Leaf senescence as a factor in the competitive and synergistic interactions of Drechslera sorokiniana and Curvularia geniculata on Poa pratensis

Abstract

Drpo1.tr7irrrt t~fHortic~rrltrr,r. lo11.o Stote Urric~t~r~.sity. Arrrrs. I A , U . S . A . 50011 Hooc;t:s. C. F.. and J . P. M A D S~N . 1979. Leaf senescence as a factor in the competitive and synergistic interactions of Drc,c,lz.sl~~.o .sorokirrirrrltr and Crrrl,rrlorio gerric~rrlotcr on Potr pr.otrrr-.\is. Can. J . Bot. 57: 1706-17 1 I.The competitive and synergistic interactions of Dr.rc~lr.slrra .sorokiriiorro and Cr~r~rrlor~irr grrlit,rrloto on pathogenesis of leaf spot was evaluated on sequentially senescent leaves of Port ~~rrrtrr~.si.s. Leafage had no effect on the mean ni~mberoflesions produced from inoculations with D . soroki~lirttrct or C. g~t~i ( , i i l~l o alone. The combination of D . sor~okir~iorro and C . ,qt,t~it.rrl(rtti producetl 21 bignificant increase in the mean number of lesions between the youngest and oldest leaves at 20.25. and 30°C. Disease severity on leaves of all ages resulting from inoculations at 20 and 25°C was greatest in response to D . .so~.okirlitrtro alone. followed by the combination of organisms. and by C. ,qrr~ic.rrltrto alone. in descending order. No difference in disease severity occurred on leaves of different ages in reponse to the inoculations at 20°C. but a significant increase in disease occurred on the two oldest leaves at 25°C in response to inoculations with D . .ror.oki)liotim and to the combination ofolganisms. At 30 and 35°C. disease severity on leaves ofall ages was greatest in response to inoculations with the combination of organisms. D . sor.okirritriltr alone, and C. goricrrlotrr alone, in descending order. Disease severity increased from the youngest to the oldest leaves at 30°C in response to inoculations with the combination of organisms or with 0. .so~.okiilitrrro alone. Reisolations established that inoculations with D . .sorokitricitro alone resulted in successfirl establishment of the pathogen in the tissue of leaves of all ages at 20.25. and 30°C. At these temperatures, inoculations with C . grrric.rrloto alone produced a significantly higher level of reisolation from the youngest to the oldest leaves of the shoot. Reisolation of the individual organisms from leaves inoculated with both organisms showed that C. gc,rricllltrt~ established more successfillly than D . .sorokirritrrrtr in leaves of all ages as temperatures were increased. It was concluded that the synergistic increase in disease produced by the combination of I). .sor~okir~ittrlo and C . gt,r~icrrltr/ri at high temperatures is the result of increasetl high-temperature growth of C . gcrlicrrlottr which is probably more saprophytic than parasitic on senescing. heat-stressed leaves and does not reflect a high-temperature increase in virulence of this organism.

Evaluation of Pathogenicity of Bipolaris and Curvularia spp. on Dwarf and Ultradwarf Bermudagrasses in Florida

“…are weak pathogens that may be part of disease complexes. The current study supports conclusions of Muchovej and Couch (13) and Hodges and Madsen (7,8) that Curvularia spp. are efficient colonizers of senescing tissue (which may be induced by mowing or high temperatures), but do not cause disease symptoms in non-stressed turfgrass and thus should be considered as senectophytes, as defined by Couch (4).…”

“…Curvularia spp. have been shown to be stronger saprophytic colonizers than Bipolaris spp., particularly at higher temperatures (7,8). Thus, Curvularia spp.…”

“…are found colonizing the majority of turfgrass samples, including healthy tissue. Curvularia geniculata competes more aggressively for necrotic tissue than the pathogenic species, B. sorokiniana (8), including faster sporulation at 30°C and increased colonization of necrotic tissue. The ability of Curvularia spp.…”

Turf Yellowing Disease in Paspalum vaginatum (Turf Grass): Identification of Causative pathogen and Chemical Control

“…The disease severity is higher under heat stress, excessive rainfall, pest attack, compacted soil and poor drainage conditions. Hodges et al, 1979 reported that Curvularia spp. are only associated with more severe disease problems at higher temperatures (> 25°C) or when plant tissue is older and/or senescent.…”

Effect of Chlorophenoxy Herbicides on Soluble Sugars and on Pathogenesis byDrechslera sorokinianain Sequentially Senescent Leaves ofPoa pratensis

“…Leaf spot is progressively more severe on pots. Plants were grown in the greenhouse under l6 hr oflight daily sequentially older leaves of P. pratensis (8)(9)(10). Application of l0-4…”