Inheritance of Tuber Greening Under Light Exposure in Diploid Potatoes

American Journal of Potato Research, May/Jun 2006 by Jakuczun, Henryka, Zimnoch-Guzowska, Ewa

Although tuber greening is caused by environmental factors, it has a genetic component. Variability in tuber greening intensity among cultivars and stocks has been observed (Akeley et al. 1962; Buck and Akeley 1967; Brown and Riley 1976; Parfitt and Peloquin 1981; De Maine et al. 1988; Reeves 1988; Dale et al. 1992; Jakuczun 1993; Griffiths et al. 1994). Reeves (1988) reported polygenic inheritance for this trait. Parfitt and Peloquin (1981) reported that additive and epistatic effects were important and found no maternal effects for this trait. Reeves (1988) distinguished three elements of tuber greening: external, internal, and depth of greening, which were found to be independently inherited.

Generally intensity of tuber greening was evaluated visually on a 1-5 (Akeley et al. 1962; Parfitt and Peloquin 1988), 0-5 (Reeves 1988; Jakuczun 1993) or 1-9 scale (Griffiths et al. 1994; Brune and MeIo 2001). The correlation between visual estimation of greening and chlorophyll accumulation has been high (Akeley et al. 1962; Harkett 1975; Dale et al. 1992; Griffiths et al. 1994).

In the Plant Breeding and Acclimatization Institute in Ml[bar]ochów, as part of a program involved in long-term recombinant breeding of diploid potatoes, genotypes expressing resistance to tuber greening upon exposure to light under greenhouse conditions were selected (Jakuczun 1993). They were composite interspecific hybrids with several wild Solanum species and dihaploids of S. tuberosum in their pedigree.

The aim of this experiment was to study the inheritance of external and depth of tuber greening due to chlorophyll accumulation under light exposure in unselected diploid families.

MATERIAL AND METHODS

The same plant material and experiment conditions used to evaluate tuber greening in this experiment were simultaneously used to examine the inheritance of glucose content in tubers (Jakuczun and Zimnoch-Guzowska 2004).

The material included 17 unselected families, their eight parents, and standard cultivars. In two parental clones, DG 88-63 and DG 88-89, a weak external tuber greening (EWG) and small depth of tuber greening (DWG) were found. External (EMG) and depth of tuber greening (DMG) were moderate in DG 88-1616. DG 88-214 and DW 88-4556 were characterized by strong external tuber greening (ESG) and moderate depth of greening (DMG). The remaining three clones, DG 86-965, DG 88-632 and DG 88-1591, expressed strong external tuber greening (ESG) and depth of greening (DSG). These diploid parents were interspecific Solanum hybrids, the origin of which has been described previously by Jakuczun and Zimnoch-Guzowska (2004). Considering external tuber greening, six families were obtained in matings between parents susceptible and resistant to greening (ESG x EWG), another six families were from crosses between parents moderate and susceptible to greening (EMG x ESG), and five families were from crosses between parents susceptible to greening (ESG x ESG) (Table 1). For depth of tuber greening two families were obtained in crosses between parents resistant and susceptible to tuber greening (DSG x DWG), nine families came from matings between parents moderate and susceptible to greening (DMG x DSG), two families were obtained between parents with moderate tendency to tuber greening (DMG x DMG), and the remaining four families were from matings between parents with moderate and weak depth of greening (DMG x DWG) (Table 1). Generally, females were strongly greened in external and strongly to moderately in depth of tuber greening. Males ranged from having a weak to strong tendency to both types of greening and were important source of variation of the trait in this experiment. Three seed parents were crossed to four pollinators in a North Carolina (NC) design II resulting in 10 families; no progenies were obtained in the other two families. Reciprocal crosses represented another three sets of families. The number of genotypes in the families varied from 35 to 158. In total, 1,229 genotypes were evaluated each year.