Download or read book Prediction of Field Emergence of Maize Zea Mays L Hybrids Exposed to Cold and Wet Conditions written by Pieter Hermanus Maree and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The cold test is one of the oldest and most acceptable vigour tests as it is used to simulate stress conditions commonly occurring in the field. In recent years, some of South Africa's top maize hybrids, with high cold test scores, have shown emergence problems under cold, wet planting conditions. It resulted in major complaints from commercial maize producers with sizable claims involved. Therefore, the need arose to find a more sensitive vigour test that takes into account cold, wet conditions. In practice, South African maize producers would not plant if it is too cold and wet. However, cold, wet conditions are commonly experienced during planting time in the main maize production regions of South Africa, especially during October and even November. Furthermore, in most of the commercial maize production areas, such as the western Free State, chances of thunder and hailstorms are high during the planting period. These weather conditions are major causes for sudden drops in temperature and flooding which can expose maize seed and emerging maize seedlings to stress conditions The effects of cold, wet conditions on germination and emergence of nine maize hybrids were investigated in laboratory, glasshouse and field experiments. Growth chamber and glasshouse experiments were conducted under 10ʻC, 20ʻC and 30ʻC and 0, 24, 48 and 72 hours flooding. Field experiments were conducted under different climatic conditions, resulting in cool and wet, cold and wet and favourable conditions during planting. The objectives were to investigate the correlations between different laboratory vigour tests and field emergence of maize hybrids under cold, wet conditions in order to identify the most suitable laboratory vigour test for predicting field emergence under cold, wet conditions. Eight different vigour tests were conducted and each was compared with field emergence under cold, wet conditions. The eight tests conducted, were the cold test, soak test, complex stressing vigour test, electrical conductivity test, accelerated ageing test, tetrazolium test, fast green test and emergence rate test. The soak test was the most sensitive vigour test when considering cold, wet conditions, as it measures seed germination, based on the warm test, after a 48 hour soak in water at 27ʻC. Correlations found between the soak test and field emergence (53%) under cold, wet conditions was unexpected, since the soak test does not account for low temperatures. The complex stressing vigour test was conducted to study the effect of fluctuating soaking temperatures on germination of maize seed. Seeds of nine maize hybrids were soaked for 48 hours at a moderate temperature (25ʻC), followed by another 48 hours soak at a low temperature (5ʻC), and then planted in sand and grown for 4 days at 25ʻC, before evaluation. Highly significant correlations were found between the complex stressing vigour test and simulated field emergence under both controlled conditions in a glasshouse (89.9%) and cold, wet conditions in the field (90.0%). The complex stressing vigour test was the best test to predict field performance under a wide range of climatic conditions, especially cold, wet conditions. Implementation of the complex stressing test as a routine vigour test, will be to the advantage of maize seed companies, especially in being proactive in predicting emergence of maize hybrids under cold, wet conditions. Copyright.
Download or read book Genetic Variation for Chilling Stress and Spectral Reflectance in Short Season Maize written by Wisam Obeidat and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing early season cold tolerance of maize (Zea mays L.) has the potential to lengthen its growing season and enhance yields. We evaluated cold tolerance across 44 inbred and 102 hybrid genotypes in field and controlled environment experiments. Cold tolerance was quantified as the proportion of dry weight (PDW) of plants subjected to cold temperatures or planted early, relative to dry weight of plants grown in control temperatures or planted late. Also, leaf reflectance spectroscopy was used as an alternate indicator of cold stress response. In field experiments, significant effects of genotype, planting date, environment and their interactions were detected for PDW; the mean dry weight per plant for the early planting was considerably lower than for the late planting in five field environments. Cold stress exposure resulted in higher leaf reflectance in the 500 ̶ 680 nm region and lower reflectance between 758 ̶ 1000 nm. We identified novel reflectance predictors, both normalized difference indices and specific wavelengths of first derivative reflectance spectra, that correlated with PDW. In some cases the strongest correlations were found when reflectance data came from unstressed plants. Multiple regression models combining first derivative reflectance at multiple wavelengths, measured on plants not exposed to cold stress, provided the best correlation with PDW; however in general these models were unique to an experiment. Genetic control and heritability of plant dry weight and leaf spectral reflectance under control and early planting conditions was investigated in the field using a North Carolina Design II mating experiment. Consistent general combining ability estimates from early and late planting indicated that additive and dominant gene effects explained hybrid biomass variation across both planting dates. A number of spectral traits were heritable, but parental contributions to hybrid values were moderate. In conclusion, we find that parents explain at most moderate levels of hybrid spectral reflectance variation, across all spectral analysis tools. Thus, selection of traits such as hybrid biomass using spectral reflectance will be inefficient. Nonetheless, we find spectral reflectances stably distinguish maize genotypes within a population irrespective of temperature treatments, so selecting inbred lines using spectral reflectance may advance breeding efforts.
Download or read book Impact of Genotype X Environment Interaction and Selection History on Genomic Prediction and Correcting for Non systematic Variability to Increase Efficiency in Maize Zea Mays L Breeding written by Martin Carlos Costa and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing cultivars with high yield potential and stability across environments is essential to sustain the increasing global population in the context of climate change. Maize (Zea mays L.) is the major crop grown in the United States. Maize breeding processes involve genomic selection and the evaluation of experimental hybrid phenotypes using small plots to estimate genotypic performance. In this dissertation, I work with an extensive multi-environmental trial dataset with the goals to (1) characterize the relative value of the three donor inbreds as sources of useful alleles representing elite, non-elite, and un-selected donor types, (2) understand genomic prediction models that effectively identify new hybrids. Results showed that the parent with additional breeding cycles (elite) produced hybrids with lower genotype by environment interaction (GxE) variance. The reduced GxE variance of the population with the longest history of selection for favorable alleles led to greater prediction accuracy), contributing to greater yield stability. My second study in the dissertation assesses the impact of plant stand (number of plants per plot) and plant spacing variability in contributing non-heritable variation in breeding trials. We evaluated the grain yield performance of five hybrids exhibiting varied ear-flex traits across five manually adjusted plant spacing setups. Results demonstrated that in 36% of the occasions, we found differences that were not a reflection of genotypic effects but rather variations in spacing conditions (significant differences). However, incorporating the plot length, stand count, and plant spacing data into the model corrected for the non-systematic variability in the breeding trial.
Download or read book Resource Allocation and Genomic Prediction in Maize Zea Mays L Hybrid Breeding and a Genetic Analysis of Pericarp Pigmentation written by Dylan Schoemaker and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Maize (Zea mays L.) is a globally important crop species sold as a hybrid and is a model system for both genetics and plant breeding research. The maize breeding process involves identification of new inbred lines, followed by the identification and production of commercial hybrids from crosses of inbreds. Genomic selection and evaluation of hybrid phenotypes are important components of this process. In this dissertation, I use a large multi-environment trial dataset to explore the impact of resource allocation when developing genomic prediction models. Resource-efficient training sets can be developed using three to five environments and a single tester to predict both plant height and grain yield. A second study in my dissertation focused on prediction of hybrid combinations and the importance of general and specific combining ability in identifying new hybrids. The results demonstrated that hybrids with the greatest grain yield result from parents with a high general combining ability, but hybrids with the greatest performance may not have the largest specific combining ability deviation. Therefore, modeling only additive genetic relationships can lead to an accurate genomic prediction model during early-stage testing in a hybrid maize breeding program. The third study in my dissertation was a genetic analysis of pericarp pigmentation in progenies of commercial dent germplasm. Allelic variation at the well-studied pericarp color1 (P1) locus was significantly associated with pericarp pigmentation. The results from these projects provide novel insight into the design of hybrid breeding programs and the allocation of resources when implementing genomic selection. The research also provides candidate genes for geneticists or maize breeders to aid in the development of inbred lines with novel pericarp hues and elite agronomic characteristics.
Download or read book Gravitropic Responses of Five Maize Zea Mays L Hybrids to Temperature and Carbon Dioxide written by Laura C. Matthews and published by . This book was released on 1995 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Validation of Crop Simulation Models to Predict the Response of Maize Zea Mays L Hybrids to Graded Levels of Nitrogen written by T.V. Santhosh Kumar and published by . This book was released on 2013 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Predictive Equations for Maize Inbred Emergence written by Robert Joel Navratil and published by . This book was released on 1979 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate estimation of maize (Zea mays L.) inbred seedling emergence are currently unavailable. Inbred planting rates are therefore adjusted using criteria normally applied to hybrid seed. In this study, temperature dependent predictive equations that would assist the seedsman in estimating planting rates to obtain acceptable stands during the planting season were developed for 15 maize inbreds. The equations were developed based on the regression of the difference of the laboratory germination minus field emergence on days to 50% emergence for all dates of planting. The slope of the regression differed among inbreds. The equations are applied by calculating the days to 50% emergence based on the known number of growing-degree units a particular inbred would require to reach 50% emergence. Past meteorological data would be used to estimate the probable number of days required to accumulate the growing-degree units for any planting date. It was initially assumed that growing-degree units to 50% emergence would remain constant while days to 50% emergence could vary for each onbred and would vary for different field plantings. Unfortunately, growing-degree units to 50% emergence for lots within inbreds, field plantings, and the field plantings by inbreds interactions were all significant at the .01 probebiblity level. The growing-degree units to 50% emergence for the 15 inbreds in this study may be of additional value in estimating emergence and subsequent silking dates in the production of hybrid seed.
Download or read book The Growth of Maize Zea Mays L Under Field Conditions as Affected by Its Water Relations written by Edmundo Acevedo Hinojosa and published by . This book was released on 1975 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Methods for Identifying Frost Injury in Immature Maize Seed written by Mindy L. DeVries and published by . This book was released on 2006 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fall frost damage is a major threat to maize (Zea mays L.) seed production in the central United States. Frost events prior to harvest can cause various physical, mechanical, biochemical, and physiological changes to immature seed corn. These changes can lead to decreased germination and vigor. Early detection of frost damage could reduce the financial loss caused by poor emergence when these seed lots are planted. The central hypotheses of this dissertation are that the severity of a frost event can be quantified shortly after seed has been harvested and dried, and that the magnitude of the damage is associated with seed development and genetic background of the seed. This information can be used to predict field emergence of frosted seed lots. Many different aspects of frost damage have been explored in this project, which provides several methods for identifying frost damage in maize seed. This project advances our understanding of seed physiology as related to frost damage and changes in physiology during seed maturation. Chapter 2 is a practical application of the tetrazolium test for identifying frost damage in seed corn and relating these results to vigor. Chapter 3 discusses the influence of female parent and moisture content at harvest in frost tolerance or injury. Chapter 3 also provides a detailed analysis of seed quality tests and their usefulness in predicting field emergence of frost damaged seed. Chapter 4 establishes the use of RNA extraction and qRT-PCR as a valid method for evaluating gene expression in dry maize seed.
Download or read book Plant Breeding Abstracts written by and published by . This book was released on 1998 with total page 1648 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Agrindex written by and published by . This book was released on 1995 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quality protein Maize written by and published by National Academies. This book was released on 1988 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Malnutrition and protein quality. Maize. Nutritionally improved maize. The promise of QPM. Limitations and uncertainties. Food and feed uses. Genetics. Experiences around the world. Research needs. QPM's future in the United States. Suggested readings. Research contacts. Biographical sketches of panel members.
Download or read book Transcription Factors for Abiotic Stress Tolerance in Plants written by Shabir Hussain Wani and published by Academic Press. This book was released on 2020-08-05 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transcription Factors for Abiotic Stress Tolerance in Plants highlights advances in the understanding of the regulatory network that impacts plant health and production, providing important insights for improving plant resistance. Plant production worldwide is suffering serious losses due to widespread abiotic stresses increasing as a result of global climate change. Frequently more than one abiotic stress can occur at once, for example extreme temperature and osmotic stress, which increases the complexity of these environmental stresses. Modern genetic engineering technologies are one of the promising tools for development of plants with efficient yields and resilience to abiotic stresses. Hence deciphering the molecular mechanisms and identifying the abiotic stress associated genes that control plant response to abiotic stresses is a vital requirement in developing plants with increased abiotic stress resilience. Addressing the various complexities of transcriptional regulation, this book includes chapters on cross talk and central regulation, regulatory networks, the role of DOF, WRKY and NAC transcription factors, zinc finger proteins, CRISPR/CAS9-based genome editing, C-Repeat (CRT) binding factors (CBFs)/Dehydration responsive element binding factors (DREBs) and factors impacting salt, cold and phosphorous stress levels, as well as transcriptional modulation of genes involved in nanomaterial-plant interactions. Transcription Factors for Abiotic Stress Tolerance in Plants provides a useful reference by unravelling the transcriptional regulatory networks in plants. Researchers and advanced students will find this book a valuable reference for understanding this vital area. Discusses abiotic stress tolerance and adaptive mechanisms based on the findings generated by unlocking the transcriptional regulatory network in plants Presents various kinds of regulatory gene networks identified for drought, salinity, cold and heat stress in plants Highlights urgent climate change issues in plants and their mitigation using modern biotechnological tools including genome editing.
Download or read book Bulletin of the Atomic Scientists written by and published by . This book was released on 1973-10 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Download or read book Specialty Corns written by Arnel R. Hallauer and published by CRC Press. This book was released on 2000-08-23 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: Completely revised and updated, the Second Edition of Specialty Corns includes everything in the first edition and more. Considered the standard in this field, significant changes have been made to keep all the information current and bring the references up-to-date. Two new chapters have been added to keep up with the latest trends: Blue Corn and
Download or read book Bibliography of Agriculture written by and published by . This book was released on 1998 with total page 2312 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Drought Resistance in Crops with Emphasis on Rice written by International Rice Research Institute and published by Int. Rice Res. Inst.. This book was released on 1982 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
