M. J. Carena

Classification of North Dakota maize inbred lines into heterotic groups based on molecular and testcross data

Establishment of the best combination among heterotic groups, heterotic patterns, is crucial to the development of successful maize (Zea Mays L.) hybrids. The use of molecular markers in maize-breeding programs might or might not increase the efficiency of heterosis prediction by classifying diverse inbred lines into heterotic groups. The objectives of present research were to classify elite North Dakota (ND) maize inbred lines into heterotic groups and evaluate the consistency between simple sequence repeat (SSR) grouping and testcross data. Thirteen ND inbred lines representing diverse genetic background were crossed in a diallel mating design in 2000. The crosses and 12 checks were evaluated across four ND environments in 2001 and 2002. In addition, these lines were crossed to commercial inbred testers representing known heterotic groups in 2002. Hybrids between public and private lines were evaluated across three ND environments in 2003. Inbred lines representing Lancaster Sure Crop, Iowa Stiff Stalk Synthetic (BSSS), Minnesota #13, Northwestern Dent, Golden Glow pedigrees and ND inbred lines were screened with 49 SSR markers. Inbred lines ND246, ND278, ND280, ND281, ND282 and ND284 were clustered within the BSSS heterotic group. Inbreds ND277, ND285, ND286, ND290, and ND291 grouped closer to the Lancaster Sure Crop heterotic group. Inbred lines ND257 and ND288 grouped within Minnesota #13. Data from ND278 and ND290 testcrosses showed good combining ability with testers representing more than one heterotic group. Our research shows that groups of genetically similar germplasm could not be identified accurately and reliably with molecular markers even when the available germplasm was diverse contrary what has been suggested. Therefore, extensive field evaluation is recommended to classify unrelated inbred lines of maize.

Maize commercial hybrids compared to improved population hybrids for grain yield and agronomic performance

Improved maize (Zea mays L.) populations and population hybrids can both be profitable alternatives to commercial single-cross hybrids as well as good elite sources of diverse inbred lines. The objective of this research was to compare grain yield and agronomic performance between early maturing maize population hybrids and current early maturing commercial single-cross hybrids. This is a consequence of our research program targeted at identifying alternative heterotic patterns for the northern Corn Belt. Improved maize populations and population hybrids (S0 generations) were evaluated in experiments arranged in randomized complete block and partially balanced lattice designs across 29 environments. Grain yield potential of population hybrids was optimally expressed under irrigated conditions. Data across environments showed that 20% of the population hybrids evaluated were not different (P ≤ 0.05) from at least one of the commercial single-cross hybrids for grain yield performance, root lodging, and stalk lodging percentages. The average mid-parent heterosis value across population hybrids from different geographic regions was 20.4% with negative estimates observed in only two population hybrids. Breeding efforts toward elite populations and population hybrids have demonstrated that germplasm improvement is extremely valuable and deserves public funding. These efforts should be supported in order to enable the development of elite sources of diverse inbred lines and the development of improved population hybrids for specific markets (e.g., organic) to increase producer options. Public maize breeding programs utilizing recurrent selection methods for germplasm improvement could address the need. These programs, however, should incorporate extensive testing of population hybrids.

Divergent recurrent selection for cold tolerance in two improved maize populations

Maize (Zea mays L.) production has significantly expanded into very short-season environments where germination and growth in cooler environments is essentially a pre-requisite. Therefore, an important goal for maize breeders is to improve local germplasm sources of inbred lines that are able to grow under these challenging conditions. The objective of this research was to evaluate direct and correlated responses in two improved early maturing maize populations [NDSCD(M)C10 and BS22(R)C7] after two cycles of S1 and full-sib intra-population recurrent selection for cold tolerance. The S1 and full-sib progenies were obtained by self-pollinating 100 random plants and by intercrossing 200 random plants, respectively. Ten percent of the families were selected, based on an index that included emergence percentage, seedling vigor, and root lodging percentage, and recombined at the same time in a summer nursery based upon data across northern North Dakota locations. The essential benefit of this breeding methodology was to achieve one year per cycle of selection based upon progenies. However, direct response to selection was not significant while some correlated responses were significant. We decided to report these results in order to encourage other scientists the evaluation of additional sources of germplasm, the screening at various dates, and the selection of target environments with more intensive cold stress before initiating long-term selection programs for cold tolerance. In addition, further research on the current and alternative long-term selection methods for cold tolerance is recommended for continuous genetic improvement of advanced cycles in the northern U.S. Corn Belt.

Testers and Combining Ability

The inbred–hybrid concept was created in the public sector with the direct influence of Darwin, Festetics, Mendel, and Vilmorin. East related those biological principles to the more practical plant improvement studies to achieve his goals (Hayes, 1956). The progeny test was defined by Allard (1960) as ‘a test of the value of a genotype based on the performance of its offspring produced in some definite system of mating.’ It was used as early as 1850 by Vilmorin in France, and it proved to be a highly effective procedure for the improvement of sugar content of sugar beets (Beta vulgaris). This method of line selection with progeny testing was known as the ‘Vilmorin method’ or ‘Vilmorin isolation principle’ and was introduced in several plant breeding programs in the latter part of the 19th century. The progeny test in maize was first used in 1896 by Hopkins, starting the well-known program for half-sib recurrent selection of maize oil and protein content (e.g., the ear-to-row half-sib selection procedure).

Response to long-term selection in early maturing maize synthetic varieties

Long-term continuous selection is essential for germplasm improvement. However, choice of germplasm for long-term genetic improvement might limit the success of germplasm enhancement programs. The objective of this research was to report the response to long-term selection in early maturing North Dakota (ND) synthetic varieties. We wanted to determine whether the performance of three ND maize synthetic varieties was improved by long-term mass selection (M) and if the performance of one of them was improved by long-term modified ear-to-row (MER) selection. The evaluation of long-term selection response was performed at two plant densities. An experiment in a randomized complete block design with split-plot arrangement was used to evaluate NDSM(M), NDSAB(M), NDSCD(M), and NDSAB(MER) under 75,000 and 42,500 plants per hectare across seven environments. Long-term mass selection for grain yield and stalk lodging resistance in NDSM(M), NDSAB(M), and NDSCD(M) was not successful, since there were no significant changes in grain yield or stalk lodging in these populations at either low or high densities. On the other hand, long-term modified ear-to-row selection was effective for grain yield improvement in NDSAB(MER). Grain yield increased non-linearly from 3.9 Mg ha−1 in cycle 0 to 5.0 Mg ha−1 in cycle 12 at a rate of 2.5% per cycle. Interaction between plant density and genotype was not detected even though selection was performed at relatively low densities (20,000 plants ha−1 for mass selection and 50,000 plants ha−1 for ear-to-row selection). The confirmation of a lack of interaction between plant density and genotype suggests that selection at low plant densities might still be able to provide high-density stress resistance through density-independent genotypes, allowing progeny testing across multiple locations with better accuracy and fewer resources. Selection methods that emphasize both additive and dominance effects such as full-sib recurrent selection are recommended to maximize genetic improvement of advanced population cycles of early maturing synthetics.

Development of cold and drought tolerant short-season maize germplasm for fuel and feed utilization

Milho se tornou uma alternativa rentavel para os agricultores e pecuaristas de North Dakota (ND). No entanto, os hibridos desenvolvidos pela industria do Norte dos EUA ainda nao tem tolerância ao frio e a seca, bem como nao tem a adequada qualidade do grao para produtos como etanol e alimentacao animal. Portanto, e necessario aumentar o valor das operacoes de alimentacao animal antes e depois da utilizacao do etanol. O programa da North Dakota State University (NDSU) iniciou o desenvolvimento de hibridos que apresentem alto conteudo de proteina atraves do projeto de milho precoce com alto conteudo de proteina de qualidade (EarlyQPMF). O Programa da NDSU atua como um fornecedor genetico para empresas de sementes basicas, companhias varejista de sementes, industria de processamento, e melhoristas, nacionais e internacionais. Nos ultimos 10 anos, NDSU obteve nove certificados de protecao (PVP) de milho e lancou 38 produtos de milho. Dentro desses, 13 linhagens foram lancadas, exclusivamente, para uma empresa de sementes basicas para fins comerciais. Alem disso, dois hibridos foram identificados para a producao comercial na regiao central e ocidental de North Dakota.

Germplasm enhancement for adaptation to climate changes

Billions of dollars and crops are being lost to drying high moisture grain; drought, cold, and salt susceptibility; and to processing poor quality grain. Maize is a model crop for adaptation to climate changes. Breeding for adaptation is best done under challenging environmental conditions where strengths and weaknesses are quickly identified and most stable genotypes are selected. The North Dakota State University (NDSU) maize breeding program is strategically located to develop products under extreme weather. It currently exploits northern U.S. environments that allow screening for adaptation traits that are as important as yield. The program focuses on germplasm adaptation and its integration into cultivar development, particularly those carrying unique alleles not present in the B73 and NAM genomes. There is a need for projects that are vital to agricultural research and will meet present and future demands of superior genotypes tolerant to climate changes in the U.S. and abroad.

Hereditary Variance: Mating Designs

Average allele frequency at segregating loci of F2 populations derived from pure line crosses is expected to be p = q = 0.5. From now on, however, we will use as source material genetic broad-based populations with arbitrary allele frequencies. This means that special case of p = q = 0.5 often does not apply. Therefore, p is not equal to q.

Resemblance Between Relatives

The degree of relationship between relatives depends on genetic resemblance. They are very important to breeders since they are not only used to estimate the genetic variances of reference plant populations but also used in breeding methods used for selection. All breeding methods deal to some extent with resemblance between relatives.

Can expired proprietary maize ( Zea mays L.) industry lines be useful for short-season breeding programs? II. Agronomic traits

U.S. Patent and Plant Variety Protection Act protect maize (Zea mays L.) inbreds and hybrids. The overall objective of this research was to assess the usefulness of patent expired maize inbred lines. Factorial crosses were made including North Dakota State University (NDSU) lines, ex-PVP lines, and top industry testers in the 2010 NDSU Fargo summer nursery and in the 2010–2011 NDSU New Zealand winter nursery. Hybrids were planted across six different ND environments in 2011 and 2012 following partially balanced lattice experimental designs. Combining ability analyses were performed following a factorial design with fixed parents. Our research identified ex-PVP inbreds PH207, Q381, PHP02, S8324, PHK76, CR1Ht, PHT77, LH205, LH54, and PHJ40 as above average lines in hybrid combinations to increase yield. Our trials suggest most ex-PVP lines are not useful directly for commercial purposes but could be used as potential breeding sources for short-season maize breeding programs. Improvements in intellectual property and re-thinking of breeding rights access are encouraged to explore more suitable hybrids for northern U.S. farms. Current industry lines have important trait weaknesses for northern U.S. climates that public sector breeders in strategic breeding locations could improve in order to develop better hybrids for farmers. Our preferred choice would be to partner with industry in order to improve current industry lines with known weaknesses, especially for northern U.S. and Canada environments.