Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 27, 2005
Publication Date: July 1, 2005
Citation: Stommel, J.R., Abbott, J.A., Campbell, A., Francis, D.A. 2005. Inheritance of elastic and viscoelastic components of tomato firmness derived from intra- and interspecific genetic backgrounds. J. Amer. Soc. Hort. Sci. 130:598-604.
Interpretive Summary: Firmness is a key quality component of tomatoes that are grown for fresh market and processing applications. Marketing of fresh tomato fruit necessitates enhanced fruit firmness so that fruit withstand the rigors of long-distance shipping. Firmness is also very important to minimize damage when tomatoes are mechanically harvested for use in processed products. We characterized inheritance of firmness in tomato breeding lines that are utilized to develop new tomato varieties. Firmness of the different breeding lines were influenced to varying degrees by respective environments, indicating that some lines will perform better at one location than at the other. This study identified breeding lines with superior firmness that can be utilized by plant breeders to develop improved varieties.
We characterized inheritance of firmness in processing tomato germplasm developed from L. esculentum x L. cheesmanii and intraspecific L. esculentum crosses. Although firmness is a key quality attribute of tomato, there is no standard method for measuring it. We measured the elastic portion of firmness by compression (compression Fmax) and puncture (puncture Fmax), and the viscoelastic portion by force-relaxation. The experimental design incorporated six genotypes in a complete 6 x 6 diallel. Compression Fmax and force measurements recorded at 0.5 s, 1.0 s, 5.0 s, and 10.0 s of relaxation were strongly related to each other; while relaxation parameters (A, B, C) describing relaxation curve shape were generally independent. Compression Fmax, relaxation curve parameter A, and puncture Fmax were significantly different among hybrids. Significant differences between Maryland and Ohio environments were evident for compression Fmax and relaxation curve parameter A. The patterns of firmness means differed among firmness measurement methods, namely for compression Fmax and puncture Fmax, indicating that they measure different aspects of tomato fruit firmness. Compression Fmax best approximated subjective assessment of fruit firmness. Puncture Fmax was subject to a significant environmental x hybrid influence in the genotypes evaluated. Shape of the force relaxation curve, i.e. parameter A, was not predictive of relative fruit firmness. General combining ability (GCA) and specific combining ability were both significant with GCA being the principal source of genetic variation. In agreement with combining ability estimates, moderate narrow-sense heritability estimates were estimated for compression Fmax and puncture Fmax.