Evaluation of desirable characteristics of wild potatoes for the improvement of cultivated potato

Abstract

Abiotic stresses, specially heat and drought, are the major factors reducing potato (Solanum tuberosum, Solanaceae) productivity by limiting the plant photosynthesis activity, reducing the production, and partitioning of assimilates to the tubers. Wild potatoes are a natural source of valuable traits for potato breeding, such as abiotic stress tolerance. However, it is necessary to identify phenotypes on a morpho-agronomic and physiological basis that could be manipulated to increase crop resilience. Thus, the morphoagronomic and photosynthetic traits of gas exchange, chlorophyll index and chlorophyll fluorescence are important to study because these factors mainly influence production and photosynthetic activity. To advance on the evaluation of desirable traits of wild potatoes for the breeding of the cultivated potato, this thesis is organized in four chapters. Chapter 1 presents a literature review on the promising role of potato wild species as a reservoir of desirable novel genetic traits for potato breeding. Chapter 2 presents a study of the genotypic response and selection of potato wild relatives for their tuber traits under heat stress. Two temperature conditions: control (14-27°C) and heat stress (24-34°C) were used. At the end of the plant life cycle morpho-agronomic traits were analyzed by statistical mixed models to rank the genotypes according to true genotypic values. Chapter 3 deals with the evaluation of genotypes grown in the same temperature conditions and their physiological traits response (net photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intra and extra cellular CO2 concentration (Ci/Ca)) and chlorophyll fluorescence traits. These physiological traits were analyzed by principal component analysis and clustering of genotypes under heat stress condition resulted in a group of genotypes tolerant to elevated temperatures. In Chapter 4, further accessions of S. commersonii and S. chacoense and, apart from gas exchange traits (Pn, Tr, Gs) and chlorophyll fluorescence traits (YII, NPQ, Fv/Fm); chlorophyll a, b and carotenoid contents, were also measured after 1 day after stress (DAS), 15 DAS and 35 DAS application. At the end of the life cycle total water content and fresh tuber weight and dry matter content were also measured. The results point out that the genotypes of S. chacoense were more tolerant and performed better under heat stress conditions. So, introducing the characterized wild potato genotypes, with improved photosynthesis traits and other studied physiological traits in adverse conditions, is important for potato breeding programs to meet the genetic gains efforts required to cope with anticipated increasing of heat and drought events worldwide due to climate change