© 2003 Heron Publishing—Victoria, Canada
Responses of Prunus ferganensis, Prunus persica and two interspecific hybrids to moderate drought stress
M. Rieger (1, 2), R. Lo Bianco (1) and W. R. Okie (3)
1. Department of Horticulture, University of Georgia, Athens, GA 30602, USA / 2. Author to whom correspondence should be addressed (mrieger@uga.edu) / 3. USDA-ARS, Southeastern Fruit & Tree Nut Research Lab, Byron, GA 31008, USA / Received February 12, 2002; accepted June 29, 2002; published online December 2, 2002
Summary
Prunus ferganensis (Kost. & Riab) Kov. & Kost, a close relative of cultivated peach (Prunus persica (L.) Batsch.), is native to arid regions of central Asia. A distinguishing feature of P. ferganensis is its prominent, elongated, unbranched pattern of leaf venation. To determine whether the long-vein trait could be used
as a marker in breeding for drought tolerance, we investigated the association between this trait and the leaf morphological
and physiological parameters related to drought response in P. ferganensis, P. persica and two interspecific hybrids, one with the long-vein trait (BY94P7585) and one without (BY94P7589). The four genotypes were
grafted onto “Guardian” peach rootstock and half of the plants were assigned to a drought treatment in which irrigation was
limited to 25–50% of the evapotranspiration (ET) rate measured in the remaining well-watered plants, which were irrigated
to runoff daily. The drought treatment reduced photosynthesis and leaf conductance by 49–83% and reduced total leaf area per
plant by 17–24%, but generally did not affect mid-morning leaf water potential. Leaf gas exchange did not differ among genotypes
in either treatment. Sorbitol accumulated in mature leaves in response to drought, but neither its amount nor its metabolism
varied systematically with climatic adaptation among genotypes. Accumulation of transport sugars was highest in P. ferganensis, indicating that growth reduction may represent an important strategy for coping with drought in this species. Prunus ferganensis and the hybrids had higher ET than P. persica, and seemed to use water opportunistically, maintaining high gas exchange rates and consequently high ET when water was available,
and avoiding low water potentials through stomatal closure as soil water declined. Leaf size (cm2 leaf–1) and specific leaf area (cm2 g–1 dry mass) were lower in P. ferganensis and the hybrids than in P. persica. We conclude that the long-vein trait is not a reliable marker for drought tolerance, but leaf traits of P. ferganensis such as size and specific leaf area may be useful in P. persica breeding programs targeting drought tolerance.
Keywords:
gas exchange, leaf venation, peach, photosynthesis, sorbitol, water potential.
