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Marques, Edward

Plant and Soil Science

2020

Ph. D.

Domestication has had a profound global impact on human history and a wide range of plants. Understanding the advertent and inadvertent effects of domestication on crops has been instrumental in bolstering food security efforts. For instance, by identifying and re-incorporating lost genotypic variation due to domestication, we can increase crop tolerance to biotic and abiotic stressors. With changing climatic conditions and the ever-growing human population, it has become more imperative to increase and fortify agricultural production. My dissertation addresses this topic in two agronomically important legumes: chickpea (Cicer arietinum) and pea (Pisum sativum). My research aims to increase the agronomic and economic value of these legumes to facilitate agricultural production as well as lessen financial burdens to farmers. To accomplish this aim, in chickpea, we identified the physiological and genetic basis of the green-seed market type and identified the effects of domestication on the response to a novel environment. Furthermore, in pea, we investigated phenotypic variation for cover cropping traits using wild accessions, landraces, and modern varieties. In chickpea, we identified that green-seeded chickpea market type was due to a loss of function mutation of the CaStGR1 (carietinum stay-green gene 1) gene involved in chlorophyll catabolism. Additionally, physiological testing in drought conditions revealed this phenotype to be of the "cosmetic" and not the "functional '' stay-green variety. Furthermore, nutritional analysis revealed that this trait was associated with a 2-3 fold increase in provitaminogenic carotenoids that are important for human nutrition. Therefore, this green-seeded trait may increase both the economic and nutritional value of chickpea. To identify how domestication has affected chickpea response to novel environments, we took a whole-plant approach and measured above- and below-ground response to increased nitrogen presence in chickpea. Results revealed that domestication has canalized domesticated chickpea response to nitrogen-rich environments. Furthermore, the variable response of wild chickpea to nitrogen illustrated the need for the use of a comprehensive assortment of wild relative accessions to fully discern the effects of domestication on domesticated organisms. Lastly, we coined the terms "rotational" and "intercropping value" and provide a mathematical equation to quantify these terms. We also discuss numerous methods on how to increase these values. To demonstrate these ideas, we measured the rotational values of domesticated and wild pea. We identified that rotational values and cover-cropping traits such as nutrient mobilization and microbial recruitment vary within field pea. These results indicate that field pea could potentially be improved as a rotational partner and that the use of wild relatives in cover cropping research, which has been underutilized, should be considered. Overall, these results illustrate the importance of understanding the effects of domestication and highlights the importance of crop wild relatives as phenotypic reservoirs for crop improvement. Collectively, my research provides insightful information that can facilitate agricultural production at the farming and breeding level.