Source limitations due to leaf rust (PucciniaTriticina) during grain filling period in wheat

SERRAGO RA; MIRALLES DJ

Crop & Pasture Science

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2014 p. 185 - 193

1836-0947

Cereals crops are commonly characterized by source or sink limitations to grain yield determination. Different evidences haves shown that wheat crops that growth under no limitations are mainly sink-limited. Late foliar diseases (especially leaf rust) reduce the assimilates supply during post-anthesis, determining fewer assimilates per grain and thereby inducing grain weight reductions. Although the assimilates reduction hypothesis is the most accepted to explain decreases in grain weight reductions due to late foliar diseases, it has not been clearly established whether i) those reductions could be completely ascribed to source-limitations or ii) if diminished in grain weight could be the consequence of reductions in grain weight potential. In this sense, leaf rust could reduce (i) grain weight potential (determining sink-limitations) and/or (ii) achievable grain weight (determining source-limitations). The objective of this work was to determine if grain weight reductions due to leaf rust during grain filling period could be the consequenceassociated with of source-sink- limitations for growing wheat grains or the consequence of reductions oin grain weight potential. Two experiments (during 2007 and 2008 growing seasons) including healthy and diseased wheat crops were conducted under field conditions to fulfill the objective. Source-sink manipulation treatments and grain water content measurements were made to test the source- and sink- limitation hypothesis due to the appearance of late foliar diseases during the grain filling period. Leaf rust was induced to be appeared exclusively during the grain filling period and in both years it reduced grain yield and grain weight in both experiment. Grain yield reductions due to leaf rust were mainly associated with grain weight decreased. However, Aas an exception ofto distal grains, there were no significant differences between healthy and diseased plots oin maximum grain water content, indicating that late foliar diseases did not affect the potential size of the grains. The reserves stored in stems were remobilized to the growing grains in both, healthy and diseased crops. However, the reserves remaining at physiological maturity wereas significantly reduced in diseased crops. The reduction in grain number by trimming the spikes increased the grain weight in diseased but not in healthy crops. The grain weight of trimmed spikes in diseased crops reached similar values than into those of healthy crops. These results support the hypothesis that foliar diseases could cause source-limitation for grain filling beyond differences ofin grain weight potential when the crops are severely affected by late foliar diseases as leaf rust.