Genetic study of bolting and stem length in sugar beet (Beta vulgaris L.) using a factorial cross design

Summary The objective was to study the genetic basis of bolting and stem length in sugar beet full-sibs, developed by a factorial mating design (N.C. design II). The extent to which the inheritance of these characters can be attributed to the additive and non-dominance variation was investigated. The genetic analysis consisted of three sets (4×10, 4×8, and 3×8) of progenies. Estimates of additive genetic variance (² _A) and variance due to dominance deviations with some fractions of epistatic variance (² _D) were obtained for both characters. Bolting had a relatively large proportion of total genetic variance accounted for by ² _A. In most cases, non-additive effects were also important in determining the type of gene action in bolting. Stem length showed similar genetic variation to bolting susceptibility. Bolting resistance seemed to be dominant to the bolting susceptibility in most cases. Narrow sense heritability estimated for bolting was generally very large (0.93 to 0.96), which suggests that early generation selection for bolting resistance in a sugar beet population would be successful.     

Genetic analysis of yield attributes inCocos nucifera L. Var. West Coast Tall

Summary The variance components analysis of characters influencing productivity in six yield groups of coconut in three sets of crosses has revealed that there is substantial additive genetic variation available for selection for yield and other associated characters like number of female flowers and percentage set as estimated by the relative sizes of _g ², _s ² and _e ². The general combining ability of the higher yield groups is considerable for number of bunches, number of female flowers, yield of nuts but is limited for percentage set. The presence of interaction between yield groups and category of crosses and the extent of non-additive genetic variation as revealed by the magnitude of _s ² indicate the necessity of maintaining substantial heterozygosity within each population. Since high yielders will be proportionally low in any unselected population, the limited diversity within these groups can be better utilized by interplanting them with similar phenotypes of diverse origin, to prevent inbreeding in their progenies and to maintain heterozygosity within the population.The results have demonstrated the stability of the superiority of high yielding groups even in poor environment. In a more favourable environment with higher doses of fertilizer, the difference between the top two yield groups and the rest could possibly be larger. Therefore, choice of mother palms with high yield either for crossing purposes or for progeny testing appear to be reliable, provided that there is sufficient genetic diversity within the population.     

A procedure for combining a quantitative inheritance study with the first cycle of a breeding program

Summary The number of effective factors controlling the inheritance of a quantitative character can be estimated by analysis of F₃ lines where the parental lines are homozygous. The procedure is illustrated with data from a study of pod length inheritance in common bean (Phaseolus vulgaris L.). The mean pod length of Sprite, the parent with longer pods, was compared statistically with the means of F₃ progenies derived from F₂ plants obtained from the appropriate tail of the F₂ frequency distribution for pod length. The data indicate that analysis of F₃ progenies avoids much of the underestimation of the effective factor number which is characteristic of other procedures. The number of effective factors was estimated to be a minimum of 4 and the correlation between random F₂ parents and F₃ progeny means was r=0.82.Florida Agricultural Experiment Station Journal Series No. 406.     

Quantitative genetic analysis of erect glandular trichome density in diploid alfalfa

The presence of glandular trichomes may protect alfalfa (Medicago sativa L.) against certain stem-, leaf-, and fruit-eating insect pests. In order to determine appropriate breeding methods to select for this trait, this study characterized quantitative genetic parameters of erect glandular trichome density in `KS94GH6' diploid (2n=2x=16) alfalfa. Eight female and five male plants were crossed in a Design II mating to produce 40 full-sib families. Glandular trichome density was determined on these families under replicated greenhouse conditions in Las Cruces and Los Lunas, New Mexico, U.S.A. The effect of males was significant (p 0.10) across the two environments. Variation among females was not significant within either location or across locations. The dominance genetic variance (<sup>2</sup> <sub>D</sub> = 0.210) was greater than the additive genetic variance (<sup>2</sup> <sub>A</sub> = 0.111). The average degree of dominance exceeded a value of `1' indicating that erect glandular trichome density in KS94GH6 may be influenced by digenic epistasis, and/or repulsion phase linkage disequilibrium. The large contribution of non-additiveeffects was reflected by a low narrow-sense heritability estimate (h ² _n = 0.25). The results indicate that further improvements in erect glandular trichome density in KS94GH6 alfalfa will require replicated progeny testing. Approaches to introgress this trait into cultivated tetraploid alfalfa are discussed.     

The effect of the ‘Golden Promise’ dwarfing gene on partial resistance to leaf rust and powdery mildew in spring barley

Summary F₂-plant progenies, derived from seven crosses between susceptible erectoides breeding lines and conventional, nutans breeding lines with partial resistance to leaf rust incited by Puccinia hordei Otth., derived from Vada x Cebada Capa, were examined in a field and a glasshouse experiment. In the field experiment, the nutans plant progenies generally were more resistant to leaf rust and powdery mildew than the erectoides progenies. In the glasshouse experiment, the components of partial resistance to leaf rust of six erectoides and six nutans progenies derived from one cross were studied. The nutans progenies generally had lower infection frequencies than erectoides progenies with a similar infection level in the field experiment. The variation for leaf rust and powdery mildew infection in the field was similar for the nutans and erectoides progenies. This suggests that erectoides lines with a fairly high level of partial resistance to leaf rust and powdery mildew can be selected from these populations.     

Inheritance of quality traits in processing tomato (Lycopersicon esculentum Mill.)

Summary The genetic basis of pH, colour and soluble solids in processing tomato is examined. In a first experiment, aimed at identifying the base populations with which to start selection, parents, F₁ and F₂ progenies of an 8 × 8 diallel cross without reciprocals were tested.The results indicate that additive, dominance and additive x additive epistatic effects were noticeable for the three characters. Higher order interlocus interactions were also detected.As to the soluble solids, a trait for which higher order epistatic effects were less marked, the breeding potential of the cross combinations was assessed by calculating the expected mean values at the F generation. Some cross populations having C33 or C35 as parent appeared to be superior.A second experiment was conducted to collect data on the heritability of the foregoing qualitative traits by utilizing the regressions of F₃ offspring on F₂ parents. The low heritability coefficients observed would suggest the ineffectiveness of individual selection in early generations.In both the F₂ and F₃ generations rather low correlation coefficients among the three quality traits were observed.     

RAPD markers linked to resistance to downy mildew disease in soybean

To determine and utilize RAPD markers linked to resistance to downymildew incited by Peronospora manshurica in soybean, a resistantcultivar `AGS129' was crossed to a susceptible cultivar `Nakhon Sawan 1'(NS1). F₂ and BC₁ populations were advanced from the F₁ and evaluatedfor resistance to the disease. ²-test demonstrated that the resistancewas controlled by a single dominant gene (Rpmx). Near-isogenic lines(NILs) and bulked segregant analysis (BSA) were used to identify RAPDmarkers linked to the gene. Six DNA bulks namely F₅(R), F₅(S),BC₆F₃(R), BC₆F₃(S), F₂(R) and F₂(S) were set up by pooling equalamount of DNA from 8 randomly selected plants of each disease responsetype. A total of 180 random sequence decamer oligonucleotide primerswere used for RAPD analysis. Primer OPH-02 (5 TCGGACGTGA 3 andOPP-10 (5 TCCCGCCTAC 3) generated OPH-02₁₂₅₀ and OPP-10₈₃₁fragments in donor parent and resistant bulks, but not in the recurrentparent and susceptible ones. Co-segregation analysis using 102 segregatingF₂ progenies confirmed that both markers were linked to the Rpmxgene controlling downy mildew disease resistance with a genetic distance of4.9 cm and 23.1 cm, respectively. Marker OPH-02₁₂₅₀ was presentin 13 of 16 resistant soybean cultivars and absent in susceptible cultivars,thus confirming a potential for MAS outside the mapping population.     

Inheritance of seed coat colour in broad bean (Vicia faba L.)

Summary The inheritance of the seed coat colours violet, spotted, brown, green, red, black and beige was investigated in a 10×10 diallel cross between broad bean (Vicia faba L. major) lines. Spotted seed colour was dominant over any uniform seed coat colouring. Brown was dominant over black, green and normal (beige colour). Black and red seed parents behaved as recessive in all F₁ progenies. A 3 (coloured): 1 (normal) segregation ratio was observed in the F₂ of crosses of violet, brown, black, red and spotted seed coat parents to nornal seed coloured parents. Green x beige gave a segregation ratio of 9:7 in F₂. When two parents with different seed coat colour were involved in a cross, the F₂ showed a typical digenic segregation ratio thus demonstrating two unlinked and sometimes epistatic loci.Segregation of a multiallelic series at two loci explains all segregation ratios observed for seed coat colour in broad bean.     

Productivity of F hybrids of botanical varieties ofBrassica oleracea L.

Summary F₁ hybrids were obtained by making pair-crosses between nine botanical varieties ofBrassica oleracea. Although non-inbred parents were used, their yield was surpassed by all F₁ hybrids. The highest yields were shown by the crosses marrow-stem kale × sprouting broccoli and marrow-stem kale × cauliflower while the highest consumable yield (assessed by feeding plants to sheep) was that of F₁ hybrids marrow-stem kale × cauliflower and wild cabbage × cauliflower. A scheme for the production of F₁ hybrid seed is suggested, based upon an adaptation ofThompson's (1964) Triple-cross technique.     

Genetic nature of low capsaicin content in the variant strains induced by grafting in Capsicum annuum L.

Summary The genetic nature of low capsaicin content in variant strains induced by grafting was elucidated by crossing the G₅S₂₃ strain with the two cultivars, Yatsubusa (Capsicum annuum L. var. fasciculatum Ilish) and Spanish Paprika (C. annuum L. grossum Sendt) originally used for grafting. Decreased capsaicin synthesis was a stable characteristic for at least several generations from G₅S₁₆ to G₅S₂₃ and was transmitted to the progenies of crosses. This fact shows that the decreased capsaicin synthesis is a genetic trait in the graft-induced variant strains. The genetically dependent characteristic of pungency of the G₅S₂₃, Yatsubusa and Spanish Paprika were analysed by High Perfomance Liquid Chromatography measurement and tasting assay.Cross experiment between the G₅S₂₃ strain, hot parent Yatsubusa and sweet parent Spanish Paprika showed that pungent and sweet for pungency chracteristics are generally controlled by at least two pairs of genes. Although segregation of capsaicin content and pungency was clearly demonstrated in F₂ progenies from reciprocal crosses between the G₅S₂₃ strain and Spanish Paprika, F₂ progenies from reciprocal crosses between G₅S₂₃ and Yatsubusa were all hot and did not develop low capsaicin plants.     

Inheritance of neurotoxin (ODAP) content, flower and seed coat colour in grass pea (Lathyrus sativus L.)

Summary A strong epidemiological association is known to exist between the consumption of grass pea and lathyrism. A neurotoxin, -N-Oxalyl-L-, -diaminopropanoic acid (ODAP) has been identified as the causative principle. This study was undertaken to investigate the mode of inheritance of the neurotoxin ODAP, flower and seed coat colour in grass pea. Five grass pea lines with low to high ODAP concentration were inter-crossed in all possible combinations to study the inheritance of the neurotoxin. Parents, F₁ and F₂ progenies were evaluated under field condition and ODAP analyzed by an ortho-phthalaldehyde spectrophotometric method. Many of the progenies of low x low ODAP crosses were found to be low in ODAP concentration indicating the low ODAP lines shared some genes in common for seed ODAP content. The F₁ progenies of the low ODAP x high ODAP crosses were intermediate in ODAP concentration and the F₂ progenies segregated covering the entire parental range. This continuous variation, together with very close to normal distribution of the F₂ population both of low x low and low x high ODAP crosses indicated that ODAP content was quantitatively inherited. Reciprocal crosses, in some cases, produced different results indicating a maternal effect on ODAP concentration. Blue and white flower coloured lines of grass pea were inter-crossed to study the inheritance of flower colour. Blue flower colour was dominant over the white. The F₂ progenies segregated in a 13:3 ratio indicating involvement of two genes with inhibiting gene interactions. The gene symbol LB for blue flower colour and LW for white flower colour is proposed.     

Genetics of resistance in the wheat cultivar chhoti lerma against stem rust race 122

Summary Genetics of rust resistance against stem rust race 122 in Chhoti Lerma was studied both by conventional and aneuploid analysis. Observations on F₁, F₂ and F₂ backcross progenies revealed the operation of two recessive genes, controlling resistance in Chhoti Lerma. Monosomic analysis confirmed the operation of two recessive genes conferring resistance to race 122 located on chromosomes 1D and 7D. A minor gene or modifier was also located on chromosome 1B. This was concluded from the fact that F₂ of mono's x Chhoti Lerma exhibited skewness in favour of resistant plants.     

Perspectives of molecular marker assisted breeding for earliness in tomato

In a tomato (Lycopersicon esculentum) breeding programme aimed at earliness, a breeding line, designated IVT-KT₁, was developed by several rounds of crossing and selection. Among its ancestors were the two wild relatives L. pimpinellifolium and L. parviflorum. The breeding line flowered and set fruit one to four weeks earlier than old and modern cultivars. To identify QTLs for earliness, an F₂ population was obtained by crossing IVT-KT₁ with the late true breeding cultivar Premier. In winter and early spring, 690 plants of this F₂ population were evaluated for earliness of which 292 were selected for RFLP analysis. Only limited parts of the genomes of IVT-KT₁ and Premier were polymorphic and these polymorphisms were likely due to introgression from the ancestor wild species. By using the interval mapping method on the combined data of the greenhouse evaluations and RFLP analyses, three loci were identified that were associated with earliness. One was mainly associated with flowering time, another with fruitset time and a third one with ripening time. Two of these loci were also associated with fruit weight. F₃ progenies selected for earliness on the basis of the QTL-data did confirm the F₂ results. Two major earliness genes explained a difference in earliness of more than three weeks. The association with reduced fruit weight seemed to be due to pleiotropic effects rather than to linked genes. Consequently, the gain in earliness will cause a reduction in fruit weight that may not be acceptable for breeding applications.     

A recurrent selection programme for grain yield in winter barley

Summary The effect of a recurrent selection procedure was evaluated in a winter barley (Hordeum vulgare L.) population. Cycle zero (C₀) was initiated by crossing six high yielding winter barley cultivars with the short straw cv Onice. The F₁'s were crossed according to a diallel scheme without reciprocals. A total of 750 S₀ plants were derived and evaluated; 329 S₀ plants were selected and their progenies (S₁ lines) tested. Fifteen S₁ lines were chosen and used as parents of cycle 1 (C₁), by producing 105 F₁ hybrids which simulated a random mating offspring. One hundred and three randomly chosen S₁ lines belonging to C₀, and 103 S₁ lines belonging to C₁, were evaluated at two locations.For grain yield a significant difference between cycles was observed. From C₀ to C₁ the grain yield increased with 307 g/m². This increase was due to a higher number of seeds per m². For plant height, heading date and 100-kernel weight no differences between cycles were observed.The positive results obtained in this study indicate the potential usefulness of recurrent selection for developing parents or lines superior for grain yield, with little change in other important agronomic traits.     

Development of elite families in oil palm (Elaeis guineensis Jacq.)

Summary Data from 29 dura female parents, 14 pisifera male parents and their offspring were assembled to obtain quantitative genetic information on optimizing selection of elite families. Phenotypic values of the offspring were partitioned into general combining ability (GCA) of the parents and their specific combining ability (SCA). Parental GCA-values for leaf-Mg content (LMG), height increment (HT), leaf area ratio (LAR), leaf area (LA), frond production (FPR), vegetative dry matter production (VDM), the rate of increase in leaf area against age (k) and maximum leaf area (L_m) were entered in a multiple regression analysis as predictors of oil-and-kernel yield and Harvest Index (HI), i.e. the proportion of dry matter used for oil and kernel production, of the offspring. The analysis revealed that both selection objectives are positively influenced by indirect selection for high LAR and LMG, and for reduced VDM with FPR as main component. But palms with high values for LA, L_m and HT should not be considered to avoid selecting palms partly for their ability to compete with neighbouring palms for light. The contribution of SCA was relatively small for most of the characters studied, except HT, FPR and HI. From the standard deviations for GCA and SCA of the dura and pisifera parents, i.e. _GCA and _SCA, it was extrapolated that selection can potentially enhance bunch yield (by 24%), oil-to-bunch ratio (19%), kernel-to-bunch ratio (29%), oil-and-kernel yield (31%) and HI (56%) above the mean phenotypic value obtained for the offspring of the present investigation. Heritabilities, calculated as the square of the correlation of the GCA-and phenotypic values of the female parents, were low for bunch yield, oil-and-kernel yield and HI, but moderate for LAR, LMG and VDM; levels were high for oil and kernel extraction rate. These outcomes were confirmed by the correlations between values of the female parent and their offspring. Among the unbalanced incomplete mating designs studied, the rectangular lattice and the alpha design are most suitable to compare GCA-values of pairs of parents. A breeding strategy adapting the recently introduced practical possibility of clonal reproduction is discussed.     

Association of gene for grain colour with monosome XIV of Avena sativa L.

Summary The F₂'s from crosses between Dyfed (S.240; a black grained cultivar) and monosomics of Sun II (non-black cultivar) were analysed. With the exception of F₂ progenies involving monosomes, II, VI, VII, X, XI, XII, XIII and XIV, all other deviated from the genetic ratio 3 black: 1 non-black. The cytological examination of the non-black individuals belonging to those families that did not deviate from the 3:1 ratio showed that they were either 41- or 42-chromosome plants. However, non-black individuals involving monosome XIV were 40-chromosome plants. The gene conferring the black colour to the grains in Avena sativa cv. Dyfed (S.240) is located on chromosome XIV.Department of Plant Breeding and Genetics, Sind Agriculture University. Tando Jam. Pakistan.     

Inheritance of zucchini yellow mosaic virus resistance in Cucumis melo L.

Summary Resistance to zucchini yellow mosaic virus has been found in the muskmelon line PI 414723 from India. This resistance is effective against the ZYMV strains E15 and 1318 belonging respectively to the NF and F pathotypes. Resistance to E15 (no vein clearing and yellowing symptoms) is governed by one dominant gene (symbol Zym) according to segregations observed in F₁, F₂ and BC₁ progenies. This gene is epistatic dominant over Fn, which induces wilting and necrosis after inoculation with F pathotype. Linkage studies suggest that Zym inherits independently from Fom-1, Fom-2, Vat, Wmv and Fn but is linked with a (13.1 ±2.4 units).     

Inheritance of the virgata pattern of partly colored seed coats in ‘Early Giant’ common bean

The inheritance of the virgata pattern of partly colored seed coats found in common bean (Phaseolus vulgaris L.) Early Giant (EG) was studied by a series of test crosses with line 5-593 and genetic stocks developed by backcrossing selected genes into the recurrent parent 5-593, a Florida dry bean breeding line with a self-colored, black seed coat with genotype T Z Bip P [C r] J G B V Rk. Analysis of the F₂ from the cross EG × 5-593 led to the hypothesis that the virgata pattern of EG has genotype t z bip^vgt, where vgt stands for virgata. The test cross EG × t z virgarcus BC₃ 5-593 confirmed the hypothesis that EG carries t z from data recorded in F₁, F₂, and 27 F₃ progenies from randomly selected F₂ plants. The F₃ segregation was also consistent with the hypothesis that a single recessive gene converts virgarcus into virgata. The test cross EG × t z bip bipunctata BC₃ 5-593 failed to show genetic complementation in F₁ progeny, and the F₂ segregated 3:1 for the parental phenotypes virgata and bipunctata, respectively. Including previously published data, all possible crosses were made among bipunctata, virgata, and virgarcus parents, supporting a multiple allelic series at Bip. We propose the gene symbol bip^vgt for the new allele at Bip, where the allelic series has the order of gene dominance Bip > bip^vgt > bip. Based on test crosses, the complete seed-coat color and pattern genotype of EG is tz bip^vgt P [C r] J G B v^lae rk^d.     

The influence of genotype and environment on seed and embryo development in barley (Hordeum vulgare L.) after crossing with Hordeum bulbosum L.

Summary Seed and embryo development was studied in crosses between H. bulbosum and the barley genotypes VK 16032, Vada and Vogelsanger Gold and subsequently the F₁ and F₂ progenies from VK 16032 x Vada and VK 16032 x Vogelsanger Gold. Both seed and embryo development are strongly influenced by the barley genotype. Favourable environmental conditions can promote seed and embryo development in genotypes with existing good characters. Dominant inheritance for good seed development and incomplete dominance for large embryos is evident. Linkage between small embryo size and winter habit exists in Vogelsanger Gold.     

Genes for resistance to stripe rust in four spring wheat varieties

Summary Four spring wheat (Triticum aestivum L.) varieties differing in origin and reaction in the seedling stage to pathotype CDL-6 (extant in California) were intercrossed and examined in greenhouse conditions in F₁, F₂, and F₃ generations. Digenic and transgressive segregation was found in all crosses. The four varieties each had infection types (1 immune, 9 susceptible) and putative resistance genes as follows: Anza, IT 7, YrA; Glennson 81, IT 2, Yr9; Yecora Rojo, IT 6, YrC; and Ollanta, IT 4–6, YrL. Anza was classified as susceptible, Yecora Rojo and Ollanta as intermediate in seedling resistance, and Glennson 81 as resistant in the seedling stage.