Rajae Kallida

Assessment of summer drought tolerance variability in Mediterranean alfalfa (Medicago sativa L.) cultivars under Moroccan fields conditions

This study was undertaken to assess levels of tolerance to summer drought in Medicago sativa genotypes and to comment on their abilities to adapt to Moroccan conditions. Sixteen alfalfa cultivars originating from the Mediterranean basin were tested at an experimental station in Morocco, located in the semi-arid bioclimatic area. Trials were conducted over three years and consisted of one continuously irrigated treatment and another irrigated treatment in which summer watering was withheld for 9 weeks. Results showed that summer water stress significantly reduced aboveground biomass in all of the cultivars tested. This reduction ranged between 23.9 and 42.6% compared with fully irrigated treatment. At the end of stress period, mean summer leaf senescence rate was 83.3%, with a significant difference between cultivars. Ground cover, estimated at the end of summer in the third year, decreased dramatically and ranged between 12 and 30.7%, depending on the cultivar. High intrinsic water-use efficiency was associated with a decrease in stomatal conductance rather than an increase in photosynthesis.

Evaluation of Drought Tolerance Variability in Mediterranean Alfalfa Cultivars in the Field Under Moroccan Conditions

Sixteen alfalfa cultivars originating from the Mediterranean basin were tested in an experimental station in Morocco, located in the semi arid bioclimatic area. This research was conducted in PERMED project during 2006–2008 and aimed to evaluate the adaptation of cultivars to drought stress. The trial was conducted under two irrigation treatments. The first treatment was normally irrigated by providing an amount of water corresponding to the potential evapotranspiration of the crop and in the second treatment with water deficit which was applied by stopping the irrigation during 9 weeks in summer. Results showed that water stress during summer significantly reduced aerial biomass of all cultivars. This reduction varied between 25 and 41% according to cultivars in comparison with a normal irrigated treatment. The difference between cultivars for biomass production was significant only in stress treatment (P< 0.001 with 15 df). Some cultivars showed high forage yield potential, mainly Ameristand, ABT 805, Sardi10, Siriver, Gabes-2355, Rich2, and Erfoud1 even in presence of stress. In the end of August (before restart of irrigation for treatment with suspended summer irrigation), the mean rate of leaf senescence of cultivars was 84% with no significant difference between cultivars. The row cover estimated in the end of summer of the third year varied between 12 and 40% according to the cultivars. Cultivars Gabes-2355, Ameristand and ABT805 showed a smaller number of dead plants under water stress. Therefore, those cultivars could be used by local farmers in this region.

Combining Drought Survival via Summer Dormancy and Annual Biomass Productivity in Dactylis glomerata L.

Under Mediterranean climates, the best strategy to produce rain-fed fodder crops is to develop perennial drought resistant varieties. Summer dormancy present in native germplasm has been shown to confer a high level of survival under severe drought. Nevertheless it has also been shown to be negatively correlated with annual biomass productivity. The aim of this study was to analyze the correlations between summer dormancy and annual biomass productivity related traits and to identify quantitative trait loci (QTL) for these traits in a progeny of a summer dormant cocksfoot parent (Kasbah) and a summer active parent (Medly). A total of 283 offspring and the parents were phenotyped for summer dormancy, plant growth rate (PGR) and heading date in Morocco and for maximum leaf elongation rate (LERm) in France. The individuals were genotyped with a total of 325 markers including 59 AFLP, 64 SSR, and 202 DArT markers. The offspring exhibited a large quantitative variation for all measured traits. Summer dormancy showed a negative correlation with both PGR (-0.34 p < 0.005) and LERm (-0.27 p < 0.005). However, genotypes with both a high level of summer dormancy and a high level of PGR were detected in the progeny. One genetic map per parent was built with a total length of 377 and 423 cM for Kasbah and Medly, respectively. Both different and co-localized QTL for summer dormancy and PGR were identified. These results demonstrate that it should be possible to create summer dormant cocksfoot varieties with a high annual biomass productivity.

Drought Survival of Some Perennial Grasses in Moroccan Rainfed Conditions: Agronomic Traits

A 4 year experiment was carried out to evaluate perenniality and some adaptive responses to drought of Dactylis glomerata, Festuca arundinacea and Phalaris aquatica, within the multi-site activity of the EU-PERMED project. The trial held in Merchouch experimental INRA station at 68 km west of Rabat/Morocco, in a vertic deep silty clay soil (> 1 m 80 deep) was sown on 20 October 2005 to compare 16 grass accessions. Measurements included: sward establishment, dry matter production, average row cover, sward senescence and phenology. Plant emergence and establishment were good and regular for almost all cultivars. In all seasons, fescue yielded significantly more than cocksfoot. The harsh conditions and summer droughts have affected significantly production and persistence of grasses, mostly cocksfoot cultivars which disappeared completely at the end of the third year except the summer dormant cultivar Kasbah. Four groups of grass cultivars have been distinguished according to their persistence under extreme drought conditions.

Evaluation of cocksfoot (Dactylis glomerata L.) population for drought survival and behavior

Climate change models predict frequent and intense droughts in the world. Development of drought-tolerant species and cultivars is necessary to cope with such changes. Forage grass species are affected, especially in the Mediterranean region. The aim of the present study was to investigate the diversity for drought survival, summer dormancy, and productivity within a cocksfoot population. The study was conducted in Morocco, under field conditions from 2011 to 2013. 283 genotypes of cocksfoot and parents were tested, characterized for dry matter yield, heading date, plant height, senescence, summer dormancy, and drought survival. Results exhibited a large variability between traits. 79% of the population had survived after severe drought summer while 57% yielded more than both parents. Also, 63% of the progeny had an intermediate score of summer dormancy estimated by senescence score. Large variability was also noticed for heading date and plant height. Several accessions combined a high yield and persistence under severe summer drought. Which explain the significant correlation (r = 0.18, P < 0.005) founded between total dry matter accumulated in 2013 and plant survival. Accordingly, our results showed that we can rise persistent and resilient genotypes among population with a good level of biomass.

Towards Productive Summer Dormant Cocksfoot for Mediterranean Climates

There are different strategies for producing fodder crops without irrigation under Mediterranean climate conditions. One strategy is to avoid the drought period by using annual plants such as cereals or Italian ryegrass. Another strategy is to use perennial forage species highly resistance to drought such as Dactylis glomerata or Festuca arundinaceae. The advantage of the second strategy is a rapid growth when favourable conditions come back after summer and good ground cover, which limits erosion. Summer dormancy, defined as an absence of growth in summer despite irrigation, is a very effective adaptation to drought which has been observed in cocksfoot. Nevertheless, summer dormancy in cocksfoot is associated with low vegetative productivity. The objective of this study is to analyse the genetic and eco-physiological determinisms of summer dormancy and vegetative growth in cocksfoot. For this purpose, the progeny between a summer dormant genotype from the variety Kasbah and a summer active genotype from the variety Medly is studied. The first results show that despite an expected negative correlation (r = −0.40) between summer dormancy and vegetative plant growth, genotypes exist with the same summer dormancy level as the genotype of Kasbah and a higher vegetative productivity than the genotype of Medly. These results are promising for the development of new cocksfoot varieties combining both summer dormancy and high vegetative productivity. The genomic regions implied in the variation of these traits are under study and should be useful for breeding.

Agronomic Evaluation of Moroccan Ecotypes of Tall Fescue

Drought or reduced water availability is the main factor limiting crop production in Mediterranean area. The aim of this study was to select ecotypes of Festuca arundinacea Schreb. adapted to the Moroccan environment. During 3 years, eleven ecotypes of tall fescue, collected from different regions of Morocco, and eight commercial cultivars were evaluated for the following agronomical traits: dry matter yield, summer growth, heading date, survival rate, leaf area index (LAI) and plant height.