported to be lethal to fungal propagules and fungi in vitro (Mehrotra, 1998) and to have good curative properties against tomato fruit rots especially those caused by Alternaria alternata and Aspergillus niger (Abdel-Mallek et al, 1995). Control of brown spots of passion fruits (caused by A. alternata and A. passiflorae ) is by pruning and destroying the debris and by spraying the passion trees (vines) regularly with fungicide (Snowdon, 1990).…”

“…The technique used for enumeration and isolation of mycobiota was adopted from Abdel-Mallek et al (1995). Individual samples were put in clean polyethylene bags and aliquots of 100 ml of sterilized tap water were added.…”

“…Some of the postharvest treatments used to destroy fungal spores are chemical (Abdel-Mallek et al, 1995; Dugan and Roberts, 1997; Schirra et al, 1997; Mehrotra, 1998), biological (Janisiewicz et al, 1998; Mari and Guizzardi, 1998) or a combination of chemical and heat treatments (Johnson et al, 1990; Schirra et al, 1997; Obeta and Ugwuanyi, 1997). …”

Rhizopus stolonifer (Soft Rot)

“…Among the identified fungi, R. stolonifer was considered as the one to cause fast and extensive rotting of a wide range of vegetable and fruit hosts (Adikaram, 1993). In markets in Asiut, Egypt, Abdel-Mallek et al (1995) and Ziedan and Farrag (2008) reported that R. stolonifer from diseased tomatoes and peaches was isolated at a frequency of 35.9% and 56.5%, respectively. This last value is only exceeded by Aspergillus niger and A. alternata.…”