Barley yield losses due to defoliation of upper three leaves either healthy or infected at boot stage by <Emphasis Type="Italic">Pyrenophora teres</Emphasis> f. <Emphasis Type="Italic">teres</Emphasis> |
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Authors: | Rajaâ Jebbouj Brahim El Yousfi |
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Institution: | 1.Faculté des Sciences et Techniques,Université Hassan 1er,Settat,Morocco;2.Cereal Pathology Laboratory,Institut National de la Recherche Agronomique (INRA), Aridoculture Centre,Settat,Morocco |
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Abstract: | This paper evaluates, in the greenhouse and under natural conditions, barley yield losses due to defoliation treatments of
the upper three leaves either healthy or infected at the boot stage by Pyrenophora teres f. teres. Defoliation was assumed as a loss of a similar leaf area caused by net blotch disease severity of 100%. Contribution to
grain yield was defined herein as a difference between defoliation treatments and a treatment where plants lost all their
upper three leaves. In contrast, yield losses referred to differences in yield between defoliations and the control. In the
greenhouse, removal of the antepenultimate leaf did not affect any yield component. For main stems, defoliating upper three
leaves reduced grain yield by 30% and this was mainly due to flag leaf removal. These losses were similar to those induced
by net blotch disease under natural conditions, but were of 42% for all tillers. Grain yield losses due to disease severity
were not equivalent to the defoliation effect of a similar healthy leaf area. On the other hand and for a significant contribution
to grain yield, flag leaf was dependent on the presence of the other two leaves. Inoculation and defoliation of 21 cultivars
induced similar grain yield losses of 32%. However, biotic stress reduced by 40% the contribution of their upper three leaves.
Under field conditions, yield losses were not significant until barley plants lost more than one upper leaf and flag leaf
contribution was equivalent to that of the remaining leaves. Characteristic roots, defined as leaf coefficients for plant
performance, were 0.13, 0.06 and 0.01 for the flag, penultimate and antepenultimate leaves, respectively. Because antepenultimate
leaves become trivial at the boot stage, we propose that coefficients of the remaining leaves should be used when modelling
yield losses due to barley foliar diseases. |
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