Flowering, Capsule and Seed Characteristics in Cuphea

Authors: Jaradat, Abdullah; Rinke, Jana

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2007
Publication Date: 5/1/2008
Citation: Jaradat, A.A., Rinke, J.L. 2008. Flowering, capsule and seed characteristics in Cuphea. Euphytica. 161:447-459.

Interpretive Summary: Cuphea seed size and weight are inherently non-uniform because of the presence of multi-ovules within a non-uniform capsule and due to the indeterminate growth habit of the plant. Seed size is an important component of life history in cuphea as even a small variation may influence seedling emergence, seedling growth and survival, seedling competition and yield. We studied the flowering and capsule set and quantified the level of variation in seed characteristics and the inter-relationships among seed and capsule physical dimensions in the potential oilseed crop, cuphea PSR23. Open flowers and formed capsules were time-dependent, biomass-dependent, and highly auto-correlated. Large variations were observed in seed weight, and seed and capsule physical characteristics. Seed weight, as the most important yield component, can be optimized in cuphea by selecting plants with large capsule perimeter, large capsule major and minor axes, large capsule area, and small capsule tissue/seed weight ratio, and few (~ 9.0) seeds per capsule. This information would help plant breeders exploit genotypic variability in seed and capsule characteristics and agronomists identify optimum trait combinations to produce high yields of this potential oilseed crop.

Technical Abstract: We modeled the flowering and capsule set dynamics, quantified the level of variation in seed characteristics, elucidated the inter-relationships among seed and capsule physical dimensions, and quantified their impact on single seed weight as the main determinant of seed yield in the indeterminate, potential oilseed crop, cuphea PSR23. Temporal patterns of flowering and capsule set were largely time-dependent and highly autocorrelated with the significant autoregressive parameters of number of flowers (0.76) and number of capsules (0.74) being associated with large 95% confidence intervals (0.55 to 0.97 and 0.52 to 0.94, respectively). Seed physical characteristics significantly deviated from normality and resulted in a bimodal distribution of seed area which is an indication of poor seed uniformity. Large numbers of seeds per capsule (range from 5 to 17) were associated with large variation in single seed weight (C.V. range from 10 to 26%). Plant dry weight was a poor determinant of seeds per plant (R2 = 0.17, n.s.) unless both were log-transformed (R2 = 0.38). Similarly, log-transformed seed number and seed weight per capsule exhibited a slope of -0.65 indicating that cuphea plants have only a limited capacity to maintain seed weight by adjusting seed number if resources vary. Capsule tissue/seed weight ratio and number of seeds per capsule have the largest potential impact on single seed weight. Sensitivity analyses indicated that capsule perimeter (>76 mm), capsule major (>23 mm) and minor axes (>7.0 mm), capsule circularity (between 0.350 and 0.375), capsule area (<85 mm2), capsule tissue/seed weight ratio (<0.40), and number of seeds per capsule (~9.0) would optimize single seed weight.