Volume 7 Number 1 2013

CONTENTS AND ABSTRACTS

David R. Liberatti, Gustavo R. Rodriguez, Roxana Zorzoli, Guillermo R. Pratta (Argentina) Tomato Second Cycle Hybrids Differ from Parents at Three Levels of Genetic Variation (pp 1-6)

Full Text [PDF]

ABSTRACT

Original Research Paper: Second Cycle Hybrids (SCHs) are produced by intercrossing Recombinant Inbred Lines (RILs) derived from the F₂ generation of two homozygous parents. Three tomato (Solanum lycopersicum) SCHs were obtained by crossing six RILs derived from an interspecific cross S. lycopersicum x S. pimpinellifolium. The objective was to characterize these SCHs and their parental RILs at different levels of genetic variation to understand the genetic causes underlying outperforming of these new genetic combinations. Fruit quality traits, pericarp polypeptide profiles at four ripening stages and AFLP were assessed. The degree of genetic determination and the degree of dominance were calculated for phenotypic traits, and the molecular polymorphism was evaluated for polypeptide and AFLP profiles. SCHs contributed with extreme values for some fruit quality traits, for which non additive gene actions were prevalent. Molecular differences were higher for polypeptide than for AFLP profiles, de novo bands being relevant to explain the increase in SCHs polymorphism. Cluster analysis showed different association among SCHs and RILs according to the level of genetic variation under study, providing a first advance for understanding the biological basis underlying the SCHs outperforming.

Adefris Teklewold (Ethiopia), Leonardo Velasco (Spain), Heiko C. Becker (Germany) Estimation of Outcrossing Rate in Ethiopian Mustard (Brassica carinata) using RAPD Markers (pp 7-11)

Full Text [PDF]

ABSTRACT

Original Research Paper: Breeders regard Ethiopian mustard (Brassica carinata) as a predominantly self-pollinated crop and employ breeding methods for self-pollinated crops. However, the proportion between self- and cross-pollination is not experimentally quantified. The aim of this study was to estimate the outcrossing rate of B. carinata and its variation across environments. Outcrossing rate was estimated by analysing the banding pattern of random amplified polymorphic DNA (RAPD) markers of offspring of two parental lines grown in open-pollinated isolation plots at Holetta (normal and delayed planting condition), Kulumsa and Debrezeit Research Centers in Ethiopia and Cordoba, in Spain. The analysis of polymorphic banding pattern based on visual inspection of gels yielded three variable loci in the parents that helped to distinguish progenies obtained from self-pollination and outcrossing. Outcrossing rate in B. carinata was on average 29.6% and varied between environments from 21.8 to 39.2%. Factors such as the abundance of pollinating agents seem to affect the rate of outcrossing more than variation in geographic location, as the lowest and highest outcrossing rates were recorded in the same location, Holetta, from normal and one month delayed planting date, respectively. This study demonstrates that B. carinata possesses a substantial amount of outcrossing. The outcrossing rate observed could be an opportunity for breeders to exploit heterosis through synthetic and/or hybrid cultivar breeding.

Vallence Nsabiyera, Mildred Ochwo-Ssemakula (Uganda), Peter Sseruwagi (Uganda/Tanzania), Chris Ojiewo (Tanzania/Malawi), Paul Gibson (Uganda/USA) Combining Ability for Field Resistance to Disease, Fruit Yield and Yield Factors among Hot Pepper (Capsicum annuum L.) Genotypes in Uganda (pp 12-21)

Full Text [PDF]

ABSTRACT

Original Research Paper: Productivity and quality of hot pepper in Uganda are low, mainly due to lack of superior cultivars. As a step towards cultivar improvement three exotic and three local hot pepper genotypes with varying genetic backgrounds were crossed in a half diallel to determine the combining ability of parents and crosses, and the gene effects of important disease, yield and related traits. The general (GCA) and specific (SCA) combining abilities were significant for most traits indicating the role of both additive and non-additive gene effects in the expression of most traits. Days to 50% flowering and fruit maturity, number of fruit per plant, number of seeds per fruit, primary branch numbers, plant width and height were predominantly controlled by non-additive gene action while fruit length, fruit width, secondary branch numbers, stem diameter, stem height were predominantly controlled by additive gene effects. Pedicel length seemed to be controlled by both additive and non-additive gene actions in equal proportions. Narrow sense heritability was low to moderate for most agro-morphological traits and for all disease incidences (16.1-46.1) and was moderate to high (43.4-98.5) for all agro-morphological traits and disease incidences. The exotic genotype PP9852-115, local genotypes CA-UGKI 09-4, CA-UGKI 09-6 and CA-UGCE 09-3 were good combiners for most traits. The Exotic genotype PP0537-7504 was a significant general combiner for reducing wilt disease incidence. Hybrids CA-UGCE 09-3xCA-UGKI 09-6, CA-UGKI 09-6xPP9852-115 and CA-UGCE 09-3xPP0337-7562 had the best SCA effects among all crosses for measured traits. For disease traits, hybrids CA-UGCE 09-3xPP9852-115 and CA-UGKI 09-6xPP9852-115 were the best for Cercospora leaf spot resistance while hybrid PP9852-115xPP0537-7504 was the best for virus resistance. The outstanding hybrids for various traits could be used to derive superior recombinant inbred lines for respective traits through transgressive segregation.

Gemechu Keneni, Endashaw Bekele, Fassil Assefa (Ethiopia), Muhammad Imtiaz (Syria), Tolessa Debele, Kifle Dagne, Emana Getu (Ethiopia) Genetic Variation and Gains from Selection for Symbio-Agronomic Performance in Ethiopian Chickpea (Cicer arietinum L.) Germplasm Accessions (pp 22-35)

Full Text [PDF]

ABSTRACT

Original Research Paper: Information on traits relationship, genetic variation and gains from selection for symbiotic and agronomic characters in chickpea (Cicer arietinum L.) are limited. An experiment was undertaken at two locations (Ginchi and Ambo) in Ethiopia in 2009/2010 to assess the relationship, genetic variation and genetic gain from selection for attributes of symbiotic and agronomic significance. The difference technique with genetically non-nodulating chickpea reference was employed to estimate the amount of symbiotic nitrogen fixation. Significant positive correlations were found between a number of symbiotic and agronomic traits. Grain yield was positively associated with fixed nitrogen assimilation efficiency (r = 0.39), shoot (r = 0.31), grain (r = 0.93), and above ground biomass nitrogen yields (r = 0.77) and NHI (r = 0.52). Grain yield was also positively influenced by agronomic characters including grain filling period (r = 0.38), pod (r = 0.57) and seed numbers (r = 0.59), shoot (r = 0.67), and total above ground biomass (r = 0.79) accumulations, HI (r = 0.53), grain production efficiency (r = 0.92) and biomass production (r = 0.81) and economic growth (r = 0.93) rates. Characters like shoot, grain and total biomass nitrogen contents and fixation, fixed nitrogen assimilation efficiency, seed size, grain filling period showed higher genetic variation, broad-sense heritability and expected genetic gains from selection. The Z-test revealed effective selection at phenotypic level for all traits. Further implications of the study in terms of selection strategy have also been discussed.

Million Fikreselassie, Nigussie Alemayehu, Habtamu Zeleke (Ethiopia) Variability in Morpho-Physiological and Nitrogen-Fixing Traits of Ethiopian Fenugreek (Trigonella foenum-graecum L.) Landraces (pp 36-41)

Full Text [PDF]

ABSTRACT

Original Research Paper: The extent and pattern of genetic variability present in a population of fenugreek a given crop is indisputably essential for further improvement. A field experiment was conducted at Ambo and Adadi during the main cropping season to assess the extent and pattern of genetic diversity of morpho-physiological and nitrogen fixation traits in which 143 random samples of fenugreek accessions along with a commercial variety ‘Challa’ were arranged in a 12 × 12 simple lattice design. Mean squares due to genotypes were highly significant for all traits studied, except for days to maturity (DM), grain-filling period (GFP) and number of secondary branches per plant which were significant indicating the presence of genetic variability for these traits in fenugreek germplasm accessions. The range of GCV observed ranged between 3.02 and 68.95% while genotypic variance ranged between 0.001 and 28.62. Broad sense heritability was 48.63% for DM and 2.92% for GFP. Genetic gains varied between 0.20% and 28.22%. Five of the ten PCAs accounted for more than 78.10% of the total variation. The average linkage technique of clustering produced a more understandable portrayal of the 144 fenugreek accessions by grouping them into five clusters and the maximum distance was found between clusters two and five (D² = 64.07). The study generally indicated the possibility for genetic improvement of fenugreek through selection and cross breeding.

Bhabendra K. Biswas, Nazmul Alam (Bangladesh), Jaime A. Teixeira da Silva (Japan), Mohammad M. Haque, Mohammad A. K. Azad, Mohammed K. Hossain (Bangladesh) Framework for Selecting Suitable Indicators to Improve Yield Potential in Fine Rice (Oryza sativa L.) (pp 42-49)

Full Text [PDF]

ABSTRACT

Original Research Paper: An experiment was conducted in the Genetics and Plant Breeding Field of Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh on 28 primitive, one modern (‘BR 34’) and one exotic (‘Philippine katari’) fine rice cultivars during the rainy season (July-December) to construct selection indices based on correlation coefficients and path analysis of 12 characters. The yield potential of these cultivars was generally poor and ranged from 2.03-5.04 t/ha. Several characters including effective tillers/hill, panicle length, spikelets/panicle, 1000-grain weight, days to 50% flowering and days to maturity showed positive and significant associations with yield (t/ha) at genotypic and phenotypic levels. In contrast, the percentage of sterility and lodging showed negative and significant associations with yield (t/ha) at both levels. Genotypic correlation coefficients were higher than corresponding phenotypic coefficients. Therefore, the former were separated into direct and indirect effects. Effective tillers/hill, spikelets/panicle, 1000-grain weight and days to 50% flowering showed positive and strong associations with yield. The negative direct effects of sterility percentage, flag leaf angle and lodging percentage were not encountered by sum total indirect effects caused by other characters, ultimately revealing significant and negative correlation coefficients with yield. A total of 31 selection indices, together with genetic worth and relative efficiencies of selection against yield (t/ha) alone were estimated. Except for yield (t/ha), days to 50% flowering singly exaggerated maximum relative efficiency (89.49%). The relative efficiency over straight was selection increased by integrating more yield-contributing characters into mathematical functions. Although a tedious approach, I₁₂₃₄₅ scored the highest relative efficiency value (246.48%). Thus, this selection function might be a suitable method to adopt for improving the yield potential of fine rice cultivars by by-passing genetic recombination or modification.

Yogendra Kalenahalli Narasimhamurthy, Paramanahally Hanumanthegowda Ramanjini Gowda (India) Line × Tester analysis in Tomato (Solanum lycopersicum L.): Identification of Superior Parents for Fruit Quality and Yield-attributing Traits (pp 50-54)

Full Text [PDF]

ABSTRACT

Original Research Paper: Postharvest losses are the main constraints in tomato production. Several approaches were used for increasing the shelf life of tomatoes. Use of ripening mutants is one such strategy. In the present study the ripening tomato mutants (alcobaca (alc), nor and rin) were crossed with commercially grown varieties such as ‘Pusaruby’, ‘Sankranti’ and ‘Vaibhav’ using Line × Tester mating design, and nine hybrids were developed. One of the hybrid obtained from ‘alc × Vaibhav’ showed extended shelf life up to 40 days, when stored at 25±1°C. The analysis of variance revealed the predominance of non-additive gene action for all the traits. In respect of both GCA and SCA effects, the parents and hybrids differed significantly. Among the parents, ‘alcobaca’ and ‘Vaibhav’ were the best general combiners for fruit keeping quality under study, and these may be used as valuable donors in the hybridization program for producing promising combinations. Between the crosses, ‘alc × Vaibhav’ is a valuable combiner for fruit keeping quality and yield characters under study could be utilized for improving the postharvest shelf life of tomato breeding programs. The highest heterotic effect over better parent was also exhibited by the crosses ‘alc × Vaibhav’ for fruit keeping quality and ‘rin × Vaibhav’ for yield per plant. The genetic parameter analyzed by mean values in parents and F₁ indicates that the cross between the commercial variety ‘Vaibhav’ and ripening mutant alc recorded high shelf life and good fruit quality.

Ijaz Rasool Noorka, Amarah Batool, Saeed Rauf (Pakistan), Jaime A. Teixeira da Silva (Japan), Ejaz Ashraf (Pakistan) Estimation of Heterosis in Wheat (Triticum aestivum L.) under Contrasting Water Regimes (pp 55-60)

Full Text [PDF]

ABSTRACT

Original Research Paper: Manipulation of heterosis is considered to be a vital approach to enhance the yield potential of wheat and is as accepted to be a safe strategy to overcome barriers in wheat yield. Twelve diverse Pakistani wheat genotypes were crossed to obtain a series of crosses to estimate the level of heterosis and heterobeltiosis among F₁ hybrids along with their parents under two contrasting environments: normal irrigation and water stress (withholding 50% water). Estimates revealed a significant relationship between the mean performance of F₁ hybrids and their parents under water stress regime only. The presence of significant heterosis for grain yield was also accompanied by heterosis for yield components, particularly length-based traits such as plant height, peduncle length and spike length. The cross Pasban-90 × Sehar-06 was an elite cultivar and showed significant heterobeltiosis. The study suggests that the obtained hybrids surpassed their better parents’ effects, indicative of commercial heterosis, and are thus candidates for the commercial production of hybrid wheat.

Tharwat El Ameen (Egypt), Akbar Hossain (Bangladesh), Jaime A. Teixeira da Silva (Japan) Genetic Analysis and Selection for Bread Wheat (Triticum aestivum L.) Yield and Agronomic Traits under Drought Conditions (pp 61-68)

Full Text [PDF]

ABSTRACT

Original Research Paper: The climate is changing all over the world, particularly in semi-arid and arid regions. This changing climate could strongly affect wheat production worldwide. As the world population continues to grow, and water resources for crop production decline and temperature increases, so the development of heat- and drought-tolerant cultivars is an issue of global concern. In this context, two cycles of selection were employed in the F₂ generation of a cross between bread wheat (Triticum aestivum L.) ‘Long spike 58’ and ‘Giza-168’ to assess the impact of selection on grain yield in response to drought. Family selection and within-family selection were adopted in the second cycle of selection. The observed response to selection for grain yield was 64.66% in the F₃ generation and 18.14 and 12.39% in the F₄ generation for family and within-family selection, respectively. The mean grain yield of F₃ selections exceeded that of two standard cultivars (‘Giza-168’ and ‘Sids 12’) by 19.67 and 16.48%, respectively, while the mean of F₄ selections exceeded that of the two standard cultivars by 15.08 and 35.53%, respectively. Significant positive correlations were obtained for 1000-grain weight (32.34), number of kernels spike^-1 (24.8) and spike length (12.55) in the F₃ generation but not in the second cycle of selection. Generally, the observed responses to selection were greater than the predicted responses indicating the presence of dominant gene effects for the traits studied.

Anandhi Selvarasu, Rajamani Kandhasamy (India) Analysis of Variability, Correlation and Path Coefficients in Induced Mutants of Glory Lily (Gloriosa superba L.) (pp 69-75)

Full Text [PDF]

ABSTRACT

Original Research Paper: Variability, correlation and path coefficients for 17 morphological characters were studied on morphologically distinct mutants of Gloriosa superba in the second generation of vegetative mutant (VM₂) along with their mother genotypes collected form Mulanur. The maximum GCV (1.24%), PCV (102.02%) was noticed for number of leaves/plant and number of secondary branches/plant. The maximum heritability (89.74%) and genetic advance was recorded for stem girth. The highest and positive correlation for dry seed yield/plant was observed with number of seeds/pod (0.928), number of leaves/plant (0.537), dry pod weight (0.454), fresh seed weight/pod (0.366), fresh pod weight (0.298), plant height (0.282) and number of secondary branches/plant (0.236). The path analysis of component characters on dry seed yield/plant of G. superba in the VM₂ generation exerted a direct positive effect through these characters: number of leaves/plant, dry pod weight, number of seeds/pod, fresh seed weight/pod.