Ultrastructural and anatomical factors associated with resistance to cuticle cracking in tomato (Lycopersicon esculentum Mill.)

Fruit anatomy and ultrastructure associated with cuticle cracking (CC) were compared for five cultigens (genotypes) of tomato. Cultigens resistant to CC had combined epidermal and cuticle (epicarp) layers significantly thicker (10.38-11.37 mu m) than susceptible cultigens (6.45-7.76 mu m). Thickness of the epicarp was negatively correlated (r = -0.43) with light reflectance and can be indirectly estimated by measuring light reflectance of the fruit. Plants producing globe-shaped fruit or jointless pedicels tended to have higher incidences of CC (more fruit affected) than did plants producing hat-round fruit or jointed pedicels, respectively, but this trend was significant for only one of four segregating populations for each trait. As fruit size increased, incidence of CC significantly increased, accounting for 16%-33% of the variance in incidence of CC over two harvests. Yield and number of fruit harvested accounted for <10% of the variance in incidence. Severity of CC (surface area of fruit showing CC) was less affected by fruit size, number of fruit harvested, and yield than was incidence of CC.