الفهرس 
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Abstract
The main objectives of the present study are to evaluate the performance, heterosis, general and specific combining ability and phenotypic correlation among characters using half diallel analysis including eight R-lines of grain sorghum.
Twenty eight gain sorghum crosses were made among the eight R-lines of grain sorghum, at shandaweel Agricultural Research Station in 2004 season. The 28 sorghum crosses, eight parental lines and one check, i.e. shandweel-2 hybrid, were evaluated at one location, i.e. shandaweel in seasons 2005 and 2006. A randomized Complete Block Design (RCBD) with three replications was used at each season.
Data were recorded on the following traits:
1- Days to 50% flowering 2 - Plant height.
3 - Panicle length 4 - Panicle width
5 - no. of green leaves 6 - 1000-grain weight
7 - grain yield/plant
Analysis of variance was done according to Gomez and Gomez, 1984. Data were analyzed for combining ability according to Griffing’s 1956 model I, method II. Phenotypic correlation was carried out according to Steel and Torrie1980.
Results obtained were summarized as follows:
I- Mean performance of crosses and their parents:
Analysis of variance:
Significant or highly significant difference were obtained among genotypes for all studied traits at the both seasons. Combined analyses of variance over
years for the studied traits showed that the mean squares due to genotypes, parents, crosses and parent vs. crosses were significant or highly significant for all studied traits except the mean squares for parents in number of green leaves trait which was not significant. Variance of interaction between genotypes and years were highly significant for all studied traits. Mean squares due to interaction between crosses x years were highly significant for all studied traits. Also, variances of interaction between parents x years were significant or highly significant for all studied traits.
1-Days to 50% flowering:
Most of the crosses were earlier than its parents reflecting presence the heterosis. Most of the genotypes (crosses and parents) were earlier in season 2006 compared to season 2005. In addition, some genotypes varied in flowering from year to year, reflecting significant of variance interactions between the genotypes × years. Moreover, the earliest crosses in flowering days were crosses (P3xP5), (P1xP4) and (P2xP5) in season 2005. While, the earliest crosses were (P3xP7), (P2xP5) and (P2xP8) in season 2006. In addition, the earliest crosses were (P2xP5) and (P2xP8) in the combined over years. Moreover, the parent MR-812(P2), ZENZEPAR(P3), KYMON(P5), and ICSR93001 (P8) gave the earliest crosses at the combined over years.
2-Plant height cm.
The cross (P1xP6) was significantly taller compared to the check hybrid Sh-2 in both seasons and in the combined over years. Most of the crosses were taller than its parents, reflecting presence of heterosis. Most of the genotypes (crosses and parents) varied in plant height from year to year, reflecting the significant of variance interaction between the genotypes × years. Moreover, the tallest cross was (P1xP6) at the two seasons. Generally 7, 9 and 8 out of 28
crosses were significantly taller compared to the check hybrid Sh-2 in seasons 2005, 2006 and combined over years, respectively. In addition, parents R-273 (P1), MR-812(P2) and ICSR 93001(P8) gave the tallest crosses compared to the other R-lines parents.
3-Panicle length cm.
Most of the crosses had longer panicle length compared to the parents, reflecting presence the heterosis. Most of the genotypes (crosses and parents) varied in panicle length from year to year, reflecting the significant of variance interaction between the genotypes with years. In the combined over two locations, the cross (P2xP5) and (P4xP6) had the longest panicle. In general the parents (P3), (P5) and (P6) gave the best crosses which had higher panicle length compared to the other parents.
4-Panicle width cm.
Most of the crosses had higher panicle width compared to the parents, reflecting presence the heterosis. Some genotypes (crosses and parents) varied in panicle width from year to year, reflecting the significant of variance interaction between the genotypes × years. The crosses (P1xP3), (P2xP5), (P3xP4) and (P4xP6) were the higher panicle width crosses in the combined over years. In general, the parents MR-812 (P2), ZSV-14 (P4) and ICSR-92001 (P6) gave the highest crosses in panicle width compared to the other parents.
5-Number of green leaves
Most of the crosses had high number of green leaves per plant compared to the parents, reflecting the presence of heterosis. Also, some of the genotypes varied in number of green leaves per plant from year to year, reflecting the significant of variance interaction between genotypes × years. In the combined over the two seasons the best crosses were (P4 x P6) and (P6 x P8) which had highest number of green leaves in the combined over years. Generally 11, 8 and
10 out of 28 crosses had significantly higher number of green leaves per plant compared to the check hybrid Sh-2 in season 2005, 2006 and combined over years, respectively. Also, parents ZSV-14 (P4), KYMON (P5) and ICSR 92001 (P6) gave the best crosses compared to the other parents.
6- 1000-grain weight gm.
Some of the crosses had high 1000-grain weight compared to their parents reflecting presence the heterosis. Most of the genotypes (crosses and parents) had higher 1000-grain weight in season 2005 compared to season2006, also, some genotypes (crosses and parents) varied in 1000-grain weight from year to year, reflecting the significant variance interaction between the genotypes × years. In the combined over two years the cross (P2xP4) and (P2xP6), were the heaviest in 1000-grain weight. In general the parents MR-812(P2) and ICSR-92003(P7) gave the best crosses in 1000-grain weight compared to other parents.
7-Grain yield per plant gm.
Most of the crosses had higher grain yield/plant compared to their parents, reflecting presence the heterosis. Generally, the crosses (P1xP3), (P1xP7), (P2xP5), (P3xP4), (P4xP6) and (P6xP8) higher grain yield/plant compared to the check hybrid Sh-2 in the combined over years. These crosses can be evaluated in a large scale and could be considered as promising crosses Also, most of the genotypes (crosses and parents) had high grain yield/plant in season 2005 compared to season 2006 and some genotypes (crosses and parents) varied in grain yield/plant from year to year, reflecting the significant variance interaction between genotypes × years. The parents (P2), (P4), (P5) and (P6) gave the best crosses compared to the other parents.
II - Combining ability:-
The combined analysis of variance over years showed that general (GCA) and specific (SCA) combining ability mean squares were highly significant for all the studied traits. Results indicate the importance of both additive and non-additive gene action in the inheritance of plant height. However, the non-additive gene effects played the major role in the inheritance of earliness, yield and yield components. Mean squares due to SCA were higher in magnitude than those of GCA for all studied traits, except plant height. These results indicated that the non-additive gene effects played an important role in the inheritance of all studied traits, except for plant height.
Mean squares due to the interactions GCA x years and SCA x years were significant or highly significant for all studied traits, except GCA x years for number of green leaves which was insignificant. The magnitude of GCA x years was higher than SCA x years for all studied traits except days to 50% flowering, panicle length and number of green leaves.
Partitioning sum of squares of crosses to their contributions, it could be indicated that both additive and non-additive effects were involved in the inheritance of all the studied traits and the non-additive effects were more important than additive effects for days to 50% flowering, grain yield/plant, panicle length, panicle width and 1000-grain weight. Whereas, the additive effects were more important than non additive effects for plant height.
A-General and specific combining ability effects:-
General combining ability effects play the major role only in the inheritance of plant height. However, SCA effects were predominate in the inheritance of earliness, number of green leaves, panicle length, panicle width, 1000-grain weight and grain yield / plant, and GCA effects of the parents were not effective in predicting the cross performance for these traits. Moreover, most of the early crosses, at Shandaweel had negative significant SCA effects.
Furthermore, most of the early crosses resulted from crossing lines having negative GCA effects. Whereas, the late flowering crosses had positive SCA. On the other side, most of the superior crosses of the studied traits at the two seasons had positive significant SCA effects.
III - Heterosis:-
1-Days to 50% flowering:
Most of the crosses exhibited negative and significant or highly significant heterosis (earliness) in season 2005, Fourteen hybrids recorded significant or highly significant negative heterosis. In addition, approximately 50% from crosses exhibited negative and significant or highly significant heterosis in season 2006 at shandaweel (20 crosses), and nineteen crosses recorded negative significant or highly significant heterosis in the combined over years, indicated that these crosses was earlier than earliest parents.
2-Plant height:
Most of the F1 crosses in season 2005 showed positive heterosis for plant height (22 crosses). In addition, most of the crosses in 2006 season exhibited positive and significant heterosis (18 crosses), and over two years (20 crosses).
3-Panicle length:
Twenty two and twenty one crosses at Shandaweel showed positive and highly significant heterosis in seasons 2005 and 2006, respectively. Moreover, at the combined over years twenty three crosses showed positive and significant or highly significant heterosis values.
4-Panicle width:
Twenty three and twenty one crosses at Shandaweel showed positive and highly significant heterosis in seasons 2005 and 2006, respectively. Moreover, in the combined over years and twenty seven crosses showed positive and significant or highly significant heterosis. Indicated that these crosses were higher than the widths parents of panicle width.
5-Number of green leaves per plant:
Fifteen, fifteen and seventeen crosses at Shandaweel showed positive and significant or highly significant heterosis in season 2005, 2006 and combined over years, respectively. Indicated that these crosses were highest than the higher parents of number of green leaves/plant.
6-1000 grain weight:
Most of the F1 crosses had negative and significant or highly significant heterosis in 2005, 2006 seasons and combined over years, indicating that these crosses had lesser 1000-grain weight than the best parent. In general, 19, 18 and 19 crosses in seasons 2005, 2006 and over years, respectively showed negative and significant or highly significant heterosis.
7-Grain yield per plant:
Most of the F1 crosses showed positive and highly significant heterosis for grain yield/plant in seasons 2005, 2006 and the combined over years, indicated that these crosses had higher grain yield/plant than the best parent.
IV- Phenotypic correlation:
Days to 50% flowering had negative and significant or highly significant correlation with number of green leaves per plant, panicle length, panicle width, and grain yield per plant. The correlation between days to 50% flowering and plant height was negative and insignificant. While, the correlation between days to 50% flowering and 1000-grain weight was positive and significant. Moreover, the correlation between grain yield/plant with each of plant height, number of green leaves, panicle length and panicle width was positive and highly significant, while it was negative and highly significant with days to 50% flowering and 1000- grain weight.