Analysis of genetic variability among maize genotypes to drought tolerance

Drought is a major abiotic factor, which significantly decreases final grain yield and its quality in maize. Predictions of global climate changes for 21st century, towards higher air temperatures, greater evapotranspiration and more frequent occurrence of drought, emphasize the importance for improved maize ability to withstand adverse environmental conditions, and the necessity of employing the multidisciplinary approach for studying the characteristics that contribute to its increased drought tolerance. The material maintained within The MRI “Zemun Polje” gene bank, considering its size (5806 genotypes) and huge genetic variability of the accessions, offers the great opportunity for modern maize breeding for different purposes (e.g. drought tolerance). Field testing for drought tolerance was performed on the entire MRI gene bank collection, subjected to controlled drought in Egypt, as well as to conditions of moderate water deficit in Zemun Polje and Skopje. In order to expose them to drought stress at aproximately the same vegetative stage, grouping the accessions into different maturity groups (acording to the duration of their vegetative period), was necessary. Identification and selection of the most drought tolerant genotypes was performed by visual scoring of drought related secondary traits (ASI - anthesis silking interval, barrenness, seed set, grain filling and stay-green) at each location, and by measuring yield / plant under moderate water deficit conditions. Besides good performances per se in field, the information on combining ability of selected material, in order to classify it into heterotic groups, was necessary to form the core. Therefore, the most drought tolerant genotypes were crossed to three inbred testers from heterotic groups that mutually combined well (BSSS, Lancaster and independent source). It is very important that 6 genotypes had a good combining ability with all three observed heterotic sources, making them a new, completely different source of favourable germplasm. Obtained results revealed the formation of core collection for drought tolerance, comprising 13 local populations, 13 introduced populations and 15 introduced maize inbred lines. Increased tolerance to drought of all genotypes at flowering, was followed by a small ASI (up to 2,69 days), lower barrenness rate (up to 13,16%), higher seed set rate (up to 93,08%), as well as higher grain filling rate (up to 95,38% ), while the trait of stay green was the most pro