Hybrid Weakness in Phaseolus vulgaris L. II. Disruption of Root-Shoot Integration |
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Authors: | J M Reiber D S Neuman |
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Institution: | (1) Department of Biological Sciences, University of Nevada, Las Vegas, 4505 Maryland Parkway, Las Vegas NV 89154-4004, USA, US |
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Abstract: | We have been examining the importance of the root system on shoot growth and development using a developmentally disabled
hybrid of the common bean Phaseolus vulgaris L. Parental cultivars (P. Vulgaris cv. Redkloud of Mesoamerican origin, and P. vulgaris cv. Batt of Andean origin) grow normally, but crosses produce F1 hybrids exhibiting hybrid weakness associated with reduced
root and shoot growth. In this study, applications of benzylaminopurine (BAP) to roots of F1 hybrids increased the number
of root tips and leaves. Reciprocal grafting was used to study the effects of the root system on shoots. Grafting of roots
of the Mesoamerican cultivar onto shoots of F1 hybrids increased the cytokinin concentrations in leaves of F1 hybrids and
removed the characteristics associated with hybrid weakness. To determine whether factors in the xylem sap enhanced leaf growth,
leaf discs were incubated on sap collected from Mesoamerican and Andean cultivars. Sap from Mesoamerican plants enhanced the
growth of leaf discs excised from F1 hybrids more than sap collected from Andean cultivars. Estimates of the transport of
zeatin riboside (ZR)–type cytokinins from roots of F1 hybrids indicated that transport out of hybrid roots was reduced compared
with those transported out of Mesoamerican or Andean roots. Results suggest that ZR-type cytokinins are involved in hormonal
integration between roots and shoots of P. vulgaris and that one of the barriers to hybridization between Andean and Mesoamerican landraces is related to hormone transport.
Received October 15, 1998; accepted May 12, 1999 |
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Keywords: | ,Phaseolus vulgaris—,Cytokinin—,Grafting—,Root to shoot communication—,DL genes |
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