The role of epicuticular wax in conferring resistance to blackspot, incited by Alternaria brassicae (Berk.) Sacc, has been investigated under field conditions in four cultivars of rapeseed and mustard. In increasing order of resistance to blackspot they were: Torch (Brassica campestris L.), Midas (B. napus L), Lethbridge (LB) 22A (B. juncea (L.) Czern.), and Tower (B. napus). The leaves of Midas and Tower have appreciable amounts of epicuticular wax, and wiping of the leaves with a dry cotton swab significantly increases their susceptibility to the blackspot disease. Torch and LB 22A have minimal amounts of epicuticular wax and their disease susceptibility is generally not significantly altered upon wiping. It is concluded that the epicuticular wax in rapeseed and mustard confers resistance to blackspot and that this character could be used in breeding cultivars resistant to this disease.
F1 and F2 barley plants from crosses of eight resistant varieties with a susceptible one were tested for reaction to an Alberta isolate of Rhynchosporium secalis (Oud.) Davis. A dominant gene was responsible for resistance in seven of the varieties. Furthermore, the same gene appeared to be common to all seven. In the eighth variety, Nigrinudum, a recessive gene governed resistance. This gene was designated rh8. The variety Turk carrying the Rh3 gene was crossed with a number of linkage testers and interchange stocks. It was confirmed that the Rh3 gene is located on chromosome. 3.
A mathematical model, which is a modification of the Gompertz equation, can determine the number of germinations and the number of appressorial formations in a population of conidia of Colletotrichum graminicola. It will determine both the maximum proportion of conidia which will germinate or which will form appressoria and the time for these events to occur. The equation parameters, which are functions of biotic and abiotic conditions, are determined using a nonlinear regression programme. The data used to test the model show that continuous light on the parent fungal colony reduces subsequent conidial germination but does not change the time taken to reach this maximum.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.