Physiological, Biochemical, and Genetic Basis of Heterosis

Five Egyptian parental genotypes of Faba bean were used for carrying out half diallel design to study heterosis and nature of gene action for earliness, vegetative, yield and yield components traits. Mean squares of genotypes were found to be highly significant for all studied traits. The results showed that the majority of crosses exhibited significant heterosis estimates for better parent for all studied traits. General combining ability (GCA) and specific combining ability (SCA) mean squares were highly significant for all studied traits. The results indicated that the magnitude of additive genetic variance (σ 2 A) were positive and lower than those of non additive (σ 2 D) one for all the studied traits, indicating that non additive gene action played a major role in the inheritance of different traits under study. The broad sense heritability estimates (H 2 b %) were more than their corresponding narrow sense heritability (H 2 n %) for all studied traits. However, estimates of narrow sense heritability were 34.2 and 14.8% for earliness traits and ranged from 15.2 to 29.8% for number of branches per plant and plant height, respectively. Respecting to yield components, the estimates of narrow sense heritability ranged from 8.8 to 70.9% for number of pod per plant and weight of 100 seed (g), respectively. The results showed that the two cultivar, Giza 843 (P 4 ) and Misr 2 (P1) was good general combiner for earliness, yield and yield components, respectively. The cross (P 1 xP 5 ) showed desirable SCA effects and significant heterosis values for earliness, and yield components. While, the two crosses, (P 1 xP 3 ) and (P 3 xP 4 ) exhibited desirable SCA effects for vegetative traits. These promising crosses could be used for breeding programs to produce pure lines.Key words: Faba bean, general combining ability (GCA), specific combining ability (SCA), heterosis, gene action. INRODUCTIONFaba bean (Vicia faba L.) is one of the most important pulse crops in Egypt; it is plays an important role in world agriculture due to the high protein content, its ability to fix atmospheric nitrogen and its capacity to grow and yield well on marginal lands (Alghamdi, 2007; Farag and Afia, 2012). Great efforts have been directed to improve yield level and quality properties in faba bean. In this trend, heterosis and combining ability provide important *Corresponding author. E-mail: naheif@yahoo.com. information for improving seed yield and other economic traits in faba bean. Superiority of hybrids over the better parent for seed yield and its attributes are associated with the magnitude of heterotic effects in important yield attributes, that is, number of branches per plant, pod setting percentage, number of pods per plant, 100-seed weight, shellout percentage and pod filling percentage. These heterotic effects may range from significantly positive to significantly negative for various traits according to genetic makeup of the parents Darwish et al., 2005;El-Hady et al., 2006; Farag and Afia, 2012).

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“…The heterotic effects of F1 crosses were estimated (as better parent) according to Singh and Khanna (1975).…”

Section: Discussionmentioning

confidence: 99%

Heterosis and nature of gene action for yield and its components in faba bean (Vicia faba L.)

Obiadalla-Ali¹,

Mohamed²,

Glala³

et al. 2013

J. Plant Breed. Crop Sci.

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“…Hybrid vigor is repeatedly observed for growth, yield, and even certain developmental characters of maize (19,20,23). Indeed, the impressive increases in yield of maize during the 20th century have largely resulted from the increased use of hybrid seed (6, 7).…”

Section: Introductionmentioning

confidence: 99%

Gibberellins and Heterosis in Maize

Rood

Pharis²,

Koshioka³

et al. 1983

Plant Physiol.

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Under controlled environment and/or fIed conditios, vegetative growth (height, internode length, leaf area, shoot dry weight, grain yield) was greater in an F1 maize hybrid than in either parental Inbred. Endogenous gibberelin (GA)-llke substances in apical meristem cylinders were also higher in the hybrid than in either Inbred, both on a per plnt and per gram dry weight basis. There were no apparent qualitative differences in GAUlke substances, however. Levels of GA-Rke substances in all genotypes were highest prior to tassel initiation. Chromatographic comparisons of the GA-Se substances and authentic standards of GA native to maize on gradient-eluted SK0 partiton and reverse-phase C1i high-pressure liquid chromatography columns are described. No consistent differences in abscisic acid levels of the three genotypes were observed. This correlation of heterosis for endogenous GA-lie substances with heterosis for growth suggests that amounts of endogenous GA may be related to hybrid vigor in maize.Hybrid vigor, the phenotype of heterosis, exists when hybrid performance exceeds that of the parental genotypes. Hybrid vigor is repeatedly observed for growth, yield, and even certain developmental characters of maize (19,20,23). Indeed, the impressive increases in yield of maize during the 20th century have largely resulted from the increased use of hybrid seed (6, 7). However, while plant breeders and agronomists have been utilizing heterosis as a means of improving crop productivity, the physiological basis of heterosis is not presently understood (23).The involvement of plant hormones in heterosis is both an attractive and logical possibility. Changes in endogenous hormone balance could amplify genotypic differences, thus leading to major phenotypic effects. Although the possibility of hormonal involvement in heterosis has been suggested previously (14), Sinha and Khanna (23) note that no correlative relationships between endogenous hormone levels and hybrid vigor had been described prior to 1975. We are unaware of any subsequent reports of such correlative relationships.In a previous study (17), it was observed that growth rate and content of endogenous two maize inbreds and their F1 hybrid grown under two lowtemperature regimes with dominance for increased growth rate being observed in the hybrid grown under the low-temperature conditions (17). Apparent 'overdominance' (inasmuch as it is difficult to separate overdominance per se from complementation, overdominance will be used in this paper) had been repeatedly observed when the same maize genotypes were grown under warmer growth cabinet or field conditions (20). Thus, the next logical question to be addressed was: under favorable temperature conditions are growth rates and levels of endogenous GA-like substances still correlated; does heterosis for increased levels of GA-like substances accompany heterosis for growth rate? The present study was initiated to investigate this question. Additionally, because ABA is sometimes assigned an inhibitory role i...

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“…Some reports have ascribed this phenomenon to a larger embryo weight (SINHA and KHANNA 1975;YAMADA et al 1985). AKITA et al (1986) compared the embryo size and dry weight of 15 F~ hybrids and their parents, and reported that the higher initial growth of the F1 hybrids was caused by the larger embryo size but not by a higher relative growth rate.…”

Section: Discussionmentioning

confidence: 99%