Resistance to Coffee Berry Disease in Arabica Coffee Variety 'Ruiru 11'

General and specific combining ability effects for resistance to coffee berry disease (Colletotrichum coffeanum Noack sensu Hindorf) in Coffea arabica variety ‘Ruiru 11’ and its parents were estimated according to the North Carolina Design II. A set of nine male parents and eleven females were crossed in all possible combinations to generate ninety-nine single cross hybrids constituting the ‘Ruiru 11’ variety. The parents and their hybrid progenies were screened and the mean score data analyzed for possible genetic variation. The contributions of the parents to the total genetic variance were low hence the low narrow sense heritability (h²= 0.04). The male and female parents accounted for 9.36 % and 0.96 %, respectively, while their interaction effect accounted for 89.68 %. In the analysis of combining ability for resistance, ExB3.96 and Cat.90 exhibited significant negative general combining ability (GCA). Specific combining abilities (SCA) were negative and significant for Cat.86 × ExB3.99, Cat.127 × ExB3.116 and Cat.119 × ExB3.879 crosses. The implications of these results in selection for highly resistant ‘Ruiru 11’ progenies are discussed.     

Hybrid performance and heterosis in strawberry (Fragaria × ananassa Duchesne), regarding acidity,soluble solids and dry matter content in fruits

A top‐cross‐mating design among 29 S₄ inbred lines and tester (cultivar ‘Dukat’) was carried out to study their breeding value in terms of general combining ability (GCA). The objectives of this study were to evaluate the acidity, soluble solids and dry matter contents in fruits of progeny F₁ in comparison with S₄ inbred lines as well as the cultivars (S₀); identify strawberry genotypes with high value of GCA for use in cultivar development; and determine mid‐parent heterosis regarding S₄ inbred lines and cultivated strawberry. The 2‐year observations showed statistically significant differences between tested genotypes in terms of the studied traits. The highest breeding value based on GCA was estimated for Chandler 123‐5 for soluble solids and dry matter content, and Kent 7‐6 for acidity. Estimated mid‐parent heterosis had positive and negative values. The highest heterosis in terms of extract and dry matter content (26.71% and 17.50%, respectively) occurred in the offspring Chandler 123‐5 × ‘Dukat’, but as regards acidity in hybrid Chandler 123‐22 with cv. ‘Dukat’. The study of genetic divergence by dendrograms may help to identify parents suitable for obtaining hybrids with higher heterosis effects.     

Value and utilization of alloplasmic common wheats with Aegilops crassa cytoplasm

Differences between alloplasmic lines and euplasmic controls indicated consistent beneficial effects of Aegilops crassa cytoplasm on common wheats. In general, the agronomic performance of alloplasmic lines was superior to that of euplasmic controls; the significant differences observed were ascribed to nucleus‐cytoplasmic (NC) interactions. A number of useful genetic attributes, for example, high yield, good quality and salt tolerance, were identified. A new NC hybrid variety ‘Xiaoshan 2134’ was bred. Field trials showed that the yield NC heterosis of ‘Xiaoshan 2134’ was 13.9% and the yield of ‘Xiaoshan 2134’ was at least 20% higher than that of a control variety widely grown in North China. The results suggested that Ae. crassa cytoplasm could broaden the genetic base of common wheat and improve common wheat cultivars by utilizing NC heterosis.     

Analysis of diallel crosses between wheat genotypes with genetically different resistance to Pseudocercosporella herpotrichoides (Fron) Deighton

Two diallels were analysed for general combining ability (GCA) and specific combining ability (SCA) to study the resistance of crosses‐between wheat genotypes, advanced to the F₅ generation, to Pseudocer‐cosporella herpotrichoides. The parents either carried the resistance‐gene Pch‐1 or had different levels of quantitative resistance, one genotype was susceptible. At medium milk‐ripening, significant effects were‐found for GCA and SCA. GCA effects were the more important. Diallel crosses between genotypes, all carrying Pch‐1, revealed interactions‐of the gene with the genotypic background. Some combinations had a‐higher level of resistance than the best parent. In these populations'CH‐75417’ was involved as a parent. Both ‘CH‐75417’ and ‘F–210.13.4.42’ had significant GCA effects. Crosses between quantitatively resistant parents yielded populations that transgressed both parents. The increased resistance level was associated with ‘Cappelle‐Desprez’, distinguished by its high GCA. In some crosses SCA contributed significantly to an increase in resistance level. Selection for resistance within the best advanced populations is recommended since it‐takes advantage of additive gene action and the high heritability estimates based on ELISA values in plant progenies.     

Combining ability,heterosis, genetic distance and their intercorrelations for waterlogging tolerance traits in chrysanthemum

Waterlogging tolerance (WT) is a major objective in chrysanthemum breeding programs, and although certain genotypes with different tolerance levels have been identified, their value as parents for WT breeding is unknown. Here, twelve F₁ crosses derived from an incomplete diallel mating scheme were conducted to investigate combining ability and heterosis for WT and their relationships with parental genetic distance. The results showed that the membership function value of waterlogging (MFVW) was controlled by additive and non-additive gene effects, whereas other growth and biomass traits were mainly controlled by non-additive gene effects. The estimated broad and narrow sense heritabilities of the MFVW were 97.5 and 51.5%, respectively. Combining ability analyses indicated that ‘Nannong Xuefeng’ showing the largest general combining ability (GCA) effect for the MFVW was the best combiner, and identified several best cross combinations with high positive specific combining ability (SCA) effects for most WT-related traits. Mid- and high-parent heterosis occurred widely. The three distance measures, based on phenotypic traits (PD), molecular markers (GD) and markers linked with quantitative trait loci (QTL-GD), presented a non-significant correlation with combining ability except for the GD with GCA for the relative root fresh weight. The correlations between the QTL-GD and heterosis were significant for certain traits and generally higher than that of the PD or GD and heterosis. The SCA effects were positively correlated with heterosis for most of the WT traits (0.51 ≤ r ≤ 0.80). The findings benefit understanding the inheritance mode and then achieving desirable improvement for WT in chrysanthemum.     

Breeding strategies for seed protein content and trypsin inhibitors inferred from combining ability and heterosis in test-crosses of Vicia faba

The relative importance of general and specific combining ability (GCA and SCA, respectively), amount and causes of heterosis and inferences for breeding strategies were assessed for trypsin inhibitors activity (TIA) and seed protein content (SPC) in Vicia faba test-crosses. Four lines with low (‘Bond’) and high (‘H2OS’, ‘98/Tunesien’ and ‘Canner Express’) TIA, and two testers (‘Rowena’ and ‘Felicia’) with low TIA were used to produce test-crosses. GCA accounted for 89% and 57% of the test-cross sums of squares for SPC and TIA, respectively; SCA accounted for 48% and 34%, and differences between reciprocals for 6% and 9%. Specific heterosis was large only in low TIA × low TIA test-crosses and tended towards an increased TIA. Epistatic interaction explained the observed specific heterosis for high TIA. Breeding faba bean hybrids for high SPC and low TIA is not convenient because non-additive gene actions exert minimal effects on SPC or are in the undesired direction for TIA. Selecting inbred lines which combine low TIA, good SPC and satisfactory grain yield is more promising] Rowena and Rowena × Bond are adequate as base materials.     

Combining ability and heterosis over environments for yield and yield components in two-line hybrids involving thermosensitive genic male sterile lines in rice (Oryza sativa L.)

Presence of substantial heterosis and economic hybrid seed production are two most desirable components for success of any commercial hybrid breeding programme. Thermosensitive genic male sterile (TGMS) lines of rice, in this regard, have tremendous potential in realizing further quantum jump in yield and economical hybrid seed cost. Analyses for combining ability and heterosis over optimum (120N : 60P₂O₅ : 40K₂O kg/ha) and high (200N : 90P₂O₅ : 60K₂O kg/ha) fertility environments for six traits were made in 2 years (2001 and 2002) using 120 hybrids of inter‐ and intra‐subspecific nature derived from hybridization of 30 elite indica TGMS lines and four cultivars, viz., ‘Pant Dhan 4’ and ‘Ajaya’ (I = indica), ‘Taichung 65’ (J = japonica) and ‘IR 65598‐112‐2’ (TJ = tropical japonica) in line × tester mating design. Predominance of non‐additive genetic variance suggested good prospects of hybrid breeding. Pooled analysis revealed highly significant variances for lines, general combining ability (GCA), specific combining ability (SCA) and line x tester. TGMS line 365‐8S was the best general combiner for all the six traits including grain yield. Trend of relative mid‐parent heterosis for grain yield, panicle length, grain number per panicle and earliness in flowering was I/TJ > I/J > I/I. For panicle number per plant and 1000‐grain weight, trends were I/TJ > I/I > I/J and I/I > I/TJ > I/J, respectively. Grain yield recorded heterosis of 49.3%, 71.9% and 92.7% for I/I, I/J and I/TJ hybrid groups respectively. Effect of environments on the hybrid performance indicated better response of hybrids at high fertilizer dose. Study suggests greater prospects of combining improved japonica and tropical japonica germplasms having wide compatible gene with indica TGMS lines for exploitation of intersubspecific heterosis.     

Fusarium resistance in Gladiolus: Selection in seedling populations

A test to select Fusarium resistant seedlings of Gladiolus is described. Seedlings of 37 populations, obtained from an incomplete diallel between eight parents with different levels of Fusarium resistance, were used. Significant differences in Fusarium infection between and within populations were detected. Most of the descendants selected had a resistant G. dalenii genotype as one of the parents. The resistance level of the parents was associated with the general combining ability for Fusarium resistance based on the seedling test. Implications for resistance breeding are discussed.     

Translation of phenotypic diversity of Sorghum bicolor axillary branched mutant into exploitable heterosis

Lack of variability in sorghum is the main reason for the stagnation in crop improvement including low heterosis. Studies on somaclonal mutations of sorghum have led to the development of a diverse axillary branched grain sorghum mutant, SbABM of postrainy season variety A‐1 (Annigeri‐1) which bears multiple panicles. Considering its developmental significance and phenotypic diversity, this mutant was subjected to detailed genetic analysis. To exploit its genetic potentiality, the mutant was involved in a full diallel study along with ruling varieties to assess the combining ability and to quantify the magnitude of heterosis. SbABM performed exceptionally well in hybrid combinations for all the traits. Mean squares due to genotypes were highly significant for all the traits. The results on general combining ability revealed that SbABM was significantly better general combiner for all the traits studied. Majority of the hybrids involving SbABM as parental line exhibited high degree of heterosis for most of the traits, finally contributing to overall plant's vigour. However, SbABM did not restore fertility on both milo and maldandi cytoplasm.     

糯高粱主要农艺性状配合力与杂种优势的关系

以7个不育系和5个恢复系为亲本,采用不完全双列杂交试验设计（NC II）配制35个杂交糯高粱组合,分析了10个主要农艺性状的配合力、杂种优势及其相关关系。结果表明：10个农艺性状的表达以加性基因效应为主,且多数性状同时受加性和非加性基因效应的共同影响。供试组合在多数性状上表现出较强的杂种优势。一般配合力（GCA）和总配合力（TCA）与竞争优势呈极显著相关,且其相关系数较大,说明本研究中可利用一般配合力或总配合力效应预测竞争优势;多数性状的一般配合力效应、特殊配合力效应（SCA）和总配合力效应与中亲优势呈显著或极显著相关,且特殊配合力效应与中亲优势的相关性多高于一般配合力或总配合力效应,但特殊配合力效应与中亲优势的相关系数较小不足以预测中亲优势,说明配合力与中亲优势的关系还有待进一步研究。     

Genetic analysis of resistance to root-lesion nematode (Pratylenchus thornei) in wheat

The inheritance of resistance to root‐lesion nematode was investigated in five synthetic hexaploid wheat lines and two bread wheat lines using a half‐diallel design of F₁ and F₂ crosses. The combining ability of resistance genes in the synthetic hexaploid wheat lines was compared with the performance of the bread wheat line ‘GS50a’, the source of resistance to Pratylenchus thornei used in Australian wheat breeding programmes. Replicated glasshouse trials identified P. thornei resistance as polygenic and additive in gene action. General combining ability (GCA) of the parents was more important than specific combining ability (SCA) effects in the inheritance of P. thornei resistance in both F₁ and F₂ populations. The synthetic hexaploid wheat line ‘CPI133872’ was identified as the best general combiner, however, all five synthetic hexaploid wheat lines possessed better GCA than ‘GS50a’ The synthetic hexaploid wheat lines contain novel sources of P. thornei resistance that will provide alternative and more effective sources of resistance to be utilized in wheat breeding programmes.     

Inheritance and potentials of a mutated dwarfing gene ndf1 in Brassica napus

A dwarf mutant ‘NDF‐1′, approximately 70 cm high, was derived from a 200‐cm high doubled haploid (DH) line ‘3529’ (Brassica napus), seeds of which were jointly treated with chemical inducers and bombardment of fast neutron. The leaves of the ‘NDF‐1’ mutant were wrinkled and thicker compared with the wild‐type control. The mutant had much lower values than its original parents for all agronomic traits, except for its seed weight. A genetic analysis revealed that dwarfism is under the control of a major gene (designated as ndf1) with a mainly additive effect and non‐significant dominance effect. Because of the high level of resistance to lodging, breeding programmes for double low dwarf oilseed rape and heterosis utilization were initiated. Some new dwarf strains with improved agronomic performance were developed. The hybrid of the cross between the tall parent and the dwarf line showed increased harvest index and significantly higher seed yield than the tall parent or the control variety ‘Zhongyou 821’ and presented an estimated heterosis vigour rate as high as 12.5–25.8%. The dwarf trait will be a promising marker for a simple, economic and efficient way to control the purity of F₁ hybrid varieties in hybrid production of B. napus.     

Genetic combining ability for concentration of mineral elements in cabbage head (<Emphasis Type="Italic">Brassica oleracea</Emphasis> var<Emphasis Type="Italic">. capitata</Emphasis> L.)

Brassica vegetables are important source of dietary nutrition. However, information on the genetic combining ability of mineral elements such as iron, zinc, copper, manganese, potassium and calcium or their types of genetic effects (i.e. additive or non-additive) is scarce but important as it influences the selection of parents and breeding approaches to be adopted for improvement of nutritional quality of cabbage. Therefore, an attempt was made to estimate combining ability in a line × tester (5 × 11) mating design for minerals. Significant mean square for line × tester interaction was observed for all minerals under study indicating the prevalence of non-additive variance; while less than unity value of σ_gca² /σ_sca² ratio for iron, zinc, manganese, potassium and calcium accumulation indicate predominance of non-additive gene action. The parents 83-2, Pride of Asia, Pusa Mukta, Red Cabbage and MR-1 were found good general combiners for four mineral elements. The general combining ability effects of the parents for various minerals revealed that none of the parents excelled for all the minerals suggesting the need for multiple crossing approaches. The cross 83-1 × AC-1019 (Poor × Poor general combiner) exhibits desirable significant specific combining ability effects for all six minerals might be due to presence of high magnitude of non-additive especially complementary epistatic effects which can be utilize for commercial exploitation of heterosis. This study shows clearly that specific combining ability is more important than general combining ability for predicting hybrid combinations for high mineral content in cabbage head.     

Genetic Structure of Three Open-Pollinated Faba Bean Varieties (Vicia faba L.)*

To study the genetic structure of open-pollinated faba bean varieties, three sets of genotypes were generated from each of the varieties ‘Minica’, ‘Kristall’, and ‘Deiniol’: (1) inbred lines developed by single-seed descent in bee-proof isolation cages, (2) intravanetal and (3) intervarietal F₁-hybrids produced by controlled hand crossing. In 1989 and 1990, a total of 144 entries, including the three open-pollinated source varieties, were grown in single-row plots with two replications at two locations in Western Germany. Performance data of the inbred lines revealed relatively large genotypic variability within each variety, for all the characters studied, which was greater in ‘Deiniol’ and ‘Kristall’ than in ‘Minica’. An average yield heterosis of 20 %, 39 % and 57 %, respectively, was found for the intravarietal hybrids, whereas that of the intervarietal hybrids varied between 70 and 73 %. Compared to the mean yield of the inbred lines the superiority of the open-pollinated source variety was small and not significant in ‘Minica’ (6 %), but it was large and highly significant in ‘Kristall’ (22 %) and ‘Deiniol’ (37 %). The present investigation revealed in faba bean that similar performance levels of open-pollinated varieties may result from either high per se performance under inbreeding with low heterosis values or from lower per se performance but with high heterosis values.     

Heterosis,molecular diversity,combining ability and their interrelationships in short duration maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) across the environments

Five inbred lines, 10 single cross maize (Zea mays L.) hybrids and two standard cultivars as check were used to study the combining abilities and heterosis under three environmental conditions. Random amplified polymorphic DNAs (RAPDs) markers were used to study the genetic diversity (GD) and further to analyze relationship of RAPDs based GD with combining ability and heterosis in short duration maize. Spearman’s rank correlation coefficients and linear regressions were analyzed to identify the most important factor determining heterosis and per se performance of the hybrids. Variances due to general combining ability (GCA), specific combining ability (SCA) and their interactions with environment were found to be significant. Twenty random primers generated 179 RAPD fragments. Of these, 102 RAPD fragments were polymorphic. GD was determined using Jaccard’s similarity coefficient, and a dendogram was constructed by UPGMA cluster analysis. The RAPDs based GD exhibited non-significant negative or positive association, non-significant linear regression along with very low coefficient of determination (R ²) with SCA, high and mid parent heterosis (HP and MP) and per se performance of the hybrids. Significant positive correlations and regressions along with high coefficients of determination were recorded for SCA with HP, MP and per se performance of the hybrids. The HP and MP also established significant positive association and linear regression along with high coefficient of determination with per se performance of hybrids whereas the parental mean did not establish any significant correlations with the GD, HPH, MPH and grain yield of F₁s. The present investigation, therefore, did not find any role of RAPDs based GD in determining hybrid heterosis and hybrid performance in short duration sub-tropical maize. The SCA, however, has emerged as the most important factor in determination of heterosis as well as per se performance of the hybrids in short duration maize.     

Combining ability for beet armyworm, Spodoptera exigua, resistance and horticultural traits of selected Lycopersicon pennellii-derived inbred backcross lines of tomato

Ten selected inbred backcross lines (IBL), from a Lycopersicon esculentum cv.‘Peto 84’×Lycopersicon pennellii IBL population, with resistance to beet armyworm (BAW), Spodoptera exigua, higher fruit mass and fruit yield, were crossed with eight elite cultivated L. esculentum inbred lines in a Design II mating design. Three elite inbreds were also crossed to ‘Peto 84′, the IBL recurrent parent, as a control for combining ability. Field plots of all resulting F₁ progenies and control cultivars were inoculated with BAW eggs and evaluated for resistance to BAW, fruit mass, fruit yield, vine size and maturity at three field locations. Reductions in fruit damage by BAW were found in four of the 10 IBL F₁ progenies. Significant male and female general combining ability (GCA) estimates for BAW resistance were observed, but significant specific combining ability for BAW resistance was not detected. The fruit mass of F₁ hybrids was significantly lower than large-fruited controls, but was not significantly different from elite inbred by ‘Peto 95’F₁ hybrids. Selection based on inbred performance identified IBL with positive GCA for BAW resistance and yields in Design II hybrids. BAW resistance in the 09 selected IBL and IBL- derived F₁ progeny was associated with two undesirable traits, later maturity and larger vine size. Index selection of IBL was more effective at identifying IBL with positive GCA for fruit mass and fruit yield than GCA for BAW resistance.     

Relationship between phenotypic and genetic diversity of parental genotypes and the specific combining ability and heterosis effects in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The purpose of the study was to evaluate the relationship between the genetic distances (GD) and phenotypic distances (PD) of parents and the specific combining ability (SCA) and heterosis effects. The experiment comprised 18 parental genotypes of wheat (Triticum aestivum L.) and 76 F₂ hybrids, obtained after crossing in a line × tester scheme. Parents and hybrids were examined in a field experiment conducted in a block design with three replications. SCA as well as mid-parent heterosis effects were estimated for selected morphological and technological traits. PDs and GDs were investigated between pairs of parental genotypes. GD between parental genotypes was evaluated by using randomly amplified polymorphic DNA markers. Heterosis was observed in all hybrids, and protein content exhibited the highest heterosis among the seven examined traits. The relationship between PD and GD as well as the SCA and mid-parent heterosis effects were evaluated using correlation coefficient. The correlation between PD, SCA and heterosis were low and not significant for the examined traits, whereas the correlation between SCA, heterosis and GDs were significant for protein content and rheological properties. The results indicate that GDs between parents can be used to predict performance of hybrids for selected technological traits.     

Phenotypic variations and heritability of bearded iris breeding

Bearded iris (Iris × hybrida Hort.) refers to the large population of iris hybrids, which is identified by thick, bushy ‘beards’ on each falls (lower petals) of the blossoms. However, the selection of iris is extremely limited due to the lack of information about genotype and phenotype. According to North Carolina Design II (NC II), a statistical method to estimate the combining ability, genetic variance components and heritability, seven male parents and two female parents were hybridized to generate 14 populations of first filial generation (F₁). Each F₁ family was generated through artificial pollination in 3 years and included 60 individuals. 11 key ornamental characters, including plant height (PH), length of leaf (LL), number of flower per scape (NFS), height of individual flower (HF), diameter of flower (DF), length of fall (LF) and width of fall (WF), were measured, and some genetic parameters (heterosis, heterobeltiosis, combining ability, heritability as well as genetic correlations) were evaluated. The results showed that HF and LW had the largest number of F₁ populations gaining heterosis, thus more likely to generate taller progenies with larger blossoms. The estimates of combing ability revealed that I. ‘White and Blue’(M1) and I. ‘Sugar Blues’(M5) appeared to be ideal pollen donators. The combination of I. ‘India Chief’ × I. ‘Champagne Elegance’ (FM1 × M6) exhibited positive special combining ability (SCA) on all the tested characters, becoming the most potential populations of all. WF and NFS had the highest broad-sense heritability (91.47%) and strict-sense heritability (53.96%), respectively. Correlation analysis showed that PH was closely associated with NBS and NFS, while LL had significant correlations with HF and LF, making it possible to select taller individuals in the vegetative stage to obtain those with abundant flowers.     

Comparisons of genetic and morphological distance with heterosis between Medicago sativa subsp. sativa and subsp. falcata

Biomass yield heterosis has been shown to exist between Medicago sativasubsp. sativa and Medica gosativa subsp. falcata. The objective of this study was to gain a better understanding of what morphological and genetic factors were most highly correlated with total biomass yield heterosis. We calculated genetic distances among nine sativa and five falcate genotypes based on amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) DNA markers. Genetic distance did not correlate with specific combining ability (SCA) or mid-parent heterosis. In contrast, a morphological distance matrix based on seventeen agronomic and forage quality traits was significantly correlated with heterosis; the agronomic traits of maturity, midseason regrowth, and autumn regrowth showed strong association with heterosis. Heterosis was also correlated with subspecies. We suggest that in many cases progeny heterosis can be accounted for by the interaction of genes controlling morphologically divergent traits between the parents. In other cases, progeny heterosis could also be due to divergence between the parents at particular genetic loci that do not control field-level phenotypic differences. Genetic distanceper se between parental genotypes, based on neutral molecular markers, however, does not reflect the potential of individual genotypes to produce heterosis in their progeny. This revised version was published online in August 2006 with corrections to the Cover Date.     

Winter × spring wheat hybridization - a promising avenue for yield enhancement

Introgression of the winter gene pool into spring wheat is being considered as one of the strategies to break through the yield plateau. However, little information is available on the combining ability of these two important but distinct groups of wheats in Indian conditions. Therefore, the present study was undertaken to determine the combining ability and gene action of yield and yield attributes in winter × spring wheat crosses. Seventy F₁ progenies developed by 14 winter and five spring wheat lines using a line × tester design were evaluated, along with their parents, for yield and yield attributes in a randomized complete block design under field conditions. The mean squares for all the characters studied showed highly significant differences. The mean squares due to female × male interactions were significant for all the characters studied except for grains per ear and grain weight per ear. Additive genetic effects were found to play a key role in controlling the expression of days to heading, plant height and spikelets per ear.‘MV 19’ and ‘Stepniak’/‘Karvuna’ among winter and ‘PBW 65’ among spring wheats were good general combiners for most of the yield attributes studied. The estimates for specific combining ability effects suggested that, although general combining ability (GCA) effects of most winter wheats are either average or poor, their combination can give desirable genotypes with spring wheat parents possessing a high GCA.