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Zbog kontinuiranog sužavanja diverziteta germplazme koja se koristi u savremenim programima oplemenjivanja kukuruza, kako bi se ostvario željeni, kontinuirani napredak u selekciji, neophodno je vršiti introgresiju nove germplazme u postojeće heterotične grupe. Bogatstvo genetičkog diverziteta lokalnih populacija kukuruza, koje se čuva u bankama biljnih gena, predstavlja vredan izvor poželjnih svojstava. Značajna količina diverziteta, posebno kod stranooplodnih vrsta kao što je kukuruz (Zea mays L.), često je raspoređena i između i unutar srodnih grupa uzoraka. Kako bi se pravilno odabrao materijal iz gen banke potrebno je pre upotrebe/izbora najboljih uzoraka za programe introgresije u oplemenjivačke programe, sprovesti višefazne procese ispitivanja i odabira (stratifikacijski proces odabira). Na taj način se obuhvata široka varijabilnost s jedne strane, a sa druge, materijal dovodi do nivoa da se može uvesti u komercijalne programe oplemenjivanja. Takav koncept odabira materijala primenjen je u pripremnoj fazi ove disertacije. Cilj ove doktorske disertacije je bio da se proceni heterotični potencijal odabranih lokalnih populacija (31) kroz njihove performanse u test cross ukrštanjima sa tri divergentna elitna testera L217, L73B013 i L255/75-5. Odabrani testeri pripadaju opozitnim heterotičnim grupama Iowa Dent (L217), BSSS × Iowa Dent (L73B013) i Lancaster (L225/75-5), a u laboratorijska istraživanja uključena su, kao standardi za ultra rani materijal i dva dodatna testera (F2 i Polj17). Takođe je urađena molekularna karakterizacija primenom SSR markera, kako bi se uporedili podaci dobijeni u polju i laboratoriji, i zajedno doprineli proceni oplemenjivačke vrednosti ispitivanog materijala. Nakon ukrštanja populacija (31) i testera (3), dobijena 93 test cross hibrida testirana su u uslovima suvog ratarenja, na četiri lokacije (Zemun Polje, Pančevo, Sremska Mitrovica i Bečej), tokom dve godine, u dva ponavljanja, sa četiri bloka unutar svakog ponavljanja. Ukrštanjem testera međusobno (L217 × L255/75-5; L73B013 × L255/75-5; L255/75-5 × L73B013), proizvedeni su dvolinijski F1 hibridi, koji su korišćeni kao standardi u poljskim ogledima sa test cross hibridima. Površina elementarne parcele iznosila je 7,5m², pri čemu je svaki hibrid posejan u dva reda. Analiza varijanse je pokazala da su za sve ispitivane osobine izvori variranja (spoljašnja sredina, efekat oca-testera, efekat majke-populacije i njihove inerakcije) bili statistički značajni u najvećem broju slučajeva, izuzev trostuke inerakcije (spoljašnja sredina × otac × majka). Preko efekta majke (lokalne populacije) identifikovani su najbolji opšti kombinatori, pre svega za prinos zrna, ali i za ostale ispitivane morfološke osobine (18) od značaja za oplemenjivanje kukuruza. Lokalne populacije MB1267, MB1346, MB197, MB1569, MB1509 i MB2036 izrazile su najbolje opšte kombinacione sposobnosti (OKS) za prinos zrna. Pokazalo se da su se lokalne populacije tipa zubana uglavnom najbolje kombinovale za prinos zrna. Statistički značajne korelacije prinosa zrna lokalnih populacija per se i prosečne performanse lokalnih populacija u ukrštanju sa inbred testerima, ukazale su da je aditivni efekat gena prevalentni faktor za determinisanje opšte kombinacione sposobnosti (OKS) za prinos zrna. Utvrđene su daleko izraženije korelacije za visinu biljke, visinu klipa, odnos visine biljke do gornjeg klipa i visine biljke do vrha metlice, dužinu lista, širinu lista, broj listova iznad klipa, dužinu klipa, prečnik klipa, prečnik oklaska, dubinu zrna, broj redova zrna, broj zrna u redu i masu 1000 semena, između populacija per se i efekata populacija u test cross hibridima. Procenjena je i posebna kombinaciona sposobnost (PKS) za prinos zrna kao najznačajnije svojstvo. Istaknute su perspektivne test cross kombinacije koje prevazilaze referentnu vrednost od 75% prinosa F1 hibrida (standarda). Lokalne populacije MB1960, MB642, MB2006, MB1945, MB1346, MB1569, MB1450, MB1534, MB1509 i MB1665 pokazale su se dobro u ukrštanju sa testerom L217, dok su populacije MB1960, MB773, MB1798, MB1665, MB632, MB877 i MB1569 dale najbolje rezultate u ukrštanju sa inbred testerom L73B013. U ukrštanjima sa inbred testerom L255/75-5, najveći heterotični efekat ispoljile su populacije MB467, MB773, MB1346, MB1534, MB2249 i MB288... Due to the permanent narrowing of the germplasm diversity used in contemporary maize breeding programmes, in order to achieve continuous progress in selection, it is necessary to introgress a new germplasm into existing heterotic groups. The wealth of genetic diversity of maize landraces conserved in gene banks is a valuable source of desirable traits. A huge diversity, especially in cross-pollinated species such as maize (Zea mays L.), is often distributed both between and within related groups of accessions. With the intention of a proper selection of a gene bank material, it is necessary to perform evaluation and selection based on stratification selection process, prior to the use of the best of the accessions for their introgression into breeding programmes. In such a way, wide variability is encompassed, allowing the material to be introduced into the commercial breeding programmes. Such a concept of the gene bank material selection was applied in the initial phase of this dissertation. The aim of this PhD thesis was to assess the heterotic potential of selected landraces (31) via their performance in test-crossings to three divergent elite testers L217, L73B013 and L255/75-5. The selected testers belong to the opposite heterotic groups Iowa Dent (L217), BSSS × Iowa Dent (L73B013) and Lancaster (L225/75-5), respectively. Except for them, two additional testers (F2 and Polj17) were used in laboratory tests as checks for the ultra early maturing material. Furthermore, molecular characterization was performed by using SSR markers, in order to compare data obtained in the field and in the laboratory, jointly contributing to the assessment of the breeding value of the tested material. A total of 93 test cross hybrids were developed from the crosses of landraces (31) and testers (3). These hybrids were tested under rain-fed conditions, at four locations (Zemun Polje, Pančevo, Sremska Mitrovica and Bečej), during two-year trial, in two replications and four blocks within each replication. The tester to tester crosses (L217 × L255/75-5; L73B013 × L255/75-5; L255/75-5 × L73B013) resulted in single cross F1 hybrids used as checks in evaluation of test cross hybrids performances in field trials. The elementary plot size amounted to 7.5 m², whereby each hybrid had been sown in two rows. Analysis of variance showed that for all examined traits, the sources of variation (environment, effects of male-tester, effects of female-population and their interactions) were statistically significant in most cases except for triple interaction (environment × male × female). Effects of female component (landraces) were used to identify populations with the highest general combining ability (GCA) effect, for the grain yield primarily, but also for the rest of observed morphological traits (18) of importance for maize breeding. Landraces MB1267, MB1346, MB197, MB1569, MB1509 and MB2036 expressed the highest GCA effects for the grain yield. Dent landraces showed the highest GCA effects for the grain yield. Statistically significant correlations of the grain yield of landraces per se and the average performance of landraces in crosses to inbred testers indicated that the additive gene effect was a prevalent factor for determining GCA for the grain yield. Far more pronounced correlations were established for the following traits: plant height, ear height, the ratio of plant height to the upper ear to the plant height to the tassel tip, leaf length, leaf width, number of leaves above the ear, ear length, ear diameter, cob diameter, kernel depth, number of kernel rows, number of kernels per row and 1000-kernel weight. Special combining ability (SCA) was estimated for the grain yield, as the most important trait. The best yielding test cross combination that exceeded the reference value of 75% of yields of F1 hybrids (checks) were emphasized. Landraces MB1960, MB642, MB2006, MB1945, MB1346, MB1569, MB1450, MB1534, MB1509 and MB1665 performed well in the cross to the tester L217, whereas landraces MB1960, MB773, MB1798, MB1665, MB632, MB877 and MB1569 showed the best results in the cross to the inbred tester L73B013. The landraces MB467, MB773, MB1346, MB1534, MB2249 and MB288 expressed the highest heterotic effect in crosses to the inbred tester L255/75-5... |
