Pairs Of Major Genes Research Articles

Heterosis and Mixed Genetic Analysis of Flowering Traits in Cross Breeding of Day-Neutral Chrysanthemum (Asteraceae)

Day-neutral multiflora chrysanthemums can flower throughout the year without being influenced by daylength and have great application value in gardens. Studying heterosis and the genetic basis of important traits in day-neutral chrysanthemums can accelerate the breeding of new cultivars. In this research, a genetic population was constructed by crossing 135 F1 hybrid progeny from the day-neutral chrysanthemum ‘82-81-19’ (female parent) and the late-flowering chrysanthemum ‘388Q-76’ (male parent). Six traits, including abnormal (crown) bud, plant height, plant crown width, budding date, full flowering date, and number of petal layers, were selected for inheritance and heterosis analyses, and a single-generation major gene plus polygene mixed inheritance model was used to perform mixed inheritance analysis on these traits. The results indicated that the six traits were widely segregated in the F1 population, with the coefficient of variation (CV) ranging from 30% to 84%. The phenomena of heterosis and extra-parent segregation existed generally in F1 progeny, and the ratio of heterosis value of mid-parents (RHm) for the six traits was 45.5%, 2%, 2%, 6%, 6%, and −0.3%, respectively. The mixed genetic analysis showed that the abnormal (crown) bud and budding date were fitted to the B-3 model and controlled by two pairs of additive major genes. The plant height and plant crown width were fitted to the A-0 model, and no major gene was detected. The full flowering date was fitted to the A-1 model and was controlled by one pair of major genes. The number of petal layers was fitted to the B-1 model and controlled by two pairs of additive–dominant major genes. The heritabilities of major genes for abnormal bud, budding date, full flowering date, and the number of petal layers were 1.0, 0.9871, 0.7240, and 0.5612, respectively, indicating that these traits were less affected by environmental factors. Using a percentile scoring method, eight day-neutral chrysanthemum genotypes were selected from the hybrid progeny.

Inheritance analysis of fruit-related traits in Chinese cherry [Cerasus pseudocerasus (Lindl.) G.Don] breeding progenies

• Heredity variation and inheritance tendency were analyzed for eighteen fruit-related traits of F 1 population derived from 'Hongfei' × 'Pujianghonghua' of Chinese cherry for two years. • Significant levels of transgressive heterosis were observed for total soluble solid, anthocyanin content and fruit stalk length, whereas negative heterosis detected in fruit weight and size. • The fruit-related traits were most likely controlled by two pairs of major genes, which exerted both additive effects and dominant effects. • The heritability of major gene controlling maturity date and fruit development period was high, while that of major genes controlling fruit quality traits was low. Chinese cherry [ Cerasus pseudocerasus (Lindl.) G.Don] is one of the important stone fruits in China. To explore the heredity variation of fruit-related traits, we investigated 18 fruit-related traits of the F 1 segregating population around 700 individuals derived from 'Hongfei' × 'Pujianghonghua' of Chinese cherry for two years. The mixed major gene and polygene inheritance model method was also evaluated for their fitness in relating to the traits. The results showed that the main fruit traits had different degrees of variation, with the coefficient of variation ranging from 4.76 to 26.71% (72.23% for anthocyanin content) in 2021, and from 4.71 to 21.57% in 2022. Significant levels of transgressive heterosis were observed for fruit stalk length, total soluble solid and anthocyanin content, whereas negative heterosis was detected in fruit weight and size. The most suitable genetic model for fruit maturity date and fruit development period was 2MG-ADI and 2MG-AD, respectively, and the heritability of major gene was greater than 90%. The optimal genetic model for ten fruit size and flavor related traits was 2MG-AD or 2MG-EA, which were controlled by two pairs of major genes with additive-dominant effect or equal-additive effect, with the major gene heritability being less than 45%. The additive effects of the fruit-related traits were mostly positive, while the dominant effects were mainly negative. These results provide a theoretical basis for quantitative trait locus (QTL) mapping and marker-assisted breeding of fruit-related traits in Chinese cherry.

Genetic analysis of leaf trichome density using mixed major gene plus polygene inheritance model in Brassica rapa ssp. chinensis

ABSTRACT Leaf trichome is an important trait for stress-resistance breeding in Brassica crops, but its scientific evaluation and identification are rarely reported. To investigate the inheritance of leaf trichome in non-heading Chinese cabbage, two inbred lines, ‘14XS23W’ (glabrous) and ‘14XS23Y’ (hirsute), were used to generate F1 and F2 populations for joint analysis using a mixed major genes plus polygene inheritance model. The density of adaxial leaf trichomes was controlled by two pairs of additive-dominance-epistasis major genes plus additive-dominance polygenes. The broad-sense heritabilities of the major genes were 93.8% and 85.51%, respectively, for greenhouse and open-field conditions. However, the density of the abaxial leaf trichome was controlled by two pairs of additive-dominance-epistasis major genes plus additive dominance-epistasis polygenes. The broad-sense heritabilities of the major genes were 91.45% and 72.20%, while the polygenes were 0% and 14.5%, respectively, for greenhouse and open field environments. These results indicated that trichome density in non-heading Chinese cabbage was primarily controlled by two pairs of major genes with high heritability, implying that this trait is suitable for rapid selection in early generations.

Genetic analysis of main flower characteristics in the F1 generation derived from intraspecific hybridization between Plumbago auriculata and Plumbago auriculata f. alba

The ornamental characteristics of Plumbago auriculata are mainly reflected in the floral organ. Exploring the genetic inheritance of flower characteristics is important for breeding new varieties. In this study, F1 segregating populations were obtained by using artificial hybridization (direct cross and reciprocal cross) between P. auriculata and its variant P. auriculata f. alba. A heterosis analysis and mixed major gene plus polygene inheritance model were used to investigate the inheritance of eight flower characteristics in the F1 generation: inflorescence length (IL), inflorescence diameter (ID), number of flowers per inflorescence (NFI), beginning of the blooming period (BBP), inflorescence number (IN), flower diameter (FD), flower length (FL) and corolla color value (CCV). In addition to the CCV, the other flower characteristics showed continuous unimodal and skewed distributions, which indicated that these characteristics were quantitative and controlled by polygenes. Although transgressive heterosis was observed only for BBP in both combinations, transgressive segregation was commonly observed, except for CCV in the F1 generation; these findings could facilitate the selection of beneficial individuals for breeding. Genetic analysis revealed that NFI could be described by a B-3 genetic model via two pairs of additive major genes; BBP could be followed by a B-2 genetic model via two pairs of additive-dominance major genes; both FL and FD could be described by a B-6 genetic model via two pairs of major genes that were equally dominant; IN was best fit by the A-1 model, which was controlled by a pair of additive-dominant-epistatic major genes; and IL and ID were best fit by the A-0 model, indicating that both characteristics were controlled by only polygenes. The heritability of the major genes controlling the NFI, BBP, FD, FL and IN traits were 92.58 %, 94.40 %, 63.42 %, 54.23 % and 65.67 %, respectively, indicating that these five characteristics were less affected by the environment. These results can provide some reference for quantitative trait locus (QTL) mapping and molecular marker-assisted breeding of the main flower characteristics in P. auriculata.

Genetic variation and QTL mapping for cold tolerance in a chrysanthemum F1 population at different growth stages

Low temperature is a major stress factor that has adverse effects on chrysanthemum production; however, there is little information regarding the genetic mechanism of cold tolerance. Based on a previously constructed F1 mapping population, genetic variations and QTL effects were investigated for cold tolerance at the vegetative, bud, flower, and rhizome stages. The results showed that the coefficient of variation for cold tolerance at the four growth stages ranged from 22.17 to 46.14%, and heterosis and transgressive segregation were observed in both directions. Mixed inheritance model analysis revealed that cold tolerance at the vegetative and flower stages was controlled by two pairs of major genes that exhibited additivity-dominance-epistasis effects, and the heritabilities of the major genes were 88.56% and 65.86%, whereas no major gene model was identified for cold tolerance at the bud and rhizome stages. A total of 15 cold-tolerance-associated QTLs that explained 6.47–68.89% of the phenotypic variation were detected across the four stages, four of which were synergistic QTLs. Most of the identified QTLs were expressed at 2–4 growth stages, but only one QTL was identified at all four stages. This finding indicated that the QTLs underlying cold tolerance were dependent on the environment and were selectively expressed at different stages. In addition, for cold tolerance at the bud and flower stages, the QTLs qBdsCTM33 and qFfsCTM33 on the M33 linkage group accounted for 65.78% and 68.89% of the phenotypic variation, respectively, but had corresponding negative additive effects of − 5.16 and − 4.57 °C, indicating that these QTLs are major contributors to the improvement of cold tolerance. The findings of the present study reveal the genetic architecture of cold tolerance at different developmental stages, and the major QTLs and linked molecular markers identified represent an important step toward molecular-marker-assisted selection and QTL pyramiding for future breeding of cold-tolerant chrysanthemum.

QTL Analysis of Head Splitting Resistance in Cabbage (Brassica oleracea L. var. capitata) Using SSR and InDel Makers Based on Whole-Genome Re-Sequencing.

Head splitting resistance (HSR) in cabbage is an important trait closely related to both quality and yield of head. However, the genetic control of this trait remains unclear. In this study, a doubled haploid (DH) population derived from an intra-cross between head splitting-susceptible inbred cabbage line 79–156 and resistant line 96–100 was obtained and used to analyze inheritance and detect quantitative trait loci (QTLs) for HSR using a mixed major gene/polygene inheritance analysis and QTL mapping. HSR can be attributed to additive-epistatic effects of three major gene pairs combined with those of polygenes. Negative and significant correlations were also detected between head Hsr and head vertical diameter (Hvd), head transverse diameter (Htd) and head weight (Hw). Using the DH population, a genetic map was constructed with simple sequence repeat (SSR) and insertion–deletion (InDel) markers, with a total length of 1065.9 cM and average interval length of 4.4 cM between adjacent markers. Nine QTLs for HSR were located on chromosomes C3, C4, C7, and C9 based on 2 years of phenotypic data using both multiple-QTL mapping and inclusive composite interval mapping. The identified QTLs collectively explained 39.4 to 59.1% of phenotypic variation. Three major QTLs (Hsr 3.2, 4.2, 9.2) showing a relatively larger effect were robustly detected in different years or with different mapping methods. The HSR trait was shown to have complex genetic mechanisms. Results from QTL mapping and classical genetic analysis were consistent. The QTLs obtained in this study should be useful for molecular marker-assisted selection in cabbage breeding and provide a foundation for further research on HSR genetic regulation.

Inheritance Analysis and Quantitative Trait Loci Detection of Head Splitting Resistance in Cabbage (Brassica oleracea L. var. capitata)

Head splitting resistance (HSR) in cabbage is an important trait closely related to appearance, yield, storability, and mechanical harvestability. In this study, a doubled haploid (DH) population derived from a cross between head splitting-susceptible inbred cabbage line 79-156 and resistant line 96-100 was used to analyze inheritance and detect quantitative trait loci (QTLs) for HSR during 2011–12 in Beijing, China. The analysis was performed using a mixed major gene/polygene inheritance method and QTL mapping. This approach, which uncovered no cytoplasmic effect, indicated that HSR can be attributed to additive-epistatic effects of three major gene pairs combined with those of polygenes. Major gene and polygene heritabilities were estimated to be 88.03% to 88.22% and 5.65% to 7.60%, respectively. Using the DH population, a genetic map was constructed with simple sequence repeat (SSR) markers anchored on nine linkage groups spanning 906.62 cM. Eight QTLs for HSR were located on chromosomes C4, C5, C7, and C9 based on 2 years of phenotypic data using both multiple-QTL mapping and inclusive composite interval mapping. The identified QTLs collectively explained 37.6% to 46.7% of phenotypic variation. Three or four major QTLs (Hsr 4.2, 7.2, 9.3, and/or 9.1) showing a relatively larger effect were robustly detected in different years or with different mapping methods. The HSR trait was shown to have a complex genetic basis. Results from QTL mapping and classical genetic analysis were consistent. Our results provide a foundation for further research on HSR genetic regulation and molecular marker-assisted selection (MAS) for HSR in cabbage.

Inheritance and molecular markers for aphid (Macrosiphoniella sanbourni) resistance in chrysanthemum (Chrysanthemum morifolium Ramat.)

Aphids have caused great damage to chrysanthemum production, and it's crucial to breed new chrysanthemums with strong aphid resistance. However, little information is available regarding the inheritance of aphid resistance in chrysanthemum. The inheritance pattern of chrysanthemum aphid resistance within an F1 segregating population was dissected with the major gene plus polygene mixed inheritance model and molecular markers. The result showed that aphid resistance of chrysanthemum is a quantitative trait with a moderate coefficient of variation >50%. The mixed inheritance model based on a single segregating generation suggested the inheritance of aphid resistance was controlled by two pairs of major genes with additive effect 0.68 and 0.39, respectively. The heritability of major gene was calculated at 89.21%. Marker-trait analysis based on one-way variance analysis uncovered 11 markers significantly associated with phenotype, cumulatively explaining ∼74% variation. Bulked segregant analysis (BSA) based on the gene bulks of high resistant and susceptive genotypes in F1 population identified two SSR markers, SSR145-93 and SSR197-205, linked to high aphid resistance (r>0.4). The QTL analysis detected 5 putative QTL for aphid resistance in two successive years, with individual QTL explaining the phenotypic variation of 14.30–28.00%. The inheritance model and molecular markers identified for aphid resistance facilitate the ongoing breeding activities in chrysanthemum.

Genetic analysis and associated SRAP markers for horticultural traits of Aechmea bromeliads

Despite the great economic importance of bromeliads in flower production, little information is available regarding the inheritance of their horticultural traits thus far. The present study was to investigate the inheritance pattern and useful molecular markers for plant height, plant width, inflorescence length, inflorescence width, and offsets of Aechmea bromeliads. The result showed that plant height was governed by two pairs of major genes exhibiting equal additivity, plant width by one pair of major genes with additivity and partial dominance, inflorescence width by two pairs of major genes with additivity-dominance-epistasis, and offsets by two pairs of major genes with additivity-dominance, whereas no major gene was detected for inflorescence length. The heritability of the detected major genes was >73%, suggesting the possibility of selecting for these traits in an early generation. The marker-trait analysis identified 22 potential SRAP markers for the five traits. The findings of major genes and associated SRAP markers are a useful start to future QTL dissection for these traits.

Inheritance of Erucic Acid, Glucosinolate, and Oleic Acid Contents in Rapeseed (Brassica napus L.)

This study was conducted to verify the inheritance of certain characters of rapeseed including erucic acid, glucosinolate and oleic acid contents by using generation mean analysis. The cross of lines III174×Zi20 (F1), F2, BC1 (F1×P1), BC2 (F1×P2), and parents (P1 and P2) were evaluated in the field. Data were measured on individual plants for oleic acid, erucic acid, and glucosinolate contents. Transgressive variations in F2 population were observed for oleic acid content, indicating that dominance and recessive genes distributed in both parents. Scaling test indicated that the effects of genes controlling these characters did not follow the additive-dominance model. The data for three characters were analyzed using six parameter models and found that one or more types of epistatic gene effects were important for glucosinolate content. High broad sense heritabilities were obtained for erucic acid, oleic acid, and glucosinolate contents with the values of 98.97%, 93.68%, and 86.17%, respectively. Two major gene pairs were found to control the expression of erucic acid and oleic acid contents, while three major gene pairs were detected to control glucosinolate content.

Genetic analysis and associated SRAP markers for flowering traits of chrysanthemum (Chrysanthemum morifolium)

The inheritance of two flowering traits of chrysanthemum, initial blooming time and the duration of flowering, was investigated using segregation within an F 1 population derived from a cross between the autumn-flowering ‘Yuhualuoying’ and the summer-flowering ‘Aoyunhanxiao’ cultivars. The analysis, based on a single segregating generation and the major gene plus polygene mixed inheritance model, showed that the inheritance of both traits was compatible with the presence of two pairs of major genes displaying additivity–dominance–epistasis, with additivity predominating. As the heritability of both pairs of major genes was high (initial blooming time ~65%, duration of flowering ~72%), it should be possible to select for both traits in early breeding generations. A marker-trait association analysis based on sequence-related amplified polymorphism (SRAP) genotyping uncovered 10 (initial blooming time) and 12 (duration of flowering) markers significantly associated with phenotype, cumulatively explaining, respectively, 46 and 54% of the variation. Some potentially useful markers were identified.

GENETIC MODEL ANALYSIS OF THE CHARACTERISTIC AROMATIC SUBSTANCE 2E, 6Z-NONADIENAL IN CUCUMBER

Six generations of P 1 , P 2 , F 1 , BC I , BC 2 and F 2 from the cross of cucumber cultivar EP326 and DE843 were employed to analyze the genetic effects of the characteristic aromatic substance 2E,6Z-nonadienal by using of the mixed major gene and polygene inheritance model. B-1 model, the additive-dominance-epistasis genetic model, which was controlled by two pairs of major genes, was the best one for genetic analysis of the characteristic aromatic substance 2E,6Z-nonadienal in cucumber. The additive effect values of two pairs of major genes were 3.07, and 3.06, dominant effect values were -1.98, and -1.96, and dominant degree were -0.64, and -0.64, respectively. The heritabilities of the major genes in BC 1 , BC 2 and F 2 were 56.96, 17.36, and 47.99%, respectively. The genetics of the characteristic aromatic substance 2E, 6Z-nonadienal in cucumber could be explained mainly by additive effects. Therefore, the strategy of cross breeding could be effective for increasing the characteristic aromatic substance 2E,6Z-nonadienal content of cucumber.

Inheritance of seed color and molecular markers linked to the seed color gene in Brassica juncea

Seed color inheritance in Brassica juncea was studied in F1, F2 and BC1 populations. Seed color was found under the control of the maternal genotype, and the brown-seeded trait was dominant over the yellow-seeded trait. Segregation analysis revealed that one pair of major genes controlled the seed coat color. To develop markers linked to the seed color gene, AFLP (amplified fragments length polymorphism) combined with BSA (bulk segregant analysis) technology was used to screen the parents and bulks selected randomly from an F2 population (Wuqi yellow mustard × Wugong mustard) consisting of 346 individuals. From a survey of 512 AFLP primer combinations, 15 AFLP markers located on either side of the gene were identified, and the average distance between markers was 2.59 cM. P11MG15 was a cosegregated marker, and the closest markers (P03MC08, P16MC02 and P11MG01) were at a distance of 0.3, 0.3 and 0.7 cM from the target gene, respectively. In order to utilize the markers for breeding of yellow-seeded varieties, four AFLP markers, P11MG01, P15MG15, P09MC12 and P16MC02 were successfully converted into SCAR (sequence characterized amplified region) markers. The seed color trait controlled by the single gene together with the available molecular markers will greatly facilitate the future breeding of yellow-seeded varieties. The markers found in the present study could accelerate the step of map-based cloning of the target gene.

Blast-Resistance Inheritance of Space-Induced Rice Lines and Their Genomic Polymorphism by Microsatellite Markers

To understand the resistance inheritance basis of space-induced rice lines to blast, and to probe mutants’ genomic DNA polymorphism compared with ground control by microsatellite markers, three space-induced lines were crossed with a highly susceptible variety LTH, and their F 1 and F 2 populations were inoculated by two representative blast isolates with broad pathogenicity to analyze their resistance inheritance basis. Meanwhile three mutant lines and the ground control were analyzed by 225 rice SSR (simple sequence repeat) primer pairs selected throughout the 12 chromosomes of whole rice genome, to scan the mutagenesis in genome of the mutant lines. The results indicated the blast-resistant genes harbored in these mutant lines were dominant. It was demonstrated that the resistance of mutant H1 to isolate GD0193 and GD3286 was controlled by a single gene, respectively; while mutants H2 and H3 were controlled by two pairs of major genes against isolate GD3286 and H2 showed complicated genetic mechanism to isolate GD0193. H3's resistance to isolate GD0193 was verified to be controlled by a single gene. According to the results of SSR analysis, three mutant lines showed different mutant rates as compared with the ground control, and the mutant rates also varied. Resistance genes can be induced from rice by space mutation, and different genomic variations were detected in blast-resistant lines.

Inheritance of time to flowering in cowpea (Vigna unguiculata (L.) Walp.)

Time to flowering and maturity is an important adaptive feature in annual crops, including cowpeas (Vigna unguiculata (L.) Walp.). In West and Central Africa, photoperiod is the most important environmental variable affecting time to flowering in cowpea. The inheritance of time from sowing to flowering (f) in cowpeas was studied by crossing a photoperiod-sensitive genotype Kanannnado to a photoperiod-insensitive variety IT97D-941-1. Sufficient seed of F1, F2, F3 and backcross populations were generated. The parental, F1, F2, F3 and the backcross populations were screened for f under long natural days (mean daylength 13.4 h per day) in the field and the parents, F1, F2 and backcross populations under short day (10 h per day) conditions. The result of the screening showed that photoperiod in the field was long enough to delay flowering of photoperiod-sensitive genotypes. Photoperiod-sensitivity was found to be partially dominant to insensitivity. Frequency distribution of the trait in the various populations indicated quantitative inheritance. Additive (d) and additive × dominance (j) interactions were the most important gene actions conditioning time to flowering. A narrow sense heritability of 86% was estimated for this trait. This will result in 26 days gain in time to flowering with 5% selection intensity from the F2 to F3 generation. At least seven major gene pairs, with an average delay of 6 days each, were estimated to control time to flowering in this cross.

Breeding of widely compatible restorer lines in rice (Oryza sativa L.) through anther culture

Following anther culture of various F1 hybrids of indica restorer (R) lines/wide compatible varieties (WCVs) and japonica R lines/WCVs, the homozygous diploid plants (2n) generated were test-crossed with indica WA type cytoplasmic-genetic male sterile (CMS) line Zhanshan 97A (WA), indica testers Nanjing 11 and Nante, japonica BT CMS line Hanfeng A (BT), and japonica testers Balilla and Akihikari to identify widely compatible restorer lines. The results of this study showed that among the diploid pollen plants generated from F1 hybrids of indica R lines/WCVs, 36.7% and 64.7% possessed normal fertility restoration ability (rate of seed-setting > 80%) to Hanfeng A and Zhanshan 97A, respectively. 71.3% and 32.3% had normal fertility restoration ability to Hanfeng A and Zhanshan 97A, respectively, in diploid pollen plants derived from the japonica R lines/WCVs F1's anther culture. Several widely compatible R lines were selected from anther culture of F1 hybrids of indica R lines/WCVs and japonica R lines/WCVs. These widely compatible R lines derived from diploid pollen plants showed good wide compatibility and restoration ability both to WA and BT type CMS lines. Strong standard heterosis of major agronomic traits and yield traits was observed in F1 test-crosses of widely compatible R lines with Hanfeng A and Zhanshan 97A. The wide compatibility in widely compatible R lines H17, H158 and H281 was studied by a set of three-way crosses. Segregation of the fertile plants with seed-setting rate > 70% and semi-fertile plants with seed-setting rate > 69.9% agreed with a ratio of 1:1, indicating that wide compatibility in these widely compatible R lines is governed by a pair of major genes.

Genetic analysis of ratooning ability of rice (Oryza sativa L.)

Genetic analysis of generation means of F1, F2, F3, F4, and the parental populations of the cross IR10154-23-3-3A/IR15795-232-3-3-2 for ratooning ability was conducted. Good ratooning ability is a recessive trait. The parents differed by at least two pairs of major genes for ratooning ability. A large proportion of transgressive segregants in F2 suggested that the expression of ratooning ability is influenced not only by major genes but also by modifiers. Broad-sense heritability estimates computed by different methods ranged from 0.66 to 0.88. Narrow-sense heritability by the F4–F3 regression method was 0.39. The heritability estimates were 0.42 and 0.33 by the variance component method. The prevalence of additive x additive type of gene effects along with prominent additive effects imply some scope for selection in the segregating generations. However, non-additive type of gene action also affects the expression of ratooning ability.

Herança da resistência da variedade de sorgo AF-28 a Contarinia sorghicola Coquillet

Foram feitos cruzamentos recíprocos entre as variedades AF-28, resistente à mosquinha-do-sorgo, e Sart, suscetível. A geração F1 derivada desse cruzamento foi quase tão danificada - nota de dano: 8,5 - quanto o pai suscetível Sart - nota de dano: 9,2. O pai resistente teve nota 1,2. Isso mostra que a suscetibilidade à mosca é dominante ou parcialmente dominante. O comportamento de famílias derivadas de plantas F2 e cultivadas na geração F3 sugere que, no mínimo, dois pares de genes recessivos são responsáveis pela herança da resistência à mosquinha. A variedade resistente AF-28 apresenta diversas características indesejáveis: colmo seco; muito tardia; não-ereta; panícula muito aberta e muito alta. Sua resistência à mosquinha, todavia, pode ser transferida facilmente e recombinada com características agronômicas desejáveis. Obtiveram-se linhas resistentes, mais baixas, precoces, eretas, com. colmo sucoso e panículas mais fechadas.

Inheritance of iron deficiency in crosses of dry beans (phaseolus vulgaris L.)1

Abstract Inheritance of iron‐deficiency chlorosis was determined in the field from crosses between a highly susceptible (PI 165078) and three resistant Great Northern CGN Valley’, ‘GN Emerson’, and “GN UI 59') cultivars of dry edible beans (Phaseolus vulgaris L.). Segregation of the F. generations indicated quantitative inheritance, with complete dominance for resistance in two crosses. Based on F, segregations, it was hypothesized that the Fe deficiency trait was controlled primarily by two major gene pairs; true breeding susceptible plants were homozy‐gous recessive and resistant plants were homozygous dominant (Fe‐1 Fe‐1, Fe‐2 Fe‐2). No significant relationships between Fe and other elements were noted in leaves, petioles, and stems. Leaves had considerably higher Fe concentrations than either the petioles or stems which were similar.

Variation in pigment content of flour color in bread wheat (Triticum aestivum L.)

Variation in pigment content of the flour of bread wheats (Triticum aestivum L.) was studied in the progenies of F1 and F2 of three crosses and their reciprocals. Reciprocal differences in pigment content were observed in the F1 and F2 means. Low pigment content was found to be partially dominant or over dominant in the crosses studied. There was evidence of substantial mid-parent F1 heterosis in all crosses and betterparent F1 heterosis in three crosses. In the F2, heritability estimates were moderate to high. The F2 frequency distributions were not normal. Estimation of effective factor pairs indicated the presence of one or two major gene pairs involved in the expression of pigment content in the flour. Action of modifiers was also assumed in one cross and its reciprocal. A factorial approach to metrical character suggested that the F2 segregation ratios of low pigment content to high pigment content were 3:1, 15:1, 13:3 and 9:7 for the different crosses. Utilization of the findings in a wheat breeding program is briefly discussed.