Ana Nikolic

A diallel cross among drought tolerant maize populations

A complete diallel without reciprocals was investigated among six drought tolerant maize (Zea mays L.) landraces from MRI Zemun Polje gene bank. Trials with parental populations, their crosses and three check hybrids were conducted at three locations in 2012 and five locations in 2013 in Serbia. The aim was to determine potential heterotic patterns for reciprocal recurrent selection (RRS) among them. The average grain yield reached 4.832 and 5.864 t ha−1 for the populations and population crosses, respectively. Mipdarent heterosis (MPH) for grain yield ranged from 10.0 to 36.7xa0%, with the average value of 21.3xa0%. Entryxa0×xa0environment interactions did not show significance for any trait, reflecting a broader adaptation of the material to different environments. The new heterotic pattern proposed for RRS was Iranian dent POP. N-425xa0×xa0Argentinean flint ARZM 06-020, which had the highest grain yield (6.871 t ha−1) and MPH value (36.7xa0%). This cross confirms the hypotesis that broader geographical origin, as well as dent x flint type of cross, is in positive correlation with high MPH for grain yield in maize. The cluster analysis based on MPH was not in accordance with the single sequence repeat (SSR) analysis of parental populations. Since both of the populations have some undesirable agronomic traits (high moisture, root and stalk lodging, bareness), two to three cycles of intrapopulation selection for improving them before starting the RRS program should be performed. In some additional grain quality research, these populations showed favorable value-added traits (high tryptophan, oil, and saturated fatty acids), indicating the possibility of improving grain quality besides grain yield in this newly discovered heterotic pattern.

The structure of sterile cytoplasm types within a maize genebank collection

Maize Research Institute (MRI) gene bank maintains a collection of 6000 maize accessions. Within this collection over 100 sources of cytoplasmic male sterility (CMS) were found in field trials, i.e. more than 2% of the total accession numbers. These sources are distributed among Yugoslav open-pollinated varieties (4.56% of them contain CMS), as well as introduced heterozygous genotypes and inbred lines. In order to identify cytoplasm types the gene-bank sources of CMS were screened using a PCR assay with specific primers for C, T and S cytoplasms. Predominant cytoplasmic male sterility type among the analyzed accessions was CMS-S. Results were inconclusive for three accessions, i.e. different results for the progenies of two ears per accession were obtained. For another two accessions a new PCR product profile was identified, consisting of one band characteristic for CMS-S and one unspecific for any of the three CMS types. The PCR approach enabled a simple, fast and reliable large scale screening of maize cytoplasm among MRI gene bank accessions, significantly reducing time for cytoplasm characterizations compared to classical method of testing with restorers for each known type of CMS.

SSR analysis for genetic structure and diversity determination of maize local populations from former Yugoslavia territories

A collection of 2178 local populations from ex-Yugoslavia territories is maintained in Maize Research Institute (MRI) gene bank. These populations were characterized mainly by morphological markers. In this work, 21 local populations belonging to seven different agro-ecological groups have been subjected to SSR analysis using a DNA-pooling strategy. The objective of this work was to develop genetic fingerprints for characterization, identification and classification of the populations, as well as for estimation of their genetic diversity. Also, a DNA-pooling strategy was employed with the aim to certify if it could be applied for population analysis with SSR markers. Statistical analysis of 25 informative SSR primers revealing 224 alleles (bands) showed that the average within-population mean number of alleles was 2.55, the average values for total and within-population diversity were 0.784 and 0.502, respectively, and GST value was 0.360. Genetic distance values calculated using Modified Rogers Distance were in the range from 0.35 to 0.60. The silver staining method of DNA used for bulked samples showed some weakness that could be overcome with a more sensitive staining method. Nevertheless, the results in this work indicate that the SSR analysis of bulks could be used for characterizing a large number of populations in gene banks.

AUPOV morphological versus molecular markers for maize inbred lines variability determination

7 CHILEAN JOURNAL OF AGRICULTURAL RESEARCH 76(1) JANUARY-MARCH 2016 4 OCTOBER DECEMBER 2016 In maize (Zea mays L.) breeding programs, it is very important to define a genetic distance of inbred lines and to establish criteria and biometric methods for the satisfactory germplasm classification. A total of 29 inbred lines from Maize Research Institute “Zemun Polje” (MRIZP) breeding program, Belgrade, Serbia, were used to compare similarities obtained by morphological (according to UPOV Union Internationale pour la Protection des Obtentions Végétales) and molecular (simple sequence repeats, SSR) markers. The aim was to assess discriminative power of applied markers in the separation of related lines, and to determine the possibility of their application in choosing parental lines for breeding programs. Application of different marker types resulted in adequate separation of inbreds into divergent groups, which facilitates the choice of parental lines. However, there were still many inconsistencies between the field and laboratory results. The quality of information from morphological markers was improved by the application of the appropriate descriptor, measurement scale and the biometric method. According to the correspondence analysis, increased number of SSR markers will enable more reliable results. Regression analysis of morphological visual assessment (MVG) and SSR similarity of individual inbreds pointed out that in some cases morphological, and in others molecular markers more accurately reflected known pedigree information of tested maize lines. In the early generations of maize inbred lines testing, we propose utilization of information resulting from morphological markers, according to UPOV descriptor. However, application of adequate number of molecular (SSR) markers has an economic justification on a smaller number of elite lines in the later generations of line testing.

Individual and combined (Plus-hybrid) effect of cytoplasmic male sterility and xenia on maize grain yield

Plus-hybrid effect refers to a combined effect of cytoplasmic male sterility (CMS) and xenia in maize (Zea mays L.) It could be used in commercial production by growing a mixture of 80% CMS hybrid and 20% of another fertile hybrid. The aim of this research was to examine individual and combined CMS and xenia effects on two hybrids widely grown in Serbia. Sterile and fertile versions of ZP 1 and ZP 2 hybrids (three-way; Iodent × Lancaster dents) were used as females, while ZP 1, ZP 2, ZP 3, ZP 4, and ZP 5 (three-way or single cross; Iodent (BSSS) × Lancaster dents) were used as pollinators. All of them belong to medium maturity group. The trial was set up at one location in Serbia (Zemun Polje) in 2009, 2010, and 2011. Molecular analysis of the five genotypes was done using simple sequence repeat (SSR) primers. Plus-hybrid effect on grain yield ranged from -6.2% to 6.2%; on thousand kernel weight from -1.7% to 5.2%; on number of kernels per area from -1.0% to 8.0%. The poor response could be due to a use of three-way instead of single cross hybrids in S type of sterility. Modified Rogers’ distance between hybrids was in the range 0.211 to 0.378 and was not relevant for the effect, which depended mostly on the sterile hybrid genotype and the fertile hybrid pollinator ability. This approach should be more suitable for female hybrids with slightly poorer performance, already being produced on a sterile base.