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The phenomenon of genotype by environment interaction (GEI) represents permanent interest for breeders, geneticists and biometricians with its practical and theoretical aspects. We investigated GEI for grain yield of medium early maturity maize (Zea mays L.) hybrids from the official variety trial network by the Department of Protection and Recognition of Varieties of the Republic of Serbia that includes experimental maize hybrids on eight sites over two years. Environmental variables explained 77.6% and 60.7% of the GEI variation for two consecutive years, respectively. Factorial regression combined with stepwise procedure revealed the model which includes variables precipitation in July (pr7), minimum temperature in May (mnt5), maximum temperature in May (mxt5) and insolation hours in April (sh4), in 2004, and environmental index (EI) and average temperature in September (mt9) in 2005, to be the most explanatory models in the region of Vojvodina (Serbia) in two consecutive years. These results provide a base for further research in GEI and stability analysis, and are a useful tool in characterizing the sub-regions of maize growing area and extending the existing results to new sites. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 451-03-68/2020-14/200032]

Studies on genetic gains in grain yield and other traits may be very useful in providing necessary information to plant breeders about the effectiveness of their breeding programs. The objective of this research was to analyze changes in grain yield, yield stability and morphological characteristics of maize hybrids released in Serbia between 1978 and 2011. Five hybrids, representatives of different breeding periods, were chosen for this study. Field trials were conducted during 2013 and 2014 at three locations in Serbia. The estimated genetic gain per breeding period was 440 kg ha(-1) which corresponds to an approximate annual linear increase in yield of 63 kg ha(-1). Changes in morphological characteristics were presented graphically, compared to the reference value and defined by the third period of breeding. Plant and ear height, kernel row number, number of kernels per row and leaf number were reduced compared to the third breeding period. Kernel depth showed higher variation through periods while in other analyzed traits, major changes in value through the periods were not found. Stability analysis distinguished the hybrids from the sixth and seventh period of breeding as the most stable, whereas the most unstable were representatives of the fifth and third period. Changes in certain morphological traits and yield stability have led to an increase in the genetic potential of the hybrids most probably through the increased tolerance to biotic and abiotic stress factors.

The aim of this study was to investigate field emergence parameters, number of plants that reached reproductive stage and yield of seed lots with different count of abnormal seedlings. In standard germination test these seedlings are discarded from the count of germinated seed, presuming that they will not develop into normal plants. Five lots of hybrid NS 640 with different percentage of abnormal seedlings were tested. Results showed that in favourable environment conditions, large number of abnormal seedlings emerged, reached reproductive stage and participated in yield formation. However, emergence of seed lots with high percentage of abnormal seedlings was longer than for lots with small number of abnormal seedlings. Laboratory germination and germination energy were more correlated with indicators of field emergence rate, while total percentage of germinated seedlings (normal and abnormal) was more correlated with grain yield. However, it can be expected that in adverse environment conditions, abnormal seedlings are less likely to develop into normal plants. Cilj ovog ispitivanja bio je da se kod partija semena sa različitim udelom atipičnih ponika ispitaju parametri brzine klijanja u polju, broj biljaka u reproduktivnoj fazi i prinos. Ovakvi ponici se u standardnom testu klijavosti ne ubrajaju u klijava zrna, jer se pretpostavlja da neće dati normalnu biljku. Testirano je pet partija hibrida NS 640 sa različitim udelom atipičnih ponika. Rezultati su pokazali da je u povoljnim uslovima veliki broj atipičnih klijanaca nikao, dostigao reproduktivnu fazu i učestvovao u formiranju prinosa. Sa druge strane, nicanje partija sa velikim brojem atipičnih klijanaca je bilo usporeno. Laboratorijska klijavost i energija klijanja su bile u većoj korelaciji sa parametrima brzine nicanja, dok je ukupna klijavost (normalni i atipični klijanci) bila u većoj korelaciji sa prinosom. Ipak, u nepovoljnim uslovima spoljašnje sredine, atipični klijanci imaju manje šanse da se razviju u normalnu biljku.

One of the most important phases in commercial maize breeding programs is the assessment of the value of newly-developed progeny by testing in hybrid combinations. In this study, non-parametric stability measures were applied to analyze the genotype × environment interaction and to assess phenotypic stability of two half-sib maize populations, each consisting of 40 genotypes, across 9 variable environments. Non-parametric tests of significance determined the presence of qualitative interaction for grain yield in both observed populations. Results of the stability analysis showed no significant differences between the two progeny groups indicating that the used testers did not bring significant increase in stability in either of the analyzed half-sib populations. Individual genotypes were also compared based on grain yield stability within both progeny groups using the stability parameters Si(1), Si(2), Si(3) and Si(6). Association between the grain yield and stability indices Si(1) and Si(2) of the analyzed genotypes was presented graphically enabling the identification of genotypes which can be recommended for further breeding process as the most promising ones. The correlations between grain yield and stability parameters were tested by Spearman’s rank correlations. Both progeny groups (HS1 and HS2) showed no significant correlations between the grain yield and stability parameters Si(1) and Si(2), but the rank correlations between Si(1) and Si(2) values were very strong and highly significant. Highly significant negative correlations were found between grain yield and stability indices Si(3) and Si(6) in both progeny groups, and very strong and highly significant correlations were found between Si(3) and Si(6) values. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR31073: Improvement of maize and sorghum production under stress conditions]

Grain yield is a result of the combined effects of genotype, environment and their interaction. The importance of the genotype x environment interaction is that it causes different reactions of maize hybrids when they are grown in different environments. This study was performed to analyse discriminativeness, representativeness and relationships of test locations for a grain yield of nine maize hybrids grown at nine locations in a 5 year period 2007-2011 in the South Pannonian Basin, a part of central and south European corn belt. A three-way mixed model revealed the highly significant (P lt 0.01) REML variance components for year x location, year x location x hybrid and residuals. The grain yield was also significantly (P lt 0.05) affected by the year x hybrid and location x hybrid interaction effect. The sites regression (SREG) model was used to determine whether mega-environments exist, and/or whether the test locations used are suitable for maize hybrids zoning. To determine which environmental factors mostly affect the hybrid x location interaction, the partial least squares regression approach was applied. The "which-won-where" pattern of the SREG biplot confirmed a rank change interaction between the locations, indicating the presence of strong and unpredictable rank-change location-by-year interactions. The main characteristic of the grouping pattern was poor repeatability, since most of the locations that made one mega-environment tended to change from year to year. Therefore, it is preferable to develop hybrids with high yielding potentials, wide adaptability and stability, rather than to develop hybrids specially designed for narrow agro-ecological regions.

Two main questions in programs introgressing exotic maize germplasm into temperate materials are the choice of available exotic sources to work with, and the proportion of exotic germplasm that should be incorporated into adapted germplasm. The objective of this study was to compare effects of different proportions of tropical maize inbred line NC298 in hybrids male parent on grain yield and grain moisture content, using method of orthogonal polynomials. Methods of direct crosses and backcrosses were used to form four hybrid groups (six hybrids each) containing 0, 25, 50 and 75 percent of tropical exotic germplasm, respectively, by their male parent (or one half of mentioned proportions in the corresponding hybrids). The linear components of the germplasm proportions sum of squares, were significant (p lt 0.01) for both grain yield and moisture content and the cubic effect (p lt 0.05) for grain yield only. Results in this study clearly suggested backcross foundation populations with an adapted line to be appropriate selection sources for both grain yield and grain moisture content. Inkorporacija egzotične germplazme u genetički materijal umerenog klimata nameće dva osnovna pitanja: izbor i proporciju odgovarajućih egzotičnih izvora. Cilj ovog istraživanja je bio poređenje efekata različitog udela tropske linije kukuruza NC298 u očinskoj komponenti hibrida, na prinos zrna i udeo vode u zrnu, primenom metode ortogonalnih polinoma. Metodom direktnih i povratnih ukrštanja dobijene su četiri grupe hibrida (po šest hibrida u svakoj) koje su sadržale 0, 25, 50 i 75 procenata tropske germplazme, u njihovoj očinskoj komponenti (ili jednu polovinu pomenutih procenata u odgovarajućim hibridima). Sume kvadrata linearne komponente, bile su značajne (p lt 0.01) za prinos zrna i za udeo vode u zrnu, dok su sume kvadrata kubnog efekata bile značajne (p lt 0.05) samo za prinos zrna. Rezultati ovih istraživanja jasno ukazuju da su početne populacije nastale povratnim ukrštanjem sa adaptiranom linijom pogodan izvor za selekciju na prinos zrna i udeo vode u zrnu.

GGE biplot analysis is a method used to identify mega-environments (i.e grouping, division of locations, which are examined in a joint mega-environment), evaluate the genotypes within these mega-environments and select the most discriminating and the most representative locations within a single mega-environment. This paper analyses twenty hybrids at five locations in 2006 and 2007. For the first year, mega-environment analysis showed a greater similarity between locations Rimski Šančevi, Pančevo and Srbobran classifying them into one group (the potential mega-environment), whereas Sombor and Sremska Mitrovica were classified into another group. In 2007 grouping was different from the previous in that Rimski Šančevi and Sombor comprised one mega-environment, whereas Sremska Mitrovica and Pančevo comprised the other, while Srbobran was separated from both groups. Discrepancies in formation of the mega-environments can be explained by different climatic conditions in two research years. This was confirmed by analyzing the ideal environment where the discrepancies between those two years are also reported. The results in this study suggest that more reliable data on the mega-environments formation should be sought in multi-year studies of the certain genotypes in a number of locations. Multilokacijski ogledi za prinos zrna izvode se svake godine kako bi se ocenila reakcija hibrida kukuruza na različite agroekološke uslove. Osnovni problem ovog načina ispitivanja hibrida jeste prisustvo interakcije genotip-spoljna sredina. Uzimajući u obzir interakciju, GGE biplot analiza pruža vizuelni prikaz ponašanja hibrida u različitim sredinama. Dvadeset hibrida kukuruza je ispitivano u toku 2006. i 2007. na pet lokaliteta po godini. Rezultati su predstavljeni preko GGE biplotova u cilju grupisanja sredina u tzv. megasredine i izdvajanja idealne sredine. Značaj izdvajanja megasredine ogleda se u odsustvu unakrsne interakcije koja remeti njihov rang, pa se hibridi mogu odabrati na osnovu prosečnih vrednosti određene osobine. Određivanje tzv. idealne sredine može biti od velikog značaja za izbor najreprezentativnijeg lokaliteta za testiranje, koji takođe ima i najveću moć diskriminacije hibrida.

Within maize breeding program at the Institute of Field and Vegetable Crops Novi Sad, Serbia, there have been seven distinct breeding cycles spanning from the mid-1960s. Each cycle is characterised by introduction of new hybrids with higher genetic yield potential. Breeding cycles were defined based on the period of hybrid introduction into production and the growing areas. In this study we analysed grain yield and moisture percentage in grain of five maize hybrids, namely NS 606, NS 640, NS 6010, NS 6030 and NS 6140, which are the representatives of the third, fourth, fifth, sixth and seventh breeding cycles. Seed of hybrids which are representatives of the first and second breeding cycles, namely NS 802 and NSSC 70, could not be produced because their parent inbred lines have lost their authenticity. According to the results of the combined ANOVA, significant differences (P lt 0,001) in grain yield were found among hybrids representatives of various breeding cycles and various environments, while the interaction cycle/ environment was found to be insignificant. A linear increase of yield by 0.44 t ha-1 (expressed by coefficient of linear regression) was found between individual breeding cycles. Since one breeding cycle lasts for approximately 7 years, average grain yield increase in maize from the third to the seventh breeding cycle was found to be 63 kg ha-1 per year. U programu oplemenjivanja kukuruza u Institutu za ratarstvo i povrtarstvo Novi Sad se može izdvojiti sedam ciklusa selekcije od sredine šesdesetih godina prošlog veka do danas. Svaki ciklus se karakteriše uvođenjem novih hibrida sa višim genetičkim potencijalom rodnosti. Kao kriterijum za definisanje ciklusa selekcije je korišten period uvođenja hibrida u proizvodnju i njegova zastupljenost. U ovom radu smo ispitivali prinos zrna i procenat vode u zrnu u berbi kod pet hibrida kukuruza: NS 606, NS 640, NS 6010, NS 6030 i NS 6140, glavnih predstavnika trećeg, četvrtog, petog, šestog i sedmog ciklusa selekcije. Seme hibrida NS 802 i NSSC 70 koji su glavni predstavnici prvog i drugog ciklusa selekcije nismo mogli proizvesti pošto su roditeljske inbred linije izgubile autentičnost. Na osnovu rezultata kombinovane ANOVE, signifikantne razlike (P lt 0.001) u prinosu zrna ustanovljene su između hibrida predstavnika pojedinih ciklusa selekcije i između sredina, dok je interakcija ciklus/spoljašnja sredina bila nesignifikantna. Između pojedinih ciklusa selekcije je ustanovljeno linearno povećanje prinosa od 0,44 t ha-1 ciklusu-1 (izraženo koeficijentom linearne regresije). Obzirom da jedan ciklus selekcije traje približno 7 godina, prosečno povećanje prinosa zrna kukuruza od trećeg do sedmog ciklusa selekcije iznosi 63 kg ha-1 godini-1.

The goal of this study was to determine correlations between grain yield and other morphological and agronomical traits in two groups of maize half-sib (HS) progenies. Progenies were obtained by crossing every S1 family with two unrelated inbred lines as testers, NS732 and NS27. Field trials with incomplete block design, with replicates within set were conducted in 2008 and 2009 at four locations. The following traits were observed: grain yield, ear length, kernel row number, kernel number per row, 1000-kernel weight, plant height, ear height, number of leaves above ear and grain moisture. Significant moderate strong negative correlation between grain yield and ear length was determined in HS1 progeny. High significant correlations occurred among plant and ear height in both HS and between plant height and number of leaves. Observed differences in levels of correlation imply significant influence of tester in each group on HS progeny. Cilj ovog istraživanja je bilo određivanje korelacija između prinosa zrna i drugih morfoloških i agronomskih osobina dve polusrodničke grupe potomstava (HS) kukuruza. Nasumično odabrane biljke iz svake S1 familije su ukrštene sa testerima NS732 i NS27. Dve polusrodničke grupe potomstava su formirane tako da je svaka S1 familija ukrštena sa oba testera. Poljski ogledi sa nepotpunim blok dizajnom sa tri ponavljanja po setu su posejana 2008. i 2009. na četiri lokaliteta. Praćene su sledeće osobine: prinos zrna, dužina klipa, broj redova zrna, broj zrna po redu, masa 1000 zrna, visina biljke, visina klipa, broj listova iznad klipa i vlaga zrna. Kod HS1 potomstva je uočena srednje jaka negativna korelacija između prinosa zrna i dužine klipa. Takođe, visina biljke i visina klipa su bile u jakoj vezi kod oba HS potomstva. Dobijene razlike u stepenu korelacije ukazuju na značajan uticaj testera u svakoj grupi HS potomstava.

The interpretation of new varieties performance is disturbed under the influence of genotype-by-environment interaction. Among several methods used for understanding this effect, one of the most frequently used methods is Additive Main Effects and Multiplicative Interaction (AMMI) analysis. In this study we used AMMI method with the aim to estimate the genotype - environment interaction of 14 barley genotypes, and to identify barley genotypes that have high and stable performance in different environments. The trials were conducted during 11 growing seasons (1995/96 - 2005/06), arranged in a randomized complete block (RCB) design with four replications in location Rimski Šančevi. The results showed that the influence of environment (seasons), genotypes and their interaction on barley grain yield were significant (p < 0.01). Based on AMMI method, two-rowed variety Novosadski 317 and the six-rowed variety Novosadski 331 can be distinguished due their high and stable yields. [Projekat Ministarstva nauke Republike Srbije, br. TR-31066]

One of the final stages in the process of maize breeding is testing the potential hybrids in pre-registration multi-location trials. The aim of this study was to evaluate six locations (Pančevo, Sremska Mitrovica, Ruma, Srbobran, Rimski Šančevi and Sombor) in the northern Serbia for testing yields of maize seed hybrid by GGE (Genotype and Genotype by Environment Interaction) biplot method in the period from 2007 to 2011. This study comprised 24 maize hybrids tested across 6 environments. Different sets of hybrid were used every year. Hybrids served as 'a random' factor for the evaluation of locations. The ANOVA indicated significant effects of genotypes (G) and environments (E) every year, while their interaction (GE) was significant in 2007, 2009 and 2011. On average, the SO location provided the smallest amount of information and therefore can be excluded from further trials and analysis. The sites SM and RU were the most similar locations and only one of these two locations should be included in further trials. The location RŠ presented the smallest repeatability. For analysis that is more detailed it is necessary to include more locations in trials and analysis. Jedna od krajnjih faza u procesu oplemenjivanja kukuruza je testiranje potencijalnih hibrida u više-lokacijskim pretkomisijskim ogledima. Cilj ovog istraživanja bila je procena šest lokaliteta (Pančevo, Sremska Mitrovica, Ruma, Srbobran, Rimski Šančevi i Sombor) u severnoj Srbiji za testiranje prinosa zrna hibrida kukuruza GGE biplot metodom u periodu od 2007 do 2011. god. Ovo istraživanje je obuhvatilo 24 hibrida kukuruza testirana na šest lokaliteta. Različiti setovi hibrida su korišćeni svake godine. Hibridi su služili kao 'random' faktor za procenu test lokaliteta. ANOVA test je pokazao značajne efekte genotipa (G) i životne sredine (E) svake godine, dok je njihova interakcija (GE) bila značajna u 2007, 2009. i 2011. U proseku, lokalitet SO je pružio najmanje informacija, pa se stoga može isključiti iz daljih ogleda i analiza. Lokaliteti SM i RU su bili najsličniji, tako da samo jedan od njih treba da se uključi u dalja testiranja. Lokalitet RŠ je imao najmanju ponovljivost. Takođe trebalo bi uključiti, druge, do sada nekorišćene lokalitete u budućim višelokacijskim ogledima.

Genetic markers, from morphological to molecular, in function with early Heterosis is a prerequisite for the successful commercial maize production. It does not appear in any cross of two inbred lines, and therefore, the determination of combining abilities of parental lines is essential. The most commonly used method for determining combining abilities is diallel analysis. Besides conventional methods for diallel analysis, a new biplot approach has been sugested. In this paper, we studied the combining ability for grain yield in a set of genotypes obtained by diallel crossing system of six inbred lines. Both, the Griffing's conventional method and the biplot approach have been used for diallel analysis. Comparing the GCA values from biplot analysis and Griffing's method, similar results can be observed, with the exception of NS L 1051 and NS L 1000 whose ranks are interchanged. Biplot analysis enables the SCA estimation of parent inbred, and the highest SCA has inbred B73D. Biplot analysis also allows the estimation of the best crosses. Inbred B73D shows the best results when crossed with testers Mo17Ht, NS L 1051 and N152, inbred N152 combines best with testers NS L 1001 and NS L 1000, whereas the cross of inbred NS L 1051 with tester B73D results with the highest grain yield per plant in comparison with other testers. Određivanje kombinacionih sposobnosti roditeljskih inbred linija, radi iskorištavanja heterozisa, je od suštinske važnosti. Najčešće korišćen metod je dialelna analiza. Pored konvencionalnih metoda dialelne analize za procenu kombinacionih sposobnosti, u poslednje vreme prisutan je i novi pristup analize kombinacionih sposobnosti. U ovom radu smo proučavali kombinacione sposobnosti za prinos zrna u setu genotipova dobijenih dialelnim sistemom ukrštanja šest linija. Pored primene konvencionalne metode analize po Griffingu, korišten je i biplot pristup za sagledavanje podataka. Upoređujući vrednosti OKS dobijenih biplot analizom i primenom Griffing-ovog metoda, dobijeni su slični rezultati, sa izuzetkom NS L 1051 i NS L 1000 čiji su rangovi zamenjeni. Biplot analiza omogućava i procenu PKS samih roditeljskih linija. Najveća vrednost PKS zapažena je kod linije B73D, a zatim slede: NS L 1051, NS L 1001, Mo17Ht, N152 i NS L 1000. Biplot analiza takođe omogućava i procenu najboljih ukrštanja. Inbred linija B73D pokazala je najbolje rezultate u ukrštanju sa linijama Mo17Ht, NS L 1051 i N152, N152 sa NS L 1001 i NS L 1000, dok se linija NS L 1051 najbolje kombinuje sa testerom B73D.