Occurrence of Leveillula taurica Cleistothecia on Honey Mesquite in Southern Texas.

Abstract

Prosopis glandulosa J. Torrey (honey mesquite) is a widespread tree that serves as an important food and cover resource for wildlife in the south plains, gulf marshes, and scrub prairies of Texas. In the fall of 2005, lower leaflets of P. glandulosa were found to be infected with the asexual reproductive structures (Oidiopsis taurica (Lév.) Salmon) of Leveillula taurica (Lév.) Arnaud in the Lower Rio Grande Valley (LRGV) of Texas. Primary conidia (69 [±2.9] × 14 [±1.1] μm) were lanceolate and apically pointed, and secondary conidia (68 [±3.0] × 16 [±1.2] μm) were obovate and cylindrical. Closer investigation revealed that some plants near the edges of mesquite thickets showed evidence of ascocarp development. Immature ascocarps were yellow and turned a dark brown as they reached maturity. Mature cleistothecia (185 [±33] μm in diameter) were often clustered in groups of 5 to 10 on leaflets and were characterized by a few mycelioid appendages. The maximum number of asci found in a cleistothecium was 28 and each ascus contained two ascospores (39 [±1.7] μm × 17 [±1.3] μm). L. taurica has been observed on Prosopis spp. (P. chilensis, P. glandulosa, and P. juliflora) in Mexico (1) and on P. chilensis in Texas (2), however, to our knowledge, this is the first report of sexual reproduction on P. glandulosa in the LRGV. The presence of sexual reproductive structures on mesquite may indicate the importance of 'alternate' hosts as a site for genetic recombination in this organism since the fungus is a pathogen of vegetable crops such as peppers, tomatoes, and onions.