Resistance Response of Maize Germplasm to Downy Mildew [Peronosclerospora philipinensis]

Two experiments to study responses of resistance of maize germplasm to downy mildew (Peronosclerospora philipinensis) have been conducted. Both experiments were arranged in randomized block design with two replication. The treatments in each experiment (2014 and 2016) were 70 maize accessions. The accessions were planted in planting distant of 75 cm × 20 cm, in 5 m rows, resulting in 20 plants per row. In every 10 rows, two check varieties were planted, i.e. one susceptible and one resistant variety. Ten days prior to planting, the soil was fertilized with mixed fertilizers consisted of urea, ZA, SP36, and KCl at a dose of 100, 100, 100, and 100 kg/ha, respectively. Fertilization II and III was given at 30 days after planting, and 45 days after planting with a dose of 100 kg urea/ha. As a source of inoculum downy mildew, around the repeated plot was planted with varieties Anoman variety (susceptible variety) that was inoculated with a suspension of downy mildew pathogen. Observation was conducted at 25, 35, and 55 days after planting, with the standard score of resistant to downy mildew, followed: 0–10% = resistant, 11–25% = moderately resistant, 26–50% = moderately susceptible, >50% = susceptible. The result of the experiments showed that there were 5 accessions resistant to downy mildew (P. philipinensis), i.e. CML 440×MR4-9-30-3, 664, 60, 572, and 554 with the intensity of downy mildew infection ranged from 5 to 10%. Twelve other accessions were classified as moderately resistant, i.e. CML 440×MR4-9-98-2, 440×MR4-9-98-4 CML, CML 440×MR4-9-124-1, 66, 71, 319, 108, 73, 48, 105, 554, and 682 with intensity of infection ranged from 13 to 25%. At the same experiments, the average intensity of downy mildew infection on susceptible check varieties reached 100 percent.