Popcorn Populations Research Articles

Characterization of temperate and tropical popcorn populations and GWAS for zeins and starch contents

AbstractBecause measuring expansion volume (EV) is simple and inexpensive, popcorn breeders have developed high‐quality single crosses ignoring the contents of zeins, starch, lipids, and cellular wall components in selection. However, some methods of quantification of these quality‐related traits can be applied to popcorn breeding, increasing the selection efficacy for quality. The objectives of this study were to assess methods of zeins and starch quantification that can be used in popcorn breeding, characterize a temperate and a tropical populations for zeins and starch contents and identify candidate genes for these quality‐related traits. We genotyped and phenotyped 286 plants. For quantification of total zeins and zein subunits we choose the ‘lab‐on‐a‐chip’ microfluidic electrophoresis. For quantification of starch and amylose/amylopectin, we choose the Megazyme's Amylose/Amylopectin kit assay. The temperate population has superior EV (36.0%), a higher level of the 19 kDa zein subunit (32.0%), lower levels of the 21, 22 and 27 kDa subunits (−1543.0%, −40.0% and −47.0%, respectively) and no statistical difference for the 10 kDa zein content, relative to the tropical population. Although there are statistical differences between the two populations regarding starch, amylose, and amylose/amylopectin ratio, the differences are not significant (−2.0% to 8.0%). Thirteen candidate genes were identified for the 19 and 22 kDa zeins, two for amylose and one for starch, with emphasis on the genes coding for the 19 and 22 kDa alpha‐zeins, located on chromosome 4. The evaluated quantification methods can be used in popcorn breeding but for a limited number of samples, mainly because costs.

Cultivation of Local Popcorn Genotypes as a Second Crop in Kahramanmaras Conditions

Popcorn is a snack plant with widespread consumption in our country and around the world. Although the increasing commercialization rate in agriculture with the spread of hybrid varieties has narrowed the production area of local plant species, the production of local pop corn varieties still continue today. Therefore, in this study, 17 local popcorn genotypes and 3 commercial popcorn cultivars were grown as the second crop in Kahramanmaraş climatic conditions. In the study, local popcorn genotypes were determined by plant height, first ear height, first node diameter, ear length, ear diameter, the row number of ear, the number of grain on the ear row, number of ears per plant, and ear tassel-out time, ear silk-out time, grain yield per decare and the relationships between these properties were investigated. According to the results of the research, the plant height of the local popcorn populations was 216 - 166 cm, the height of the first ear 107 -63 cm, the diameter of the first node 22.6 - 16.7 mm, the diameter of the node of ear 16.4 -11.8 mm, ear length 17.267 – 12.833 cm, ear diameter 32.513 – 26.120 mm, the row number of ear 16.8 -12.26, the number of grain on the ear row 38.86 -26.33, the number of ears per plant 1.8 -12 pieces, ear silk-out time 56 -48 days, the ear tassel-out time 68 -56 days and grain yield per decare 478 -260 kg da-1. In the study, positive correlations were found between first ear height and plant height, ear length and ear diameter, the number of grain on the ear row and ear length, the ear tassel-out time and grain yield per decare, ear silk-out time and first node diameter, ear silk-out time and the ear tassel-out time.

Phenotyping Latin American Open-Pollinated Varieties of Popcorn for Environments with Low Water Availability.

Drought is a common abiotic stress in tropical and subtropical regions that limits the growth and development of agricultural crops, mainly impacting grain yield. Acting through plant breeding is the most viable alternative for obtaining genotypes more tolerant of environments with stress. This work aims to select popcorn genotypes for environments with drought and to identify discriminating traits for the evaluation of drought tolerance in popcorn germplasm. Fifteen Latin American populations of popcorn were evaluated in water stress (WS) and well-watered (WW) conditions. The evaluated traits were based in morpho-agronomic, physiological and radicular descriptors. Data were submitted to individual and joint ANOVA and GT Biplot analysis. Variability was detected between populations for all traits in both conditions. The drought caused a reduction of 30.61% and 3.5% in grain yield and popping expansion, respectively. Based in GT biplot analysis, 880POP was the most stable in WS and WW, being indicated as a promising population for cultivation in environments with water limitation. This study is going to allow the establishment of a collection of great importance to maize germplasm and to provide information to facilitate the process of selection in breeding programs focused on drought tolerance.

Genetic Diversity and Phylogenetic Relatıonshıps of Turkish Local Popcorn (Zea mays everta) Populations By Simple Sequence Repeats (SSRs)

Maize (Zea mays everta) is preferred as a good dietary in Turkey and it is important to know its genetic diversity to improve the yield. Genetic markers are very important in determining genetic diversity in popcorn populations. The aim of this study was to evaluate the genetic diversity of landraces popcorn populations by simple sequence repeats (SSR) markers. A hundred seventy five accessions of popcorn from thirty five populations grown in Turkey were analyzed using twenty SSR markers. As a result of molecular analysis, 65 of 66 alleles obtained were showed polymorphisms and the polymorphism rate was 98.5%. The average number of alleles for each SSR loci was 3.3, and this the number of alleles varied from 1 to 5. The average the polymorphism information content (PIC) value was calculated to be 0.57 for SSR locus ranging from 0.00 to 0.89. The number and percentage of polymorphic loci of the genotypes were determined to vary between 29/47% and 43.94/71.21 % and the mean values were calculated as 39.114 and 59.265 % respectively. The value of genetic change in the phylogenetic tree obtained from landraces popcorn populations was determined as 0.05, and the genetic difference among genotypes varied from 14.7 to 97.1%. Among the markers used in the study, it was observed that code ‘phi064’ was the most effective marker for determining genetic diversity in popcorn and the highest allele frequency also on this marker was obtained.

Diallel analysis of popcorn populations for yield, popping expansion and resistance to fall armyworm

ABSTRACT The objective of this study was to estimate the varietal and heterotic effects related to grain yield, popping expansion and resistance of popcorn against fall armyworm. Twelve open-pollinated varieties were intercrossed in a complete diallel mating scheme. The 66 experimental hybrids, together with their parents and controls Zapalote Chico, BRS 1030 and IAC 125, resulted in a total of 81 treatments, evaluated in an experiment in a 9x9 triple-square lattice design, in Maringa-PR and Araruna-PR. The data were analyzed according to the diallel model of Gardner and Eberhart (1966). The following traits were evaluated: grain yield (GR); mean plant height (PH) and insertion height of the highest ear in the stem (EI); silking (SIL); final plant density (FD) and popping expansion (PE). Variety PR 023 is indicated for intrapopulation improvement for grain yield. Regarding popping expansion, the results indicated cross SAM x UNB 2U C5 for recurrent reciprocal selection. In relation to resistance to fall armyworm, the varieties PARA 172, PA 091, PR 023, and SE 013 were selected for intrapopulation improvement. On the other hand, the crosses PARA 172 x BOZM 260, PA 091 x BOYA 462 and SAM x UNB 2U C5 can be indicated for interpopulation improvement.

Determination of popping traits and grain quality of landraces popcorn populations.

In this study; the local varieties (Nermin Cin) and 34 local popcorn populations which obtained from Turkey's different regions were used to determine the popping traits and grain quality of populations by growing in Kahramanmaraş conditions. The differences among examined features of genotypes, years and genotype x year interactions were statistically significant (p < 0.01). The varieties among popcorn genotypes were 70.177-96.017 cm3g-1 for popping volume; 3.767-22.658% for popping grain ratio; 4.150-29.823% for un-popping grain ratio; 9.882-11.537% for protein ratio; 68.727-72.920% starch ratio; 4.230-5.608% for fat ratio and 88.050-89.837% for dry matter ratio. The highest and the least values of the features investigated in terms of import of popping criteria and grain quality features were obtained 5 and 32 number populations for the popping volume, 16 and 26 number populations for the ratio of popping grain, 20 and 6 number populations for the starch ratio of grain respectively. The accuracy of reseach has been showed to create relation groups each other and rich variations in terms of features studied on popcorn genotypes, because the maize plant has an open dusty genetic structure. As a result of this research, the genetic variation of popcorn populations in the country was been studied to determination.

Relationships among American popcorn and their links with landraces conserved in a microcenter of diversity

This study describes the genetic diversity and the population structure of 66 popcorn landrace collections in a recently discovered microcenter of maize (Zea mays L.) diversity in southern Brazil. Furthermore, we elucidate their phylogenetic relationships with a diverse panel of 575 popcorn populations from 18 countries of American Continent. The germplasm, representing distinct landraces, was genetically characterized as population bulks using single nucleotide polymorphism markers (SNPs). Five main groups were identified for the popcorn germplasm of the southern region of Brazil. This pattern was associated with phenotypic diversity in grain shape and color. The germplasm of the American Continent was structured in nine groups associated with geographical region with significant differences in terms of genetic diversity and expansion capacity or popping expansion (the formation of large flakes after the kernels explode in response to heating). The popping expansion pattern of the American groups displayed a North-South geographical continuum, in which the average values increased with geographical distance from the center of origin in Mexico. The highest averages were obtained for the Lowland groups of South America. These results raise two hypotheses: the first one is the possibility of a continuous evolution of this characteristic, which is popcorn did disperse North - South, but interbreeding with local varieties drove up the diversity of the gene pool, and at the same time allowed more efficient selection on the trait of expansion capacity. The second is the possibility of a second domestication event of Zea mays ssp. mays L., in South America, which would assume an independent origin of popcorn, but not an independent domestication of maize. Both hypotheses would be based on popcorn populations brought from Mexico by human migrations. The germplasm collected in the microcenter of diversity in southern Brazil, most of them originated in the Lowlands of South America, a part of germplasm established phylogenetic relationships closer to the popcorn populations of Brazil collected in the last century. The study contributes to improved understanding of the origin and phylogenetics of this maize group and as such to conservation of those valuable genetic resources and future breeding efforts. This is valuable genetic research which led to better insight into grouping and dispersion of studied genotypes in the target region, but also its place vis-a-vis origin and migration of popcorn genotypes in South America in general.

Genomic selection helps accelerate popcorn population breeding

AbstractRecurrent selection is a method for developing new popcorn (Zea mays L.) cultivars. We aimed to determine the selection accuracy and genetic gains for different selection strategies: estimates based exclusively on phenotypic data (PhEN), estimates based on phenotypic and genotypic data (PhEN + GEN), and estimates based exclusively on single nucleotide polymorphism (SNP) marker genotyping (GEN). For the GEN strategy, we tested, via simulation, the possibility of reducing the number of SNPs and increasing the training population. The traits evaluated were 100‐grain weight, ear height, grain yield, popping expansion, plant height, and popping volume. Field trials were undertaken with 98 S1 progenies at two locations in an incomplete block design with three replications. The progenies’ parents were genotyped with a panel of ∼10,507 SNPs. As predicted by the GEN strategy at different selection intensities, the average annual genetic gain for the different traits were 29.1 and 25.2% higher than those of PhEN and GEN + PhEN for 98 candidates; 148.3 and 140.9% higher for 500; and 187.9 and 179.4% higher for 1,000 selection candidates, respectively. Recurrent genomic selection may result in high genetic gain, provided that: (a) phenotyping is accurate; (b) selection intensity is explored by genotyping several progenies and increasing the number of candidates; (c) genomic selection is used for early selection; and (d) the model is adjusted for a few more cycles of phenotyping. The simulation suggests that desirable values of genetic gain may be obtained by reducing the number of SNPs and increasing the training population size.

Linkage disequilibrium and haplotype block patterns in popcorn populations.

Linkage disequilibrium (LD) analysis provides information on the evolutionary aspects of populations. Recently, haplotype blocks have been used to increase the power of quantitative trait loci detection in genome-wide association studies and the prediction accuracy of genomic selection. Our objectives were as follows: to compare the degree of LD, LD decay, and LD decay extent in popcorn populations; to characterize the number and length of haplotype blocks in the populations; and to determine whether maize chromosomes also have a pattern of interspaced regions of high and low rates of recombination. We used a biparental population, a synthetic, and a breeding population, genotyped for approximately 75,000 single nucleotide polymorphisms (SNPs). The sample size ranged from 190 to 192 plants. For the whole-genome LD and haplotype block analyses, we assumed a window of 500 kb. To characterize the block and step patterns of LD in the populations, we constructed LD maps by chromosome, defining a cold spot as a chromosome segment including SNPs with the same LDU position. The LD and haplotype block analyses were also performed at the intragenic level, selecting 12 genes related to zein, starch, cellulose, and fatty acid biosynthesis. The populations with the higher and lower frequencies of |D'| values greater than 0.75 were the biparental (65–74%) and the breeding population (26–58%), respectively. There were slight differences between the populations regarding the average distance for SNPs with |D'| values greater than 0.75 (in the range of approximately 207 to 229 kb). The level of LD expressed by the r2 values was low in the populations (0.02, 0.04, and 0.04, on average) but comparable to some non-isolated human populations. The frequency of r2 values greater than 0.75 was lower in the biparental population (0.2–0.5%) and higher in the other populations (0.2–1.6%). The average distance for SNPs with r2 values greater than 0.75 was much higher in the biparental population (approximately 80 to 126 kb). In the other populations, the ranges were approximately 6 to 19 and 6 to 35 kb. The heatmaps for the regions covered by the first 100 SNPs in each chromosome, in each population (1 to 3.3 Mb, approximately), provided evidence that the comparatively few high r2 values (close to 1.0) occurred only for SNPs in close proximity, especially in the synthetic and breeding populations. Due to the reduced number of SNPs in the haplotype blocks (2 to 3) in the populations, it is not expected advantage of a haplotype-based association study as well as genomic selection along generations. The results concerning LD decay (rapid decay after 5–10 kb) and LD decay extent (along up to 300 kb) are in the range observed with maize inbred line panels. The LD maps indicate that maize chromosomes had a pattern of regions of extensive LD interspaced with regions of low LD. However, our simulated LD map provides evidence that this pattern can reflect regions with differences in allele frequencies and LD levels (expressed by |D'|) and not regions with high and low rates of recombination.

GENETIC GAINS IN THE POPCORN POPULATION UENF-14: DEVELOPING THE NINTH GENERATION OF INTRAPOPULATION RECURRENT SELECTION

ABSTRACT The occurrence of negative correlations between grain yield (GY) and popping expansion (PE) in popcorn complicates the selection process. In an attempt to overcome this inconvenience, we proposed the use of the importance characteristic volume per popcorn per hectare (PV). The objectives of this study were to develop the ninth cycle of the UENF-14 popcorn population, to estimate the direct and indirect effects of PV and to verify the genetic progress among all selective cycles. We obtained and evaluated 200 inbred progenies in randomised blocks arranged in replicates within sets, with nine sets consisting of 25 progenies and one set with all previous eight cycles with three replicates. The average height of the plants, prolificacy, 100-grain weight, grain yield, grain popping expansion and volume per popcorn per hectare were evaluated. Track analysis was performed to determine the direct and indirect effects, and the Mulamba and Mock selection index was calculated for the selection of the 40 superior progenies. There was genetic variability among progenies in all evaluated traits, with a cause-and-effect relationship between PV with GY and PE, allowing simultaneous gains with indirect selection. The selection of the best progenies was more effective when using arbitrarily assigned weights, which provided higher predicted gains for PV (20.73%). The means obtained in all cycles indicated increases, demonstrating the efficiency of using continuous recurrent selection in popcorn breeding programs.

SNP-based mixed model association of growth- and yield-related traits in popcorn.

The identification of the genes responsible for complex traits is highly promising to accelerate crop breeding, but such information is still limited for popcorn. Thus, in the present study, a mixed linear model-based association analysis (MLMA) was applied for six important popcorn traits: plant and ear height, 100-grain weight, popping expansion, grain yield and expanded popcorn volume per hectare. To this end, 196 plants of the open-pollinated popcorn population UENF-14 were sampled, selfed (S1), and then genotyped with a panel of 10,507 single nucleotide polymorphisms (SNPs) markers distributed throughout the genome. The six traits were studied under two environments [Campos dos Goytacazes-RJ (ENV1) and Itaocara-RJ (ENV2)] in an incomplete block design. Based on the phenotypic data of the S1 progenies and on the genetic characteristics of the parents, the MLMA was performed. Thereafter, genes annotated in the MaizeGDB platform were screened for potential linkage disequilibrium with the SNPs associated to the six evaluated traits. Overall, seven and eight genes were identified as associated with the traits in ENV1 and ENV2, respectively, and proteins encoded by these genes were evaluated for their function. The results obtained here contribute to increase knowledge on the genetic architecture of the six evaluated traits and might be used for marker-assisted selection in breeding programs.

Genetic variability in popcorn synthetic population

The Brazilian popcorn has low genetic variability and the successful development of advanced lines, new popcorn cultivars with high grain yield (GY) and expansion volume (PE) is dependent on parental selection and precise determination of heterotic groups. The aim of this study was to evaluate genetic variability and identify heterotic groups in synthetic populations of popcorn, using diallel crosses. Thus, nine synthetic populations were crossed using complete diallel scheme. The GY and PE traits of 36 hybrids and reciprocals were evaluated in a randomized complete block design with 72 treatments and two replicates in two years. The effects of non-additive genes were the most important in the genetic control of these traits, indicating a favorable situation to produce hybrids. The reciprocal effect is mainly due to non-maternal effects for GY and PE. The highest GY values were obtained for the 02 x 08, 04 x 09, 05 x 09, and 01 x 09 crosses and the highest PE were obtained for the 07 x 01 and 03 x 04 crosses. The exploitation of synthetic populations from S3 lines can be an alternative to increase the genetic variability for grain yield and popping expansion in popcorn breeding programs.

Genetic gain capitalization in the first cycle of recurrent selection in popcorn at Ceará’s Cariri

Popcorn lacks cultivars that are productive, stable and adapted to the cultivation regions. Therefore, the present work aimed to estimate the genetic gain in the first intrapopulation recurrent selection cycle between full-sibs, by means of selection index, at Ceará’sCariri. It was obtained 210 families from the “Dona Iva” population, belonging to the Federal University of Cariri - UFCA’s germplasm bank. The progenies were evaluated in two environments: Granjeiro-CE and at the experimental field at UFCA, Crato-CE, using randomized block design with two repetitions inside “sets”. For the assessment, it was evaluated plant height (AP), ear height (AE), plant final stand (NP), mass of ear with grains (PE), grain yield (RG) and expansion capacity (CE). Data were submitted to analysis of variance by the F test and estimated genetic and phenotypic parameters. The prediction of the selection gains were obtained by the indexes of Mulamba and Mock and of Smith and Hazel. When the Smith and Hazel selection index was evaluated, it was not possible to predict gains for CE. On the other hand, Mulamba and Mock selection index with the economic weight PA (arbitrage weight by attempt) provided the highest gain for expansion capacity (8.15%) and elevated gain for RG (24.29%). Therefore, based on this weight it was selected 38 superior genotypes for recombination and the aforementioned gains are expected in the first selection cycle of the “Iva” popcorn population.

GENETIC GAINS AND SELECTION ADVANCES OF THE UENF-14 POPCORN POPULATION

ABSTRACT Recurrent selection can generate successive gains for characters of economic interest without causing genetic narrowing in the population. However, it has rarely been used in breeding programs in popcorn, especially when using full-sibling progenies to generate more expressive gains. The objective of this study was to estimate the genetic gain of the UENF-14 popcorn population through recurrent selection, and verify the evolution of the gains between the selection cycles four and eight. A total of 200 full-sibling progenies were evaluated in randomized blocks arranged in eight sets within three replicates in two environments; each set containing twenty-five progenies and six controls (selection cycles 4, 5, 6 and 7 of the UENF-14, BRS-Angela and IAC-125). The average height, prolificacy, 100-grain weight, ear weight, grain yield, and grain popping expansion of the plants were evaluated. In the selection of the thirty superior progenies for the eighth cycle, the Mulamba and Mock selection index was used, which generated estimated genetic gains of 4.60 for grain yield and 3.61% for popping expansion. The grain yield increased 111.99 kg ha-1 and the popping expansion increased 1.75 mL g-1 per cycle. The evolution of the cycles resulted in an accumulated genetic gain for the main characters of economic importance, allowing the prediction of success in the continuity of the recurrent selection.

&lt;b&gt;Population structure and impact of recurrent selection on popcorn using EST-SSR markers

The success of any recurrent selection program depends on the genetic variability of the evaluated population, which is used to refer to the diversity of existing alleles at many genetic loci. Thus, the goal of the present study was to investigate the impact of recurrent selection across nine cycles of a UENF-14 popcorn population through the analysis of genetic diversity and structure using microsatellite markers (EST-SSRs). Genomic DNA was extracted from young leaves of 25 individuals from each cycle (C0, C1 C2, C3, C4, C5, C6, C7, and C8), totaling 225 samples from the UENF-14 population. Fifty EST-SSR markers were used for the analysis of genetic diversity across the recurrent selection cycles, 16 of which were polymorphic. Thirty-four alleles were detected, with an average of 2.13 alleles per locus. Throughout all the recurrent selection cycles, there was a reduction in heterozygosity and an increase in inbreeding. The population structure showed a sharing of alleles, inferring that some may be directly related to the main selection characteristics.

&lt;b&gt;History of northern corn leaf blight disease in the seventh cycle of recurrent selection of an UENF-14 popcorn population

To investigate the genetic resistance to northern corn leaf blight (Exserohilum turcicum) disease in the UENF-14 popcorn population and the inclusion of this trait in the analysis, two hundred ten popcorn half-sib families were evaluated using an incomplete block design with treatments arranged in replicates Sets. Regarding the Families within Set (F/S) source of variation, enough genetic variability was found for northern corn leaf blight disease resistance to be explored in the next cycles of the UENF popcorn breeding program. The open-pollinated UENF-14 variety has a source of resistance to this disease in its genetic basis, given that it originated from crossing with an American cultivar with yellow grains that is resistant to disease. These results strengthen the possibility of selecting resistant families across the cycles, so it is concluded that the selection was effective at maintaining the balance in the occurrence of the disease in the study population and that the source of resistance is not lost with advancing cycles. The addition of the foliar disease variable in the analysis is of the utmost importance for the improvement of popcorn as it makes it possible to aggregate genes for resistance to this disease along with agronomic traits of interest.

New popcorn races in a diversity microcenter of Zea mays L. in the Far West of Santa Catarina, Southern Brazil

The last classification of corn races in Brazil was performed in 1977, when were described 19 races and 15 sub-races within four groups. However, this classification, which considered the race diversity in Brazil and South American lowlands, did not include popcorns. Therefore, there is a diversity in situ-on farm, which not yet was described after almost 40 years from the last study. This work aimed at identifying popcorn races from populations conserved in situ-on farm in the micro-region of the Far West of the State of Santa Catarina, Southern Brazil, and verifying their relationships with other races of the American continent. Thus, 218 ears of 70 popcorn populations were collected from small-scale farms, aiming to evaluate them for corn descriptors through 16 morphological characters related to ear and kernel. The populations showed variability for all characters, mainly for kernel color. The cluster analysis and principal coordinates, based on Gower index, have highlighted the presence of four distinct groups and one isolated population: I and II Groups, and the population 2279X are not grouped with other popcorn races of Americas, and Groups III and IV have different relationships with other popcorn races of Americas. Thus, in the region of study, there are at least five popcorn races conserved in situ-on farm.

Effect of recurrent selection on the variability of the UENF-14 popcorn population

This study aimed to evaluate the effect of recurrent selection on the genetic variability of UENF-14 population after six selections. Two hundred and ten half-sib families were evaluated in two environments in the state of Rio de Janeiro, using incomplete randomized blocks design with treatments arranged in replication within Sets. There was significant effect for Families within the Set (F)/S, proving that there is enough genetic variability to be exploited in the popcorn breeding program of UENF. The significance for the source of variation Environment (E) shows that the environments were distinct enough to promote differences between the evaluated characteristics. It was found that for both characteristics of greatest interest, GY and PE, the magnitude of the additive variance remains with close values in advanced cycles of UENF-14 population, indicating that variability remains, with no evidence of decreases in advanced cycles. This is concluded by the longevity of UENF breeding program.

Linkage disequilibrium, SNP frequency change due to selection, and association mapping in popcorn chromosome regions containing QTLs for quality traits.

The objectives of this study were to assess linkage disequilibrium (LD) and selection-induced changes in single nucleotide polymorphism (SNP) frequency, and to perform association mapping in popcorn chromosome regions containing quantitative trait loci (QTLs) for quality traits. Seven tropical and two temperate popcorn populations were genotyped for 96 SNPs chosen in chromosome regions containing QTLs for quality traits. The populations were phenotyped for expansion volume, 100-kernel weight, kernel sphericity, and kernel density. The LD statistics were the difference between the observed and expected haplotype frequencies (D), the proportion of D relative to the expected maximum value in the population, and the square of the correlation between the values of alleles at two loci. Association mapping was based on least squares and Bayesian approaches. In the tropical populations, D-values greater than 0.10 were observed for SNPs separated by 100-150 Mb, while most of the D-values in the temperate populations were less than 0.05. Selection for expansion volume indirectly led to increase in LD values, population differentiation, and significant changes in SNP frequency. Some associations were observed for expansion volume and the other quality traits. The candidate genes are involved with starch, storage protein, lipid, and cell wall polysaccharides synthesis.

Comparison of three tester parents in evaluating popcorn families derived from IAC-125

Thirty-eight S3 families obtained by selfing from IAC-125 popcorn hybrid were evaluated by three different topcross tester parents: an inbred line P3.3- S7 generation taken from popcorn population CMS-42, an open-pollinated variety BRS Angela and the commercial three-way hybrid Jade. Manual crossings were performed according to a partial diallel mating design. Topcross hybrids were evaluated in individual experiments for each tester carried out in randomized block designs with three replications in two locations (Maringa-Parana and Sabaudia-Parana). The results for grain yield and popping expansion were gathered in a combined analysis. Estimates of general and specific combining ability were obtained according to Griffing's methodology (1956), adapted by Geraldi and Miranda Filho (1988). The hybrid Jade was considered the most appropriate tester because it discriminated the evaluated families well for both grain yield and popping expansion according to Fasoulas index of differentiation. Families F4, F7, F16 and F31 are the most promising due to their high general combining ability for both traits as well their performance regardless of the effect of locations.