Induced resistance of cucumber plants against downy mildew disease

الملخص EN

Two greenhouse experiments conduction during autumn season of 2008 at El-Haram and El-Boston location in Egypt to study the effect of certain chemical inducers against downy mildew disease of cucumber caused by Pseudoperonospora cubensis.

Seedlings of cucumber hybrids i.e., Boshra, DP167 and 566 were sprayed at 20, 30, 40 and 50 after sowing with different chemical inducers i.e.

salicylic acid (SA), oxalic acid, bion, ethephon and catecol at concentrations of 0.05g and 0.1 g / L.

Cucumber plants treated with these chemical inducers at both concentrations developed different degrees of resistance.

Resistance induced by these applications resulted in percentage of protection ranged from 26.4 to 72.6 % as compared with untreated plants.

All chemical inducers reduced disease severity and gave high percentages of protection and increased number of flowers in most cases.

The most effective treatment was salicylic acid at o.05g / L which recorded the lowest disease severity on the three tested hybrids.

Hybrids, 566 were more resistance.

In addition, with plant height followed by Boshra but DP167 was less susceptible for the downy mildew.

All chemical inducer treatments increased in lignin contents in two tested hybrids (566 and DP 167) of cucumber when sprayed on cucumber plants with 0.1 g / L Plants which sprayed with salicylic acid showed the highest contents of lignin.