Comparison of selection procedures in breeding for seed yield in segregating sesame populations

Summary Four hundred sesame (Sesamum indicum L.) lines selected by five methods from five crosses were tested for yield and other agronomic characters in F₆ and F₇. More high yielding lines were isolated by the bulk method and in the cross involving two local cultivars when two seasons means and performance in each individual season were considered. The cross involving two exotic cultivars did not produce a single line superior to local recommended variety. The 80 highest yielding lines recorded a 10.8% increase in yield compared to the mean of 400 lines. Thirty five lines were among the top 20% both seasons with a 13.2% increase in yield. Highly significant seasonal and population effects were recorded. There were no significant differences among the methods of selection although the yield differences among lines were highly significant. Interactions of seasons × populations, seasons × methods, populations × methods and seasons × populations × methods were highly significant. The results indicate that simple and less expensive bulk method may be used with equal success as the pedigree, single seed descent or early generation testing methods when selecting for yield in segregating sesame populations. The importance of inclusion of a high yielding, locally adapted cultivar in the crossing programmes for yield breeding of sesame has also been revealed.Abbreviations BM Bulk method - EGT Early generation testing - G × E Genotype × environment - MSS Modified single seed descent - PM Pedigree method - SSD Single seed descent     

Comparative efficiency of honeycomb and conventional pedigree methods of selection for yield and fiber quality in cotton (Gossypium spp.)

The effectiveness of honeycomb pedigree selection (HPS) as compared to conventional pedigree selection (CPS) was studied in one intraspecific (G. hirsutum L. × G. hirsutum L.) cross population (population I) and one interspecific (G. hirsutum L. × G. barbadense L.) cross population (population II). Combined selection for yield and lint quality traits was applied for four cycles at two locations for population I and atone location for population II. Finally, the best F₆ lines derived by each method, together with the unselected population derived by single seed descent (SSD) and three check cultivars, were tested in comparative experiments, separately for each cross, at the same locations. In both populations the analysis of variance indicated significant differences among the groups of the material tested for seed cotton yield, mean boll weight, micronaire reading, staple length, and uniformity ratio. No significant differences were found with respect to plant height, lint percentage, and fiber strength in population I and with respect to lint percentage and fiber strength in population II. In population I, on the basis of mean seed cottonyield and number of superior lines derived by each method as compared to the check varieties and the unselected SSD population, HPS-lines were superior to CPS-lines for seedcotton yield, fiber length and boll weight. HPS-lines, however, did not differ significantly in seedcotton yield from the best check cultivar Eva. Finally, the material derived by CPS was earlier in maturity than the material derived by HPS and SSD. Also in population II, on the basis of mean seedcotton yield and number of superior lines derived by each method as compared to the unselected SSD population, HPS-lines were superior to CPS-lines. No significant differences, however, were identified between the material of the two methods for lint quality traits. It was concluded that in both populations HPS was more effective than CPS in identifying lines with high yielding ability and good lint quality. This superiority of HPS is attributed, at least partially, to its effectiveness in early generation selection. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effectiveness of early generation (F3) yield testing and the single seed descent procedures in two cowpea (Vigna unguiculata (L.) Walp.) crosses

Summary Two breeding procedures were compared in two cowpea crosses. Both procedures were started from the same selected F₂ plants in each cross. For the early generation yield testing, the F₃ lines were yield tested and a pedigree and bulk methods followed in F₄ and F₅. Each F₅ line was bulked to provide seed for a yield test in F₆. In the Single Seed Descent (SSD) procedure, a single seed was taken from each F₂ plant to produce the F₃ generation. The procedure was repeated for the F₄ and F₅. The F₆ SSD lines and the F₆ yield testing lines were compared in yield tests.The results showed that differences in yielding ability of F₃ lines persisted over generations indicating that selection was effective. This was confirmed by the high significant correlations between F₃ yields and those of later generations which ranged from r=0.51^* to 0.85^**.The grain yields of lines derived by the single seed descent procedure were as good as those derived from early generation yield testing.Significant linear correlation between visual rating of F₃ and F₆ yields with actual yields revealed that it is possible to identify promising lines of cowpea visually.     

Improvement of large-seeded common bean cultivars under sustainable cropping systems in Spain

Approaches are needed to broaden the genetic base and improve earliness and yield potential of large-seeded beans under sustainable cropping systems. The objective of this research was to develop adapted dwarf bean populations having a commercial seed quality and yield suitable for the production in the South of Europe. The original base populations were produced from crosses between genotypes within each Mesoamerica, Nueva Granada and Peru races, and between Peru and Nueva Granada, and Mesoamerica and Nueva Granada races. Visual mass selection for plant performance was practised in the F₂ and F₃ generations. In the F₄ and F₅, single plants were harvested under two cropping systems (sole cropping and intercropping with maize). From F₄, selection was based on precocity, combined with seed yield and seed commercial type. The F_4:7 selected lines from each original population were compared with their parents and five checks at four environments and two cropping systems. Differences among environments, populations, parents and checks were observed for all traits. Under intercropping with maize, there was a 50% reduction in seed yield. Yield of parents and checks belonging to Andean South American races, intraracial (Nueva Granada × Nueva Granada) and interracial (Nueva Granada × Peru) populations, was higher than that of those of Middle American origin. Intraracial crosses within large-seeded Andean South American (Peru race) and Middle American gene pools (Mesoamerica race) did not produce lines yielding more than the highest yielding parent. Only two large-seeded lines selected from crosses between small- and large-seeded gene pools out-yielded the best parent and check cultivar.     

Direct and indirect selection for yield in chickpea

Summary The efficiency of indirect selection for seed yield was compared with direct selection for yield per se in chickpea. A total of 2500 single F₂ plants, derived from 50 crosses with 50 plants from each cross, were divided into five sub-populations (SP1 to SP5) of 500 plants each by including 10 plants from each of the 50 crosses. The five sub-populations were advanced upto F₆ by exercising 10% selection intensity for four successive generations for number of pods per plant in SP1, number of seeds per pod in SP2, seed weight in SP3, seed yield in SP4 and random selection in SP5. The efficiency of direct and indirect selection for yield was evaluated by comparing groups of 50 F₆ lines from each sub-population. SP1 and SP3 F₆ lines showed higher mean grain yield than the other three methods. SP1 and SP3 were found to be almost equally efficient in developing F₆ lines which were significantly superior to the check. This suggests that indirect selection for yield via pod number and seed weight is more efficient than direct selection for yield.     

Heterosis and epistasis in rapeseed estimated from generation means

Summary Heterosis and epistasis in spring oilseed rape (Brassica napus L.) was analysed by comparing generation means for ten agronomic traits. Parents, F₂, F₃ and F₆ generations of four crosses with Swedish and French material were investigated. The F₂ was 11% higher in yield, earlier in flowering time, and slightly later in maturation when compared with the parents. Randomly derived single seed descent lines had an 8% lower yield, were later flowering and maturing than the parents in F₆. This poorer average performance of recombinant lines is explained by the loss of favourable epistatic interactions present in the parents.     

Comparison of heritabilities derived from single F2 seed populations and bulk seed from F2 plant populations for oleic,linoleic and linolenic acids in oilseed rape

Summary The heritabilities for oleic, linoleic and linolenic acids in oilseed rape (Brassica napus) were determined using single F₂ seeds on F₁ plants and bulk seed samples of F₂ plants. The heritabilities by the use of single F₂ seeds were found to increase, remain constant, or decrease relative to those obtained from F₂ plant populations, depending on the fatty acid and the cross. However, the change in heritabilities was not great in most cases. Therefore the half-seed technique could be used for early generation selection for these fatty acids.     

Effect of plant density on selection for seed yield in two population types of Phaseolus vulgaris L.

Summary Pedigree selection for seed yield, using early generation yield tests, was practiced from the F₂ to F₇ in two populations of common bean (Phaseolus vulgaris L.) in three plant densities: 66, 133, and 266 thousand plants ha^-1 at CIAT-Palmira, Colombia. The six highest yielding lines selected from each plant-density, along with 13 parents, were evaluated in a 7×7 lattice design with three replications at the three densities utilized for selection, and at 399,000 plants ha^-1 in 1988 and 1989.Based on the mean performance of selected lines and the mean of the parents, selection for seed yield was effective in all densities in both populations. However, none of the lines selected from the population within the race Mesoamerica (TC 4673) significantly outyielded their best parent under any plant density. The highest yielding lines selected from the interracial population (TR 4635) outyielded their best parent irrespective of the plant-density used for selection. The highest yielding line originated from the highest density used for selection. Low density was neither good for selection nor for evaluation and identification of high-yielding cultivars of common bean. There was no significant difference between the mean yield of lines selected at the intermediate and high population densities. The effects of plant density, year, and their interactions were significant for seed yield.     

Mass selection for seed width in oat populations

Heterogeneous and segregating oat populations subjected to no selection and to mass selection for seed width for five consecutive generations were evaluated for 100-seed weight, heading date and plant height.The mass-selection technique, which consisted of passing the seeds over a screen with 12.7×2.4 mm slots and propagating the seeds too wide to go through the slots, was repeated for five consecutive generations (F₃ through F₇). Comparable unselected populations were grown each year. Remnant seeds from each check and mass-selected population were stored for future studies.In 1963, 500 random seeds from each of the six unselected populations (F₂ through F₇), from each of the five mass-selected populations (F₃ through F₇) and from a pure line were space-planted in the field. In 1964, the progenies from 75 random strains (a strain was the progeny of one spaced plant) from each of the 12 populations were sown in a randomized-block experiment with three replicates. In 1966, the strains from the last (F₇) generation of the unselected and mass-selected lines of descent (75 strains from each) were tested for yield in a 7-replicate randomized block experiment.The mass-selection technique increased the mean 100-seed weight, whereas in the unselected line of descent, the mean 100-seed weight did not change. The mean heading dates became later and the mean plant heights taller with the mass-selection procedure. The mean yield of the final mass-selection population was nine percent higher than that of the comparable unselected population.In spite of the associated changes between 100-seed weight and plant height and heading date in successive generations; the genotypic correlations among strains within populations indicated that these three traits were inherited independently. In advanced generations (F₆ and F₇), the genotypic variances for heading date and 100-seed weight were reduced in both the unselected and mass-selected lines of descent, whereas, for plant height no significant change occurred in either.Journal No. J-5586 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa, Project 1176. In cooperation with the Crops Research Division, Agricultural Research Service. U.S. Department of Agriculture.Professor of Plant Breeding.     

Selection for seed yield in Andean intra-gene pool and Andean × Middle American inter-gene pool populations of common bean

Yields of large-seeded Andean (A) common bean (Phaseolus vulgaris L.) cultivars of Chile and Nueva Granada races are 40 to 60% lower compared to their Middle American (M) counterparts of small-seeded Mesoamerica and medium-seeded Durango races. Our objective was to use the concept of congruity backcrossing between Andean x Middle American inter-gene pool [AM 11833 = A 483 (A)///// A 686 (M) //// PVA 800A(A)/// ‘Carioca’ (M)// Carioca (M)/ G 19833 (A)] and between races within Andean gene pool [i.e., intra-gene pool Andean, AA 11834 = A483 (A)//// ‘Cardinal’(A) /// ‘Blanco Español’(A) // BlancoEspañol (A) / ‘Taylor’ (A)] to compare selection for seed yield improvement of large-seeded Andean beans. Seven hundred sixty seven F₂-derived F₃ (F_2:3) families were produced for each population. Visual appraisal for total plant performance, combined with seed yield from non-replicated plots was used for selection of 551 families in F_2:3, 182 families in F_2:4, and 91 families in F_2:5 in each population. Eight hundred twenty three F_5:6 lines were developed from the 91 F_2:5 families in each population. Visual selection, combined with seed yield in non-replicated plots was again used to select 294 lines in F_5:6 in each population. Similarly, 44 highest yielding F_5:7 lines were selected in AM 11833 and 39 F_5:7 lines in AA 11834. Thus, single plant selections were made in the F₂ and F₅, and plants within each plot were harvested in bulk in F₃, F₄, F₆, and F₇. Thirty nine F_5:8 lines from AA 11834 and 44 lines from AM 11833, parents, and checks were evaluated at Popayán and Quilichao, Colombia in 1998 and 1999. Selected lines in both populations, on average, out-yielded the mean of their large-seeded Andean parents. Mean yield of the lines selected from AM 11833 was 50% higher than AA 11834 lines. Twelve F_5:8 lines out-yielded the highest yielding Andean parents G 19833 and A 483 in AM 11833, whereas only one line yielded significantly higher (p < 0.05) than the highest yielding parent A 483 in AA 11834. However, none of selected lines out-yielded small-seeded Middle American parents used in AM 11833 (A 686 and ‘Carioca’). The mean 100 seed-weight of AA 11834 was 36 g compared to 28 G for AM 11833 F_5:8 lines. Selected lines had similar days to maturity as parents in AM 11833, and matured 3 d later in AA11834. Correlation coefficients between yield and 100 seed-weight were negative in both populations. Yield and days to maturity were positively correlated in AA 11834.     

Evaluation of microspore-derived embryos as models for studying lipid biosynthesis in seed of rapessed (Brassica napus L.)

Summary Microspore culture of rapeseed (Brassica napus L.) has provided a powerful tool not only for breeding but also in developmental studies. In this study, microspore-derived embryos (MDE) of B. napus were evaluated as a model in seed for studying accumulations of triacylglyceride (TAG) fatty acids in both a low and high erucic acid rapeseed line; and accumulations of TAG and free fatty acids (FFA) in a high erucic acid rapessed line. The accumulation patterns confirmed that MDE had a similar TAG fatty acid profile to seed during the embryo development within each genotype. The oil accumulation in MDE after 36 days in culture (DIC) approached levels similar to those in zygotic seed 25 days after flowering (DAF). Significant differences were detected in contents of both total free fatty acids and specific free fatty acids between MDE and seed. During the developmental period, total free fatty acids changed from 16% to 2.1% in MDE, but from 10.5% to 0.1% in seed. MDE had much higher percentage of free linolenic and erucic acids than seed, particularly during the late developmental stages. The current study indicated that MDE can be used as a model to study TAG and TAG fatty acids in seed but caution must be taken to study free fatty acid metabolism.     

Segregation of 12 isozyme genes among doubled haploid lines derived from a japonica x indica cross of rice (Oryza sativa L.)

Summary The segregation of 12 heterozygous isozyme markers was analyzed among F₂ plants and 51 anther culture (AC)-derived lines obtained from the japonica × indica cross of rice, IRAT 177 × Apura. All the lines except two were homozygous products of recombination of the two parental phenotypes. Doubled haploid (DH) lines derived from plants regenerated from the same callus were identical, confirming previously obtained results in rice. Surprisingly, some lines derived from different calli were also identical, suggesting a phenomenon of early callus fragmentation. All these observations at the isozyme level were confirmed by field evaluation. Deviations of segregations from the expected 1 : 1 ratio were observed at 4 loci among the DH lines. Among these, two were also noted among the F₂ plants. The two other distortions, both in favor of the japonica allele, were observed specifically in the AC-derived materials.Although this concerns a small proportion of the genes under study, it suggests that the embryogenic microsporal population does not represent a random gametic array. On the other hand, evaluation of recombination between isozyme genes located on chromosome 6 appears consistent with F₂ data and data previously recorded on the other japonica × indica crosses. The potential use of isozymes in breeding doubled haploids derived from remote crosses in rice is discussed.Abbreviations MCPA = 2-methyl-4-chlorophenoxyacetic acid - IAA = indolacetic acid - AC plant or line = anther culture-derived plant or line - DH line = doubled haploid line     

Embryonic heterosis in the linolenic acid content of Matthiola incana seed oil

Summary The fatty acid composition of seed-oil of breeding lines and F₁ hybrids of Matthiola incana was analyzed, using direct esterification and gas chromatography. The breeding lines tested differed significantly with respect to the levels of palmitic, oleic, linoleic and linolenic acids. Embryonic-stage heterosis in linolenic acid concentration was demonstrated by F₁ hybrid seeds, derived from mating horticulturally different lines of M. incana. Linolenic acid content was negatively correlated with both oleic acid content (r=–0.85) and linoleic acid content (r=–0.66). None of the breeding lines or the F₁ hybrids significantly passed the limit of 67% linolenic acid. Possible genetic and biochemical explanations for the above phenotypic data are discussed.     

Inheritance of ‘domestication’ traits in bambara groundnut (Vigna subterranea (L.) Verdc.)

Controlled crosses in bambara groundnut were attempted between a range of thirty-six bambara groundnut landraces (thirty domesticated (V. subterranea var. subterranea) and six wild (V. subterranea var. spontanea)). Ten F₁ seed were produced. Of these, eight germinated producing F₂ populations. On seed set, four populations could be unambiguously confirmed as true crosses by F₃ seed coat colour. A single F₂ population, derived from a domesticated landrace from Botswana (DipC; female parent) crossed with a wild accession collected in Cameroon (VSSP11; male parent) was used to study a range of agronomic and domestication traits. These included; days to emergence, days to flowering, internode (fourth) length at harvest, number of stems per plant, leaf area, Specific Leaf Area (SLA), Carbon Isotope Discrimination (CID), 100 seed weight, testa colour and eye pattern around the hilum. On the basis of variation for internode length and stems per plant, 14 small F₃ families were selected and grown under field conditions to further investigate the genetic basis of the ‘spreading’ versus ‘bunched’ plant character, a major difference between wild and cultivated bambara groundnut. Results presented suggest that traits including leaf area, SLA, CID and 100 seed weight are controlled by several genes. In contrast, the variation for traits such as internode length, stems per plant, days to emergence and seed eye pattern around the hilum are likely to be under largely monogenic control. The results of this work are discussed in relation to the domestication of bambara groundnut.     

Evaluation of Pedigree and Single Seed Descent Selection Methods for Cultivar Development in Cowpea (Vigna unguiculata L. Walp)

Three crosses of cowpea (Vigna unguiculata [L.] Walp) were used to assess the effectiveness of two selection procedures in cowpea. The selection procedures were pedigree selection (PD) and single seed descent selection (SSD). Lines developed through each procedure were yield tested and selected at F₆ and F₇ for PD and SSD, respectively. The selected lines for both procedures were compared at F₈ for grain yield per plant (YLD), number of pods per plant (NPO), and pod development period (PDP), in two locations. Lines developed through both procedures differed more in their population means than in the performance of their top 10% or highest yielding lines. There was no consistent relationship between magnitude of genetic variability and percentage of superior lines obtained from each procedure. Both procedures have been effective in producing superior genotypes for yield and number of pods. The PD method produced superior transgressive segregants in two out of the three crosses for PDP. SSD allowed a more rapid generation than PD.     

Comparison of pedigree selection and single seed descent for oil yield in linseed (Linum usitatissimum L.)

Summary Four populations of linseed derived from five parents were advanced from the F₂ to the F₆ generation by SSD and to the F₅ by pedigree selection. These populations were used to compare the efficiency of the two methods in order to provide superior genotypes with respect to grain yield and oil content, i.e. oil yield. The results showed minimum differences between pedigree and SSD lines for grain yield, where in only one cross the SSD lines were significantly superior to the pedigree lines. Since pedigree selection was carried out for both, seed yield and oil content, a positive response to selection was expected. However, early selection for yield, a character with low heritability, was not successful. On the contrary, significant differences for oil content were detected between the two groups of lines in three of the four crosses studied. In these cases the pedigree lines were superior to the SSD lines. These results demonstrate that strict selection in early generations for oil content, a character with comparatively high heritability, is feasible and successful in linseed. However, selection for seed yield should be postponed to later inbred generations. Consequently, in breeding for maximum oil yield of linseed a two-step selection procedure is recommended.Abbreviations PS pedigree selection - SSD single seed descent - TGW thousand grain weight     

Breeding the common bean (Phaseolus vulgaris L.) for resistance to bean common mosaic virus: alternatives to backcrossing

A series of field experiments was undertaken in order to determine whether resistance to bean common mosaic virus (BCMV) could be incorporated into genotypes of the common bean (Phaseolus vulgaris L.) suitable for cultivation in Zimbabwe without recourse to backcrossing. Six inbred genotypes carrying the resistance-conferring alleles at the loci I and Bc-3 were crossed with five locally-adapted inbred genotypes. The first experiment comprised F₃ progeny rows, each derived from a single unselected F₂ plant, the second, F₃ bulks selected for resistance, and the third, a comparison of selected and unselected F₂-derived F₄ lines. The number of days to flowering and to maturity, the incidence of mosaic and necrosis symptoms, seed yield and seed size were recorded. There was evidence that late flowering and maturity were associated with BCMV resistance in some crosses, though not strongly enough to present an obstacle to plant breeding. The incidence of virus symptoms and seed yield were influenced by genetic factors additional to the major resistance genes, and variation in seed yield was present not only between bulk populations of crosses, but also between single-row plots of lines within crosses. This indicates that early-generation selection for yield in the presence of BCMV, even among progeny selected for BCMV-resistace, is likely to be effective. However, the variation in yield among F₄ lines was least in the highest-yielding crosses, which may represent a limit to successful selection for yield. Seed size was partly under additive genetic control, but there was also evidence of non-allelic interactions. There was no association between large seed size, preferred by consumers, and susceptibility to BCMV in the progeny, indicating that the association between these characters in the parent lines is fortuitous and will not present an obstacle to plant breeding. It is noted that a considerable amount of useful genetic information can be obtained without recourse to elaborate crossing schemes, provided that unselected progeny are included in experiments as controls. The evidence presented indicates that resistance to BCMV can be combined with appropriate values of maturity date, yield and seed size without the need for backcrossing.     

Phenotypic distribution of barley SSD lines and doubled haploids derived from F1 and F2 hybrids

Summary The doubled haploid (DH) system and the single seed descent (SSD) technique are frequently applied in breeding of self-pollinated crops to rapidly obtain homozygous lines from heterozygous hybrids. This study presents a comparison of populations of barley DH and SSD lines in terms of traits of stem structure. The SSD and DH lines derived from F₁ and F₂ hybrids Roland x Apex were examined in a field experiment. On the basis of a comparison of means, variances and correlations between traits in the F1DH, F2DH and SSD populations the occurrence/absence of linkage between genes responsible for the analysed traits was inferred. Independent inheritance was found for 1000-grain weight and the length of particular internodes, spike length and stem wall thickness. Moreover, no linkage was found for stem wall thickness and spike length, length of internodes I, II and thickness of stem walls, stem diameter and thickness of stem walls. The results obtained for the other pairs of traits indicate the presence of linkage.     

Association of isozyme markers with quantitative trait loci in random single seed descent derived lines of lentil (Lens culinaris Medik.)

Summary Polymorphism at isozyme loci was used to locate factors responsible for variation in quantitative traits of lentil. Eight sets of random single seed descent (RSSD) derived lines were developed by advancing individual F₃ plants of interspecific (L. culinaris Medik. × L. orientalis Boiss.) hybrids to the F₆. The RSSD lines in each of the eight sets differed for alleles at 2–8 isozyme loci. In each set, association of isozyme loci with variation in seven quantitative traits (days to flower, days to mature, plant height, biomass, seed yield, harvest index, seed weight) was determined for each pairwise combination of a quantitative trait with a marker locus. Loci affecting variation in all seven quantitative traits were detected by their association with 14 isozyme markers (Aat-c, Aat-m, Aat-p, Adh-1, Fk, Gal-1, Gal-2, Lap-1, Lap-2, Pgd-p, Pgi, Pgm-c, Pgm-p, Skdh). The known position of 10 the 14 isozyme loci on the lentil genetic map was used to mark the genomic regions for possible location of associated quantitative trait loci (QTL). Detected QTL were found to be located in six of the seven linkage groups on lentil genetic map. Regions of the genome represented by linkage groups, 1, 5 and 7 appeared to affect a greater number of traits than other genomic regions represented by linkage groups 2, 3 and 4. Results indicated that the mean expression of quantitative traits at segregating marker locus classes can be used to locate the genetic factors in lentil which influence the behavior of economically important traits.     

Identification of Genes Controlling Pod Length in Spring Rapeseed, Brassica napus L., and their Utilization for Yield Improvement

Experiments were undertaken to determine the inheritance of pod length in a cross with spring rapesecd, Brassica napus, and to assess the value of pod length as a criterion of selection for high seed yield. Analyses of patterns of variation in F₂; and backcross populations derived from a cross between a short-pod line TB42 and long-pod line CA553 indicated that much of the variation in pod length could be attributed to two major genes interacting in a complementary manner. Short-pods were produced when cither one or both genes were homozygous for the recessive allele. Analyses of F₃ progenies of selected F₂ and inbred-backcross lines derived from the same cross supported the two-gene hypothesis but also indicated that the effects of the major genes on pod length were possibly modified by genes of minor effect. Field testing of families derived from random intermating between F₂, plants of the TB42 × CA553 cross showed that number of pods per plant varied independently of pod length, but seed weight per pod tended to increase with increasing pod length. As a result, families with the longest pods generally had significantly higher yields than those with short pods. It was concluded that yield improvement in B. napus could be achieved through introgression of long-pod genes into cultivars with an appropriate genetic background to ensure that selection for the long-pod character would be accompanied by an increase in seed weight per pod with little or no reduction in number of pods per plant.