Authors:M. Stojaković, M. Ivanović, G. Bekavac, and Ž. Stojaković
Hybrid maize is produced using inbred lines that originate from genetically different (divergent) sources (heterotic groups). Inbred lines from at least two different sources that produce heterotic F1 progeny make up a heterotic pair. Thus far, a large number of heterotic pairs differing in their heterotic potential for grain yield and other traits have been identified. The BSSS × Lancaster heterotic pair is often used in the temperate zone to develop medium-late to late maize hybrids beloning to FAO maturity groups 500 to 700.The lines B73, Mo17 and derived lines are typical representatives of the BSSS × Lancaster heterotic pair. In order to determine the contribution of breeding to the increase of grain yield in B73 × Mo17 hybrids, lines had been introduced from America (the original versions of B73 and Mo17) or developed at the Institute of Field and Vegetable Crops in Novi Sad between 1980 and 2000 and represent three different cycles of selection. B73- and Mo17-type inbreds were used to study the combining abilities for grain yield of the lines and hybrids and assess the contributions of the selection cycles to grain yield increases in the lines and hybrids. With both types of germplasm, s the lines from the third cycle of selection had the highest grain yields. Based on the coefficient of linear regression, the increase of yield in the hybrids from the third selection cycle compared with the first cycle was found to be over 124 kg cycle with B73, and 677 kg cycle with Mo17 inbreds.
Authors:B. Purar, G. Bekavac, Đ. Jocković, É. Toldi Tóth, L. Kálmán, E. Raspudić, and M. Dimitrijević
Corn reddening (CR) was observed for the first time in Serbia in 1957. After that, it occurred periodically, mainly in the region of Banat. In 2002 and 2003, a severe outbreak happened in late July / early August. Initial symptoms were the occurrence of a red-violet color on the leaves, leaf sheaths, husks and the bare portion of internodes. The symptoms typically appeared at the milk maturity stage and the discoloration was the most intensive at top leaves, around the main vein and along the edges, from leaf base to tip. Soon after the occurrence of the symptoms, the affected plants wilted, the foliage dried rapidly, the red pigmentation disappeared for a greater part and finally plant died off. The ears were underdeveloped and gummous and kernels were shriveled and unfilled.Several experiments were conducted to determine a possible connection between CR occurrence and the studied factors. Corn stunt spiroplasma was not identified in the CR-affected plants, and there was no apparent relationship between CR and soil fertility or nematode species identified in soil and plant samples. Insecticide-treated plots had lower CR incidence than untreated (control) plots, indicating that biotic factors could be involved.
Authors:G. Bekavac, B. Purar, M. Stojaković, Dj. Jocković, M. Ivanović, and A. Nastasić
One of the major challenges for maize breeders is to develop hybrids that have an advantage in water-limited environments. A considerable number of grain production studies in maize include correlations between agronomic and physiological characteristics and grain yield. The main objective of this study was to identify traits that may relate to stay-green and grain yield in two maize synthetic populations. S
progenies were evaluated in an incomplete block design in four environments. Correlations and path coefficient analysis showed that the leaf water content had the greatest impact on stay-green. At the same time, stalk water content had a less direct effect on stay-green than it could be expected from its correlations. The highest positive direct effect on grain yield was determined for stay-green in both populations (P
=0.717** and P
=0.649**, respectively). Breeding for stay-green seems to be feasible in many applied breeding programs, especially due to its simplicity to score on a large number of entries.