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Volume 2 Number 1 & 2 2008 
CONTENTS AND ABSTRACTS
Number 1
Guoyou Ye, Kevin F. Smith (Australia) Marker-assisted Gene Pyramiding for Inbred Line Development: Basic Principles and Practical Guidelines (pp 1-10)
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ABSTRACT
Invited Review: Gene pyramiding, which aims to assemble multiple desirable genes into a single genotype, is a commonly used method in breeding for self-pollinated crops. Traditionally, the main use of gene pyramiding is to improve an existing elite cultivar through introgression of a few genes of large effects from other sources, since the presence of the target genes has to be monitored by phenotyping, which is only effective for major genes. Depending on the trait and inheritance of the targeted genes, gene pyramiding may require much labour, time and material resources. The development of modern plant molecular techniques and quantitative genetics in the last two decades has dramatically widened the applicability of gene pyramiding. It provides enhanced knowledge of the genetics of the breeding traits and of the relative genomic location of functionally related as well as neutral markers associated with the genes responsible for the traits. It facilitates the identification of genes with large effect for traits which are traditionally regarded as quantitative and not targeted by gene pyramiding program. Marker-based selection reduces/eliminates extensive phenotyping, provides more effective options to control linkage drag, makes the pyramiding of genes with very similar phenotypic effects possible, and reduces the breeding duration. Marker-based gene pyramiding is now the method of choice for inbred line development targeted at improving traits controlled by major genes. In this review, we focus on aspects of designing an efficient marker-based gene pyramiding strategy for inbred line development. The basic principles of gene pyramiding, the process and useful guidelines for designing an efficient strategy, and the integration of gene discovery and pyramiding are discussed in this paper, while the successful use of gene pyramiding in practical breeding is summarised in a companion paper.
Guoyou Ye, Kevin F. Smith (Australia) Marker-assisted Gene Pyramiding for Inbred Line Development: Practical Applications (pp 11-22)
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ABSTRACT
Invited Review: Aimed at assembling multiple desirable genes into a single genotype, gene pyramiding is a commonly used breeding strategy in self-pollinated crops. The use of this strategy has been greatly facilitated and widened by the rapid development of plant molecular biology and genomics. Marker-assisted gene pyramiding including introgression may be so far the most productive application of marker-assisted selection (MAS) in plant breeding. As part of a comprehensive review, the current literature in the practical applications of gene pyramiding is summarised in this paper. The basic principles of gene pyramiding, the process and useful guidelines for designing an efficient strategy, and the integration of gene discovery and pyramiding are discussed in a companion paper. Marker-assisted gene introgression as an intermediate step towards pyramiding multiple genes is also discussed. By targeting few genes with large effects, improved (converted) versions of some elite cultivars have been successfully developed in various crops. Experimental results in the improvement of quantitative trait by combining quantitative trait loci (QTL) varied from disappointing to promising with few successful examples. It is important that QTL should be precisely mapped and validated in the target genetic backgrounds before introgresion starts. It is anticipated that QTL pyramiding will be more fruitful if near isogenic lines in the same elite background are used as parents. Genetic transformation, which can introduce one or a few extraneous genes into crop species, can be used alone or in combination with sexual crossing to pyramid genes.
Sridhar Bhavani, Urmil K. Bansal, Ray A. Hare, Harbans S. Bariana (Australia) Genetic Mapping of Stem Rust Resistance in Durum Wheat Cultivar ‘Arrivato’ (pp 23-26)
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ABSTRACT
Original Research Paper: Genetic analysis of seedling stem rust resistance in the durum wheat cultivar ‘Arrivato’ indicated the presence of three independent genes. Replicated tests on F3 families derived from ‘Arrivato’/‘Bansi Strain 168’, putatively segregating at a single locus, were performed to confirm monogenic segregations. These families represented three distinct infection types, viz., IT;1, IT2= and ITX and the genes conditioning these different phenotypic expressions were temporarily named SrAr1, SrAr2 and SrAr3, respectively. Up to 100 plants from at least one family representing segregation for each distinct infection type were grown and harvested individually. These monogenically segregating populations were progeny tested. Bulked segregant analyses were conducted and SrAr1 was mapped 0.7cM proximal to Xgwm47 in thechromosome 2BL. SrAr2 mapped 5.7cM distal to Xwmc59 in the long arm of chromosome 6A, whereas SrAr3 showed genetic association (4.6cM) with Xgwm334 in chromosome 6AS. Based on combinations of infection type with genomic locations and/or pathogenic specificities of previously characterized stem rust resistance genes SrAr1, SrAr2 and SrAr3 were concluded to be Sr9e, Sr13 and Sr8b, respectively.
Sami S. Adawy, Ayman A. Diab, Mohamed A. M. Atia, Ebtissam H. A. Hussein (Egypt) Construction of Genetic Linkage Map Showing Chromosomal Regions Associated with Some Agronomic Traits in Cotton (pp 27-38)
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ABSTRACT
Original Research Paper: Cotton is the world’s leading fiber crop and the second most important oil seed crop. In Egypt, plant breeders have made major contributions to the productivity of this crop; however, this has led to a decrease in the genetic variation among Egyptian cotton varieties. Enhancing the productivity of cotton could be addressed through improving different agronomic traits including early flowering and maturation. In the present investigation, an interspecific cross (G. barbadense x G. hirsutum) was performed between two genotypes, cvs. ‘Giza 83’ (late flowering) and ‘Deltapine’ (early flowering) to develop an F2 segregating population. Analysis of segregation among the 71 F2 individuals was performed using 3 RAPD, 10 SSR, and 6 AFLP primer combinations. Twenty four AFLP primer combinations were used in bulked segregant analysis for flowering time. Linkage analysis and map construction were performed using Map Manager. The map showed 22 linkage groups with 140 markers covered a total length of 1556.7 cM. The average length of linkage groups ranged from 1.4 to 649.5. Single point analysis was used to identify the genomic regions controlling traits for plant height, number of nodes at flowering time, bolling date, days to flowering and number of bolls. In total, 30 significant QTL were identified for the five traits on ten linkage groups, among these 11 QTL for plant height, 8 for number of bolls, 4 QTL for each of days to flowering and bolling date and 3 QTL for number of nodes at flowering time. This work represents the first linkage map for the intercross between ‘Giza 83’ and ‘Deltapine’ showing chromosomal regions associated with some agronomic traits.
Reza Mohammadi, Abdulvahab Abdulahi (Iran), Ahmed Amri (Syria) Repeatability of Some Agronomic Traits in Durum Wheat (pp 39-42)
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ABSTRACT
Original Research Paper: Analysis of variance (ANOVA), principal component (PC) method and Spearman’s rank correlation (SRC), between single vs. multi-year trials, were used to study the repeatability of some agronomic traits i.e., grain yield (GY), day to heading (DH), thousand kernel weight (TKW) and plant height (PH) using 20 durum wheat genotypes grown during 2000-2006 cropping seasons in Iran. Repeatabilities calculated from ANOVA were in agreement with those obtained from PC and SRC methods. These results also clarified that the repeatability for PH is high and less influenced by the systematic factors such as climatic conditions. Repeatability estimates were low (ρ^ < 0.20) for GY, DH and TKW, whereas these estimates for PH were high based on ANOVA (ρ^ = 0.733) and PC (ρ^ = 0.920) methods. The highest coefficient of determination (R2 = 94.3 up to 98.6%) was observed for PH, which indicates good precision of the procedure applied. Repeatability estimates using correlations derived from single and multiple year trials showed that PH had the highest repeatability, with correlations between years ranging from 0.54 (P <0.05) to 0.95 (P <0.01), whereas the correlations for the other traits (DH, TKW and GY) showed large fluctuations and were less predictable. A high magnitude of repeatability estimates indicated a predominant genetic control of the trait PH. However, the consistency of the repeatability estimates shown by the three procedures of estimation reinforces the regularity in the expression of the traits studied.
Number 2
Guillermo Ortiz-Ferrara, Ram C. Sharma, Madan R. Bhatta (Nepal), Gyanendra Singh (India), Dinabandhu Pandit (Bangladesh), Arun K. Joshi (India), Abu B. Siddique (Bangladesh), Etienne Duveiller, Rodomiro Ortiz (Mexico) Introduction and Exchange of Improved Bread Wheat Germplasm in the Eastern Gangetic Plains of South Asia (pp 43-51)
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ABSTRACT
Original Research Paper: Wheat (Triticum aestivum L.) yield must be increased in the Eastern Gangetic Plains (EGP) of South Asia to improve the livelihoods of poor farmers. The International Maize and Wheat Improvement Center (CIMMYT) and its partners in South Asia initiated a regional yield trial, the Eastern Gangetic Plains Wheat Yield Trial (EGPYT) in 2000 to identify wheat cultivars with high and stable grain yield, superior agronomic traits and disease resistance. Advanced breeding lines from CIMMYT, Mexico and wheat programs in the region were assembled each year and tested at key sites in Bangladesh, India and Nepal. A total of 168 experimental genotypes and four checks were tested over eight years (2000–2007). The wheat genotypes showed arrays of genetic variation in grain yield, days to heading, plant height, 1000-kernel weight (TKW), and spot blotch severity in the eight years. Several experimental genotypes were superior to checks in yield, TKW, spot blotch resistance in individual country and across the region. We identified two sets of superior lines across the region that could be used as parents (Parent 1 = ‘BL1804’, ‘BL1968’, ‘BL2324’, ‘G162/BL1316//NL297’, ‘NL750’, ‘NL835’ and ‘Shatabdi’; Parent 2 = ‘BL2966’, ‘Milan/Shanghai#7’, ‘NL966’, ‘PBW373’, ‘BL3122’, ‘BL3124’, ‘BL3191’ and ‘SW89.5124*2/Fasan’) to develop new improved lines with high grain yield and TKW, spot blotch resistance, early maturity and acceptable plant height. New cultivars have been developed through this effort, and many outstanding lines selected by wheat breeders in the region are being used as parents in the breeding programs of different centers. This regional effort has helped in the introduction and exchange of superior wheat genotypes, thus enriching the germplasm base in the region. The findings underline the importance of region-focused varietal testing approach in developing and disseminating high yielding wheat germplasm.
Kumarse Nazari (Australia/Syria), Colin R. Wellings, Robert F. Park (Australia) Characterisation of Seedling Resistance to Rust Diseases in Wheat Cultivars from Central Asia and the Caucasus (pp 52-63)
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Original Research Paper: The diseases stripe rust (caused by Puccinia striiformis f. sp. tritici, Pst), leaf rust (P. triticina, Pt), and stem rust (P. graminis f. sp. tritici, Pgt) are major threats to wheat production in the regions of Central Asia and Caucasus (CAC). Multi-pathotype tests on 32 winter wheat cultivars grown in CAC countries were used to characterise seedling resistance to Pst, Pt, and Pgt and where possible to postulate the identities of genes present. The most commonly postulated seedling stripe rust resistance gene was Yr9 (eight cultivars). Evidence for the presence of Yr1 (five cultivars), Yr3+Yr4 (two cultivars), Yr27 (one cultivar), and Yr7+Yr9 (one cultivar) was also obtained. Twelve cultivars were seedling susceptible to all Pst pathotypes used, while the resistance of two cultivars could not be identified. Leaf rust resistance genes Lr1, Lr2a, Lr3a, Lr3bg, Lr3ka, Lr13, Lr14a, Lr16, and Lr26 were postulated, present either singly or in combination in the cultivars. Of these, Lr26 was the most common (nine cultivars) and Lr13 was postulated frequently in combination with other Lr genes. Evidence was obtained for the presence of gene LrB in two cultivars, but this gene could not be differentiated clearly in this study. Stem rust resistance genes Sr5, Sr7b, Sr8b, Sr9e, Sr9b, Sr11, Sr17, Sr30, and Sr31 were postulated in the cultivars either singly or in various combinations. Gene Sr31 was the most common (10 cultivars), followed by Sr8b (six cultivars).
Balakrishna P. Venkata (Australia/USA), Urmil K. Bansal (Australia), Ravi P. Singh (USA), Robert F. Park, Harbans S. Bariana (Australia) Genetic Analyses of Durable Adult Plant Resistance to Stripe Rust and Leaf Rust in CIMMYT Wheat Genotype 11IBWSN50 (pp 64-68)
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ABSTRACT
Original Research Paper: The CIMMYT wheat genotype 11IBWSN50 exhibited high levels of resistance to Australian pathotypes of stripe rust and leaf rust pathogens. Genetic analyses based on BC1- derived F2 and/or F6 and F7 families demonstrated the digenic and trigenic control of stripe rust resistance against Puccinia striiformis f. sp. tritici (Pst) pathotypes 134 E16A+ and 110 E143A+, respectively. Digenic inheritance of adult plant stripe resistance was observed when BC1F6 families were tested in Mexico. Comparison of rust response data across different experiments indicated that at least one of the adult plant stripe rust resistance genes was not effective against the Pst pathotype 134 E16A+ and the Mexican Pst pathotype Mex96-11. Four independent genes controlled leaf rust resistance in 11IBWSN50. Genotype 11IBWSN50 was observed to carry Lr13, which was effective against the Puccinia. triticina pathotype used to create field epidemic in this study. Marker genotyping demonstrated the presence of Lr34/Yr18 and Lr46/Yr29 in 11IBWSN50. Pedigree information also supported the presence of these gene combinations. Genotype 11IBWSN50 carried another uncharacterised gene for adult plant leaf rust resistance. High levels of adult plant resistance against leaf rust and stripe rust pathogens in 11IBWSN50 makes this genotype a suitable source of resistance in wheat improvement programs.
Lakshmi Kant, Vinay Mahajan, Hari Shanker Gupta, Mohan Chandra Pandey (India) Winter x Spring Wheat Hybridization: A Potential Source for Yield Advancement (pp 69-73)
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Original Research Paper: Introgression of winter wheat gene pool in spring wheat is one of the potential approaches to break the yield barrier. However, little information is available on the combining ability of these two important groups. To assess the combining ability of yield and secondary traits, 42 F1 hybrids developed by (7 × 7) diallel of four winter and three spring wheat parents were evaluated in replicated plots over 2 years. Additive gene effects were more important in determining yield. Reliable prediction of GCA (General Combining ability) effects from mean values was indicated for ear length, grain number per ear and 1000-grain weight. ‘UP 2425’ spring and ‘Druchamp’ winter wheat were good general combiners for maximum number of traits including yield. Cross ‘HD 2687’/‘Zhong 65’ had significant Specific Combining ability (SCA) effects for seven traits. Although GCA effects of most winter wheats ranged from average to poor, their combination with spring wheat possessing high GCA can give improved genotypes. The chances of selecting improved genotypes were better in the case of winter × spring and winter × winter crosses as compared to spring × spring crosses.
Reza Mohammadi, Kouresh Nader Mahmoodi (Iran) Stability Analysis of Grain Yield in Barley (Hordeum vulgare L.) (pp 74-78)
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Original Research Paper: Identifying high-yielding and stable genotypes is a primary objective of most applied breeding programs. Several parametric and non-parametric statistics of phenotypic stability were used for assessing yield performance and stability simultaneously of thirteen advanced barley genotypes across eighteen environments during 2003-2005 in Iran. Spearman's rank correlation analysis indicated that the non-parametric methods can be used as a good alternative for most parametric methods. The parameters of ecovalence (W2i), variance in regression deviation (S2di), coefficient of determination (R2) and AMMI stability value (ASV) had a significant positive correlation with variance of ranks (Si(1), Si(2), Si(3)). Genotypic mean yield had a significant positive correlation with coefficient of variation (CV), geometric adaptability index (GAI), superiority index (Pi), yield reliability index (Ii), coefficient of regression (bi), rank-sum, while was negatively correlated with variance of ranks (Si(3) and Si(6)). Corresponding to most phenotypic stability measures, genotypes G5 (Antares/KY36-1294//SLR) and G8 (Antares/KY36-1294//Lignee131) were identified as the most stable genotypes with high yielding performance and a high degree of reliability, whereas genotypes G13 (Sahand), G3 (Alpha//Gumhuriyet/Sonja) and G4 (Antares/KY36-1294//SLR) with highest yielding performance considered to be unstable. In conclusion, both yield and stability should be considered simultaneously to exploit the useful effect of GE interaction and to make selection of genotypes more precise and refined.
Vijayakumar Rathod, Nagamangala Chaluvarangaiah Narasegowda, Narayanaswamy Papanna (India), Luke Simon (UK/India) Evaluation of Genetic Diversity and Genome Fingerprinting of Bitter Gourd Genotypes (Momordica charantia L.) by Morphological and RAPD Markers (pp 79-84)
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Original Research Paper: In this study, morphological features along with Random Amplified Polymorphic DNA (RAPD) markers were used for assessing genetic diversity and relationships among 20 genotypes of bitter gourd (Momordica charantia L.) collected from different parts of India. The morphological data was recorded for their vegetative and reproductive characters along with the data on diseases infesting for two successive cycles. DNAs from 20 genotypes were isolated using the CTAB method and a total of 143 polymorphic amplified products were obtained from 14 decamer primers, which discriminated all the accessions with a mean of 10.2 amplified bands per primer, 48.3% (69 bands) of which were polymorphic bands. A dendrogram grouped the genotypes into two clusters ‘A’ and ‘B’ at 29 linkage distances. Cluster ‘A’ consisted of one variety ‘Arka Harit’ characterised by plants that are highly susceptible to fruit fly and downy mildew infestations. Cluster ‘B’ was sub-divided into ‘B1’ and ‘B2’ clusters at a linkage distance of 26 with one (‘Nanjangood Local’) and 18 genotypes, respectively. The accessions of sub-cluster ‘B2’ were further divided into two minor clusters ‘B2a’ and ‘B2b’ at a 24 linkage distance with three small groups each. The genetic dissimilarity matrix based on Squared Euclidean Distance, showed a maximum dissimilarity (52%) between the genotypes ‘Nanjangood Local’ and ‘IC-42261’ and a minimum dissimilarity (9%) between the genotypes ‘IC-42261’ and ‘VRBT-93’, ‘DARA-1’, and ‘IC-065782’. The analyses showed the potential of the commercial variety ‘Panrushy’ with respect to its capacity to resist fruit fly and downy mildew infestations, as well as high yield.
Rakesh K. Dubey, Hari Har Ram (India) Characterization of Advanced Breeding Lines and Assessment of Genetic Diversity in Bottle Gourd (Lagenaria siceraria (Mol.) Standl.) through SDS–PAGE (pp 85-86)
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Original Research Paper: Seed proteins of eight advanced breeding lines and two F1 hybrids of bottle gourd were resolved by SDS-PAGE. An electrophorogram for each line was scored and Jaccard’s similarity coefficient was calculated. The round-fruited cultivar, PBOG 13 had a distinguishable protein profile. All the eight advanced breeding lines and two F1 hybrids were found to be grouped into four major groups. Leaf morphological variation (normal leaf vs. segmented leaf) was not the major component of overall diversity. We conclude that even though seed protein profiles are potentially useful markers in the study of genetic diversity of bottle gourd, the accuracy with which the information is linked to leaf morphology is low. |
