Browsing by Person "Senger, Elisa"

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Characterization and management of Jatropha curcas L. germplasm
(2018) Senger, Elisa; Melchinger, Albrecht E.
Jatropha curcas L. (jatropha) is a perennial plant of the Euphorbiaceae family that grows in the tropics and subtropics worldwide. Jatropha is targeted to be grown in marginal environments. The seeds are used mainly for production of food products and bioenergy, amongst others. Jatropha breeding is at an early stage. The first obstacle is to generate competitive cultivars for economically feasible cultivation. Mayor breeding objectives are to increase seed yield and yield stability, to decrease production costs, and to improve product quality adapted to specific markets. Jatropha breeding needs to be optimized in several research areas, such as methods and tools for germplasm characterization and breeding techniques, while considering requirements of the agronomic management and product processing. The germplasm can be separated into two naturally occurring germplasm pools that differ in the presence of phorbol esters (PE). These chemical compounds have antinutritional effects on humans and animals and cannot be inactivated or eliminated from the plant material on an industrial scale yet. Therefore, food production is based on cultivars lacking PE, while bioenergy production is less affected from PE presence. The germplasm needs to be characterized and grouped depending on breeding objectives and strategies. Tools for identification of plants that synthesize PE exist, but bear decisive disadvantages or need to be advanced. These tools are exploited for germplasm management and food safety strategies. The objectives of this study were to i) examine the variation of relevant traits among genotypes and between germplasm pools, ii) estimate phenotypic and genotypic trait correlations, iii) investigate location effects and genotype by environment interactions, iv) investigate parental and heterotic effects of genotypes from different germplasm pools as well as the effect of the mating type on expression of relevant traits, and v) develop recommendations for implementation of the findings in jatropha breeding programs. In the first two publications, stress response was investigated. Leaf chlorophyll content (SPAD) was used as a dynamic trait that can be influenced by e.g. water stress and nutrient deficiency. Different genotypes were screened at several locations and at different time points. High genetic diversity was found not only in stress response but also in SPAD value. The fast and non-destructive method is highly promising to be applied in further screenings or stress response studies. In the second publication, genotypic differences in aluminum tolerance were found among seedlings in a greenhouse trial. The rapid test method is applicable in further screenings. However, it needs to be proven that aluminum tolerance at the seedling stage observed under greenhouse conditions is expressed also at later plant developmental stages in the field. In the consecutive three publications, several traits were assessed on seeds and seedlings to detect significant differences between genotypes and/or between germplasm pools. Such traits would be highly valuable for germplasm management. We found that random variation is a disadvantage of quantitative traits and hinders clear assignment of each experimental unit to the respective germplasm pool. Thus, qualitative traits might be favored, such as the “silver shimmer inside the seed testa” that differentiated toxic from non-toxic seeds with a low error rate. However, these results need to be validated. Another application area of the investigated traits is the identification of self-fertilized material within hybrid progeny. In our study, self-fertilized seeds could be differentiated from cross-fertilized ones in specific genotype combinations. Similarly, many seedling traits showed heterotic effects. In the sixth publication, genotype by environment interactions were investigated and recommendations for breeding programs elaborated. A large set of genotypes was grown for four years at three different locations. We showed that selection at only one testing location is highly risky because cultivars with low yield stability could be selected. Therefore, it is indispensable for breeders to work in a network of testing locations that differ in edapho-climatic conditions and apply appropriate experimental designs and statistical tools. In the final publication, several parameters related to the nutritional value of kernels of non-toxic genotypes grown at two locations were assessed. The high nutritional value of this material was presented and compared to soybean, peanut, hazelnut, and corn. Furthermore, preliminary conclusions related to location effects and product processing were drawn. The findings of this thesis contribute to characterization of this novel crop with regard to stress tolerances, seed and seedling characteristics as well as food quality, and help to increase breeding efficiency by presenting simple methods for fast genotype screening as well as grouping of germplasm and by efficient exploitation of testing facilities.