Browsing by Person "Heinrich, Nicole"

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Quantitativ-genetische Untersuchungen zur Vererbung der Resistenz gegen Ährenfusarium bei Triticale (x Triticosecale Wittmack)
(2004) Heinrich, Nicole; Miedaner, Thomas
Fusarium head blight (FHB), caused by Fusarium culmorum (W.G. Smith) Sacc. and F. graminearum Schwabe, is recognized as one of the most destructive diseases of small-grain cereals. Fusarium infection can cause substantial yield losses. Infected grain may also be contaminated by mycotoxins that are harmful to humans and livestock. Agronomical measures and fungicides are only partly effective in controlling FHB. The development of disease-resistant cultivars together with appropriate crop management practices are effective strategies to control FHB. In this study, seven triticale cultivars and three breeding strains, representing a range of FHB resistances, their 45 diallel F1 crosses, progenies of 15 F2s from a six-parent diallel and their 30 backcrosses (BC, 15 to each parent), and five F2:3 bulks were investigated. Parents and their progenies were grown in several environments (years, locations) and tested for FHB resistance after artificial inoculation with Fusarium culmorum. Within the scope of this study, three experiments were conducted to estimate various quantitative-genetic parameters of several traits. In Experiment 1, the influence of FHB on yield-related traits of the ten parents was assessed. Compared to a non-inoculated variant, Fusarium reduced 1000-grain weight by 10.0%, spike weight by 9.3%, the number of kernels per spike by 4.3%, and test weight by 7.4%. Inoculation also increased deoxynivalenol (DON, 26.4 mg kg-1) and exoantigen (1.34 OD). content of the kernels. Genotypic variation and genotype-environment interaction were significant for all traits. The correlation between symptom ratings (spikes, kernels) and yield traits and between spike weight and kernels per spike were negative and high. The aim of Experiment 2 was to estimate combining ability, hybrid performance and heterosis for FHB ratings, DON and exoantigen content. Heterosis of FHB for spike and kernel rating was small. Across environments, the DON content in F1 crosses, however, was 15.5% higher than their mid-parent value. A high and significant (P = 0.01) correlation of r = 0.8 was found for both spike and kernel FHB symptom ratings between mid-parent and F1 performance. Except for exoantigen content, the general combining ability (GCA) was the main source of variation, suggesting additive gene effects for FHB resistance. Significant specific combining ability variance implies non-additive types of allelic interaction also. Therefore, in some crosses dominant effects can play an important role. The relationship between the GCA effect of a parent and its per se performance was close. In Experiment 3, genetic variation and effects for FHB resistance were estimated in segregating generations. The resistance level of the parents and their F2 progenies were similar. In contrast, the resistance of the BC progenies to the resistant parent was considerably higher than that of the backcrosses to the susceptible parent. Significant differences between the means of the 15 crosses and a high genetic variation within crosses were observed. Transgression could not be detected. F2:3 bulks and their parents had a comparable resistance level. For F2 and BC progenies, the additive effect was more important than the dominant effect. In contrast, the F1 crosses had a higher dominant effect, but with a large error. The study revealed considerable genetic variation in all generations for FHB resistance that can be exploited in a breeding programme. The mainly additive genetic effect makes it possible to select crossing parents on the basis of their per se performance. Due to the importance of genotype-environment interaction, resistance tests in various environments are strongly recommended. Screening for FHB resistance can best be accomplished by assessing symptom ratings of spikes and/or the spike weight relative to a non-inoculated variant. The high cross-environment interaction variance in the F2 generation points to the problem of selecting in unreplicated segregating material. Selection should be postponed to the F3 or later generations. The large genetic variation of FHB resistance and the preponderance of additive gene effects are encouraging to further increase resistance in triticale by recurrent selection.