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This article in CS

  1. Vol. 21 No. 1, p. 15-18
    Received: Nov 13, 1979

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Genetic and Soil Moisture Effects on the Branching-Root Trait in Alfalfa1

  1. M. S. McIntosh and
  2. D. A. Miller2



The inheritance of the branching-root trait in alfalfa, Medicago saliva L., was studied in diallels at two field locations. Diallel progenies of seven clones were grown in spaced plantings at Champaign-Urbana and Brownstown, Illinois. Roots of 6-month-old alfalfa branched more at Brownstown than Champaign-Urbana. At Champaign-Urbana significant differences were found for general but not specific combining ability. At Brownstown, differences were significant for specific combining ability but not for general combining ability. General combining ability × location interaction also was significant. Reciprocal and selfing effects were not important at either location. Regression estimates of offspring on S1 parent were 0.128 and 0.002 for the Brownstown and Champaign-Urbana locations, respectively.

A greenhouse experiment was conducted to determine whether moisture stress contributes to the genotype × environment interaction for the branching-root trait. Progeny of six crosses, whose parents represented a wide range in rooting habit, were grown in pots with soil moisture levels increased daily to − ⅓ ) bar onto 50% of the − ⅓ bar moisture level. Low moisture levels resulted in plant stress exhibited as a decrease in plant height and dry weight. Plants grown in the low moisture regime also had a lower incidence of branching roots. The genotype × moisture interaction was nonsignificant. Among moisture-stressed plants, height and weight were positively correlated with root branching (r = 0.81 and 0.60, respectively. Both are significant at the 0.01 level.). For unstressed plants, only plant weight was significantly correlated with the branching root habit (r = 0.49, significant at the 0.05 level.).

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