Effect of irrigation system and climatic Conditions on maize infection by leaf spot Disease [electronic resource].

Includes references.

Twenty nine maize genotypes (13 inbreds, 13 hybrids and 3 populations) were evaluated for their resistance to maize leaf spot caused by Helminthosporium maydis and 3 other agronomic traits under flooding and sprinkler irrigation at Nubaria Agric. Res. Station and under flooding irrigation at Sakha Agric. Res. Station in 1999. From 2000-2003, further evaluation for leaf spot resistance was pursued only at Sakha location under flooding irrigation on 12 genotypes only (3 inbreds, 3 sing/e¬ crosses, 3 three-way crosses and 3 populations). Results of 1999 showed higher disease severity under surface irrigation at Sakha as compared to surface irrigation at Nubaria for most tested genotypes. Moreover, disease severity at Nubaria under surface irrigation was higher than under sprinkler irrigation. All tested inbreds were either MR or MS while all single, three-way crosses and populations were either R or HR. The treatments were arranged in a randomized complete block design with 3 replications. . Resistance response in F, hybrid plants seemed to be due to maternal or paternal effects of either parent. In some other cases, the F, hybrid resistance response was due to complementary effects of both parents. Results for disease severity at Sakha from 1999-2003 showed that disease severity on maize genotypes had increased with increased temperature and relative humidity and decreased solar radiation during disease development in September as for years 1999, 2002 and 2003 except for SC.122, TWC.310, Tep.S and Comp.S populations which were not affected, to some extent, by changes in these three factors. The opposite trend was found for years 2001 and 2002. These results are of big importance to any breeding program aiming at developing inbred lines resistant to maize leaf spot disease. In regard to results of grain yield, days to mid-silking and plant height at Nubaria in 1999 under surface and sprinkler irrigation systems results showed that grain yield and plant height of tested genotypes was less under sprinkler irrigation as compared to that under flooding irrigation. Also, silking was delayed by 1-3 days under sprinkler irrigation. Due to importance of results for grain yield, plant height and silking date under both irrigation systems, results need to be confirmed for these traits over a wide range of environments.

Summary in Arabic.

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