Corn Breeding Programs Research Articles

Use of simulation to optimize a sweet corn breeding program: implementing genomic selection and doubled haploid technology.

Genomic selection and doubled haploids hold significant potential to enhance genetic gains and shorten breeding cycles across various crops. Here, we utilized stochastic simulations to investigate the best strategies for optimize a sweet corn breeding program. We assessed the effects of incorporating varying proportions of old and new parents into the crossing block (3:1, 1:1, 1:3, and 0:1 ratio, representing different degrees of parental substitution), as well as the implementation of genomic selection in two distinct pipelines: one calibrated using the phenotypes of testcross parents (GSTC scenario) and another using F1 individuals (GSF1). Additionally, we examined scenarios with doubled haploids, both with (DH) and without (DHGS) genomic selection. Across 20 years of simulated breeding, we evaluated scenarios considering traits with varying heritabilities, the presence or absence of genotype-by-environment effects, and two program sizes (50 vs 200 crosses per generation). We also assessed parameters such as parental genetic mean, average genetic variance, hybrid mean, and implementation costs for each scenario. Results indicated that within a conventional selection program, a 1:3 parental substitution ratio (replacing 75% of parents each generation with new lines) yielded the highest performance. Furthermore, the GSTC model outperformed the GSF1 model in enhancing genetic gain. The DHGS model emerged as the most effective, reducing cycle time from 5 to 4 years and enhancing hybrid gains despite increased costs. In conclusion, our findings strongly advocate for the integration of genomic selection and doubled haploids into sweet corn breeding programs, offering accelerated genetic gains and efficiency improvements.

Utilizing genomic prediction to boost hybrid performance in a sweet corn breeding program.

Sweet corn breeding programs, like field corn, focus on the development of elite inbred lines to produce commercial hybrids. For this reason, genomic selection models can help the in silico prediction of hybrid crosses from the elite lines, which is hypothesized to improve the test cross scheme, leading to higher genetic gain in a breeding program. This study aimed to explore the potential of implementing genomic selection in a sweet corn breeding program through hybrid prediction in a within-site across-year and across-site framework. A total of 506 hybrids were evaluated in six environments (California, Florida, and Wisconsin, in the years 2020 and 2021). A total of 20 traits from three different groups were measured (plant-, ear-, and flavor-related traits) across the six environments. Eight statistical models were considered for prediction, as the combination of two genomic prediction models (GBLUP and RKHS) with two different kernels (additive and additive + dominance), and in a single- and multi-trait framework. Also, three different cross-validation schemes were tested (CV1, CV0, and CV00). The different models were then compared based on the correlation between the estimated breeding values/total genetic values and phenotypic measurements. Overall, heritabilities and correlations varied among the traits. The models implemented showed good accuracies for trait prediction. The GBLUP implementation outperformed RKHS in all cross-validation schemes and models. Models with additive plus dominance kernels presented a slight improvement over the models with only additive kernels for some of the models examined. In addition, models for within-site across-year and across-site performed better in the CV0 than the CV00 scheme, on average. Hence, GBLUP should be considered as a standard model for sweet corn hybrid prediction. In addition, we found that the implementation of genomic prediction in a sweet corn breeding program presented reliable results, which can improve the testcross stage by identifying the top candidates that will reach advanced field-testing stages.

GENETIC PURITY AND DIVERSITY ASSESSMENT OF PARENTAL CORN INBRED LINES USING SSR MARKERS FOR PHILIPPINE HYBRID BREEDING

Accurate data and relevant insights on parental corn inbred lines' and hybrids’ genetic purity and diversity are essential for hybrid development and seed production. Here, the genetic purity and diversity of 19 parental yellow corn inbred lines were assessed using SSR markers. A total of 91 SSR markers were utilized, of which 61 were highly polymorphic and had high polymorphism information content value (PIC = 0.379). Genetic purity and diversity parameters were calculated from the generated SSR marker data. Observed pairwise genetic distances ranging from 0.257 to 0.808 implied high genetic dissimilarities among the accessions. Cluster analysis separated the parental lines into three distinct subclusters, which can potentially be a basis for generating heterotic groupings among the parental lines. Eight (8) out of the 19 parental lines showed considerable residual heterozygosity of ≤10%. Inbred line CML 431 displayed complete homozygosity across all 61 SSR markers. Inbred lines that have residual heterozygosity of >15% need purification through further breeding and selection. Out of the resultant F1 hybrids analyzed, only four (4) showed genetic impurity of ≤10%. It may be attributed to the intrinsic genetic impurity of parental line CML 452 (21.67%). In contrast, hybrids generated from two genetically pure parents (e.g., CML 431 and CML 575) showed low to no off-types. Overall, genetic purity and diversity determination of promising parental lines can be valuable for future yellow corn breeding programs in the Philippines.

Winds of Change: Plant Pathology, Transnational Wheat Rust, and the Environmental Origins of the Green Revolution, 1904–1953

Abstract Created in 1943, the Mexican Agricultural Program (MAP) was a collaborative program between the Rockefeller Foundation and the Mexican government aimed at improving yields of corn and wheat varieties in Mexico. The MAP's wheat program was more influential than its corn breeding program, and wheat became the centerpiece of the Green Revolution beginning in the 1960s. This article reveals that the environmental origins of the MAP's wheat program lay in combating a plant disease fungus commonly known as wheat rust, which harmed farmers in both northern Mexico and the US hard red spring wheat region. Rust outbreaks originated in US barberry bushes, so one might think that Mexican scientists would have entered the United States to solve this problem with transnational wheat rust. Instead, the reverse occurred. Nevertheless, the MAP successfully produced new rust-resistant wheat during the formative years of the MAP's wheat program. Between 1943 and 1953, rust-resistant wheat helped increase Mexican wheat production 84 percent and yields 59 percent. Rust-resistant wheat offered an alternative model for a sustainable, resource-neutral green revolution. Rather than remain in their field of expertise, plant pathologists pivoted to semidwarf wheat and fertilizer use after 1953, a shift that defined the course of the Green Revolution.

COMBINING ABILITY ANALYSIS FOR MATURITY AND YIELD ATTRIBUTES IN SWEET CORN ACROSS ENVIRONMENTS

Early maturity and genotype by environment interaction (GEI) have always been challenging concerns for breeders in selecting appropriate parents for breeding programs. The presented study aimed to investigate early maturity and the dimension of gene action, as well as, assess the performance of half-diallel populations using eight advanced sweet corn inbred lines and their 28 F1 hybrids with two commercial checks for maturity and yield-related traits in the spring of 2018 at the Nowshera (plain) and Swat (hilly) areas, Khyber Pakhtunkhwa, Pakistan. Analysis revealed significant differences among the genotypes for the studied traits over both locations. General combining ability (GCA) effects were significant for all the traits at both the agro-climatic conditions, except 100-kernel weight, with the specific combining ability (SCA) effects relevant for grain yield at both locations. The GCA-SCA ratio for studied traits indicated dominance gene action, which also gained support by higher values of SCA than GCA variances. Based on the results, the identified inbred lines SWTS-1-8 and SODS-1 serve as good general combiners for traits like earliness and grain yield attributes, making them better parents to improve the stated characteristics in sweet corn. However, the F1 hybrids, i.e., NARCCCRI-19 × CCRI-34 at Nowshera and CCRI-34 × SODS-1 at Swat, showed the best specific combiners for maturity. Likewise, F1 hybrids, i.e., SWTS-1-4 × SWTS-1-8 and SWTS-1-8 × CCRIS-34, emerged as desirable for grain yield at Nowshera and Swat, respectively. The inbred lines for the mentioned hybrids can be a source of germplasm improvement, breaking through undesirable linkages in future sweet corn breeding programs.

Maize Inbred Mp708 is Highly Susceptible to Western Corn Rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), in Field and Greenhouse Assays.

The western corn rootworm (WCR), Diabrotica vifgirera virgifera LeConte, (Coleoptera: Chrysomelidae) causes significant economic damage in corn production each year. Resistance to insecticides and transgenic corn with Bacillus thuringiensis (Bt), Berliner toxins have been reported throughout the United States Corn Belt. Corn breeding programs for natural resistance against WCR larvae could potentially assist in rootworm management. Root damage and root regrowth of eight corn lines were evaluated in field assays at three different locations. Results indicated the inbred 'Mp708' had the greatest root damage and was significantly greater than damage for the susceptible control, B37×H84. In greenhouse assays, we evaluated four of these lines plus a hybrid expressing the mCry3A Bt toxin for damage. The results indicated that Mp708 had significantly higher root damage when compared to 'CRW3(S1)C6' and 'MIR604'. Despite previous work suggesting otherwise, we conclude that Mp708 is highly susceptible to the WCR larvae based on root damage in field and greenhouse plant assays.

Population structure and marker-trait association study for kernel quality traits in sweet corn (Zea mays var. saccharata)

The study utilized 63 microsatellite markers linked with QTLs affecting different seed quality traits viz., pericarp thickness, soluble sugar, dextrose, sucrose, and amylose content, for validation in 39 sweet corn inbred lines. Observations were recorded on two quality traits viz., total soluble solids (TSS) and reducing sugar. Out of 63 SSR markers, 30 showed polymorphism and were subjected to population structure study and, single marker analysis for detecting their association with TSS and reducing sugar. The estimate of the likelihood of ΔK (where K= 2), classified the 39 sweet corn inbreds into two genetically distinct groups. The single factor ANOVA revealed five SSR markers, having P-value ≤ 0.05, had a high association with each of the quality traits. The markers viz., phi027, umc2056, umc1633, bnlg1265, and umc1031, located on chromosome number 9, 6, 2, and 4, were found to have a significant association with TSS. Likewise, five markers viz., umc1465, umc1633, umc1492, bnlg1079, and umc1320 had a significant association with reducing sugar. The marker, umc1633, had a significant association with both TSS and reducing sugar and can play a significant role in the selection of inbred lines superior in terms of TSS and reducing sugar for use in sweet corn breeding program.

Corn Starch: Quality and Quantity Improvement for Industrial Uses.

Corn starch serves as food, feed, and a raw material for industrial use. Starch makes up most of the biomass of the corn hybrid and is the most important and main yield component in corn breeding programs. Starch is composed of two polymers, branched amylopectin and linear amylose, which normally constitute about 75% and 25% of the corn starch, respectively. Breeding for corn starch quality has become economically beneficial because of the development of niche markets for specialty grains. In addition, due to the increased demands of biofuel production, corn ethanol production is receiving more attention. Consequently, improving starch quantity has become one of the most important breeding objectives. This review will summarize the use of corn starch, and the genetics and breeding of grain quality and quantity for industrial applications.

359 Intake and Growth Performance of Feedlot Lambs Fed Diets with Hi-a and Low-a Corn Cobs and Bermudagrass Hay

Abstract Hi-A™ corn is a unique type of lines and hybrids that were developed by the Texas A&M AgriLife Corn Breeding Program and have high anthocyanin and antioxidants. A completely randomized design trial was used to evaluated effects of Hi-A and low-A (regular) corn cobs and bermudagrass hay (BGH) in feedlot diets fed to female Rambouillet lambs (n = 10/treatment), with initial body weight (BW) of 30.7+1.2 kg, on dry matter intake (DMI), BW, average daily gain (ADG), and growth:feed ratio (G:F). After 14 days of adaptation, lambs were individually fed a total mixed ration with 80% concentrate and 20% of one of the roughages (Hi-A, low-A, or BGH) for 63 days. Hay was chopped, while cobs were ground using a hammermill with a 9.52-mm screen. Data were analyzed using repeated-measures ANOVA. The BW was not affected by the diet but increased (P < 0.001) during the trial. Diet did not influence the ADG. However, the ADG was lower (P < 0.001) in the d-42 (0.12 kg/d) than the rest of the trial (0.22 kg/d), after a period of constant high temperatures. The interaction diet vs. day affected (P < 0.05) DMI. In general, lambs increased (P < 0.05) DMI (g/d) and decreased (P < 0.05) relative DMI (%BW) in the final part of the trial, when the animals were getting closer to the harvesting date. Lambs had lower (P < 0.05) DMI of BGH diets than Hi-A diets from d-42 to d-63 and Low-A diets from d-49 to d-56. The G:F ratio was not affected by the diet but decreased (P < 0.05) from the middle to the end of the trial. Corn cobs are valuable as alternative roughage for feedlot lambs, with intake and growth performance comparable to BGH.

CO477, CO478, CO479, and CO480 inbred lines

CO477, CO478, CO479, and CO480 are mid- to late-season [75–81 d to flowering, crop heat units (CHU) = 1720–1855] corn (Zea mays L.) inbred lines with high stalk sugar levels. The level of sugar in the stalks are very high especially when grown as inbred lines. On average, the inbred lines yield three times more sugar than their testcrosses. These inbred lines are the first to be developed and released for biofuel production, from the corn breeding program of Agriculture and Agri-Food Canada. Additionally, these inbred lines can be used for sugar and (or) silage production. They have moderate to intermediate resistance to common rust, eyespot, northern corn leaf blight and fusarium stalk rot but are susceptible to gibberella ear rot.

The application of Tukey’s mean difference (Tukey’s HSD) for identification of local genetic sources of corn in selecting prospective parental lines

Extensive use of corn hybrids in Indonesia started in 1980 became expensive to farmers. In fact, the hybrids became obsolete and were replaced with the new ones. The obsolete hybrids, however, expressed superior traits toward detrimental hindrances in situ. The traits were identified, the obsolete hybrids were worthy to select for being local genetic sources (LGS) in a corn breeding program. The research was done to identify the LGS collected from Padang, Palembang, Jogjakarta, West Kalimantan and Lampung. In 2018 the LGS were planted in two rows and open-pollinated among themselves. The seeds were harvested separately to make female lines. A synthetic line was made by mixing 100 seeds of each female line. In 2019 the six lines: five female and one synthetic, and Pioneer36 (P36) F1-hybrid as control were planted in a randomized complete block design with 3 replicates. The data were collected for traits: plant height, leaf number plant−1, time to tasseling, time to silking, ear length, ear diameter, 100 seed weight and seed yield m−2. The data were variance-analysed and Tukey’s HSD was applied to separate and group the lines. A dendrogram was constructed to decide lines suitable to recombine. The result indicated that the Padang, Palembang, Lampung and Synthetic lines could be used as the male parents to recombine with the Jogjakarta and West Kalimantan lines. The Tukey’s HSD and dendrogram statistics could be useful to identify line superior and pairing appropriate lines as parents in a breeding program.

Allelic variation in sugary1 gene affecting kernel sweetness among diverse-mutant and -wild-type maize inbreds.

Sweet corn is popular worldwide as vegetable. Though large numbers of sugary1 (su1)-based sweet corn germplasm are available, allelic diversity in su1 gene encoding SU1 isoamylase among diverse maize inbreds has not been analyzed. Here, we characterized the su1 gene in maize and compared with allied species. The entire su1 gene (11,720bp) was sequenced among six mutant (su1) and five wild (Su1) maize inbreds. Fifteen InDels of 2-45bp were selected to develop markers for studying allelic diversity in su1 gene among 19 mutant- (su1) and 29 wild-type (Su1) inbreds. PIC ranged from 0.15 (SU-InDel7) to 0.37 (SU-InDel13). Major allele frequency varied from 0.52 to 0.90, while gene diversity ranged from 0.16 to 0.49. Phylogenetic tree categorized 48 maize inbreds in two clusters each for wild- type (Su1) and mutant (su1) types. 44 haplotypes of su1 were observed, with three haplotypes (Hap6, Hap22 and Hap29) sharing more than one genotype. Further, comparisons were made with 23 orthologues of su1 from 16 grasses and Arabidopsis. Maize possessed 15-19 exons in su1, while it was 11-24 exons among orthologues. Introns among the orthologues were longer (77-2206bp) than maize (859-1718bp). SU1 protein of maize and orthologues had conserved α-amylase and CBM_48 domains. The study also provided physicochemical properties and secondary structure of SU1 protein in maize and its orthologues. Phylogenetic analysis showed closer relationship of maize SU1 protein with P. hallii, S. bicolor and E. tef than Triticum sp. and Oryza sp. The study showed that presence of high allelic diversity in su1 gene which can be utilized in the sweet corn breeding program. This is the first report of comprehensive characterization of su1 gene and its allelic forms in diverse maize and related orthologues.

Variable levels of antibiosis and/or antixenosis of Bt and non-Bt maize genotypes on Dalbulus maidis (Hemiptera: Cicadellidae)

The corn leafhopper Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) poses a serious threat to the crop, causing direct and indirect damage to plants. The present study aimed to investigate the possible expression of resistance by antixenosis and/or antibiosis against D. maidis in 11 corn genotypes [8 non-Bt (60XB14, 90XB06, XB 9003, XB 8018, XB 8010, IAC 8390, IAC 8046, and IAC AIRAN) and 3 Bt (XB 7116 Bt, XB 8010 Bt, and DKB 310 Bt)] previously selected in a greenhouse. Initially, no choice preference tests for oviposition were performed to characterize the expression of antixenosis. To characterize the expression of antibiosis/antixenosis, the insects were confined to leaves of different genotypes to assess the following parameters: duration of each nymphal stage, nymphal period, viability per instar, total viability, and adult longevity. Additionally, morphological and physical analyses of the genotypes were carried out to establish correlations with the resistance categories. The genotypes 90XB06, IAC 8390, XB 9003 and DKB 310 PRO3 expressed antixenosis against leafhoppers, reducing insect oviposition. The genotypes 60XB14, 90XB06, IAC 8046, XB 8018 and IAC 8390 expressed antibiosis and/or antixenosis against leafhoppers, reducing nymphal viability. The hardness of the ribs is probably associated with the resistance of some of the evaluated genotypes and is an important morphological defense against leafhoppers. The results of this study are novel and can aid in corn-breeding programs focused on plant resistance to sucking insects, with relevant impacts on the integrated pest management of the crop.

Combining Ability Analysis in Sweet Corn (Zea Mays Saccharrata L.) Using Line by Tester Design

Aim The purpose of this study was to investigate the different combination of testcrosses for morphological and yield relating traits and to investigate general combining ability of the inbred lines. Materials and Methods This research was conducted at The University of Agriculture Peshawar, Pakistan during 2016. Line x-tester analysis was used to test general combining ability (GCA) effects of 24 S4 lines of sweet corn. Alpha lattice design with two replications and two checks was used during the experiment. Research data were recorded on various flowering, morphological and yield parameters. Results Highly significant variations were recorded among the testcrosses for the studied traits except anthesis silking interval (ASI), 100-kernel weight. Minimum days to tasseling (48-days) and silking (53.5-days) was exhibited by pop-syn-swt (9-4)×synthetic sweet. GCA effect was -2.14 for tasseling and -2.00 for silking. Maximum value (3.5-days) for ASI was recorded for Pop-synswt 1(8-3)×synthetic sweet, while GCA effect for ASI was -0.71. Lowest plant height (129.8 cm) was recorded for pop-syn-swt 1(3-3)×synthetic sweet, while GCA effect for plant height was observed to be -14.79. Maximum cob length (16.6 cm) was revealed by pop-syn-swt 1(12-2)×synthetic sweet. For cob length GCA effect of 1.01 was recorded. Maximum 100 kernel weight (31.3 g) was estimated for pop-syn-swt 1(2-1)×synthetic sweet. GCA effect of 1.85 was recorded for 100-kernel weight. Highest mean (7143.9 kg ha-1) for grain yield was recorded for pop-syn-swt 1(9-4)×synthetic sweet. GCA effect for grain yield was found to be 1370.93. Conclusion Generally a low GCA value, either positive or negative indicates that the mean of a parent does not largely vary from its offsprings. In contrast, high GCA value suggests that parent is either superior or inferior to the general mean and it has high heritability and less environmental effects. Based on the findings in this research, the above mentioned testcrosses can be included in future sweet corn breeding programs where early flowering and yield attributes is desired.

Evaluation of Corn Germplasm Accessions for Resistance to Clavibacter nebraskensis, Causal Agent of Goss's Bacterial Wilt and Leaf Blight.

Goss's bacterial wilt and leaf blight of corn (Zea mays), caused by Clavibacter nebraskensis, is a reemerging disease in the Midwestern United States. From 2011 to 2013, field studies and a greenhouse study were conducted to assess the University of Illinois maize inbred collection for putative sources of resistance to Goss's bacterial wilt and leaf blight. This inbred collection consisted of over 2,000 diverse inbred corn lines that have been collected from all over the world. An initial field screen of over 1,000 inbred lines from the collection was conducted in Urbana, IL in 2011. These lines were inoculated with a C. nebraskensis cell suspension and rated for Goss's bacterial wilt and leaf blight severity using a 1-to-9 scale, with a score of 1 being most resistant. Means for Goss's bacterial wilt and leaf blight ratings ranged from 1 to 8.5. The initial screen identified over 150 lines that had high levels of resistance (severity score of ≤2.5). In total, 177 lines were used in the second stage of field screening. In the second stage, average Goss's bacterial wilt and leaf blight severity ranged from 1.1 to 7.4. Nine lines with high levels of resistance in 2011 and 2012 were advanced to the third stage of field screening. The mean Goss's bacterial wilt and leaf blight severity rating of the resistant lines in the last stage was 1.9, while the susceptible check had a mean score of 6.4. These nine lines were also used in the greenhouse to assess whether resistance varied based on inoculating roots, stems, or leaves. Disease severity was significantly (P ≤ 0.05) less when roots were inoculated compared with both leaf and stem inoculations, which were not significantly different from each other. Lines having high levels of field resistance were also found to be resistant in greenhouse screening regardless of inoculation method. Clustering of pedigree distance of the 34 resistant lines (severity score of ≤2.5) with known pedigree information found that 21 clustered with the Lancaster heterotic family, 4 were related to the Iowa Stiff Stalk Synthetic family, and 9 did not cluster with an identifiable heterotic family. These results show that the Lancaster family is an excellent source of Goss's wilt resistance, and that fewer sources of resistance were found in other families. The most resistant lines identified from this research are potential sources of resistance to Goss's bacterial wilt and leaf blight, and their lineage can be used in corn breeding programs to develop resistant hybrids.

The Application of Metabolomics for the Study of Cereal Corn (Zea mays L.).

Corn (Zea mays L.) is an important cereal crop indigenous to the Americas, where its genetic biodiversity is still preserved, especially among native populations from Mesoamerica and South America. The use of metabolomics in corn has mainly focused on understanding the potential differences of corn metabolomes under different biotic and abiotic stresses or to evaluate the influence of genetic and environmental factors. The increase of diet-linked non-communicable diseases has increased the interest to optimize the content of bioactive secondary metabolites in current corn breeding programs to produce novel functional foods. This review provides perspectives on the role of metabolomics in the characterization of health-relevant metabolites in corn biodiversity and emphasizes the integration of metabolomics in breeding strategies targeting the enrichment of phenolic bioactive metabolites such as anthocyanins in corn kernels.

Draft Genome Sequence Resource for Phyllachora maydis-An Obligate Pathogen That Causes Tar Spot of Corn with Recent Economic Impacts in the United States.

Phyllachora maydis is an important fungal pathogen that causes tar spot of corn and has led to significant yield loss in the United States and other countries. P. maydis is an obligate biotroph belonging to the Sordariomycetes class of Ascomycota. Due to the challenges posed by their obligate nature, there is no genome sequence available in the Phyllachora genus. P. maydis isolate PM01 was collected from a corn field in Indiana and the genome was determined by next-generation sequencing. The assembly size is 45.7 Mb, with 56.46% repetitive sequences. There are 5,992 protein-coding genes and 59 are predicted as effector proteins. This genome resource will increase our understanding of genomic features of P. maydis and will assist in studying the corn-P. maydis interaction and identifying potential resistant candidates for corn breeding programs.

Development and selection of super-sweet corn genotypes (sh2) through multivariate approaches

ABSTRACT The aim of the present study was to investigate relations among ten traits in super-sweet corn genotypes assessed by means of simple correlation, path and canonical variable analyses, as well as to investigate the relative importance of such traits to the super-sweet corn breeding program developed at Darcy Ribeiro Northern Fluminense State University in order to develop strategies able to improve the efficiency in the selection of superior genotypes. Thus, trials comprising 3 × 6 partial diallel of super-sweet (sh2) corn were carried out, according to a short_textrandomized block design (RBD)short_text with four repetitions, in two different environments located in Northern Rio de Janeiro State, Brazil (Itaocara and Campos dos Goytacazes counties). The correlation study showed that traits such as ear diameter and useful short_textearshort_text length contributed the most to increase short_textearshort_text yield (without husk); the variable ear diameter stood out for having stronger direct effect on ear yield, as well as for presenting high heritability (0.95). The trait number of grains per ear row contributed the most to the variation between hybrids, whereas the trait useful ear length contributed the least. The canonical variables showed that the genetic backgrounds of sh2-gene donor populations had effect on recurrent populations, even after five backcrossing cycles, thus resulting in the formation of two divergent groups.

Development of correction tools and algorithms for breeding programs on corn

Aim and tasks of the study. To establish implementation and correction vectors for regional breeding programs on corn.Results and discussion. It was established that Kharkovskaya, Kirovogradskaya and Kievvkaya were leading among corn hybrids bred by the Plant Production Institute named after VYa Yuriev of NAAS in terms of sown areas (53%, 20% and 13%, respectively, in the region). At the same time, at the existing specialized markets, Plant Production Institute named after VYa Yuriev of NAAS, as a model breeding center, presents 20 corn hybrids orientated both at the parochial market (Kharkivska region) and at the outer market (other regions of Ukraine). Of the 20 hybrids analyzed as model breeding objects in 11 regions of Ukraine in 2014-2017, Rusich, Kredit, Vympel MV, Varta MV, and Svitanok MV were distinguished over the monitoring period.Conclusions. The approaches presented and the results obtained should be considered as components of the correction toolkit and algorithms for corn breeding programs and breeding innovation parameters. With this approach, enhanced coordination between corn breeding and marketing programs is achieved.

Keragaan Agronomi dan Potensi Hasil Genotipe Jagung (Zea mays L.) Generasi S1 dan S2 di Dua Lokasi

Hybrid maize breeding relies on the availability of good performing inbred lines with superior combining ability. The objectives of this study were to: (1) estimate genetic paramters and heritability for agronomic and yield traits, (2) estimate correlations among traits, and (3) estimate selection-balanced inbreeding depression level from S1 to S2 generations. The S1 trial was planted from June to September 2014 at two locations, followed by the S2 trial from January to May 2015 at the same locations. Each trials was arranged in an augmented design with three blocks consisting of 72 unreplicated test genotypes, 3 unreplicated inbred lines, and 5 replicated commercial hybrid varieties as checks. The results showed that the heritability estimates were medium to high for most observed traits. Best yielding genotypes in S1 and S2 generations were derived from P27xNK6326, Pertiwi3xP31, NK6326xP31, P31xNK6326, and P31xNK33 populations. Grain yield was positively correlated with plant height, ear height, ear length, and ear diameter in S1 and S2 generations. The S2 generation exhibited inbreeding depression for grain yield. The estimates of heritability, correlations, and inbreeding depression obtained from this study could be useful for selection in corn breeding programs.<br /><br />Keywords: correlation, heritability, inbreeding depression<br /><br />