Susceptibility of pure and hybrid willows to isolates ofMelampsora epitea rust

Abstract

Pure species and F1 hybrid families of Salix viminalis and S. dasyclados were tested for resistance to four single uredinium isolates of Melampsora rust in laboratory experiments using excised leaves. Rust isolates were derived from: S. viminalis, S. dasyclados, a S. viminalis x triandra hybrid, and S. daphnoides. Incidence of infection, number of uredinia per leaf, and numbers of spores per uredinium were measured. As expected, the isolate from S. daphnoides did not infect any of the willow species or hybrids tested. For the other three rust isolates that were tested, the parent from which the isolate was derived was susceptible, the other parent was resistant, and hybrids were intermediate in resistance for incidence and uredinia per leaf. These patterns indicate additive inheritance of 'these resistance traits in hybrids. Numbers of spores per uredinium were similar on the hybrids and the susceptible parent for one rust isolate, suggesting dominant inheritance of this trait in the hybrids.

Clonal structure and hybrid susceptibility to a smut pathogen in microscale hybrid zones of northern wetlandCarex(Cyperaceae)

“…Fritz, Nichols-Orians, and Brunsfeld (1994) proposed four hypotheses for the responses of hybrids to herbivores: hybrid resistance, hybrid susceptibility, additivity, and dominance. Other studies have demonstrated that the response of hybrids to pathogens may follow similar patterns (Strauss, 1994;Fritz et al, 1996;Hjältén, 1998). Whether all of these hybrid responses are widespread in natural systems, however, is not clear, particularly for pathogens.…”

Mendelian inheritance of rust resistance to Melampsora larici‐epitea in crosses between Salix sachalinensis and S. viminalis

“…In comparison with research on rust resistance in poplars, very limited work has been done on the genetics of rust resistance in willows. Previously, Gullberg & Ryttman (1993), Fritz et al. (1996) and Johansson & Alström (2000) examined hybrids within and between S. viminalis and S. dasyclados.…”

“…In intraspecific hybrids of S. viminalis , Gullberg & Ryttman (1993) found considerable additive variation in field resistance to rust in Sweden. Fritz et al. (1996) tested intra‐ and interspecific F 1 hybrids of S. viminalis and S. dasyclados (syn.…”

“…They suggested that inheritance of resistance was additive based on the results that the hybrids between resistant and susceptible parents showed intermediate resistance. Johansson & Alström (2000) assessed the same crosses tested by Fritz et al. (1996) for field rust resistance during 1997–9.…”