الفهرس 
ACKNOWLEDGEMENT
Path coefficient analysisOnly 14 pages are availabe for public view
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Abstract
The present investigation was undertaken, at South Valley University Experimental Farm, during 2014/2015 and 2015/2016 seasons, to study the effects of sowing dates and genotypes x environment interaction on forage and seed yield production of alfalfa varieties and their stability. A set of six varieties from Egypt (Aswan, Balady, Dakhla, Ismailia-1, Nitrogen fixed, Siwa and one from U.S.A. (Genan) were sown on the three sowing dates (20th of October, November and December). The randomized complete block design with three replications was used in both seasons. Plot size was one meter square. Three cuts were taken from each sowing date at 80, 125 and 165 days from sowing (80, 45, 40 days intervals). At the time of each cut, the plant height, number of branches/plant, leaves/ stem ratio as well as fresh, dry and protein forage yield were recorded. In addition, after the three cuts for each sowing date, the plants were left for flowering and seed production. At seed maturity stage the number of pods/plant, number of seed/pod, 1000-seed weight, seed yield/plant and seed yield/m2 were recorded.
The results were statistically analyzed and the treatments were compared by R.L.S.D. test. In addition, to measure the direct and indirect effects of characters influencing each of protein forage yield and seed yield path-analysis suggested by Dewey and Lu (1959) was used. Also, the genotypic stability as estimated by Tai (1971) was carried out to propose the stability of these varieties performance.
The aims of these studies were to determine the influence of temperature conditions resulting from different sowing dates on the forage and seed yield production and their components. Also, to study the stability of forage and seed yield and their components of alfalfa varieties tested under different environments (sowing dates x seasons). The results obtained are summarized in the following:
I- Forage yield and its components:
I.1- Plant height:
Sowing dates had a highly significant effect on plant height in both seasons and over the two seasons. The tallest plant height was obtained from the plants sown in 20th December in both seasons. Moreover, varieties showed significant differences in the plant height in both seasons and over the two seasons. The combined data over the two seasons indicated that Ismailia-1 variety in the third date (December 20th) gave the longest plant.
I.2- Number of branches/plant:
The results showed highly significant differences between seasons, and sowing dates for number of branches/plant. Also, significant difference among varieties was obtained. In addition, significant interactions effects were obtained for sowing dates x seasons, varieties x seasons and sowing dates x varieties x seasons. The highest number of branches/ plant of the seven varieties were obtained from plants sown on December 20th in both seasons. Ismailia-1 variety produced the highest number of branches in both seasons.
I.3- Leaves/stem ratio:
Highly significant differences among sowing dates and varieties were obtained. Moreover, the mean squares for sowing dates x seasons, sowing dates x varieties, varieties x seasons and sowing dates x varieties x seasons interactions were significant. Plant sowing at November 20th gave the highest mean value of leaves/stem ratio. American variety ”Genan” produced the highest leaves/stems ratio as compared with the other tested varieties when sowing was performed on November 20th in both seasons. On the other hand, Aswan variety produced the lowest leaves/stem ratio in both seasons.
I.4- Seasonal fresh forage yield (kg/m2):
The mean squares of combined analysis revealed that, seasons sowing dates and varieties had a highly significant effects. Moreover, the mean squares for sowing dates x varieties, sowing dates x seasons, and sowing dates x varieties x seasons interactions were statistically highly significant. Seasonal fresh forage yield was significantly increased as sowing date was delayed. Ismailia-1 variety produced the highest fresh forage yield. In general, all most the studied varieties had the highest seasonal fresh forage yield when they were sown at December 20th in both seasons.
I.5- Seasonal dry forage yield (kg/m2)
The results showed that sowing dates were not significant in seasonal dry forage yield. But the mean square for this trait revealed significant differences among the seven varieties of alfalfa. The maximum seasonal dry forage yields were obtained when sowing was performed at December 20th in both seasons.
I.6- Seasonal protein forage yield:
The results showed highly significant differences between seasons and varieties. Also, varieties x sowing dates interaction was highly significant. But sowing dates had no significant differences in seasonal protein forage yield of the three sowing dates. The maximum seasonal protein forage yields were obtained when sowing was performed at December 20th in both seasons. Aswan variety produced the highest seasonal protein forage yield over three sowing dates in each and over two seasons.
II- Seed yield and its components:
II.1- Number of pods/plant:
The results showed highly significant differences between, seasons, sowing dates and varieties for the number of pods/plant. Also, sowing dates x seasons, sowing dates x varieties, varieties x seasons and sowing dates x varieties x seasons interactions were highly significant. The highest numbers of pods/plant were obtained from plants sown at November 20th in both seasons. Siwa variety produced the highest number of pods/plant in both seasons.
II.2- Number of seeds/pod:
The results showed that seasons, sowing dates and varieties had a highly significant influence on the number of seeds/pod. Also, the interactions sowing dates x seasons, sowing dates x varieties and sowing dates x varieties x seasons had highly significant influence on the number of seeds/pod. The highest numbers of seeds/pod were obtained from plants sown at December 20th in both seasons. Dakhla variety significantly produced the highest number of seeds/pod.
II.3- 1000-seed weight (seed index):
The combined analysis of variance revealed highly significant differences between sowing dates and varieties for 1000-seed weight. Also, sowing dates x seasons, sowing dates x varieties, varieties x seasons and sowing dates x varieties x seasons interactions were highly significant. The heaviest 1000-seed weights were obtained from the plants sown on November 20th in first and over two seasons. Aswan and Balady varieties produced significant heavier seed than the other used varieties over three sowing dates.
II.4- Seed yield:
The combined analysis of variance over the two seasons showed highly significantly differences among seasons, sowing dates and varieties. Also, highly significant differences were found for varieties x seasons, sowing dates x varieties and seasons x varieties x sowing dates interactions, respect to seed yield/plant and seed yield/m2. Seed yield increased when sowing date was performed at October 20th in both seasons. Aswan variety significantly produced the highest seed yield/m2 as compared with the other studied varieties over the two seasons.
III- Correlation:
Protein forage yield was positively correlated with ach of plant height, fresh forage yield, dry matter and protein percentage in each sowing dates. But the plant height was negatively correlated with each of leaves/stem ratio and dry matter percentage in each sowing date. Leaves/stem ratio was negatively correlated with fresh forage yield.
Seed yield per unit area was negatively correlated with each of number of pods/plant and number of seeds/pod. Also, negative correlations were found between 1000 seed weight and each of number of pods/plant and number of seeds/pod. But positive relationships were found between seed yield and 1000-seed weight.
IV- Path-coefficient analysis:
IV.1- Forage yield and its components:
The fresh forage yield had the greatest influence on protein forage yield. However, its indirect effects via mean dry matter percentage were negative and via protein percentage were -0.830, -0.008 and 0.035 for first, second and third sowing dates, respectively.
Fresh forage yield, dry matter percentage and protein percentage are important traits for selection of high protein forage yield.
IV.2- Seed yield and its components:
Direct effects of number of pods/plant on seed yield/plant were 0.511, 0.390 and 0.823 in first, second and third sowing dates, respectively. While, the direct effects of number of seeds/pod on seed yield/plant were 1.186, 0.997 and 0.359, respectively. The direct effects of 1000-seed weight on seed yield/plant were 0.526, 0.359 and 0.141, respectively.
V- Stability analysis:
V.A- Stability analysis for forage yield and its components:
Analysis of variance across varieties and environments (sowing dates x seasons) indicated that the environments, varieties, and varieties x environment were significant for plant height, number of branches/plant and fresh, dry, and protein forage yields, while the leaves/stems ratio was not significant. Varieties of Aswan, Ismailia-1 and Genan had the highest values for plant height, therefore, they were unstable. But the stability area contained Balady, Dakhla, Siwa and Nitrogen fixed varieties for plant height but for number of branches/plant all seven varieties were not significantly different in the amount of deviation from the linear response (). Thereby all varieties were located in the area of average stability region except Dakhla variety which was near from stability region for number of branches/plant.
The average stability area for fresh forage yield contained the varieties of Ismailia-1 and Genan. For dry forage yield, all varieties were located in the area of average stability except Genan variety which was unstable. The Aswan and Dakhla varieties were distributed in the average stability region and showed the highest dry forage yield.
The average stability area for protein forage yield contained all varieties except Aswan and Dakhla varieties. The highest yielding varieties were unstable.
V.B- Stability analysis for seed yield and its components:
The environments, varieties, varieties x environments (GE) interactions were highly significant for all studied traits. For number of pods/plant, all varieties except Ismailia-1 had significant value and were located in the area out of stability region. For number of seeds/pod, the stability area contained three out of seven varieties. The Ismailia-1. Balady and Nitrogen fixed varieties were the most stable ones. For 1000-seed weight, the stability area contained one out of the seven varieties, Ismailia-1 variety was the most stable one, but the other varieties were unstable.
All varieties except Nitrogen fixed and Genan varieties had significant values for seed yield/m2. But for seed yield/plant only Aswan and Dakhla varieties had significant values. The average stability area for seed yield/plant contained five out of the seven varieties. While, the average stability area for seed yield/m2 contained only Nitrogen fixed variety. The highest seed yielding varieties were unstable.