Epsilon Archive for Student Projects

Abstract

Barley is one of the major crops in the world, and spot blotch, caused by the
fungus Cochliobolus sativus, is an important disease that affects it. Spot blotch
can cause major yield losses and reduce the quality of the seeds, especially in
wet, warm climates. The pathogen can also infect the roots of barley plants,
causing common root rot. Due to climate change and the spread of the pathogen
through modern transportation, the risk of yield losses due to spot blotch has been
increasing. Cochliobolus sativus is a hemibiotrophic fungus that is usually found in
nature in its asexual form (Bipolaris sorokiniana).
I used the tape method, a so far little used technique for testing resistance, to try
to find good sources of resistance to C. sativus in barley. The tested lines were
provided by Nordic breeders, who previously tested them under standard field and
greenhouse conditions. Different fungal isolates that had been isolated from
different locations in Sweden were used in this experiment. The lesions were later
scored with a 1-9 scale, and the plants were classified as resistant, moderately
resistant, moderately susceptible, or susceptible to a certain fungal isolate.
It was found that there is a significant barley genotype-fungal isolate interaction,
which means that barley lines may respond differently to each fungal isolate. The
barley lines suggested as resistance sources were resistant or moderately
resistant to all three fungal isolates. The barley lines coded as PPP112, PPP201,
PPP206, PPP207, PPP250, PPP252, PPP260, PPP265, PPP269, PPP272 and PPP274
are the genotypes thus identified as potential resistance sources for breeding. I
found that there is a positive correlation between lesions in the leaves with diffuse
necrotic reactions and gray spots and fungal aggressiveness, suggesting possible
mechanisms of infection that could be studied further. In the end, I could not
compare the results from the tape method with the results provided by breeders,
since the fungal isolates used in these experiments were too different.
SLU, Swedish