Heritability and gain from selection for field resistance against multiple root-knot nematode species (Meloidogyne incognita race 1 and M. javanica) in carrot |
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Authors: | Jairo V Vieira João M Charchar Fernando A S Aragão Leonardo S Boiteux |
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Institution: | 1. Centro Nacional de Pesquisa de Hortali?as (CNPH) / EMBRAPA Hortali?as, CP 0218, CEP 70359-970, Brasília-DF, Brazil
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Abstract: | Heritability and gain from selection of traits associated with field resistance to multiple root-knot nematode species were
estimated in carrot (Daucus carota L.). Experimental plots were uniformly and simultaneously infested with Meloidogyne incognita race 1 and M. javanica. Forty-seven half-sib families derived from the cv. ‘Brasília’ were evaluated for: (1) percentage of commercial roots with
non-galling symptoms (%RNG); (2) percentage of commercial roots with gall symptoms (%RGS) and (3) percentage of non-commercial
roots (%NCR). The cultivars ‘Brasília’ (resistant), ‘Carandaí’ (intermediate) and ‘Nova Kuroda’ (susceptible) were employed
as standards. Broad-sense heritability estimates were 61.9 % for %RNG; 30.6 % for %RGS and 67.9 % for %NCR. However, the gains
from selection were very small for all traits. The
genotypic correlation between %RGS and %NCR was –0.38 and the correlation between %RNG and %RGS was 0.13. Selection on increasing
%RNG resulted in a negative correlated response on %NCR (genotypic correlation = –0.99) indicating repulsion phase linkage(s)
between the genetic factor(s) controlling these traits. The phenotypic correlation of –0.88 between %RNG and %NCR suggested
that incomplete penetrance and dosage effects might be involved in the expression of these traits. Selection of superior genotypes
(i.e. high %RNG, low %RGS, and low %NCR) can be achieved. ‘Brasília’ was among the genotypes selected for the following cycle
of recombination reinforcing the notion that this cultivar is one of the most promising sources of stable, wide-spectrum field
resistance to Meloidogyne species in D. carota.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | genetic correlation heritability Meloidogyne spp resistance |
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