Physiological and genetic studies of leaf growth often focus on short-term responses, leaving a gap to whole-plant models that predict biomass accumulation, transpiration and yield at crop scale. To bridge this gap, we developed a model that combines an existing model of leaf 6 expansion in response to short-term environmental variations with a model coordinating the development of all leaves of a plant. The latter was based on: (1) rates of leaf initiation, appearance and end of elongation measured in field experiments; and (2) the hypothesis of an independence of the growth between leaves. The resulting whole-plant leaf model was integrated into the generic crop model APSIM which provided dynamic feedback of environmental conditions to the leaf model and allowed simulation of crop growth at canopy level. The model was tested in 12 field situations with contrasting temperature, evaporative demand and soil water status. In observed and simulated data, high evaporative demand reduced leaf area at the whole-plant level, and short water deficits affected only leaves developing during the stress, either visible or still hidden in the whorl. The model adequately simulated whole-plant profiles of leaf area with a single set of parameters that applied to the same hybrid in all experiments. It was also suitable to predict biomass accumulation and yield of a similar hybrid grown in different conditions. This model extends to field conditions existing knowledge of the environmental controls of leaf elongation, and can be used to simulate how their genetic controls flow through to yield.

~ ~We have analyzed the possibility that chemical signaling does not entirely account for the effect of water deficit on the maize (Zea mays 1.) leaf elongation rate (LER) under high evaporative demand. We followed time courses of LER (0.2-h interval) and spatial distribution of elongation rate i n leaves of either water-deficient or abscisic acid (ABA)-fed plants subjected to varying transpiration rates in the field, in the greenhouse, and in the growth chamber. At low transpiration rates the effect of the soil water status on LER was related to the concentration of ABA in the xylem sap and could be mimicked by feeding artificial ABA. Transpiring plants experienced a further reduction in LER, directly linked to the transpiration rate or leaf water status. Leaf zones located at more than 20 mm from the ligule stopped expanding during the day and renewed expansion during the night. Neither ABA concentration in the xylem sap, which did not appreciably vary during the day, nor ABA flux into shoots could account for the effect of evaporative demand. In particular, maximum LER was observed simultaneously with a minimum ABA flux in the droughted plants, but with a maximum ABA flux in ABA-fed plants. All data were interpreted as the superposition of two additive effects: the first involved ABA signaling and was observed during the night and i n ABA-fed plants, and the second involved the transpiration rate and was observed even i n wellwatered plants. We suggest that a hydraulic signal is the most likely candidate for this second effect.Response of LER to water deficit has most often been analyzed by considering the behavior of plants subjected to both low soil water potential and low evaporative demand. In this case, at least a large part of the control of LER is linked to a message originating from roots and traveling to shoots. This was demonstrated using experimental designs where I)l was maintained high and constant by pressurizing (Passioura and Gardner, 1990) or splitting (Gowing et al., 1990) the root system while soil water was progressively depleted. ABA could play a major role in this message (Saab et al., 1992; for review, see Munns and Sharp [1993]; Dodd and Davies 1996), and has recently been shown to induce mRNA populations in intact plants (Griffiths and Bray, 1996), with some of them being associated ' This work was supported by an Institut National de Ia Recherche Agronomique grant (AIP valorisation et protection des ressources en eau). * Corresponding author; e-mail tardieu@ensam.inra.fr; fax 33-4-67-52-21-16. 893with inhibition of the elongation of maize mesocotyl at low soil water potential (Saab et al., 1995). However, a11 of the above-mentioned experiments were carried out with a nu11 or low evaporative demand compared with those observed in the field. As pointed out by Kramer (1988), such situations with low soil water potential and artificially high $, might maximize the role of integrated control involving root-to-shoot messages, and minimize local control involving leaf water status or wate...

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Sensitivity of 159 isolates of Zymoseptoria tritici collected from durum wheat fields in Tunisia in 2012 was analysed towards pyraclostrobin, fluxapyroxad, epoxiconazole, metconazole, prochloraz and tebuconazole using microtiter tests. All isolates were found to be highly sensitive to pyraclostrobin with EC50 <0.01 mg/l with the exception of three isolates from the same field with higher EC50 values (>0.5 mg/l). These three isolates carried a mutation in the cytochrome b gene encoding the G143A substitution. This is the first report of quinone outside inhibitors (QoI) resistance in Z. tritici in Tunisia. Sensitivity towards r fluxapyroxad was in a narrow range with EC50 values ranging between 0.013 and 0.125 mg/l, which can serve as baseline sensitivity data for the future. Demethylation inhibitors sensitivity varied across a broad range with the data indicating a slight shift in sensitivity when compared to a previous study on the 2010 population. No highly sensitive strains were isolated from samples from fields, which had received three or four DMI applications.

Drought can alter stem apex temperature and plant phenological development and it can then have an effect on the duration of the durum wheat stages. Thermal responses of plants to water stress are tentatively analysed as regards microclimate conditions by applying three different water treatments. Apex temperature measurements showed that they are related to radiation and that acceleration of apex development could be related to their increase.