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Vadez V.,Indian International Crops Research Institute for the Semi Arid Tropics | Kholova J.,Indian International Crops Research Institute for the Semi Arid Tropics | Zaman-Allah M.,Indian International Crops Research Institute for the Semi Arid Tropics | Zaman-Allah M.,International Maize and Wheat Improvement Center | And 2 more authors.
Functional Plant Biology | Year: 2013

Water deficit is the main yield-limiting factor across the Asian and African semiarid tropics and a basic consideration when developing crop cultivars for water-limited conditions is to ensure that crop water demand matches season water supply. Conventional breeding has contributed to the development of varieties that are better adapted to water stress, such as early maturing cultivars that match water supply and demand and then escape terminal water stress. However, an optimisation of this match is possible. Also, further progress in breeding varieties that cope with water stress is hampered by the typically large genotype×environment interactions in most field studies. Therefore, a more comprehensive approach is required to revitalise the development of materials that are adapted to water stress. In the past two decades, transgenic and candidate gene approaches have been proposed for improving crop productivity under water stress, but have had limited real success. The major drawback of these approaches has been their failure to consider realistic water limitations and their link to yield when designing biotechnological experiments. Although the genes are many, the plant traits contributing to crop adaptation to water limitation are few and revolve around the critical need to match water supply and demand. We focus here on the genetic aspects of this, although we acknowledge that crop management options also have a role to play. These traits are related in part to increased, better or more conservative uses of soil water. However, the traits themselves are highly dynamic during crop development: they interact with each other and with the environment. Hence, success in breeding cultivars that are more resilient under water stress requires an understanding of plant traits affecting yield under water deficit as well as an understanding of their mutual and environmental interactions. Given that the phenotypic evaluation of germplasm/breeding material is limited by the number of locations and years of testing, crop simulation modelling then becomes a powerful tool for navigating the complexity of biological systems, for predicting the effects on yield and for determining the probability of success of specific traits or trait combinations across water stress scenarios. © 2013 CSIRO.

Giannini A.,Columbia University | Salack S.,Cheikh Anta Diop University | Salack S.,Center Detude Regional Pour Lamelioration Of Ladaptation Secheresse | Salack S.,Center Regional | And 3 more authors.
Environmental Research Letters | Year: 2013

We propose a re-interpretation of the oceanic influence on the climate of the African Sahel that is consistent across observations, 20th century simulations and 21st century projections, and that resolves the uncertainty in projections of precipitation change in this region: continued warming of the global tropical oceans increases the threshold for convection, potentially drying tropical land, but this 'upped ante' can be met if sufficient moisture is supplied in monsoon flow. In this framework, the reversal to warming of the subtropical North Atlantic, which is now out-pacing warming of the global tropical oceans, provides that moisture, and explains the partial recovery in precipitation since persistent drought in the 1970s and 1980s. We find this recovery to result from increases in daily rainfall intensity, rather than in frequency, most evidently so in Senegal, the westernmost among the three Sahelian countries analyzed. Continuation of these observed trends is consistent with projections for an overall wetter Sahel, but more variable precipitation on all time scales, from intra-seasonal to multi-decadal. © 2013 IOP Publishing Ltd.

Boureima S.,Center Detude Regional Pour Lamelioration Of Ladaptation Secheresse | Boureima S.,Ghent University | Oukarroum A.,University of Quebec at Montreal | Diouf M.,Center Detude Regional Pour Lamelioration Of Ladaptation Secheresse | And 2 more authors.
Environmental and Experimental Botany | Year: 2012

Drought is one of the major constraints limiting crop productivity in African Sahel. The aim of this study was to select mutant sesame (Sesamum indicum L.) lines with improved levels of drought resistance. Twenty-one M4-M5 sesame lines of unknown drought tolerance, and their three parental sources with well-known and contrasting drought tolerance levels were evaluated at the vegetative stage in a factorial pot experiment, using a completely randomized design with three replicates. After 2 weeks of growth, water was withheld for 16 days as drought stress treatment. Chlorophyll a fluorescence data, as well as stomatal conductance and flag leaf temperature were recorded during the stress period. Recorded chlorophyll a fluorescence transients were analyzed by the JIP-test to translate stress-induced damage in these transients to changes in biophysical parameters allowing quantification of the energy flow through the photosynthetic apparatus. Large genotypic differences in the extent to which drought stress affected chlorophyll a fluorescence transients were observed. Drought stress reduced the performance index and stomatal conductance, and increased flag leaf temperature but had little effect on maximum quantum yield of primary photochemistry. A drought factor index is proposed in this work to screen for improved drought tolerance in twenty-one M4-M5 sesame lines. Mutant lines shi165, lc162, mc112, lc164, icn115, icn141, mt169, dwf172 and cc102 exhibited drought factor index values superior to those of the known drought tolerant cultivars Birkan and 38-1-7. A significant and negative relationship was found between the drought factor index and the leaf temperature index. Finally, we succeeded in obtaining drought tolerant lines with good secondary traits by using mutagenesis and chlorophyll fluorescence technique. © 2012 Elsevier B.V..

Kholova J.,Indian International Crops Research Institute for the Semi Arid Tropics | Kholova J.,Charles University | Zindy P.,Indian International Crops Research Institute for the Semi Arid Tropics | Malayee S.,Indian International Crops Research Institute for the Semi Arid Tropics | And 9 more authors.
Functional Plant Biology | Year: 2016

Traits influencing plant water use eventually define the fitness of genotypes for specific rainfall environments. We assessed the response of several water use traits to vapour pressure deficit (VPD) in pearl millet (Pennisetum glaucum (L.) R.Br.) genotypes known to differ in drought adaptation mechanisms: PRLT 2/89-33 (terminal drought-Adapted parent), H 77/833-2 (terminal drought-sensitive parent) and four near-isogenic lines introgressed with a terminal drought tolerance quantitative trait locus (QTL) from PRLT 2/89-33 (ICMR01029, ICMR01031, ICMR02042, and ICMR02044). Plant water use traits at various levels of plant organisation were evaluated in seven experiments in plants exposed either transiently or over the long term to different VPD regimes: biomass components, transpiration (water usage per time unit) and transpiration rate (TR) upon transient VPD increase (gH2Ocm-2h-1)), transpiration efficiency (g dry biomass per kg H2O transpired), leaf expansion rate (cm per thermal time unit) and root anatomy (endodermis dimensions)). High VPD decreased biomass accumulation by reducing tillering, the leaf expansion rate and the duration of leaf expansion; decreased root endodermis cell size; and increased TR and the rate of TR increase upon gradual short-Term VPD increases. Such changes may allow plants to increase their water transport capacity in a high VPD environment and are genotype-specific. Some variation in water use components was associated with terminal drought adaptation QTL. Knowledge of water use traits' plasticity in growth environments that varied in evaporative demand, and on their genetic determinacy, is necessary to develop trait-based breeding approaches to complex constraints.

Salack S.,Cheikh Anta Diop University | Salack S.,Center Detude Regional Pour Lamelioration Of Ladaptation Secheresse | Sultan B.,University of Paris Descartes | Oettli P.,University of Tokyo | And 4 more authors.
Science et Changements Planetaires - Secheresse | Year: 2012

The strong influence of climatic factors on agriculture and food security in sub-Saharan Africa in addition to climate change perspectives have prompted the scientific community to document the impacts of climate in this region. However, if many studies quantifying the impacts of climate rely on downscaling, very few address the uncertainty associated with their use. However, the choice of a particular method and of a particular regional model can strongly influence the final result since crop models are very sensitive to the quality of the input climate forcing. The objective of this study is to address this issue by analysing the dispersion of rainfall provided by eight regional models and how this dispersion spreads in the estimation of millet yields in Senegal. The SARRAH crop model is used to simulate millet yields. The study shows that there is a wide dispersion in the representation of rainfall from one regional model to another (and even sometimes for the same regional model with two sets of parameters) at both the seasonal and intra-seasonal scales. These biases introduce significant errors in estimating the agronomic impacts, which might invalidate conclusions about the impacts of climate change based on the use of a single regional model. The use of a bias correction method is indispensable.

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