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Australia’s zero-weed tolerance, waterlogging in barley plants, the spreading wheat curl mite

Post a commentBy Maggie Hennessy , 28-Aug-2014
Last updated on 28-Aug-2014 at 15:08 GMT

Lessons from Australia in wheat herbicide resistance, waterlogging stress tolerance and how the wheat curl mite spreads.

A lesson in weed reduction: Australia

Herbicide resistance continues to proliferate among weed populations infesting global wheat crops, threatening grain production and thereby food supply, but growers can learn from Australia, which has implemented novel techniques that resulted in considerable weed population reduction.

Australia’s 20-year escalation in the extent and frequency of herbicide resistance combined with a depletion in herbicide resources drove growers to develop and adopt alternative weed control technologies in combination with a new focus on zero-weed tolerance. The inclusion of harvest weed seed control (HWSC) techniques in herbicide-based weed control programs is now delivering considerable reductions in weed populations, resulting in herbicide conservation and substantial production benefits.

Combined with an emphasis on “driving weed populations towards zero”, Australian producers offer a clear example for global wheat growers for managing herbicide-resistant weed populations.

Source: Pest Management Science
DOI: 10.1002/ps.3704
“Management of herbicide resistance in wheat cropping systems: learning from the Australian experience”
Authors: Michael J Walsh and Stephen B Powles

Understanding waterlogging tolerance in barley plants

Oxygen deprivation is key to understanding root growth and functioning under waterlogging, claim reseachers.

The team examined changes in net potassium flux and measured membrane potential of root cells from elongation and mature zones of two barley varieties under hypoxia and anoxia conditions, and as influenced by ability to transport oxygen from the shoot. They concluded that the ability of root cells to maintain membrane potential and cytosolic potassium homeostasis is central to plant performance under waterlogging.

Oxygen deprivation led to an immediate potassium loss from roots, in a tissue- and time-specific manner, thus affecting root potassium homeostasis. Both anoxia and hypoxia induced transient membrane depolarization, though the extent of such depolarization varied based on the severity of oxygen stress, and was less pronounced in a waterlogging-tolerant variety.

Intact barley roots were able to maintain hydrogen-pumping activity under hypoxic conditions, while disrupting oxygen transport from shoot to root resulted in more pronounced membrane depolarization under oxygen-limited conditions and in anoxia a rapid loss of the cell viability. The researchers also concluded that efficient oxygen transport from the shoot may enable operation of the plasma membrane H+-ATPase in roots even under conditions of severe oxygen limitation in the soil solution.

Source: Plant, Cell & Environment
DOI: 10.1111/pce.12422
“Linking oxygen availability with membrane potential maintenance and K+retention of barley roots: implications for waterlogging stress tolerance”
Authors: Fanrong Zeng, Dennis Konnerup, Lana Shabala, Meixue Zhou, Timothy David Colmer, Guoping Zhang and Sergey Shabala

The spreading wheat curl mite

A recent study of highly invasive wheat curl mites suggests that the most polyphagous (feeding on many types of food) species are the best colonizers and warrant additional study on the crops and grasses to determine how and why they’re spreading.

A pest that transmits wheat streak mosaic virus and several other plant viruses that has long been considered a single polyphagous species, recent studies in Poland on the wheat curl mite (WCM) unveiled a complex of genetically distinct lineages with a range of host-acceptance traits, from highly polyphagous to host-specific. Such diversity of WCM genotypes and host-acceptance phenotypes in Europe (where WCM is believed to have originated) raised questions about the lineage identities of invasive WCM populations on other continents and their relationships to European lineages.

In an effort to examine the global presence of WCM and determine the relatedness of lineages established in different continents, researchers performed host-range bioassays of a highly polyphagous WCM lineage to supplement existing data on this lineage's ability to colonize graminaceous and non-graminaceous hosts.

Invasive WCM populations in North and South America and Australia assorted with the only three known polyphagous and pestiferous WCM lineages (‘MT-1’, ‘MT-7’ and ‘MT-8’) from a total of eight current lineages. These results show that the most polyphagous lineages were more successful colonizers and demonstrate a need for extensive surveys for WCM on both crops and wild grass species in invaded continents. The most invasive lineage (‘MT-1’) successfully colonized all 10 plant species tested in three families and has spread to North and South America and Australia from its presumed origins in Eurasia.

Source: Annals of Applied Biology
DOI: 10.1111/aab.12130
“Global spread of wheat curl mite by its most polyphagous and pestiferous lineages”
Authors: A. Skoracka, B. Rector, L Kuczynski, W. Szydlo, G. Hein and R. French

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