Characterization of Yr15 resistance to stripe rust of wheat
Abstract
English: Stripe (yellow) rust, caused by Puccinia striiformis Westend f. sp. tritici,
is a major disease of bread wheat, Triticum aestivum L., in South
Africa. The objective of this study was to evaluate the Yr15 gene as a
potential resistance source for breeding purposes.
Histological evidence was provided that Yr15 conditions a
hypersensitive reaction typical of non-durable resistance.
Fluorescence, phase contrast and scanning electron microscopy
complemented each other and may be used to quantify various
aspects of resistance expression in the wheat stripe rust pathosystem.
The frequency of stomatal penetration was extremely low and no
meaningful differences in early infection structures were observed
between the resistant Yr15 and susceptible Avocet 'S' lines. Papillae
were not involved in the resistance response to pathotype 6E16.
In studies of defense-related proteins, an induction of β- 1,3-glucanase
activity in both resistant and susceptible wheat genotypes was
detected within 96 h post-inoculation (hpi). This induction, however,
was constitutive and did not depend on the infection process. Likewise,
no changes in chitinase activity were observed between resistant and
susceptible plants. A pronounced increase of peroxidase activity
between 0 and 168 hpi, in both infected and uninfected resistant and
susceptible plants was observed, suggesting a constitutive expression
of this enzyme.
Using AFLP (Amplified Fragment Length Polymorphism) technology to
detect possible molecular markers for Yr15, two primer combinations
yielded polymorph isms between the bulked susceptible and resistant
SST55 x Yr15/6*AvS F2 DNA, as well as between the susceptible and
resistant parents. Fragment sizes ranged from 50 to 420 bp. Of these,
one 95 bp fragment identified using primers MseCAA + Eco-ACA and
one 205 bp fragment identified using primers MseCAA + Eco-AAC
were detected in the resistant parent and the resistant F2 group. This
indicates that these fragments are closely associated with Yr15 making
them ideal candidates for further investigation. Afrikaans: Streep (geel) -roes, veroorsaak deur Puccinia striiformis Westend f.
sp. tritici, is In belangrike siekte van broodkoring, Triticum aestivum L.,
in Suid-Afrika. Die doelwit van hierdie studie was om die Yr15 geen as
In potensiële weerstandsbron te evalueer vir verdere aanwending in
telingsprogramme.
Histologiese bewyse is gelewer dat Yr15 In hipersensitiewe reaksie
tipies van nie-volhoubare weerstand bemiddel. Fluoressensie, fasekontras
en skandeer-elektron-mikroskopie het mekaar
gekomplementeer en kan gebruik word om sekere aspekte van
weerstanduitdrukking in die koringstreeproes-patosisteem te
kwantifiseer. Die frekwensie van stomata le penetrasie was laag en
geen beduidende verskille in vroeë-infeksiestrukture kon tussen die
bestande Yr15 en vatbare Avocet'S' lyne waargeneem word nie.
Papillae was nie betrokke by die weerstandsreaksie teen patotipe 6E16
nie.
In studies van proteïne wat met verdedigingsmeganismes geassosieer
word, is In induksie in β1 ,3-glukanase-aktiwiteit in beide bestande en
vatbare lyne, binne 96 h na inokulasie waargeneem. Hierdie induksie
was konstitutief en is nie beïnvloed deur die infeksieproses nie.
Soortgelyk het geen verskille in chitinase-aktiwiteit tussen bestande en
vatbare lyne voorgekom nie. In Toename in konstitutiewe peroksidaseaktiwiteit
tussen 0 en 168 h na inokulasie is waargeneem by
geïnfekteerde en kontrole bestande en vatbare plante.
In die toepassing van AFLP ("Amplified Fragment Length
Polymorphism") tegnologie om moontlike molekulêre merkers vir Yr15
te vind, het twee priemstuk-kombinasies polimorfismes tussen SST55 x
Yr15/6*AvS F2 DNA, onderskeidelik saamgevoeg vir bestande en
vatbare segregate, aangedui. Fragmentgroottes het gewissel tussen
50 en 420 bp. Een 95 bp fragment, soos geïdentifiseer deur die
priemstukke MseCAA + Eeo-ACA en een 205 bp fragment, soos
geïdentifiseer deur die priemstukke MseCAA + Eeo-AAC het in beide
die bestande ouer en die bestande F2 groep voorgekom. Hierdie
fragmente is dus nou geassosieer met Yr15 en is ideale kandidate vir
verdere ondersoek.