EFECTIVENESS OF VISUAL SELECTION OF MAIZE UNDER CONDITIONS OF ARTIFICIAL STALK INFECTION

U uvjetima umjetne infekcije stabljike smjesom izolata više uzročnika truleži od ukupno 85 linija kukuruza porijeklom iz sorte Beljski zuban vizualno je izabrano 47. lzabrane su linije otpornije prema truleži i lomu stabljike, međutim to nije imalo većeg učinka na smanjenje loma i polijaganja kod izabranih testkrižanaca. Nije utvrđena korelacijska povezanost između otpomosti linija prema truleži odnosno lomu i polijeganju stabljike i otpornosti njihovih testkrižanaca prema lomu i polijeganju stabljike. Vizualnim izborom povećan je relativni prosječni prinos u odnosu na standard s 96,3 na 101,3%. Svih pet najrodnijih testkrižanaca je u skupini izabranih, ali nažalost s povećanim sadržajem vode u zrnu kod berbe. Prinos testkrižanaca nije bio u korelaciji s otpornošću linija "per se" prema truleži, odnosno lomu i polijeganju stabljike.Of the 85 maize inbred lines originating form the variety Beljski zuban, 47 were chosen by visual selection under conditions of artificial stalk infection with a mixture of several stalk rot pathogens. The selected lines were more resistant to stalk rot and breakage, however without any appreciable effect on reduced breakage and lodging in selected testcrosses. No correlation association was found between line resistance to stalk rot, stalk breakage and lodging and resistance of their testrcrosses. By visual selection relative average yield was increased from 93.3 to 101.3% in comparison with the standard. All five most yielding testcrosses are in the group of selected testcrosses, but unfortunately with increased grain moisture at harvest. Yield of testcrosses was not in correlation with line resistance per se to stalk rot, stalk breakage and lodging

COMBINING ABILITY OF SOME NEW Bc MAIZE INBREDS

U dvogodišnjim poljskim pokusima na dvije lokacije ispitana je kombinacijska sposobnost sedam srodnih samooplodnih Bc linija kukuruza križanih s četiri testera (Bc252, F2, Bc16881, Rx370-811). Efekti opće kombinacijske sposobnosti (OKS) linija za svojstvo sadržaj vode u zrnu su bili opravdani u sva četiri pokusa, za prirod zrna u dva, a za broj poleglih i polomljenih biljaka u tri pokusa. Linija Bc21491 je imala najviše pozitivne efekte OKS za svojstvo priroda zrna, međutim najkasnija je s najvećim pozitivnim efektom OKS za sadržaj vode u zrnu kod berbe. Linije Bc01/84, Bc706-43 i Bc24331 su se pokazale kao rane s negativnim efektom OKS za sadžaj vode u zrnu kod berbe. Linije Bc24331, Bc01/84 i Bc706-9 su se na osnovi efekata OKS pokazale kao najotpornije prema lomu, dok su najbolji opći kombinatori za broj poleglih biljaka bile inbred linije Bc706-43, Bc706-9 i Bc24331. Specifična kombinacijska s posobnost je najznačajnija za svojstvo priroda zrna gdje su u tri pokusa dobiveni opravdani efekti SKS. Križanci Bc24331xBc16881, Bc24331xRx370-881, Bc406-87xF2 i Bc21491xBc252 su se istakli pozitivnim efektima SKS za prirod zrna. To su uz rani hibrid Bc706- 9xBc252 i gospodarski najvrednije kombinacije. Primijenjena shema linija x tester pokazala se djelotvornom u praktičnom oplemenjivanju kukuruza.Combining ability of seven related Bc maize inbreds, crossed with four testers (Bc252, F2, Bc16881, Rx370-811) was tested in two year field trials, at two locations. GCA effects of the lines were significant for grain moisture in all four trials, for grain yield in two trials, and for lodged and broken plants in three trials. The line Bc21491 had the highest positive GCA effects for grain yield. However, it was latest, with the highest positive GCA effect for harvest grain moisture. The lines Bc01/84, Bc706-43, and Bc24331 proved to be late with negative GCA effect for harvest grain moisture. Based on GCA effects, the lines Bc24331, Bc01/84 and Bc706-9 proved as most resistant to breakage. The best general combiners for number of lodged plants were the lines Bc706-43, and Bc706 and Bc24331. Specific combining ability was omst significant for grain yield. In three trials, SCA effects were significant. The crosses Bc24331 x Bc16881 ,Bc24331 x Rx370-811 , Bc406-87 x F2, and Bc21491 x Bc252 were distinguished by their positive SCA effects for grain yield. Along with the early hybrid Bc706-9 x Bc252, they are economically the most valuable combinations. The applied line x tester scheme proved to be effective in practical maize breeding

Changes of genetic diversity of maize inbred lines over four decades of hybrid breeding in the Bc institute revealed by SSR markers

In this paper, changes of genetic diversity of the most important maize inbred lines used for hybrid production within the Bc Institute in the 1970s, 1980s, 1990s and 2000s were examined using the SSR markers. The average number of alleles per SSR locus was 3.14, 3.43, 3.07 and 3.25 for lines from 1970s, 1980s, 1990s and 2000s, whereas the number of private alleles for the same four decades was 8, 4, 0 and 6, respectively. Mean genetic distance among inbreds within decades steadily decreased over time from 0.64 in 1970s to 0.57 in 2000s, but the observed differences were not statistically significant. The clustering of the studied inbred lines indicates the exploitation of a known BSSS x LSC heterotic pattern within the Bc Institute maize breeding program. The overall results show that recycled inbred lines within these pools do not decline in genetic variation over the past 40 years