Physiological and Morphological Changes Over the Past 50 Years in Yield Components in Tomato
Tadahisa Higashide and Ep Heuvelink
Horticultural Supply Chains Group, Wageningen University, Marijkeweg 22, 6709 PG Wageningen, The Netherlands
Citation
Higashide, T., & Heuvelink, E. (2009).Physiological and Morphological Changes Over the Past 50 Years in Yield Components in Tomato . Journal of the American Society for Horticultural Science, 134(4), 460-465.
Background
Greenhouse tomato yield in The Netherlands has more than doubled since the 1980s. This increase is caused by environmental effects such as greenhouse and controlled environment production practices and improved cultivation techniques. In addition to production environment improvements there are genetic effects that positively influence performance that are attributable to breeding efforts.
The aim of this research was to investigate whether tomato cultivars that were released between 1950 and 2000 show an increasing trend in the trait “yield” which is an aggregate of many traits that are influenced by plant morphology and plant physiology.
Experimental Design
Eight Dutch tomato cultivars [Moneymaker (release in 1950), Premier (1960), Extase (1960), Sonatine (1975), Calypso (1982), Liberto (1988), Gourmet (1991), and Encore (2002)] and one Japanese cultivar [Momotaro Fight (2001)] were tested in a randomized complete block design with each cultivar (genetic treatment) occuring in each block randomly. Two blocks were tested under the same environmental conditions to account for spatial variation. All cultivars were indeterminate type and had medium–large round fruit. Plants were measured destructively and non-destructively for various morphological and physiological traits that are considered to be components of yield.
Results
An increase in tomato yield because of breeding efforts was not caused by an improvement in resource partitioning to the fruit but by an improvement in resource partitioning to vegetative characteristics that resulted in higher dry matter. This increase in vegetative dry matter production was caused by higher light use efficiency and is influenced by tomato morphology and architecture. This result is consistent with previous studies in maize (Hay, 1995).
The leaf photosynthetic rate of the modern cultivars increased proportionally to light use efficiency indicating that there is a positive relationship between light use efficiency and leaf photosynthetic rate. Light use efficiency and leaf photosynthetic physiological traits were indirectly selected for over the course of 50 years as a product of selecting and releasing cultivars that had the highest yield. Yield an aggregate trait of many physiological and morphological characteristics. A more detailed study of leaf photosynthetic rate would need to be done to clarify the cause of its increase over the 50 years of variety release.
Yield of the Japanese cultivar was significantly lower than the other Dutch cultivars. This is likely because breeding objectives of Japanese cultivars are geared more toward quality instead of yield. Soluble solids in the Japanese cultivar was significantly higher than the dutch cultivars.
We can use this knowledge to inform future breeding efforts
Yield as we measure it is an aggregate of many components (Figure 2). From the results of this study we know that all components of yield do not contribute to yield improvement equally. We can optimize future breeding efforts to improve morphological and physiological characteristics that directly improve performance of a variety measured as yield. Focusing on yield components that are directly proportional to variety performance measured as yield could improve our ability to map regions of the genome that are associated with specific morphological and physiological traits to determine the genetic basis of yield. To better implement morphological and physiological traits resulting in measurable yield increase into a breeding program seed companies would need to develop high throughput phenotyping techniques as many of these measurements are not cost effective in larger population sizes.
Literature cited
Hay, R.K.M. 1995. Harvest index: A review of its use in plant breeding and crop physiology. Ann. Appl. Biol. 126:197–216.