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A computer program was developed to calculate the percent contribution of the founding parents for any given peach or nectarine (Prunus persica) cultivar. The founding parents used most frequently for three low-chill (0 to 500 chill units) peach and nectarine breeding programs (Florida and Pelotas and Campinas, Brazil) were determined. The Florida program used several low-chill honey type peaches (`Hawaiian', `Okinawa') as a source of low chilling and then did extensive crossing with higher quality cultivars developed mainly in the northeastern United States. About 50% of the background of the Brazilian peach releases consists of local selections that were originally brought by the Portuguese explorers. Although each of the Brazilian programs used local peach materials, the local peaches used by each program are different. In addition, the program at Pelotas used germplasm from the Georgia–Florida and New Jersey breeding programs and the Campinas program used `Jewel' (honey peach) and several Florida nectarines (`Sunlite', `Sunred') in their development work. The founding parents among these three programs, although there is some common parentage, are different, and the intercrossing of materials from the various programs would be a useful approach to create more diversity in this germplasm.
Mild winter weather conditions reduce fruit yield and quality of many peach cultivars grown in the Medium Chill Region of the United States. Peach fruit shape instability limits marketing options for growers in this region. The Stonefruit Breeding Program at Texas A&M University evaluated a wide range of peach cultivars and breeder selections from throughout the world during the mild winters of 1988-198 9 and 1989-1990. Fruit shape response was highly variable among genotypes with similar chilling requirements. The implication of this is that the potential is high for eliminating fruit shape instability due to highly variable winter conditions in the Medium Chill Peach Production Region.
`TexPrince' is being released by Texas A&M University to provide a medium chilling, commercially acceptable peach that ripens after `Texstar' and with or a few days after `Juneprince' and `TexRoyal'. This large, freestone, attractive, yellow-flesh peach ripens early June in the medium chill zones of the United States. `TexPrince' is a replacement for `Juneprince' where `Juneprince' fruit inconsistently due to problems with insufficient chilling.
Peach trees when grown in calcareous soils frequently exhibit lime-induced iron chlorosis. There have been numerous reports of rootstock tolerant to soil alkalinity but given the wide range of field conditions under which the comparison were made, it is difficult to quantify the relative tolerance of the different rootstock. A greenhouse screening procedure using a 0.5g/liter potassium bicarbonate solution (pH 8.0-8.3) was employed to compare the tolerance levels of 50 peach, almond and hybrid lines. Most peach lines tested were very susceptible (Nemaguard) to susceptible (Nemared, Lovell). A few exhibited a low level of tolerance (Montclar, Rutger Red Leaf, Rancho Resistant). High levels of tolerance were found with in almond and almond-peach hybrid families.