The heritability of resistance to early blight in diploid potatoes (Solanum tuberosum, subsp.Phureja andStenotomum)

Effects of One Cycle of Recurrent Selection for Early Blight Resistance in a Diploid Hybrid Solanum phureja-S. stenotomum Population

“…Recurrent maternal half-sib selection has been utilized in order to maintain broad genetic variability in the population while selecting for various traits over the course of development: first tuberization response (Haynes 1972(Haynes , 1980, then high specific gravity (Haynes 2001), and finally, late blight resistance (Haynes and Christ 2006), and early blight resistance (current study). The high heritability of early blight resistance in this population has been supported by our study and agrees with the studies of Herriott et al (1986), Ortiz et al (1993) and Christ and Haynes (2001). Narrow-sense heritability was similar in both cycles, but there was no actual genetic gain.…”

“…After several cycles of recurrent selection this population now tuberizes readily, has improved horticultural characteristics, and is earlier maturing (Haynes 2001). Germplasm derived from this population has been developed and tested for resistance to internal heat necrosis (Sterrett et al 2003), late blight resistance Christ 1999, 2006) and early blight resistance (Christ and Haynes 2001;Christ et al 2002;Herriott et al 1986Herriott et al , 1990Mendoza et al 1986;Ortiz et al 1993). Analysis of the second cycle phu-stn population for late blight resistance showed that AUDPC decreased by about 1/6 as compared to the first cycle population, and predictions are for additional decreases in AUDPC of similar magnitude in future cycles with the recurrent selection approach (Haynes and Christ 2006).…”

“…During the third period, clones were evaluated in replicated plantings and sub-populations were established for high specific gravity, late blight resistance, and early blight resistance, thus expanding the recurrent selection cycle to four years. Herriott et al (1986) and Christ and Haynes (2001) reported that resistance to early blight in their diploid hybrid phu-stn populations were moderately highly heritable (h 2 =0.64-0.78). A mapping population was developed by crossing two individuals from this phu-stn population, and five quantitative trait loci (QTLs) linked to early blight resistance were identified on chromosomes IV, V, IX, XI and XII, that explained over 62% of the total phenotypic variation (Zhang 2005).…”

“…However, additive effects have been predominant in the diploid potato populations studied by Herriott et al (1986) and Ortiz et al (1993). The use of diploid potato species in northern hemisphere breeding programs has been limited because of their lack of adaptation to long-day photoperiods.…”

Tomato early blight (Alternaria solani): the pathogen, genetics, and breeding for resistance

“…Fungicide treatments are generally the most effective control measures, but are not economically feasible in all areas of the world and may not be effective under weather conditions favorable for epidemics (Herriot et al 1986). Resistant cultivars are potentially the most economical control measure because they can extend the intervals between fungicide sprays while maintaining control of the disease (Madden et al 1978;Shtienberg et al 1995;Keinath et al 1996).…”