Exotic germplasm has potential to provide new alleles for disease and insect resistance. US maize (Zea mays L.) currently lacks genetic resistance to Aspergillus flavus, a fungal pathogen that produces aflatoxin in maize kernels. Aflatoxin is one of the main limitations to maize production in hot, dry regions like the Southern US because of the harmful effects on humans and animals and subsequent marketing regulations. Two experiments were conducted to evaluate different exotic maize collections for response to aflatoxin. Exotic adapted maize lines, known as LAMA lines, were found to accumulate less aflatoxin than US hybrids in tests across Southern Texas. Exotic introgression lines developed by The International Center for Maize and Wheat Improvement (CIMMYT) including inbred lines, yellow hybrids, and white hybrids, were more resistant to aflatoxin than US inbred lines and hybrids in field trials in Texas, Georgia, and Mississippi. Another experiment evaluated the grain composition of hybrids with exotic adapted LAMA maize lines and a collection of US hybrids, quality protein maize (QPM) hybrids, and advanced breeding lines using near-infrared spectroscopy. Individual LAMA lines and advanced breeding lines have higher starch content than US hybrid checks. Starch content was the primary grain composition trait of interest as an enhanced-value market has emerged for high starch maize hybrids. Limited germplasm has been analyzed for grain composition because wet chemistry analysis methods required large sample sizes and were time and labor intensive. The near infrared spectroscopy (NIR) method requires a relatively small sample and is a non-destructive analysis method. In this study, NIR was effective at ranking genotypes based on starch, oil, and protein content of the grain.

Exotic germplasm has potential to provide new alleles for disease and insect resistance. US maize (Zea mays L.) currently lacks genetic resistance to Aspergillus flavus, a fungal pathogen that produces aflatoxin in maize kernels. Aflatoxin is one of the main limitations to maize production in hot, dry regions like the Southern US because of the harmful effects on humans and animals and subsequent marketing regulations. Two experiments were conducted to evaluate different exotic maize collections for response to aflatoxin. Exotic adapted maize lines, known as LAMA lines, were found to accumulate less aflatoxin than US hybrids in tests across Southern Texas. Exotic introgression lines developed by The International Center for Maize and Wheat Improvement (CIMMYT) including inbred lines, yellow hybrids, and white hybrids, were more resistant to aflatoxin than US inbred lines and hybrids in field trials in Texas, Georgia, and Mississippi. Another experiment evaluated the grain composition of hybrids with exotic adapted LAMA maize lines and a collection of US hybrids, quality protein maize (QPM) hybrids, and advanced breeding lines using near-infrared spectroscopy. Individual LAMA lines and advanced breeding lines have higher starch content than US hybrid checks. Starch content was the primary grain composition trait of interest as an enhanced-value market has emerged for high starch maize hybrids. Limited germplasm has been analyzed for grain composition because wet chemistry analysis methods required large sample sizes and were time and labor intensive. The near infrared spectroscopy (NIR) method requires a relatively small sample and is a non-destructive analysis method. In this study, NIR was effective at ranking genotypes based on starch, oil, and protein content of the grain.

Doctor of Philosophy / Genetics - Plant Pathology / Jesse A. Poland / The global population is estimated to reach 9.1 billion by 2050. Together with climate change, insuring food security for this population presents a significant challenge to agriculture. In this context, a large number of breeding objectives must be targeted. The focus of the work presented here is to explore genomic approaches for tapping exotic germplasm for valuable alleles to increased yield, disease resistance and abiotic stress tolerance. The loss of genetic diversity in bread wheat (Triticum aestivum L.) due to bottlenecks during polyploidization, domestication and modern plant breeding can be compensated by introgressing novel exotic germplasm. Here, the potential of genomic selection (GS) for rapid introgression of synthetic derived wheat is evaluated in field trials. Overall, the GS models had moderate predictive ability. However, prediction accuracies were lower than expected likely due to complex and confounding physiological effects. As such, implementation of rapid cycle GS for introgression of exotic alleles is possible but might not perform very well with synthetic derived wheat. Disease resistance is another important trait affecting grain yield. Stem rust (Puccinia graminis f. sp. tritici) has historically caused severe yield loss of wheat worldwide. In a quantitative trait loci (QTL) mapping study with a synthetic-derived mapping population, QTLs for resistance to stem rust races TRTTF and QTHJC were identified on chromosomes 1AS, 2BS, 6AS and 6AL. Some of these genes could be new resistance genes and useful for marker-assisted selection (MAS). In addition to food insecurity through lack of sufficient source of calories, nutrient deficiency is considered the ‘hidden hunger’ and can lead to serious disorders in humans. Through biofortification, essential nutrients are increased in staple crops for improved quality of food and human health. A high-throughput elemental profiling experiment was performed with the same synthetic derived mapping population to study the wheat ionome. Twenty-seven QTL for different elements in wheat shoots and two QTL in roots were identified. Four “hotspots” for nutrient accumulation in the shoots were located on chromosomes 5AL, 5BL, 6DL and 7AL. Overall, exotic germplasm is a valuable source of favorable alleles, but improved breeding methodologies are needed to rapidly utilize this diversity.