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Abstract Detail

Botanical foundations for perennial agriculture: Evolution and ecology of perennial herbaceous plants

Peterson, Kelsey [1], Van Tassel, David [2].

Exploiting phenotypic plasticity during the domestication of Silphium integrifolium (Asteraceae).

During early stages of domestication of the prairie plant Silphium integrifolium (Michx.) as a perennial, drought-tolerant oilseed grain, we focused on increasing the number of ray florets per capitulum and the average weight of achenes. These are the kind of high-heritability, low-plasticity traits preferred by breeders and we made progress. However, many other important traits are plastic, making phenotypes difficult to measure and/or reducing the apparent heritability of traits because patchy environmental variation within a breeding nursery.
Silphium capitula are highly variable in diameter, even on a single stalk, yet this trait likely affects other important domestication traits (e.g., seed number, seed size) and was central to the domestication of the close relative, sunflower (Helianthus annuus L. var. macrocarpus). Lacking the resources for genomic selection or genetic modification, we are looking for strategies to exploit and/or reduce this plasticity within a largely phenotypic breeding program. In one study, we compared the seed production of capitula infested with a Eucosma giganteana moth caterpillar, a native specialist herbivore capable of devastating seed yield in cultivated silphium. For several hundred heads on 9 plant genotypes, we compared the ability of variation in anthesis, capitulum diameter, receptacle diameter, seed size, and other traits, to explain Eucosma tolerance (ability to produce seeds despite infestation). We found that capitulum diameter best predicted tolerance (at the capitulum level). Capitulum plasticity, therefore, allowed us to hold genotype constant, revealing a mechanism for tolerance that would have been difficult to disentangle from many other traits in a more conventional comparison of genetic groups (e.g. inbred lines, half-sib families).
However, the very plasticity that led to this insight also impedes our efforts to breed for capitulum diameter. If we could create an environment that reliably induces the maximum capitulum diameter for each genet in a population, we could subsequently look for (a) mutations that reproduce this extreme phenotype in a wider range of environments (“genetic assimilation”) and (b) additive genetic variation in maximum capitulum diameter that may normally be invisible (i.e., exposing previously cryptic variation). We have found that reducing the number of competing capitula increases the size of the largest (remaining) capitulum and are currently comparing the heritability of capitulum diameter calculated from capitulum-thinned ramets vs. control ramets, using the same set of genets.

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Related Links:
Progress and Bottlenecks in the Early Domestication of the Perennial Oilseed Silphium integrifolium, a Sunflower Substitute

1 - The Land Institute, 2440 E Water Well Rd, Salina, KS, 67401, United States
2 - The Land Institute, 2440 E Water Well Rd,, Salina, KS, 67401, USA

none specified

Presentation Type: Colloquium Presentations
Session: C02, Botanical foundations for perennial agriculture: Evolution and ecology of perennial herbaceous plants
Location: 102/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 10:30 AM
Number: C02009
Abstract ID:584
Candidate for Awards:None

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