الفهرس 
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Abstract
The present investigation was undertaken into two experiments at Experimental Farm, Agronomy Department, Faculty of Agriculture, Assiut University, i.e. experiment I (2017 to 2019) and experiment II (2018 to 2020). The aim of this research it to study the effect of sowing dates and genotypes and their interaction on forage and seed yields production and their components of alfalfa genotypes as well as the stability of the studied genotypes across the sowing dates and years. A set of nine genotypes from Egypt namely, Ismailia-1, Nubaria-1, Ramah-1, Populations from Kharja, El-Dahlia, Farafra, Balady, Aswan and one genotype from U.S.A. (Cuf 101) were sown on the five sowing dates [three at Autumn i.e. October 10th (D1), November 10th (D2), December 10th (D3), and two at springi.e. March 20th (D4), April 20th D5)]. Each experiment included all autumn and spring sowing dates. The split block design with three replications was used in both experiments. Plot size was one meter square. Fifteen cuts were taken from each sowing date. At the time of each cut, the plant height, leaves/stems ratio as well as fresh, dry and protein forage yield were recorded. In addition, the plants were left for flowering and seed production in the second years at first of march for D1 and D4, April for D2 and D5 and May for D3. At seed maturity stage, the number of pods/plant, seed yield/plant and per seed yield/m2, 1000-seed weight. Beside number of inflorescence/plant was recorded.
The results were statistically analyzed and the treatments were compared by L.S.D. test. In addition, to measure the direct and indirect effects of characters influencing each of protein forage yield and seed yield were detected using path-coefficient analysis (Dewey and Lu, 1959). Also, the correlation, stepwise regression and stability analysis were carried out.
A- Forage yield and its components
A.1- Plant height
Sowing dates as well as genotypes had a highly significant effect on plant height in both experiments. The tallest plant height was obtained from the plants sown in 20th April in experiment I. While in the experiment II the tallest plant was obtained from plants sown in 20th March. Moreover, results indicated that Ramah-1 genotype gave the longest plant in both experiments.
A.2- Leaves/stems ratio
Highly significant differences among sowing dates and genotypes were obtained. But, the mean squares for sowing dates x genotypes interaction was insignificant in both experiment.Plant sowing at November 10th and December 10th in experiment I gave the highest mean value of leaves/stems ratio. While, plant sowing at April 20th gave the highest mean value of leaves/ stems ratio in experiment II. El-Dahlia population genotype gave the highest mean value of leaves stems ratio both experiments.
A.3- Total fresh forage yield (kg/m2)
The mean squares of total fresh forage yield showed that sowing dates and genotypes had a highly significant effect in both experiments. But, the mean squares for sowing dates x genotypes interaction wasstatistically insignificant in both experiments. The highest total fresh forage yield was obtained from the plants sown in March 20th in experiment I, while in experiment II the highest total fresh forage yield was obtained from plants sown in October 10th. Ramah-1 genotype produced the highest total fresh forage yield in both experiments.
A.4- Total dry forage yield (kg/m2)
The results showed that each of sowing dates and genotypes produced highly significant differences for total dry forage yield for both experiments. The maximum total dry forage yield was obtained when sowing performed at March 20th and October 10th in experiment I and II, respectively. Ramah-1 genotype gave the highest total dry forage yield in both experiments.
A.5- Total protein forage yield (kg/m2)
The results showed highly significant differences between sowing dates in both experiments. Also, genotypes had significant differences in total protein forage yield in experiment I, but no significant differences recorded among them in experiment II.
The interaction sowing dates x genotypes had no significant differences in total protein forage yield for both experiments. The maximum total protein forage yield was obtained when sowing performed at March 20th and October 10th in experiment I and II, respectively. Ramah-1 genotype produced the highest total protein forage yield over five sowing dates in each experiment.
B- Seed yield and their components
B.1- Number of inflorescence/plant
The results showed highly significant differences among sowing dates and genotypes for number inflorescence/plant in both experiments. Also, sowing dates x genotypes interaction was significant in both experiments. The highest number of inflorescence/plant was obtained from plants sown at April 20th in both experiments. Balady population and Nubaria-1 produced the highest number of inflorescence/plant in experiments I and II, respectively.
B.2- Number of pods/plant
The results showed highly significant differences between sowing dates and genotypes for the number of pods/plant in both experiments. Also, sowing dates x genotypes interaction was significant in both experiments. The highest number of pods/plant were obtained from plants sown at April 20th and October 10th in experiments I and II, respectively. Cuf 101 genotype produced the highest number of pods/plant in both experiment.
B.3- Number of seeds/pod
Sowing dates and genotypes had a highly significant influence on the number of seeds/pod in both experiments. Also, the interaction between sowing dates x genotypes had significant influence on the number of seeds/pod. The highest number of seeds/pod were obtained from plants sown at November 10th in both experiments. Balady population produced the highest number of seeds/pod in both experiments.
B.4- Number of seeds/plant
Sowing dates and genotypes had a highly significant influences on the number of seeds/plant in both experiments. Also, the interaction among sowing dates x genotypes had significant influence on the number of seeds/plant for both experiments. The highest number of seeds/plant were obtained from plants sown at April 20th and November 10th in experiments I and II, respectively. Aswan population produced the highest number of seeds/plant for both experiments
B.5- Seed yield
Highly significantly differences were recorded among sowing dates and genotypes for seed yield/plant and seed yield/m2. Also, significant differences were found for sowing dates x genotypes interaction respect to seed yield/plant and seed yield/m2 in both experiments, except seed yield/m2 in experiment I was insignificant. The highest seed yield/m2 were obtained from plants sown at March 20th in both experiments. Aswan population produced the highest seed yield/plant and seed yield/m2 in both experiments.
B.6- 1000-seed weight
The results revealed significant differences between sowing dates and genotypes for 1000-seed weight in both experiments except between genotypes in experiment I was insignificant. The interaction between sowing dates x genotypes was significant differences in experiment II only. The heaviest 1000-seed weight was obtained from the plants sown at December 10th in both experiments. Aswan population approximately produced the heavier 1000-seed weight in both experiments.
C- Correlation
Total protein forage yield was positively correlated with each of fresh and dry forage yields and protein percentages in both experiments and all five sowing dates and over sowing dates. But, it was negatively correlated with leaves/stems ratio in both experiments and all five sowing dates and over sowing dates.
Seed yield/m2 was positively correlated with each of number of pods/plant, number of seeds/plant and seed yield/plant in both experiments and all five sowing dates and over sowing dates. While, negative correlated was recorded between number of seeds/pod and 1000-seed weight in most of sowing dates.
D- Path-coefficient analysis
D.1- Forage yield and it components
The fresh forage yield had the greatest influence on protein forage yield. However, its indirect effects were negative via mean dry matter percentage or negligible via protein percentage in both experiments and all five sowing dates. Fresh forage yield, dry matter and protein percentages are important traits for selection the high protein forage yield.
D.2- Seed yield and it components
The path-coefficient analysis revealed that the number of pods/plant and number of seeds/pod contributed most direct effect on seed yield/plant for each sowing dates in the two experiments. But, the values were negative or positive and negligible for indirect effect via number of seeds/pod and 1000-seed weight in both experiments for most sowing dates.
E- Stepwise regression analysis
E.1- Stepwise regression for protein yield
It is clear results that the model 2 which included two independent traits i.e. dry forage yield and protein percentage resembled to be the fit model for protein yield in both experiments.
E.2- Stepwise regression for seed yield/plant
It is remarkable result that the model 2 which possessed two independent traits (number of seeds/plant and 1000-seed weight) had strong contributions for seed yield/plantin both experiments.
E.3- Stepwise regression for seed yield/plot
The results revealed that the seed yield/plant, number of inflorescence/plant and number of pods/plant had strong contribution for seed yield/plot.
F- Stability analysis for seed yield
The environments exhibited high contribution to the total sum of squares for seed yield/plant(SYP) and seed yield/m2(SYW) and explained 60.69 and 60.80%, respectively, which accounted ten times of genotypes contribution.
The partition of genotype and genotype x environment interaction through GGE-biplot analysis showed that PC1 and PC2 were significant factors, explaining 40.23 and 21.36% of total sum of squares for seed yield/ plant and 37.04 and 17.83% for seed yield/m2, respectively.
Conclusion
In general, from the obtained results, it could be concluded that:
1. It is recommended to sow alfalfa in autumn (from October to the beginning of December), or in spring (from March to April) to obtain a high forage yield. It depends on the weather conditions, especially temperature, during these months. It is not recommended to sow alfalfa from May until summer months as the high temperature affects the seed germination.
2. To obtain a high seed yield, alfalfa should be kept for flowering during March and April due to the high insect activity during this period.
3. It is recommended to plant genotypes like Rammah-1 and Ismailia-1 to obtain high forage yield. However, to obtain high seed yield it is recommended to plant Aswan population.
4. Forage yield was found to contribute in increasing protein forage yield. In addition, number of pods/plant contributed in increasing seed yield. These traits help alfalfa breeder to improve conduct breeding programs, forage and seed yields.