First Report of Endophytic Candida Ipomoeae Isolated from Ovules of Upland Cotton in Mississippi

Authors: Sacks, Erik; Abbas, Hamed; Mengistu, Alemu

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2006
Publication Date: 10/11/2006
Citation: Sacks, E.J., Abbas, H.K., Mengistu, A. 2006. First Report of Endophytic Candida Ipomoeae Isolated from Ovules of Upland Cotton in Mississippi. Plant Disease. 90:1362, 2006; DOI: 10.1094/PD-90-1362B

Interpretive Summary: Microbes are commonly found within field-grown upland cotton plants and can be an obstacle to obtaining clean plant tissue cultures. When cotton ovules from field-grown fruit were cultured, a species of yeast (Candida ipomoeae) that had not been previously observed on cotton grew out of some of the ovules. In earlier studies, this species of yeast had been observed on flowers of morning glory species and their insect pollinators. By identifying the contaminant, a targeted strategy for controlling it in cotton tissue cultures is now possible. Moreover this yeast and its relatives had been thought to grow only on dying flowers but finding it on cotton ovules from young growing fruit suggests that it might cause disease under some conditions.

Technical Abstract: Candida ipomoeae, a recently-described asexual yeast species, was isolated from ovules of upland cotton (Gossypium hirsutum) grown in-vitro. The isolate was identified by a perfect match between a partial 176 bp sequence for the D2 domain of the large subunit rDNA and sequences of two strains in the Genbank database. During August and September 2005, as part of an effort to rescue interspecific cotton hybrids, ovules were cultured in-vitro 4 d after pollination from plants grown in a field at Stoneville, MS. Fruit were washed in soap and water, then surface sterilized in a laminar flow hood by immersion in an aqueous solution of 2.6% sodium hypochlorite and 0.1% tween-20 for 10 min with intermittent shaking, followed by immersion in ethanol for 10 min, and then allowed to air-dry. Ovules were placed Petri dishes containing modified Murashige and Skoog media. Ovule cultures contaminated with C. ipomoeae were also observed for pure upland cotton ovules as well as those derived from interspecific crosses. Of 120 fruit derived from selfing the upland cultivar FiberMax 832, 22 produced ovule cultures contaminated with C. ipomoeae. Candida ipomoeae grew on media with or without 50 mg l-1 benomyl. Though C. ipomoeae grew slowly in culture, it caused infected ovules to become necrotic and die, in contrast to uninfected ovules. This report is the first of C. ipomoeae on cotton and this yeast was found on ovules of the most commercially important cotton species in a major cotton growing region.