Leaf Senescence in Wheat: A Drought Tolerance Measure

*Hafsi Miloud and Guendouz Ali*

### **Abstract**

The present study was conducted on the experimental site of INRAA, unit research of Setif. A set of 10 genotypes of durum wheat (*Triticum durum* Desf.) planted during four cropping seasons (2009–2013). The objectives of this study are to evaluate the performance of some durum wheat genotypes and tested the efficiency of using senescence parameters in screening under semi-arid conditions. The analysis of variance demonstrates significant effects of genotypes and years on the grain yield and senescence parameters. Based on the means comparison, the values of total mean grain yield (2009–2013) varied from 37.84 q/ha for Oued Zenati to 44.7 q/ha for Altar84 with general mean of 42.71 q/ha. The mean rankings based on the mean grain yield demonstrate that the genotypes Mexicali75, Hoggar, and Sooty have the best ranking with highest grain yield. The mean values over years of Sa% varied between 47.91% for the genotype Oued Zenati and 59.45% for Waha. The genotypes with highest values for the parameter mid-senescence (Σ50s) are the most tolerant and adapted genotypes.

**Keywords:** durum wheat, senescence, screening, semi-arid

#### **1. Introduction**

Durum wheat is one of the most cultivated cereals in the world; it is growing under the Mediterranean regions [1]. Water stress is the abiotic stresses limiting wheat distribution and productivity [2]. Water stress adaptation is considered as the major aim for breeding target in the stabilization of crop performance, by breeders and molecular biologists; at the moment, there is a lack of information to be able to measure with precision the plant resistance under drought stress conditions [3]. Photosynthesis is the primary source of dry biomass production and grain yield in plants. The improvements of leaf photosynthesis have occurred with the advance of breeding high-yielding cultivars. During the period of wheat spike growth, the important moment of assimilation that supplies carbon for the grain depends on the amount and quality of light on the surface of the green area after anthesis. This assimilation area normally decreases due to natural senescence and various stresses. Senescence is considered the final stage in leaf development; senescence in plants is defined as the age-dependent programmed degradation and degeneration process of cells, organs, or the entire organism, leading to death [4]. The most remarkable events in leaf senescence are the loss of chlorophyll and the disassembly of the photosynthetic apparatus, which result in decreases in the photosynthetic energy conversion capacity and efficiency. In addition, chloroplasts of senescing leaves show reduced volume, their shape is spherical, and the thylakoid

system is reduced. In cereals, the processes involved in senescence are important because they occur during grain filling, and evidence suggests that early senescence may be yield-limiting [5]. Wheat genotypes vary in the timing of senescence initiation and also in the subsequent rate of leaf senescence. In wheat, the senescence rate was also found to be related to the yield under drought conditions [6, 7]. The quest of the causes of differences in leaf photosynthetic rate among interspecies and/or intraspecies of crops may be one of the important strategies of crop engineering [8]. In all these studies, leaf senescence was evaluated visually. Since senescence corresponds to yellowing due to chlorophyll loss [5], the identification of senescent parts of the leaf is quite easy. In this work, we used an alternative method for the evaluation of the leaf senescence based on numerical analysis of image. In addition, we study the efficiency of using the flag leaf senescence as tools for select adapted durum wheat genotypes under semi-arid conditions.

**3. Results and discussion**

*Leaf Senescence in Wheat: A Drought Tolerance Measure*

*DOI: http://dx.doi.org/10.5772/intechopen.89500*

Year effect \*\*\* LSD 5% 4.37

**Table 2.**

**Table 3.**

**83**

*Ranking of tested genotypes based on the grain yield.*

*N.B: Means followed by the same letter are not significantly different (P* ≤ *0.05).*

*ANOVA analysis and means comparison of grain yield over four cropping seasons.*

**2009/2010 2010/2011 2011/2012 2012/2013**

**Genotype Ranking based on GY Mean ranking SD of ranking**

Oued Zenati 8 10 9 6 8 1.48 Altar84 4 7 8 1 4 2.74 Sooty 6 3 7 3 3 1.79 Polonicum 9 6 4 2 5 2.59 Waha 5 1 2 9 2 3.11 Dukem 10 2 6 8 7 2.96 Mexicali 75 1 5 3 4 1 1.48 Kucuk 7 9 1 5 6 2.96 Hoggar 3 4 5 7 3 1.48 Bousselem 2 8 1 10 5 3.83

The ANOVA analysis demonstrates significant effect of genotypes and years on senescence parameters and GY. Based on the means comparison, the values of mean grain yield (2009–2013) varied from 37.84 q/ha for Oued Zenati to 44.7 q/ha for

**Genotype Grain yield (q/ha) Mean over**

Oued Zenati 25.50(ab) 52.20(d) 21.45 (b) 47.11(ab) 37.84(b) Altar84 29.31(a) 55.94(bcd) 24.86 (ab) 64.97(a) 44.79(a) Sooty 26.56(ab) 63.14(abc) 27.33 (ab) 52.92(ab) 44.29(ab) Polonicum 24.68(ab) 56.47(abcd) 32.68 (ab) 55(ab) 43.30(ab) Waha 26.93(ab) 64.63(a) 35.24 (a) 37.31(b) 43.18(ab) Dukem 22.00(b) 63.94(ab) 29.75 (ab) 44.44(ab) 41.87(ab) Mexicali 75 31.93(a) 59.64(abcd) 32.90 (ab) 49.34(ab) 44.69(a) Kucuk 26.50(ab) 53.96(d) 36.87 (a) 47.87(ab) 42.54(ab) Hoggar 29.68(a) 60.05(abcd) 30.23 (ab) 47.03(ab) 43.42(ab) Bousselem 29.81(a) 55.01(cd) 36.87 (a) 37(b) 41.26(ab) Mean 28.00(c) 59.04(a) 30.81(c) 48.3(b) 42.72 Min 22.00 52.2 21.45 37.00 37.84 Max 31.93 64.63 36.87 64.97 44.79 Genotype effect \*\*\* \*\*\* \*\*\* \*\*\* \*\*\* LSD 5% 6.45 8.15 13.60 22.26 6.45

**2009/2010 2010/2011 2011/2012 2012/2013 all seasons**
