MATERIALS AND METHODS

This investigation was directed in Agronomy Department laboratory of the Faculty of Agriculture Faculty, Mansoura University, Egypt during May 2011. Five alfalfa cultivars were particular i.e., Balady 1, Ismailia 1, Sewa 1, El-Wady El-Gaded 1 and Siriver, to study the encouragement of different physical seed treatments and mechanical seed scarification on seed dormancy breakdown of hard seed above mentioned alfalfa varieties. Alfalfa seeds were gotten from Forage Research Department, Agriculture Research Center, except Siriver variety was obtained from private company which were hand harvested. About 10.000 intact seeds were carefully selected by hand for the study. Seeds were stored at laboratory conditions in cloth bags inside paper bags under laboratory conditions. Germination tests of alfalfa were determined. Nineteen seed treatments for physical dormancy breakdown were applied as following:

Control: Seed was not subjected to any seed treatment, 2-Seed exposed to 5°C for 5 h (Seed exp. to 5°C for 5 h), 3-Seed exposed to 5°C for 5 h plus sandpaper scarification (Seed exp. to 5°C for 5 h+S), 4-Seed exposed to 10°C for 5 h (Seed exp. to 10°C for 5 h), 5-Seed exposed to 10°C for 5 h plus sandpaper scarification (Seed exp. to 10°C for 5 h+S), 6-Seed exposed to 20°C for 5 h (Seed exp. to 20°C for 5 h), 7-Seed exposed to 20°C for 5 h plus sandpaper scarification (Seed exp. to 20°C for 5 h+S), 8-Seed exposed to 40°C for 5 h (Seed exp. to 40°C for 5 h), 9-Seed exposed to 40°C for 5 h plus sandpaper scarification (Seed exp. to 40°C for 5 h+S), 10-Seed exposed to 80°C for 5 h (Seed exp. to 80°C for 5 h), 11-Seed exposed to 80°C for 5 h plus sandpaper scarification (Seed exp. to 80°C for 5 h+S), 12-Pre-cooling at (-5°C) for 5 h (Seed exp. to -5°C for 5 hr), 13-Pre-cooling at (-5°C) for 5 h plus sandpaper scarification (Seed exp. to -5°C for 5 h+S), 14-Pre-cooling at (-10°C) for 5 h (Seed exp. to -10°C for 5 h), 15 Pre-cooling at (-10°C) for 5 h plus sandpaper scarification (Seed exp. to -10°C for 5 h+S), 16-Pre-cooling at (-20°C) for 5 h (Seed exp. to -20°C for 5 h), 17-Pre-cooling at (-20°C) for 5 h plus sandpaper scarification (Seed exp. to -20°C for 5 h+S), 18-Pre-cooling at (-80°C) for 2 h (Seed exp. to -80°C for 2 h), 19-Pre-cooling at (-80°C) for 2 h plus sandpaper scarification (Seed exp. to -80°C for 2 h+S).

After pre-treatments of alfalfa, seed was germinated for 7 days, incubating in a growth chamber adjusted to 20±1°C in dark. For each treatment, 50 seeds were counted at random and placed on a moist germination paper in a Petri dish. There were four replicates at each treatment, dishes were inspected daily and sterilized water was added as required. The number of normal seedlings, abnormal seedlings, dead seeds and hard seed in each replicate were recorded. Every 24 h the number of germinated seeds was counted. Seeds were categorized as germinated (radical 2 mm), hard (no imbibition or swelling) or nonviable (abnormal, dead or infected seeds) as described by ISTA (1993). It could distinguish hard or (dormant) seeds from dead seeds by pushing down on each un-germinated seed with the flat part of a pencil eraser. If the seed does not flatten with gentle pressure, it is considered as hard seed. All seeds which had taken up no water in six days were considered as hard seed. Dead seeds which at the end of test period neither were hard or did not produced any part of a seedling were estimated.

Studied characteristics: Seedlings were evaluated for:

where, (n) is the number of seeds which were germinated on day (d) and (d) is the number of days counted from the beginning of germination.

where, N is the number of seeds germinated on day I and T is the number of days from sowing (Scott et al., 1984). In general, a higher CV value reflects increased germination and shorter germination time.

where, a, b, c..., respectively represent the number of seeds which germinated after 1, 2, 3... days of imbibition, x is the number of seed for day n and S the total number of seeds sown.

Statistical analysis: All data of this study were statistically analyzed according to the technique of variance (ANOVA) for the factorial Randomized Complete Block Design, by using means of "MSTAT-C" computer software package as published by Gomez and Gomez (1984). Least Significant Difference (LSD) method was used to test the differences between treatment means at 5% level of probability as described by Snedecor and Cochran (1980).

RESULTS AND DISCUSSION

Performance of varieties: The five tested varieties of alfalfa significantly varied for averages of hard seed percentage, percentage of abnormal seedlings, percentage of dead seeds, germination percentage free of hard seed, normal germs percentage, energy for germination percentage, coefficient velocity percentage, Mean Germination Time (MGT) by days and value of the vigour percentage as showed in Table 1-3. Balady 1 variety significantly exceeded other studied varieties in percentage of normal germs percentage while; El-Wady El-Gaded 1 variety produced the lowest averages.

Table 1:	Averages percentage of hard seed, abnormal germs and dead seed as affected by alfalfa cultivars and break down dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5%, **: Significant at 1%

Table 2:	Averages of germination percentage free of hard seed, normal germs and energy for germination as affected by alfalfa cultivars and break down dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5%, **: Significant at 1%

However, Siriver, Sewa 1 and Ismailia 1 varieties produced intermediate values of these characters, respectively. Balady 1 and Siriver varieties significantly exceeded other studied cultivars in germination percentage free of hard seed, energy for germination percentage, coefficient velocity percentage and value of the vigour percentage, followed by Sewa 1 and Ismailia 1 varieties in the second and third ranks, respectively, Vice versa, El-Wady El-Gaded 1 variety produced the lowest values of these characters. El-WadyEl-Gaded1 variety had significantly exceeded other studied varieties in hard seed percentage, percentage of abnormal seedlings and Mean Germination Time (MGT) by days. Balady 1 and Siriver varieties did not show significant differences in all characters except normal germs percentage and percentage of abnormal seedlings characters, Balady 1 variety surpassed Sewa 1, Ismailia 1 and El-Wady El-Gaded 1 varieties in germination percentage free of hard seed by 7.684, 10.447, 32.632, respectively, in normal germs percentage by 14.947, 15.158 and 42.974, respectively, in energy for germination percentage by 8.000, 11.815 and 36.631%, respectively, in coefficient velocity percentage by 2.201, 3.606, 8.600%, respectively and in value of the vigour percentage by 5.110, 7.095, 19.704%.

Table 3:	Averages coefficient velocity (C.V%), mean germination time (MGT by days) and values of the vigour as affected by alfalfa cultivars, break down dormancy treatments and their interaction
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5%, **: Significant at 1%

Vice versa, El-Wady El-Gaded 1 variety surpassed Balady 1, Siriver, Sewa 1 and Ismailia 1 varieties in hard seed percentage by 3.00, 3.394, 2.631 and 1.684%, respectively, in abnormal germs percentage by 9.369, 6.487, 0.921 and 4.684%, respectively, in dead seed percentage by 29.698, 29.540, 22.356 and 20.685%, respectively and in mean germination time (by days) by 19.290, 19.097, 14.969 and 12.153%, respectively. Similar conclusions were reported by Acharya et al. (1999), Rutar et al. (2001) and Balouchi and Sanavy (2006).

Break down dormancy treatments effect: The results in Table 1-3 indicated that break down dormancy treatments had significant effects on averages of hard seed percentage, abnormal seedlings, dead seeds, germination, normal germs, energy for germination, coefficient velocity, Mean Germination Time (MGT) by days and value of the vigour in percentage. Exposed alfalfa seed to cold stratification treatment at (-80°C) for 2 h plus sandpaper scarification treatment and exposed alfalfa seed to cold stratification treatment at (-80°C) for 2 h treatment significantly reduced hard seed% by 70.455 and 63.636% compared with control treatment, respectively. Exposure seed to a temperature of cold stratification treatment at (-5°C) for 5 h treatment had significant positive effects that were reflected in the highest value for germination percentage free of hard seed and energy for germination (%) without significant negative effects for other traits when compared to control treatment. While, cold stratification treatment at (-80°C) for 2 h resulted in the lowest value and significantly reduced hard seed (%) with significantly increase of germination (%) free of hard seed and energy for germination (%) but with significant negative effects for dead seed (%) and coefficient velocity (%) when compared to control treatment, Vice versa, exposed seed to a temperature of (80°C) for 5 h plus sandpaper scarification and exposed seed to a temperature of (80°C) for 5 h treatments had a negative effects for all traits. Similar finding were recorded by Egley (1989), Rutar et al. (2001), Uzun and Aydin (2004) and Narem and Xu (2009).

Interactions effect: The results in Table 4 to 11 indicate percentage of abnormal seedlings, of dead seeds, germination free of hard seed, normal germs, energy for germination, coefficient velocity, Mean Germination Time (MGT) by days and vigour which were significantly affected by the interaction between varieties and break down dormancy treatments.

Table 4:	Abnormal germs percentage as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5%, **: Significant at 1%

Table 5:	Percentages of dead seed as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: significant at 5% **: Significant at 1%

Vice versa, hard seed% were not affected by the interaction. Exposed Balady cultivar seed to a temperature of 10°C for 5 h surpassed other treatments which recorded the highest averages of normal germs and energy for germination percentage, while the lowest %averages were of abnormal seedlings and of dead seeds. In addition, exposed Balady 1 cultivar seed to cold stratification at -10°C for 5 h plus scarification treatment surpassed other treatments which recorded the highest averages of germination percentage free of hard seeds and energy for germination percentage, Exposed Balady 1 cultivar seed to cold stratification at -20°C for 5 h had the lowest averages of abnormal seedlings%. Exposed Balady 1 cultivar to control treatment had the lowest averages of dead seeds%. Balady 1 cultivar exposed seed to cold stratification at (-20°C) for 5 h plus scarification treatment surpassed other treatments which documented the lowest %averages of abnormal seedlings. The highest averages of coefficient velocity% were obtained with exposed Balady 1 cultivar seed to cold stratification at (-5°C) for 5 h treatment or exposed seed to a temperature of (10°C) for 5 plus scarification treatment. Exposed Siriver cultivar seeds to cold stratification at -5°C for 5 treatment recorded the highest %averages of energy for germination, value of the vigour and the lowest %averages of Mean Germination Time (MGT) by days. In addition, exposed Siriver cultivar seed to cold stratification at -80°C for 2 treatment surpassed other treatments where recorded the highest %averages of energy for germination.

Table 6:	Percentages of germination free of hard seed as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant *: Significant at 5% **: Significant at 1%

Table 7:	Percentages of normal germs as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant *: Significant at 5% **: Significant at 1%

Table 8:	Percentages of energy for germination as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5% **: Significant at 1%

Table 9:	Percentages of coefficient of velocity as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: scarification, NS: Not significant, *: Significant at 5%, **: Significant at 1%

Table 10:	Mean germination time by days as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5%, **: Significant at 1%

Table 11:	Value of the vigour as affected by the interaction between cultivars and break gown dormancy treatments
h: Hours, S: Scarification, NS: Not significant, *: Significant at 5% **: Significant at 1%

It could be noticed that exposed Siriver cultivar seed to a temperature of (10°C) for 5 treatment surpassed other treatments where recorded the lowest %averages of dead seed, exposed El-Wady El-Gaded 1 cultivar seed to a temperature of (80°C) for 5 plus sandpaper scarification treatment recorded the lowest percentage (%) value of germination of free of hard seed, normal germs, energy for germination, coefficient velocity and value of the vigour and the highest percentage (%) value of were dead seed and Mean Germination Time (MGT) by days. In addition, exposed Ismailia 1 variety seed to a temperature of (80°C) for 5 treatment had the highest value percentage of abnormal seedlings.

CONCLUSIONS

For maximizing breakdown dormancy of hard seed and improving germination characters by cultivation of Balady 1 and Siriver varieties which surpassed other studied varieties under laboratory testing conditions, El-Wady El-Gaded 1 variety was more affected by break down dormancy treatments when compared to other studied cultivars.

Exposing seed to a temperature of cold stratification treatment at (-80°C) for 2 plus sandpaper scarification. It had the lowest value and significantly reduced hard seed percentage and significantly increase %germination of free of hard seed and %energy for germination. Exposing seed to a temperature of cold stratification treatment at -5°C for 5 treatment resulted in significant positive effects that were reflected highest %germination of free of hard seed and energy for %germination.