Fruit and Vegetable Quality

CHAPTER 2

Quality and Breeding—

Cultivars, Genetic Engineering

P. WEHLING

INTRODUCTION

AMONG the variety of agricultural and technical factors that determine
the quality of field crops, fruit and vegetables, the choice of a specific
cultivar by the grower, i.e., the choice and combination of genes con-
trolling economically important traits, may be considered the most ini-
tial step for defining quality and productivity. It is the factor that
determines farmers’ potential output long before any other agricultural
measures are taken and even before the seed is sown in the field or green-
house. As a consequence, the breeding of a cultivar that is adapted to
specific demands of the farmer and the consumer may be considered as
a preharvest factor per se, even if certain quality characters of this cul-
tivar apply to postharvest stages.
The classical approach for breeding cultivars is to select suitable phe-
notypes or mutants, which are then crossed, selfed, cloned or combined
with populations depending on their reproductive biology (Table 2.1).
A major drawback of this approach is that for most agronomically im-
portant traits, the phenotypic variance is the base for selection, which,
however, is not only composed of the genotypic variance but also com-
prises an environmental component as well as interactions between geno-
types and environment. This tends to obscure selection progress and is
one of the reasons why breeding for quantitatively or polygenically in-
herited traits is so tedious and time-consuming. In addition, a combina-

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