Open Pollinated Maize Varieties Research Articles

Stability and Adaptability of Nine Open Pollinated Varieties of UB Maize

Open pollinated maize and two check varieties were evaluated in four locations, i.e. Malang, Jombang, Kediri, and Trenggalek regencies for two seasons from March to November 2009. The research objective was to determine stability and adaptability of the open pollinated maize. The experiment was conducted using a randomized complete block design. The treatment had nine lines, i.e. UB4101, UB3101, UB4201, UB7201, UB4202, UB3301, UB4301, UB7301, UB3302 and two check varieties, Bisma and Arjuna. The treatment was repeated three times. Percentage point of variance ratio was applied to determine homogeneity error. Variance analysis of combined experiment was conducted to determine genotype x environment interaction. Yield stability and adaptability were analyzed using Eberhart and Russell linear models. There was genotype x season x location interactions on maize yield. It mean that there were population yield performance changes at different environments. There were four populations have stability point, i.e. UB4101 (5.5 t ha-1), UB3301 (5.7 t ha-1), UB7301 (5.7 t ha-1), and UB3302 (5.4 t ha-1). Population UB4201 (5.1 t ha-1) was adaptable to productive environment, and UB4301 (5.8 t ha-1) was adaptable to marginal ones. Keywords: G x E interaction, stability, adaptation, open pollinated maize variety, UB line

Combining ability for maize grain yield and other agronomic characters in a typical southern guinea savanna ecology of Nigeria

Field experiments were conducted at the University of Ilorin Teaching and Research Farm in 2005 and 2006 cropping seasons with the objective to evaluate the combining ability for maize grain yield and other agronomic characters in 10 open pollinated maize varieties, which have been selected for high yield and stress tolerance. General combining ability (gca) and year (y) effects were significant for all the parameters except plant height, while specific combining ability (sca) and gca x year effects were significant only for grain yield. However, Tze Comp4 Dmr Srbc2, Tze Comp4 C2 and Acr 94 Tze Comp5 which are good general combiners for maize grain yield, also showed positive significant gca x year effects for flowering traits. Significant sca x year interaction effects were recorded for maize grain yield and days to flowering, with Hei 97 Tze Comp3 C4 combining very well with 3 parents (Acr 90 Pool 16-Dt, Tze Comp4-Dmr Srbc2 and Tze Comp4 C2). These parents and their hybrids probably have genes that can be introgressed into other promising lines in developing early maturing and high yielding varieties for cultivation in the Nigeria savannas.

Combining ability for maize grain yield and other agronomic characters in a typical southern guinea savanna ecology of Nigeria

Field experiments were conducted at the University of Ilorin Teaching and Research Farm in 2005 and 2006 cropping seasons with the objective to evaluate the combining ability for maize grain yield and other agronomic characters in 10 open pollinated maize varieties, which have been selected for high yield and stress tolerance. General combining ability (gca) and year (y) effects were significant for all the parameters except plant height, while specific combining ability (sca) and gca x year effects were significant only for grain yield. However, Tze Comp4 Dmr Srbc2, Tze Comp4 C2 and Acr 94 Tze Comp5 which are good general combiners for maize grain yield, also showed positive significant gca x year effects for flowering traits. Significant sca x year interaction effects were recorded for maize grain yield and days to flowering, with Hei 97 Tze Comp3 C4 combining very well with 3 parents (Acr 90 Pool 16-Dt, Tze Comp4-Dmr Srbc2 and Tze Comp4 C2). These parents and their hybrids probably have genes that can be introgressed into other promising lines in developing early maturing and high yielding varieties for cultivation in the Nigeria savannas. Key words: Zea mays L., general combining ability, specific combining ability, grain yield, Nigeria savannas.

Environmental stratification based on a 28 x 28 diallel of open-pollinated maize varieties

The objective of this study was to assess the representativeness of the test environments used by the maize breeding program of Embrapa in the first phase of genotype evaluation. Ear weight of 378 hybrids from a diallel of 28 open- pollinated varieties (OPVs) evaluated in ten environments were used. The following environments were evaluated: two growing seasons (1991-92 and 1992-93), at three locations (Sete Lagoas, MG, Londrina, PR, and Goiania-GO); in two growing seasons (1991/92 and 1993/94) in Aracaju-SE; and in two growing seasons (1992-93 and 1993-94), in Ponta Grossa-PR. The complex part of the interaction accounted for nearly 75% of the genotype by environment interaction (G x E). The environments of Londrina-91/92, Ponta Grossa-93/94 and Aracaju-93/94 differed from the others and also from each other, as shown by stratification analysis. The phenotypic correlation between genotype means in the pairwise grouped environments, interpreted as coefficient of genotypic determination, indicated that non-genetic causes were responsible for 64.40% of the mean phenotypic variances. The results confirmed the discrimination of three major environmental groups, representing the Northeast (Aracaju), Central Southeast (Sete Lagoas, Goiania and Londrina) and South (Ponta Grossa) regions.

Evaluation of mineral content in maize under flooding

This study examined the effects of plant mineral content on different cycles of recurrent selection of the flood- tolerant, open-pollinated maize variety BRS 4154 - Saracura, under soil flooding. Experiments with the main treatments flooded or unflooded were conducted in Sete Lagoas, MG - Brazil. Samples of the cycles 1, 5, 9 and 15 were sown in a randomized block design. The open-pollinated variety BR 107 and single-cross hybrid BRS 1010 were used as flood- susceptible controls. The stress caused by water excess in the soil reduced the nitrogen content in the cycles 5 and 9, and calcium in cycle 15; but increased potassium in cycle 1. However, it did not significantly influence the content of phosphorus, magnesium, sulfur, zinc, and copper. Additionally, recurrent selection under flooding diminished potassium and calcium content along the cycles.

Evaluation of early to medium maturing open pollinated maize varieties in SADC region using GGE biplot based on the SREG model

Analysis of multi-environment trials (METs) of genotypes (G) and genotype × environment (GE) interactions for yield performance across environments, and selection of the best genotypes is an important routine in maize breeding programs. Analysis and interpretation of METs data have been limited to analysis of variance and mean comparison among genotypes. This type of analysis has not been effective in exploiting GE interactions encountered in METs data sets. The objectives of this study were to exploit METs data sets from maize regional trails using G plus GE interaction (GGE) biplot based on the site regression (SREG) model. The GGE biplots displays graphically the relationship among test environments, genotypes and GE interactions. Grain yield data of 35 early to medium maturing open pollinated maize varieties (OPVs) from five seasons (1999–2003) across 59 locations in Southern African Development Community (SADC) were analyzed. The GGE biplots based on the SREG model indicated that yield performance of maize OPVs were under major environments and of GE interactions. The construction of GGE biplots based on SREG model analysis showed the ideal test environments that discriminate well performing maize OPVs from poor ones, the performance of each OPV in specific year, the discrimativiness versus representativeness view of the GGE biplot of the test locations across the years, the relation among OPVs relative to grain yield, the stability of OPVs across environments and which OPVs is best for what.

Potential causes of linkage disequilibrium in a European maize breeding program investigated with computer simulations

Knowledge about the forces generating and conserving linkage disequilibrium (LD) is important for drawing conclusions about the prospects and limitations of association mapping. The objectives of our research were to examine the importance of (1) selection, (2) mutation, and (3) genetic drift for generating LD in a typical maize breeding program. We conducted computer simulations based on genotypic data of Central European maize open-pollinated varieties which have played an important role as founders of the European flint heterotic group. The breeding scheme and the dimensioning underlying our simulations reflect essentially the maize breeding program of the University of Hohenheim. Results suggested that in a plant breeding program of the examined dimension and breeding scheme, genetic drift and selection are major forces generating LD. The currently used population-based association mapping tests do not explicitly correct for LD caused by these two forces. Therefore, increased type I error rates are expected if these tests are applied to plant breeding populations. As a consequence, we recommend to use family-based association tests for association mapping approaches in plant breeding populations.

Participatory maize breeding in Portugal. A case study

Participatory maize breeding (PMB) was initiated in Portugal in 1984 by Dr. Silas Pêgo at Sousa Valley. The VASO project was intended to answer the problem facing small farmers, i.e. yield increasing without losing the parameters defined by farmers in polycropping systems maintaining the quality traits under a sustainable agriculture. This model is based on the Integrant Philosophy, which contrasts with the Productivist Philosophy. The Integrant Philosophy is intended to fit a multicrop agricultural system that corporate agriculture does not reach due to incipient market conditions. The present document intends to be a contribution to: 1) the study of 20 years of VASO; 2) methods used in PMB for Portuguese open-pollinated maize varieties and 3) present research.

English

Field trials testing the effects of five rates each of N, P and K application on three hybrid and two openpollinated maize varieties were conducted in three separate experiments on an Arenic haplustalf (USDA) at Ilora in the derived savanna and Typic paleustalf (USDA) at Mokwa in the southern guinea savanna of Nigeria. The hybrid maize varieties planted were 8516-12, 8321-18 and 8329-15 and were compared with the open-pollinated maize, TZSR-Y and TZSR-W. Nitrogen was applied at rates 0-200 kg ha -1 in the first trial, while P and K were supplied as basal nutrients. In the second trial, P was applied at rates 0- 80 kg P2O5 ha -1 using basal N and K fertilizers. In another trial, K was applied at rates 0-120 kg ha -1 with blanket application of N and P. The hybrid maize gave higher yields and used N and P more efficiently than the open pollinated at both trial locations. The yield of maize was higher in the southern guinea savanna than in the derived savanna. The performance of the hybrid varieties followed in the ascending order of 8516-12, 8321-18 and 8329-15. The optimum rates of N and P for maize grown in the derived savanna were 100 and 40 kg ha -1 respectively. In the southern guinea savanna the open pollinated and hybrid varieties responded up to 150 and 200 kg N ha -1 respectively. The 8516-12 showed higher N and P use efficiency than other varieties. Consequently, planting such variety could be advantageous, using minimal dose of fertilizer most especially, where farmers have less access to fertilizer.

A new search for restorer cytoplasm: the restorer cytoplasm for the gene ms10 most probably does not exist in maize.

Since the suggestion concerning the hypothesis of the existence of restorer cytoplasms for some of the known and currently available male sterile (ms) genes in maize, a relatively limited amount of research effort has been made in order to test the hypothesis. Considering the importance of such a phenomenon, we designed a large, two-part experiment to test the idea more seriously. In the first part, 50 randomly chosen, medium-late open-pollinated (OP) varieties of maize from the Zemun Polje (ZP) collection were tested for the presence of the restorer cytoplasm in some currently known ms-genes in maize (ms1, ms2, ms3, ms4, ms5, ms6, ms7, ms8, ms9, ms11, ms12, ms13, ms17, ms22, ms23, and ms24). In the second part, the whole ZP collection of maize germplasm (more than 4,000 entries) was tested for the presence of the restorer cytoplasm for the gene ms10. After the first basic screening of OP varieties, more than 70 nonsegregating "candidates" were identified; however, after additional screening of the collection and the direct testing with respective homozygous ms-testers, all of them showed segregation, indicating that the restorer cytoplasm does not exist, especially the gene ms10. While performing this experiment, we discovered almost a hundred sources of male sterile cytoplasm, which were distinguished by their overwhelming frequency of male sterile plants in segregating test progenies.

Inbreeding depression of 28 maize elite open pollinated varieties

The study of inbreeding depression is important for breeding strategies such as use of inbred progenies or extraction of inbreed lines. A diallel of 28 maize open-pollinated varieties was evaluated in 10 environments in the early 1990s. At the same time, S1 populations for each of the 28 varieties were evaluated in the same 10 experiments (environments). Yield reductions of the populations from S0 to S1 (mean of the 10 environments), varied from 34.6% (CMS-01) to 59.2% (CMS-30), with an average of 49.1%. Inbreeding depression was greater in populations with a wider genetic base, which had never been exposed to inbreeding (CMS-30, BR-107, PH4, Cunha, Saracura, Nitrodent, and Nitroflint). Inbred lines with greater yield means should be obtained from the BR-105, BR-111, CMS-01, CMS-03, BR-106, CMS-14c, and CMS-28 populations. The use of parameter estimates generated by analysis of inbreeding depression, allow to make inferences about frequencies of deleterious alleles in the population. The frequencies of favorable alleles in the parents can be obtained by diallel analysis. The association of these two types of information, can provide a better interpretation of the genetic parameters and also can improve the process of selection of parents for either an intra- or an inter-populational breeding program.

Genetic Variation in Total Carotene, Iron, and Zinc Contents of Maize and Cassava Genotypes

Deficiencies of vitamin A, iron, and zinc are widespread in sub-Saharan Africa, where the diets are mainly plant-based and the intakes of animal products are low. The overall objective of this investigation was to determine the extent of genetic variation of these micronutrients in 16 yellow-seeded improved maize varieties, 109 maize inbred lines (60 from mid-altitude and 49 from lowland/savannah agroecologies), and 162 cassava clones resistant to the cassava mosaic disease. The yellow-seeded improved maize varieties were analysed for physical and chemical characteristics and total carotene content; the maize inbred lines and cassava clones were analysed for iron and zinc content. The results showed statistically significant and large genotypic differences in total carotene content among the 16 yellow-seeded improved, open-pollinated maize varieties. The total carotene content ranged from 143 to 278 μg/g. Significant genotypic variation was also observed for iron and zinc concentrations in maize inbred lines and cassava storage roots. Iron concentration ranged from 15 to 159 ppm for mid-altitude and from 14 to 134 ppm for lowland maize inbred lines; zinc concentration ranged from 12 to 96 ppm for mid-altitude inbreds and from 24 to 96 ppm for lowland inbred lines. For cassava storage roots, the range was 4 to 95 ppm for iron and 4 to 18 ppm for zinc. A strong and positive relationship was observed between iron and zinc concentrations for both mid-altitude and lowland maize inbred lines, but this relationship was weak for the cassava clones. The potential exists for improving carotene, iron, and zinc contents in maize and cassava genotypes through plant-breeding.

CHARACTER ASSOCIATION AND COMPONENT ANALYSIS IN MAIZE

An experiment with four hybrids and one open pollinated maize variety was conducted to study the association of seven characters with grain yield by subjecting it to path coefficient analysis. Ear girth, kernel rows, 1000-seed weight, kemels per row and car length had significant and positive correlation with seed yield. Ear length and ear girth play major role in deciding grain yield since they had inter-conclation with other yield contributing characters. High and positive direct effects were observed for kernel rows and 1000-seed weight. Considerable indirect effect of most of the yield contributing characters through kemel rows was observed. Hence, ear girth and kernel rows should be given more importance while formulating selection indices for yield improvement in maize.

Adoption, management, and impact of hybrid maize seed in India

This paper presents results of a 1995 survey of 864 maize-growing households in six states that account for more than 70% of India's maize area: Andhra Pradesh, Bihar, Karnataka, Madhya Pradesh, Rajasthan, and Uttar Pradesh. The current adoption of improved open-pollinated maize varieties (OPVs) and hybrids is quantified, the relationship between adoption of improved germplasm and use of improved crop management practices is examined, the economic impacts of adoption are estimated, farmers' seed procurement and management practices are described, and implications for maize research and development policy are discussed. On the whole, the survey results confirm that India's national maize seed industry is expanding rapidly. Since seed policy reforms were introduced in the late 1980s, the area planted to improved OPVs and hybrids has grown rapidly, and adoption of improved germplasm has fueled important changes in farmers' crop management practices. However, special policy measures may be needed to ensure that the benefits of improved germplasm are widely shared, such as the introduction of targeted input subsidies designed to reduce the cost of adopting improved seed and complementary inputs, government investment in irrigation infrastructure to reduce production risk in drought-prone environments, and market development initiatives to provide small-scale producers with access to stable and reliable outlets where they can sell surplus grain.

The maize seed industries of Brazil and Mexico: past performance, current issues and future prospects

This paper describes results of a study of the main factors affecting the development of the maize seed industries in Brazil and Mexico (and, by extension, other developing countries). The authors develop a framework that researchers and policy makers can use to evaluate seed industry performance in developing countries. This framework is used to analyze the seed industries of Brazil and Mexico, where very different sets of circumstances influence seed industry development, efficiency, and structure. The analysis gives special attention to the different maize breeding strategies pursued by the public and private sectors, measures of industry competitiveness and efficiency, and the trade-offs involved in developing and producing different kinds of maize seed, particularly improved open-pollinated maize varieties versus different types of hybrids. The authors identify key seed industry issues for researchers, administrators of national maize programs, and agricultural policy makers in developing countries, especially issues related to the appropriate roles for public and private organizations in maize seed industries in the developing world.

Diallel study of open-pollinated maize varieties in Trinidad

In Trinidad, maize (Zea mays L.) is primarily harvested in the immature stage as green ears for human consumption. The purchase of popular imported hybrid seed has become a substantial component of the economic inputs of maize production. The objectives of this study were to investigate combining abilities and heterotic patterns among available open-pollinated varieties and to assess correlations among five important traits: time to silking, plant height, grain yield, ear size, and marketable ears per hectare. General combining ability was significant for all traits. Specific combining ability was significant for all traits except ear size. Three intervarietal crosses showed moderate levels of heterosis (10–27%), and several yielded similarly to the control hybrids, Pioneer X304 and Pioneer 3078. The cross Acid Soil Tolerant 1991 SA-3 X ICTA Farm Corn was selected as the most suitable base population for mass selection. Phenotypic and genotypic correlations among the five traits studied were all positive and significant. Populations which flowered early were shorter and yielded less than the late flowering and taller populations and population crosses included in this study.

Variation in the ribosomal DNA intergenic spacer of a maize population mass-selected for high grain yield

Variation in the intergenic spacer of ribosomal DNA (rDNA) was detected among individual plants of the open-pollinated maize variety 'Hays Golden' and populations derived from this variety. rDNA intergenic spacer-length variants were detected at approximately 200 bp intervals, consistent with the number of 200 bp subrepeats as the basis for this variation. Inheritance data revealed that more than one spacer-length class may be present on an individual chromosome. Fourteen different predominant rDNA intergenic spacer hybridization fragment patterns were detected. C-29, a population developed by 29 cycles of mass-selecting Hay Golden for high grain yield, exhibited a significant change in rDNA intergenic spacer hybridization fragment pattern composition in comparison to Hays Golden. This change included a reduction in frequency of the shortest predominant space-length variant (3.4 kb) and an increase in a 5.2 -kb hybridization fragment. I-31, a population developed through thermal neutron irradiation of Hays Golden and 31 generations of mass selection for high grain yield, did not exhibit a significant change in overall rDNA intergenic spacer composition. I-31 did exhibit an increase in frequency of the 5.2-kb hybridization fragment and a significant change in two specific hybridization fragment patterns that had also changed in C-29. These data, particularly for the C-29 population, suggest that rDNA intergenic spacer-length variants and/or associated loci were influenced by selection.

A comparison of results obtained with two methods for assessing yield stability

A major objective of the CIMMYT Maize Program is to develop open-pollinated varieties of maize (Zea mays L.) that are well adapted to a wide range of environments. To achieve this breeding goal, it is essential that the program use a stability technique that will identify high-yielding, stable genotypes accurately in international trials conducted under different environmental conditions. The objective of this study was to compare a spatial method with a modified conventional regression analysis method to determine the yield stability of 27 CIMMYT maize varieties evaluated at 37 locations. The methods also were compared on the basis of their consistency in assessing the stability of varieties when certain locations were omitted, and when subsets of varieties were analyzed. The varieties found to be stable by the spatial method with all sites included in the analysis were also stable (1) when the lowest and highest yielding sites were excluded from the analyses, and (2) when the varieties were considered, along with others, as a subset of the original group of materials. Stability parameters determined by regression analysis, however, varied for some varieties when (1) extreme sites were excluded, and (2) a subset of entries was considered in isolation. Because the spatial method was more consistent in identifying high-yielding stable varieties, it was considered the more useful of the two methods.

Occurrence and behavior of the components of the 02-m(r)-Bg system of maize controlling elements

o2-m(r) is an unstable allele of the O2 locus responding to the regulatory element Bg by somatic reversion. The spontaneous occurrence and the properties of the components of this system of controlling elements have been investigated. The system appears to have some degree of specificity for the O2 locus, because the majority of spontaneous O2 mutations are responsive to Bg. The component at the controlled locus undergoes frequent changes in state, while the Bg element appears more stable. Bg activity was revealed in 11 out of 108 open-pollinated varieties of maize. Most of the newly isolated Bg elements are linked with the O2 locus. The timing of induction of reversion events (which are restricted to mitotic division leading to egg or pollen maturation and to the developing endosperm) appears to correlate with the degree of linkage between Bg and the O2 locus. Germinal reversions of o2-m(r) to wild type give rise with a frequency around 5×10-4 to unstable phenotypes. Some peculiar features of the o2-m(r)-Bg system of controlling elements are discussed.

Comparison of Open-Pollinated Maize Varieties and Hybrids for Preharvest Aflatoxin Contamination in the Southern United States

Comparison of Open-Pollinated Maize Varieties and Hybrids for Preharvest Aflatoxin Contamination in the Southern United States