Here’s a taste of some of the latest stories about plant health, including the postharvest pathology of beans, a reduction in the proportion of shade grown coffee and the filamentous fungus that may be effective at controlling sugarcane nematodes.
New research at Washington State University shows that barley plants are able to recognise stem rust spores (Puccinia graminis) and begin to activate their plant defences within just 5 minutes of the spore touching the leaf surface. This goes against the previously held view that pathogens had to penetrate a plant in order to trigger the internal plant defence mechanisms. This new knowledge could revolutionise the way that farmers deal with pathogens of cereal crops such as stem rust.
In terms of food security the big story recently is that two regions of southern Somalia are in the midst of a famine. More than 10 million people are currently at risk of starvation with 1.8 million people displaced in East Africa’s worst drought for 60 years. Ethiopia and Kenya are neighbouring food insecure populations according to the UN food security classification.
However East Africa may soon experience more food shortages in the future due to yellow rust. Yellow rust (Puccinia striiformis) is a fungal disease which reduces wheat yields and can be found in many countries (Where is yellow rust found?). It causes the formation of necrotic areas and yellow pustules which together form stripes on the leaves. In the past it has not been found to destroy entire crops and was managed by the introduction of yellow rust resistant varieties in the 1970s. Recently a more aggressive strain of yellow rust has appeared and has already affected parts of Europe, Australia and the US. It is able to generate more spores than previous strains and spread more rapidly.
The international community had largely ignored this new strain in its fight against another wheat disease. Ug99 is a strain of stem rust (Puccinia graminis) which was first detected in 1998 and is traditionally regarded as more of a threat than yellow rust in the areas that it exists in (Where is stem rust found?). However this new strain of yellow rust is now considered more of a threat to wheat yields.
All cereals, except rice, are susceptible to rust. Wheat, maize, barley, millet, triticale, and oats all get rust. The spores of rust fungi land on a host plant, germinate, and grow toward a stomatal pore on the leaf surface to initiate infection. Rust infections produce red or yellow pustulating spores that give infected plants a “rusty” look. In susceptible plants, rust cuts off the plants’ ability to photosynthesise nutrients in their leaves and transport nutrients in their stems, causing stems to weaken and plants to fall over, making what little yield there is nearly impossible to harvest.
Rice, the “stainless steel” among cereal grasses, has long intrigued plant breeders and plant pathologists. For decades scientists have believed that, by discovering the genes that make rice immune to rusts, they might be able to introduce these genes into other cereal grains such as wheat and maize.