Effects of water stress on two genotypes of Durum wheat (Triticum durum Desf.) and Common wheat (Triticum aestivum.L) inoculated with Frankia CCI3 Azospirillum brasilense and Mycorrhiza

Wassila Nadji. This study aims to evaluate the response of common and durum wheat to inoculation by micro-symbionts. Two common and two durum wheat genotypes were inoculated by three inoculums Frankia CCI3 (IF), Azospirillum brasilense (IA) and Mycorrhiza (IM) in presence or in absence of water stress in a greenhouse assai. After the heading stage plants were collected. The parameters of growths and the dry weight of plants and roots were measured as well as SPAD index and nitrogen dosage. The obtained results are significant. They showed that the inoculation with the IM treatment enhanced leaves, ear and roots length. IA treatment has a favorable effect on the nitrogen accumulated in leaves of inoculated plants under control and water stress condition.

Statistical analysis:-The results are statistically interpreted by an analysis of variance (ANOVA) and principal component analysis (PCA) through the XLSTAT software (2014) using XLSTAT 2014 software. The Newman-Keuls test lists the averages with a threshold of 5 % meaning.

Results:-Growth parameters:-
The obtained results show genetic variability among the tested varieties. The variance analysis presented in tables (2,3,4,5) showed a significant genotype, treatment and water regime effect. For leaf, root and ear length, data analysis shows that the higher significant values (p<0.0001) are observed with IM treatment for all wheat varieties (Hidhab, Ain Abid, Boussellem, Waha) compared to controls and the other treatments. In case of stressed plants inoculated with IA, we noted that the growth of the variety Ain Abid (Table 3) is the highest compared to the others.

Root and plant dry weight:-
The effects of water stress on roots and plant dry weight are significant (p<0.0001) tables (2,3,4,5). These two parameters were measured in all wheat varieties. We observed that for root dry weight, the varieties Hidhab, Boussellem, Ain Abid with AI inoculum accumulated more dry matter in their roots, they seem to have the ability to develop a more important root system. While the variety Waha seems less responsive. The results of plant dry weight were significant (p<0.001) for the IA inoculated and unstressed varieties Hidhab and Ain Abid, this treatment induced a higher response compared to controls. On the other hand Boussellem and Waha are distinguished under Mycorrhiza treatment. For inoculated plants under water stress, the greatest value of the root mass was noted in the variety Ain Abid inoculated IF compared with the control stressed, on the other hand the dry weight of plants is the highest recorded in waha inoculated by IA.

Rate of chlorophyll:-
The values of total chlorophyll levels indicate a difference between treatments. The non-stressed inoculated varieties have the highest chlorophyll content values compared to control plants and stressed inoculated plants. The evaluation of the chlorophyll content showed that all varieties respond negatively to water stress. Statistical analyzes tables (2, 3, 4, 5) showed a significant difference (p<0.0001) between the inoculated plants and the controls ones. The highest values were obtained with the IF and IM treatments in Hidhab, Ain Abid and Boussellem, IA treatment in Waha As for the inoculated plants under water stress, the best treatment was IA with all varieties.
Nitrogen assay:-For nitrogen assay analysis of variance (ANOVA) tables (2, 3, 4, 5) shows a significant difference (p <0.0001) between the inoculated and control plants. The best treatment is AI for all varieties As well as under water stress, the highest values are obtained for the IA treatment of four the tested varieties.

Correlation among the studied parameters:-
The correlation analysis of the studied parameters was used to select the most discriminating variable. The ear length has been chosen. The majority of the correlations were highly significant (p <0.0001), however, only values greater than 0.5 will be discussed. It seems that the highest correlation is the one between ear length (cm) with chlorophyll rate (SPAD unit) (r = 0.70***), followed by the correlation between ear length (cm) and leaf length (cm) (r = 0.50***) ( Table 6).

PCA analysis Hidhab:-
The performed analysis is a PCA centered reduced. According to the Kaiser criterion, only two factors were selected (F1 and F2) which represent 71% of the total variance, which is quite good and can be used to identify the main parameters and the discriminating treatment. Thus, it seems that the first factor F1 represents 49% of the variance. It is positively correlated, and rather strongly, with the ear length, chlorophyll rate followed by nitrogen and root length which is less important. Regarding root and plant dry weight we notice that, there is a negative correlation. The axis F2 represents 17% of variance we notice a reverse trend which has a lower inertia than the first, these are the variables: plant and root dry weight (positive correlations), ear length and chlorophyll rate (negative correlations). It is therefore an opposition axis between photosynthesis or growth parameters and dry weight parameters (plant and root).

PCA analysis Waha:-
The two factors (F1 and F2) represent 89.79% of the total variance, which is good to identify key parameters and discriminating treatment. It is noted that the first factor F1 represents 73.46% of the variance; it is positively with nitrogen, plant dry weight, root dry weight and leaf length. Moreover root length, ear length and chlorophyll rate show a negative correlation. The

Discussion:-
This study aims to compare between varieties of durum and common wheat under two water regimes and different treatments of microsymbionts strains. The results have shown that the effects of microbial inoculation on varieties vary according to the inoculants used. Stimulation of leaf length is observed with IM treatment that improves leaf length (+ 60%) compared to controls. Concerning the AI treatment, it improves the water-stressed plants behavior for all varieties. These results on the inoculation of Azospirillum are in agreement with those reported by Ramdani (2002) on durum wheat inoculation (Triticum durum var. Hedba3) by a Azospirillum sp., in the presence or in absence of nitrogen fertilizers, which resulted in a significant increase of leaf length (+ 12%). SH Li (1990) worked on Prunus persica, they said that leaf growth is sensitive to drought since limiting effect of water stress appears early and with intensity. Benmahioul (2009) also confirms our results and said that the reduction of aerial observed growth in seedlings can be explained by increasing levels of some growth regulators, including abcissique acid and cytokinins induced by stress. Furthermore the results for ear length showed that IM inoculation can improve growth in length (+ 67%) compared to controls. These inoculated Furthermore IM treatment allowed an increase in root length (+ 60%) in Hidhab, Ain Abid and Waha. The IA treatment, under water stress, increased root length of all varieties over treatments and controls. Those results are in agreement with Dodd (1994), he reported that the extracellular mycelium Glomus geosporum and G. monosporum may extend a distance of 6 to 9 cm from the root. The effectiveness of mycorrhizal root systems is mainly due to an extension of the absorption surface and soil volume explored through hyphae fungal. Bizet (2014) showed that roots are able to grow in a more or less ground forced through physical support provided by the soil. The efficiency of extracting water from the soil by the roots is one of the adaptation characters that allow the plant to avoid or, more exactly, to delay its tissue dehydration. Moreover, Slama (2005) showed that the increase of absorption may be due to an extension in absorption depth and area, to growth rate and root extension. Simard (2014) noted that a decrease in the resistance to transport water to the roots is lost when there is addition of nutrients to the soil, thus demonstrating an indirect effect of mycorrhiza on plant water balance. This fact lead to this conclusion: in soils low in nutrients, water is better absorbed by the plant, because the fungus allows it to draw a greater amount of minerals (especially phosphorus) thereby generating a good water absorption which became more important as the roots ensure their growth.
In this study, the tested wheat varieties have a considerable fall and highly significant (p<0.0001) in chlorophyll content under water stress. However, with good water supply, results show values with an average order of 38 U.SPAD for all studied varieties. The chlorophyll content decrease in stressed plants is reported by many authors as one of the major cause"s productivity and growth reduction (Guerfel, 2009;Ghobadi, 2011;Wang, 1997).These results confirm the observations of Booba (2009), who mentioned that the lack of water causes a drop in leaves chlorophyll content. The amount of chlorophyll leaves can be influenced by many factors such as leaf age, leafs position, and also by environmental factors such as light, temperature and water availability (Hikosaka et al., 2006).
According Chandrasekhar (2000), the reduction of chlorophyll is mostly due to lower thylacoidal protein content in chloroplasts and a decrease in photosystems in the cell thylacoïdale (Quartacci et al., 1995). According Tambussi  The results for root and plant dry weight showed that the production of dry matter was improved by inoculation. This dry material was used to produce new roots, their proliferation (root volume), their elongation (increase in length) and their maintenance. (El Fakhri et al., 2010). IA treatment allows an increase in dry weight roots (+59%) in Bousellem and waha in comparison with controls and (+ 74%) in Ain Abid. On the other side IM treatment allows an increase in dry weight of the plant (+ 91%) in Boussellenm and Waha. These results were reported by several authors on various culturs such as the work of Pedraza (2010) on strawberry, the roots inoculated by Azospirillum brasilense strains had a high rate of root system infection where a high dry matter production in aerial part and especially root portion. This explains the accumulation of root dry weight in non-stressed inoculated plants and in plants inoculated under water stress. In argan tree (Argania spinosa), Nouaim (1994) observed that mycorrhizal could increase by 3 to 4 times the solids formed, while decreased from 40 to 50% the ratio root part / aerial part and showed the best efficiency of a mycorrhizal root system. The results of this study invalidate those of other authors (Dib (1992); Benlaribi (1990);Al Hakimi (1993), for the durum wheat, showing that the water deficit inhibits further growth of root system as that of above.
The PCA analysis shows that the two varieties of common wheat have behaved in the same way and similar results were observed in both varieties of durum wheat. On one hand the two varieties of wheat showed that increasing nitrogen content results not only in increasing chlorophyll rate chlorophyll but also leaf length, ear and root elongation.
On the other hand the two varieties of durum wheat showed that inoculation by microsymbionts varies considerably between treatments. We noticed that the fixing nitrogen increases chlorophyll levels, also helps leaves, ear and roots elongation, it also makes a significant reserve of dry matter. It is assumed that this result may be representative of the nitrogen fixation process by microorganisms. So we can say that mycorrhizae help the plant to absorb nutrients from the soil such as nitrogen that is absorbed in nitric or ammonium form. Nitrogen is a major constituent of the chlorophyll and proteins. According to Evans and Seeman (1989) between 50 and 80% of the nitrogen of the leaf is allocated to photosynthetic proteins, this complex process of photosynthesis allowed the plant chloroplasts multiplication and its development.

Conclusion:-
Through this study, it appears that the best tested inoculation treatments for durum and common wheat under both water regimes are the mycorrhiza and Azospirillum brasilense (PGPR bacteria).Our tests show that the inoculated varieties are more tolerant to water stress (Boussellem with mycorrhiza and Waha with Azospirillum brasilense). The mycorrhizal fungi are among the most important soil organisms to consider. The mycorrhizae are involved in mineral nutrition, absorption of water and protection against abiotic stresses. Thus mycorrhizae can contribute as an alternative to establish and develop adequate agriculture as the use of chemical fertilizers has reached their limits. Today, agriculture must move towards to more sustainable practices.