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Effects of calcium nitrate and chlortetracycline on papilla formation, ml-o resistance and susceptibility of barley to powdery mildew

1986; Elsevier BV; Volume: 29; Issue: 1 Linguagem: Inglês

10.1016/s0048-4059(86)80043-1

1096-1178

R. E. Gold, James R. Aist, Beth E. Hazen, Mark C. Stolzenburg, Michael R. Marshall, Herbert W. Israel,

Powdery Mildew Fungal Diseases

Penetration sites of Erysiplie graminis f. sp. hordei on partially dissected coleoptiles of near-isogenic resistant and susceptible ml-o barley were examined in vitro to study the effects of Ca(NO3)2 and the Ca2+ chelator and ionophore, chloretracycline, on penetration efficiency and papilla formation. Compared to water controls, incubation on 10 mM Ca(NO3)2 allowed a marked expression of ml-o resistance. Time-course studies of coleoptiles incubated on Ca(NO3)2 showed that papillae, on the average, were initiated in the resistant isoline 1·0 h before penetration pegs; in the susceptible, 0·7 h after. These differences were coincident with a penetration efficiency of 5% and 62% and a papilla frequency of 87% and 77% in the resistant and susceptible coleoptiles, respectively. Growth rates of papillae in the two isolines were not significantly different during the first 2 h of development on Ca(NO3)2; however, papillae in the resistant isoline were twice the size of those in the susceptible isoline at the time of penetration peg initiation. In comparison to Ca(NO3)2, incubation on Chlortetracycline delayed papilla initiation relative to penetration peg initiation by 2·2 h on average, decreased papilla frequency nearly 30% and increased penetration efficiency to 74% in the resistant isoline, but caused no significant effects on these parameters in the susceptible isoline. These results suggested that earliness of the papilla response in the resistant isoline is an important component of the disease resistance mechanism, that Chlortetracycline neutralized the mechanism by delaying the average time of papilla initiation, and that ml-o resistance may be calcium-dependent.