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Selection for new pear rootstocks: in vitro screening and field evaluation for tolerance to iron chlorosis

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Authors: R. Dolcet-Sanjuan, E. Claveria, J. Bonany, I. Iglesias, L. Asín, M.H. Simard
Issue: 99V-1 (157-164)
Topic: Plant Production
Keywords: Pyrus, lime induced chlorosis, selection, in vitro

Crosses have been done between the new INRA pear rootstock selection 'Pyriam' and four "Mediterranean" Pyrus species: P. communis cordata, P. amygdaliformis, P. a. persica, and P. elaeagrifolia. An in vitro test, to evaluate tolerance to lime-induced chlorosis has been applied to these progenies. Embryos were dissected out of fruits and cultured in a basal medium to ensure proper plantlet development. One week later, plantlets with roots and leaves emerging out of the cotyledons, were transferred to a paper bridge in a Magenta flask containing a liquid medium with 2µMFe³+DTPA and 10mM NaHCO3. After two weeks of culture, different levels of iron deficiency chlorosis, on the newly formed leaves, were observed. All evaluated plants were acclimated, grown in the greenhouse and transferred to a field plot with a clay loam soil with 26% of calcium carbonate equivalent. Total chlorophyll content of each seedling was measure twice, during spring of 2000 and 2001 , and once after grafting with 'Conference', during fall of 2001. No good correlation between in vitro and field conditions was observed at the individual seedling level of tolerance. However a good correlation was found comparing hybrid crosses. The in vitro tolerance to iron deficiency was similar to the known differential tolerance of each Pyrus species. Being P. amygdaliformis, P. amygdaliformis persica, and P. communis cordata the most tolerant. The results also confirm a good correlation between in vitro seedling evaluation for tolerance to iron deficiency conditions and field tolerance of grafted plants to lime induced chlorosis. To solve the lack of correlation at the individual seedling level the next assays contemplare in vitro cloning of each individual prior to the in vitro test. In vitro propagation of some preliminarily selected clones was satisfactory.

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