Three partially resistant spring wheat cultivars, with a long latency period were crossed among each other and with the highly susceptible Little Club, with a very short latency period . Parents, F3 and F5 plants have been inoculated with the leaf rust race Flamingo in the young flag leaf stage to determine the latency period .From the crosses with Little Club, it was concluded that Westphal 12A carries three, Akabozu two and BH 1146 two or three genes for a longer latency period . BH 1146 appears to carry also one hypersensitive resistance gene .Transgressive segregation occurred in crosses between partially resistant cultivars . From crosses between the partially resistant cultivars, it was concluded that the genes in Akabozu and Westphal 12A are different, while those in Akabozu and BH 1146 are at least partly different . The possibilities of accumulation of LP-prolonging genes are discussed .

Crosses were made between the highly susceptible Little Club and the partially resistant cultivars Westphal 12A, Akabozu and BH 1146 to obtain F1, F2 and backcross generations . Latency period (LP) was determined in plants inoculated at the young flag leaf stage with a monospore culture of race `Flamingo' of wheat leaf rust . Broad sense heritability of LP in the F2 averaged 0 .8 . The genes showed partial to almost complete recessive inheritance . Scaling tests indicated that additive gene action was the most important factor in the inheritance of partial resistance . The tests showed that there were no indications for additive x additive, additive x dominance or dominance x dominance interactions . The number of effective factors was estimated as one or two for Akabozu, three or more for Westphal 12A, and two or three for BH 1146 . BH 1146 also possessed a (semi-)dominant gene for a lower infection type which was temperature sensitive in its expression . The genes of the various parents had unequal effect on LP .

In two experiments, the presence of cell wall appositions in flag leaves of spring wheat genotypes susceptible and partially resistant to wheat leaf rust was studied. More cell wall appositions were observed near aborted infection struetures than in estabhshed colonies. There was not a marked difference in the number of cell wall appositions per colony between susceptible and partially resistant genotypes. More cell wall appositions per unit area colony were present in partially resistant genotypes. It was concluded that the low number of cell wall appositions could not be responsible for the observed difference in colony size between susceptible and partially resistant genotypes. Partial resistance in wheat to wheat leaf rust can be divided into two phases. The first phase is pre-haustorial and results in a reduction of the number of colonizing infection structures. In the second phase a posthaustorial retardation of fungal growth rate occurs. The latter appears to be the more important phase. ZusammenfassungDas Vorhandensein von Zellwandappositionen in den Fahnenblattern von Sommerweizensorten, die anfallig und teilresistent gegenuber dem Weizenbraunrost sindIn zwei Versuchen wurde das Vorhandensein von Zellwandappositionen in den Fahnenblattern von Sommerweizensorten, die sich als anfallig oder teilresistent gegenuber dern Weizenbraunrost darstellen, untersucht. In der Nahe von verkummerten Infektionsstrukturen wurden mehr Zellwandappositionen beobachtet als bei etablierten Kolonien. Es gab keinen deuthchen Unterschied in der Anzahl von Zellwandappositionen je Kolonie zwischen anfalligen und teilresistenten Genotypen. U.S.

Twenty downy mildew isolates were collected in south, central and north Ecuador and inoculated on seedlings of 60 quinoa lines. A scale for scoring quinoa downy mildew infections was developed. Four virulence groups and three resistance factors were identified. In southern Ecuador only isolates of virulence group 2 were collected, while in the central region only virulence group 4 was found. In the north of Ecuador isolates of all four virulence groups were collected. Resistance factor R3 was found most frequently in seedlings of 13 high‐yielding Ecuadorian quinoa lines. No effective resistance against group 4, the most virulent group, was observed. Lines ECU‐288 (susceptible), ECU‐291(R1), ECU‐470 (R2) and ECU‐379 (R3) could be used as a preliminary quinoa differential set for identifying downy mildew virulence groups.

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