New Zealand Journal of Crop and Horticultural Science abstracts
Inheritance of durable adult plant resistance to stripe rust (Puccinia
striiformis f. sp. tritici) in ‘Otane’ wheat (Triticum aestivum)
Muhammad Imtiaz
Soil, Plant and Ecological Sciences Division
P.O. Box 84, Lincoln University
Christchurch, New Zealand
M. G. Cromey*
New Zealand Institute for Crop & Food
Research Limited
Private Bag 4704
Christchurch, New Zealand
email: cromeym@crop.cri.nz
*Corresponding author.
J. G. Hampton
New Zealand Seed Technology Institute
P.O. Box 84, Lincoln University
Christchurch, New Zealand
M. Ahmad
New Zealand Institute for Crop & Food
Research Limited
Private Bag 4704
Christchurch, New Zealand
Abstract Stripe rust, caused by Puccinia striiformis
f. sp. tritici, is an important disease of wheat (Triticum aestivum)
in New Zealand and throughout the world. The wheat cultivar ‘Otane’ carries
durable resistance to stripe rust that has remained effective in New Zealand
since the cultivar’s release in 1984. To determine the mode of inheritance
of this durable adult plant resistance to stripe rust, ‘Otane’ was crossed
with the stripe rust susceptible ‘Tiritea’, and 140 F1-derived
double haploid (DH) lines were evaluated in glasshouse and field experiments
for their reaction to the stripe rust pathogen. Transgressive segregation
occurred, indicating that both cultivars possess resistance genes. Genetic
gain as a percentage of the moderately resistant parent for the most resistant
5% of the DH lines was statistically significant (83% and 68% in the glasshouse
and field experiments, respectively). The distribution of DH lines assessed
through infection types (IT) in the glasshouse supported a digenic ratio,
whereby resistance genes from both parental cultivars act additively to produce
resistant DH lines. Moderately resistant DH lines were produced when only
the gene from ‘Otane’ was present, and the absence of the ‘Otane’ gene produced
susceptible DH lines. The distribution of reaction of DH lines in the field
fitted a trigenic ratio. This model proposed that resistant DH lines were
produced when at least two genes from both parents interact; moderately resistant
DH lines were produced when either two genes (one modifier) or one gene from
‘Otane’ were present, and susceptible DH lines were produced when either
resistance genes from both parents or the major gene from ‘Otane’ were absent.
Segregation of final disease severity measured in the field also supported
the segregation of three genes in the DH population. The demonstrated durability
of stripe rust resistance in ‘Otane’ in New Zealand, which is influenced
by environment, may be the result of a combination of resistance alleles
at two loci at least.
Keywords Triticum aestivum; durable disease resistance;
double haploid; transgressive segregation; genetic models
H02058 Received 14 August 2002; accepted 20 December 2002; published 26
March 2003
New Zealand Journal of Crop and Horticultural Science, 2003, Vol. 31:
23-31
0014-0671/03/3101-0023 $7.00 © The Royal Society of New Zealand
2003
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