Traditional and commercial apple and pear cultivars as sources of resistance to fireblight¹

Abstract

In Hungary, fireblight research programmes were initiated on pear in 1999 and on apple in 2000, with the aim of evaluating the susceptibility or resistance of commercial cultivars. Sources of resistance for future breeding were also sought among traditional apple cultivars collected from Ukraine and pear cultivars in the Hungarian gene bank (Szigetcsép). Experiments were done under secure conditions. Inocula were mixtures of characteristic Erwinia amylovora isolates from pear and apple in Hungary. Host responses (symptom development, disease severity and multiplication rate of bacterial cells in host tissues) were assessed on shoots, flowers and fruits. About 30 pear and 30 apple cultivars, and 35 apple hybrids, were tested and grouped into four categories for pear and three for apple. Of the pear cultivars tested, 50% were susceptible, 30% moderately susceptible and only 10% of low susceptibility. Different plant organs occasionally displayed different responses. Members of the last two groups might serve as useful candidates for growing under IPM conditions. Among the traditional Hungarian varieties tested, we found high resistance in 'Sikulai' and 'Szemes alma', which could be used as sources of fireblight resistance in breeding programmes and also grown in organic orchards. Furthermore, among the offspring of the apple 'Prima' (scab-resistant), we have found highly resistant lines.

Identification of marker alleles linked to fire blight resistance QTLs in apple genotypes

“…In contrast, the shoots of ‘Artemisz’ (breeder's reference: MR‐03) were considered to be FB resistant previously (Hevesi et al. , Tóth et al. ), although one resistance allele of FBF7 was also located in ‘Artemisz’ explaining its resistance as well.…”

“…As expected, data given by minor QTLs should be handled cautiously. In contrast, the shoots of 'Artemisz' (breeder's reference: MR-03) were considered to be FB resistant previously (Hevesi et al 2004(Hevesi et al , T oth et al 2012, although one resistance allele of FBF7 was also located in 'Artemisz' explaining its resistance as well. Based on other investigations with SSR markers, the paternal genotype of 'Artemisz' is proved to be 'Jonathan' (T oth et al 2012) which Fire blight resistance in apple genotypes may explain that it contains all of the three resistance alleles associated with FLO10.…”

Estimation of resistance pear cultivars to Erwinia amylovora using artificial immature pear fruits method

“…Za ispitivanje otpornosti sorata kruške prema E. amylovora postoji više metoda: inokulacija jednogodišnjih mladara na stablima i sadnicama kruške, inokulacija cvasti, i inokulacija nesazrleih plodova (Paulin et al, 1990;Hevesi et al, 2004).…”

“…Plodovi su inokulisani nanošenjem kapi suspenzije bakterija pomoću bakteriološke igle na prethodno napravljenu povredu ploda. Kontrolni plodovi su tretirani sterilnom vodom (Hevesi et al, 2004). Ocena intenziteta infekcije vršena je posle 5 dana od inokulacije prema skali od 0-4 (Paulin et al, 1990).…”

“…Kao rezultat selekcionih programa, u Kanadi je stvoreno više sorata kruške otpornih prema E. amylovora, ali se po svom značaju izdvajaju Harrow Delight, Harrow Quen, Harrow Sweet (Hunter, 1993). Istraživanja na selekciji otpornijih sorata kruške prema E. amylovora sprovede se i u Češkoj i Mađarskoj (Sillerova et al, 2010;Hevesi , et al, 2004). Navedeni podaci ukazuju na veliki značaj stvaranja otpornnih sorata jabučastih voćaka prema E. amylovora.…”