Genetic analysis of four self-incompatible lines in Brassica napus

Reciprocal hybridization between four self-incompatible lines of Brassica napus: 271, 181, 184 and ‘White Flower’, revealed incompatibility. The reciprocal F₁s obtained by bud pollination showed self-incompatible reactions, and no segregation for self-incompatibility was observed in all the reciprocal F₂ populations, indicating that lines 271, 181, 184 and ‘White Flower’ were genetically identical with regard to self-incompatibility. Observations of self-incompatibility in 17 hybrids from crosses between line 271 and 17 varieties of B. napus showed 10 of the F₁ hybrids to be self-compatible, while four were partially self-compatible and three were self-incompatible. Genetic analysis based on F₂ and BC₁ populations from five self-compatible F₁ hybrids and two self-incompatible F₁ hybrids suggested the existence of at least two loci controlling the self-incompatibility of line 271: one is the S locus, with dominant and recessive relationships between the S alleles, and the other is the suppressor (sp) of the S locus. The sp locus is genetically different from the S locus, and also shows dominant and recessive relationships between the sp alleles.     

Application of isozyme electrophoresis for purity testing and cultivar identification of F1 hybrids of Brassica oleracea

Summary Six isozyme genes were analyzed in seed samples of 65 commercial F₁ hybrids of four horticultural groups of Brassica oleracea (cabbage, Brussels sprouts, sprouting broccoli and cauliflower). Results obtained from electrophoretic assays led to the following conclusions: 1) the electrophoretic test of F₁ hybrid purity was possible in 59 (91%) of the hybrids analyzed, since their inbred parents were apparently fixed each for a different allele in at least on of the loci studied; 2) forty-eight (74%) of the hybrids were individually distinguished by their isozyme phenotype; 3) high levels of segregation in the inbred parents were inferred from the analysis of a sample of seeds of each hybrid.     

Inheritance of resistance to stripe rust (Puccinia striformis) in crosses between wild emmer (Triticum dicoccoides) and cultivated tetraploid and hexaploid wheats. I. Triticum durum

Summary Reciprocal crosses were carried out between Triticum dicoccoides sel. G-25-highly resistant to Puccinia striiformis race 20A-and Triticum durum cultivar Nursith 163-which served as susceptible parent.F₁ hybrids in one of the crosses showed a wide range of infection types to the test isolate, whereas in a repeated cross all F₁ plants proved highly resistant. The variable reaction pattern observed in the F₁ hybrids of the first cross suggests incomplete penetrance of the resistance factor in certain environmental conditions.The segregation ratio displayed by the F₂ progenies indicates that a single dominant factor for resistance to stripe rust race 20A was transferred from wild emmer to cultivated durum wheat.Contribution from the Agricultural Research Organization, Volcani Center, Bet Dagan, Israel. 1973 Series, No. 291-E.     

Reproductive behaviour and broomrape resistance in interspecific hybrids of sunflower

Interspecific hybrids and backcross generations between the wild perennial species Helianthus resinosus, Helianthus paucifiorus, Helianthus laevigatus, Helianthus nuttallii ssp. nuttallii T. & G. and Helianthus giganteus, resistant to broomrape (Orobanche cernua) and susceptible inbred lines were obtained to study crossability to cultivated sunflower and the transmission and expression of resistance to this parasitic weed. Conventional crosses with all the species tested were successful except for the crosses with diploid H. giganteus, for which embryo rescue techniques were needed to overcome hybrid incompatibility. Pollen viability and seed set were highest for F₁ hybrids with hexaploid species and lowest for those with the diploid H. giganteus. We evaluated F₁, BC₁F₁, some BC₂F₁ plants and the wild and cultivated parents. The wild species and interspecific hybrids were resistant to broomrape infection except for H. nuttallii, which showed segregation, indicating that the resistance is dominant. The crossability and resistance of F₁, and back-cross generations of species with different ploidy levels indicate that the transfer of broomrape resistance to cultivated sunflower is feasible.     

Major gene control of tolerance of bread wheat (Triticum aestivum L.) to high concentrations of soil boron

Summary The genetic control of tolerance of wheat to high concentrations of soil boron was studied for five genotypes. Each genotype represented one of five categories of response to high levels of boron, ranging from very sensitive to tolerant. Tolerance to boron was expressed as a partially dominant character, although the response of an F₁ hybrid, relative to the parents, varied with the level of boron applied. The F₁ hybrids responded similarly to the more tolerant parent at low B treatments and intermediate to the parents at higher treatments. Ratios consistent with monogenic segregation were observed for the F₂ and F₃ generations for the combinations (WI^*MMC) × Kenya Farmer, Warigal × (WI^*MMC) and Halberd × Warigal. The three genes, Bo1, Bo2 and Bo3, while transgressive segregation between two tolerant genotypes, G61450 and Halberd, suggested a fourth locus controlling tolerance to boron.     

Genetic analysis of resistance to leaf-rust (Puccinia recondita f. sp. tritici) pathotypes in the durum wheats 'PBW 34' and 'DWL 5023'

Genetic analysis of leaf-rust resistance was conducted on two durum wheats. Triticum durum cvs. ‘PBW 34’ and ‘DWL 5023’ were crossed with the leaf-rust-susceptible durum wheat ‘Malvi Local’. The F₁, F₂ and F₃ generations were tested against leaf-rust pathotypes 1, 77A and 108. In ‘PBW 34’, a single dominant gene was effective against each of the pathotypes 1 and 108, whereas two independently inherited dominant genes were effective against pathotype 77A. In ‘DWL 5023’, two independently inherited dominant genes were operative against pathotypes 1 and 77A, whereas a single dominant gene was identified as being operative against pathotype 108. Allelic tests on F₂ generation and joint segregation analysis on F₃ generation seedlings, suggested that two different genes in each cultivar are effective against these three leaf-rust pathotypes. Cultivar ‘PBW 34’ has Lrd1 and Lrd2 genes whereas Lrd1 and Lrd3 genes are present in ‘DWL 5023’.     

Development of cytoplasmic-genic male sterility in safflower

An interspecific cross was made between Carthamaus oxyacantha and the cultivated species C. tinctorius to develop a cytoplasmic‐genic male sterility (CMS) system in safflower. C. oxyacantha was the donor of sterile cytoplasm. The 3: 1 segregation pattern observed in BC₁F₂ suggested single gene control with dominance of male‐fertility over male‐sterility. The information obtained from crossing male sterile X male fertile plants in BC₁F₃ and BC₁F₄ generations showed statistically significant single gene (1: 1) segregation for male sterility vs. male fertility. The results demonstrated that C. tinctorius possesses a nuclear fertility restorer gene and that a single dominant allele restored fertility (Rf) in progeny carrying CMS cytoplasm of C. oxyacantha. Male sterility occurred with the homozygous recessive condition (rfrf) in a sterile C. oxyacantha cytoplasm background and not in the normal cytoplasm of C. tinctorius. The genetic background of different restorer lines of C. tinctorius having normal cytoplasm did not effect fertility restoration. The absence of male sterile plants in C. tinctorius populations ruled out the possibility of genetic male sterility. Normal meiosis in F₁ and BC₁F₂ ruled out a cytogenetic basis for the occurrence of male sterility.     

All hermaphrodite progeny are derived by self-pollinating the sunrise papaya mutant

Self‐pollination of a hermaphroditic cultivar normally gives a ratio of 2 : 1 hermaphrodite to female papayas with genotypes M₂m and mm, respectively. Much effort has been dedicated to marking the sexual types of papaya at the seedling stage to distinguish hermaphroditic from female papayas. A hermaphroditic papaya mutant (SR*) has been obtained, derived from the ‘Sunrise’ papaya cultivar mutant. Self‐pollination of the mutant resulted in all progenies being hermaphroditic. The genotype of the female was lethal, as a result of a lethal gene being linked to the mm female gene complex in this case. However, a 3 : 1 segregation ratio was obtained from the progeny of the hermaphroditic cultivar ‘Thailand’ crossed with SR*, indicating that all genotypes survived. Homozygous genotypes (M₂M₂) would be lethal according to Storey's model. Randomly selected F1 plants of the ‘Thailand’ SR* combination were self‐pollinated to obtain an F₂ generation. The F₂ segregation ratio suggested that the SR* mutant had a different form of the M₂ allele, now designated as M_@, which allowed the dominant M_@M₂ to survive in cross combinations. Genetic study has proved that SR* has the M_@ml genotype, a new mutant. It is capable of producing all hermaphroditic papaya progenies.     

Aseptic culture of gynophores to obtain peanut intersectional hybrids

Summary Cross-incompatibility between cultivated peanuts and their wild relatives outside the section Arachis has impeded the utilization of many species possessing high resistances or good qualities. Despite the great efforts made to culture immature ovules or embryos, few hybrid offspring have been obtained. In this study, gynophores from Arachis hypogaea L. pollinated with A. glabrata Benth. were cultured and F₁ hybrids seeds were harvested, and F₂ and F₃ generations produced. The characters of F₂ generation exhibited a wide range of segregation. Leaf peroxidase isozyme PAGE analysis revealed that the hybrids were quite different from their parents in relation to band number, width and isozyme activity. The zymograms of the hybrids and their parents were partially alike. This verified the authenticity of the hybrids.     

Inheritance of siliqua locule number and seed coat colour in Brassica juncea

The inheritance of siliqua locule number and seed coat colour in Brassica juncea was investigated, using three lines each of tetralocular brown seeded and bilocular yellow seeded. Three crosses of tetralocular brown seeded × bilocular yellow seeded lines were attempted and their F₁, F₂ and backcross generations were examined for segregation of these two traits. Brown seed colour and bilocular siliqua characters were found to be dominant over yellow seed and tetralocular siliqua, respectively. Chi‐square tests indicated that each trait is controlled by different sets of duplicate pairs of genes. Bilocular siliquae or brown seeds can result from the presence of either of two dominant alleles, whereas tetralocular siliquae or yellow seeds are produced when alleles at both loci are recessive. A joint segregation analysis of F₂ data indicated that the genes governing siliqua locule number and seed colour were inherited independently.     

Inheritance of resistance to broomrape (Orobanche cumana Wallr.) race F in a sunflower line derived from wild sunflower species

Genetic resistance to broomrape (Orobanche cumana Wallr.) race F in sunflower line J1, derived from the wild perennial species Helianthusgrosseserratus Martens and Helianthus divaricatus L., has been reported to be controlled by dominant alleles at a single locus, Or6. However, deviations from this monogenic inheritance have been observed. The objective of the present study was to gain insight into the inheritance of resistance to broomrape race F in the sunflower line J1. F₁, F₂, F₃ and BC generations from crosses between J1 and three susceptible lines, P21, NR5 and HA821 were evaluated. F₁ hybrids showed both resistant (R) and moderately resistant (MR) plants, the latter having a maximum of five broomrape stalks per plant compared with >10 in the susceptible parents. This indicated incomplete dominance of the Or6 alleles. F₂ plants were classified as R, MR or susceptible (more than five broomrape stalks per plant). Three different segregation ratios were observed: 3 : 1, 13 : 3 and 15 : 1 (R + MR : S), suggesting the presence of a second gene, Or7, whose expression was influenced by the environment. A digenic model was confirmed, based on the evaluation of F_2:3 families.     

The inheritance of resistance to blue mold (Peronospora tabacina Adam) in two cultivars of tobacco (Nicotiana tabacum L.)

Summary Two blue-mold resistant cultivars of Nicotiana tabacum L. were crossed with each other and with the susceptible Israeli local cultivar Mikhal. F₁, F₂ and F₃ progenies of these crosses, F₁ and F₂ of backcrosses and the parental varieties were grown in a series of experiments, in which the seedlings were exposed to heavy natural infection with Peronospora tabacina Adam. The genetic basis of resistance was found to be identical in the two resistant strains Bel-61-10 and Chemical mutant. A single dominant major gene determined the segregation of resistance versus susceptibility in the crosses of these strains with Mikhal. The level of resistance of resistant segregates was shifted by environment and by quantitatively modifying genes. The index of resistance, which was calculated as a weighted mean of the degree of blue-mold expression of the resistant segregates, differed in the generations of cross progeny. This could be explained by the different expected levels of the modifying genes in these generations. Heritability of the index of resistance was calculated by parent-offspring regression and it was found to be 0.542 in the F₃ and 0.227 in F₂ backcross progenies.     

Aluminium tolerance in lentil (Lens culinaris Medik.) with monogenic inheritance pattern

The objectives of this study were to determine genetics of Al tolerance and whether the Al tolerance observed is governed by the same gene. The lines ‘L‐7903’ and ‘L‐4602’ have been developed through breeding programme as Al‐tolerant lines. These lines showed maximum root regrowth and minimum accumulation of Al and callose as compared to sensitive genotypes (‘BM‐4’ and ‘L‐4147’). Al tolerance in the parents, F₁, F₂ and backcross generations was estimated using the regrowth of the primary root after staining and scoring of fluorescent signals. The F₁ hybrids responded similarly to the tolerant parents, indicating dominance of Al tolerance over sensitivity. The segregation ratios obtained for Al tolerance and sensitivity in the F₂ and backcross generations were 3 : 1 and 1 : 1, respectively. Test of allelism confirmed the same gene was conferring Al tolerance in both genotypes (‘L‐7903’ and ‘L‐4602’) as the F₁ was also tolerant and no segregation of tolerant : sensitive was recorded. These results indicated that Al tolerance is a monogenic dominant trait that can be easily transferred to agronomic bases through backcross breeding technique.     

Inheritance of trichomes and resistance to pod borer (Helicoverpa armigera) and their association in interspecific crosses between cultivated pigeonpea (Cajanus cajan) and its wild relative C. scarabaeoides

The legume pod borer, Helicoverpa armigera, is one of the most devastating pests of pigeonpea. High levels of resistance to pod borer have been reported in the wild relative of pigeonpea, Cajanus scarabaeoides. Trichomes (their type, orientation, density and length) and their exudates on pod wall surface play an important role in the ovipositional behavior and host selection process of insect herbivores. They have been widely exploited as an insect defense mechanism in number of crops. In the present investigation, inheritance of resistance to pod borer and different types of trichomes (A, B, C and D) on the pod wall surface in the parents (C. cajan and C. scarabaeoides) and their F₁, F₂, BC₁ (C. cajan × F₁), and F₃ generations has been studied. Trichomes of the wild parents (high density of the non-glandular trichomes C and D, and glandular trichome B and low density of glandular trichome A) were dominant over the trichome features of C. cajan. A single dominant gene as indicated by the segregation patterns individually will govern each trait in the F₂ and backcross generation. Segregation ratio of 3 (resistant): 1 (susceptible) for resistance to pod borer in the F₂ generation under field conditions was corroborated with a ratio of 1:1 in the backcross generation, and the ratio of 1 non-segregating (resistant): 2 segregating (3 resistant: 1 susceptible): 1 non-segregating (susceptible) in F₃ generation. Similar results were obtained for pod borer resistance under no-choice conditions. Resistance to pod borer and trichomes associated with it (low density of type A trichome and high density of type C) are governed individually by a dominant allele of a single gene in C. scarabaeoides. Following backcrossing, these traits can be transferred from C. scarabaeoides into the cultivated background.     

Fingerprinting of alfalfa meiotic mutants using RAPD markers

Summary A calendar of female sporogenesis and gametogenesis was made for both apomictic tetraploid (2n=4x=36) Brachiaria brizantha and Brachiaria decumbens and their apomictic F₁ hybrids with sexual tetraploid (2n=4x=36) Brachiaria ruziziensis. Microgametogenesis was used as a reference. Apospory was facultative in both species and hybrids. Environmental conditions had variable effects on the level of apomixis according to each genotype. Ratios of segregation into sexuals and apomicts in the interspecific hybrids suggest an oligogenic determinism with dominant apomixis in the genus Brachiaria. Highly apomictic and partially male fertile hybrids were identified and will be used in an improvement program to transfer genes for apomixis into the sexual species B. ruziziensis.     

Inheritance of resistance to angular leaf spot in Nicotiana tabacum L. cultivars burley 21 and kentucky 14

Summary The genetics of resistance to angular leaf spot caused by Pseudomonas syringae pv. tabaci in Nicotiana tabacum cultivars Burley 21 and Kentucky 14 was investigated by studying disease reactions to three isolates of parental, F₁, F₂ and backcross generations derived from crosses between the resistant cultivars and the susceptible cultivar Judy's Pride. Studies were conducted in the greenhouse and in field plant beds. Chi-square values were computed to determine whether the observed ratios for disease reactions deviated from expected Mendelian ratios for a single, dominant gene controlling resistance to angular leaf spot in tobacco. Based on the resistance of the F₁ and the backcross generation to the resistant parent (BC-R), a 3 resistant: 1 susceptible segregation ratio in the F₂, and a 1 resistant: 1 susceptible segregation ratio in the backcross generation to the susceptible parent (BC-S), it was concluded that resistance to three isolates of Pseudomonas syringae pv. tabaci is governed by a single, dominant gene.     

Genetics of tolerance to high concentrations of boron in Brassica rapa

The inheritance of tolerance to high concentrations of boron in Brassica rapa was studied in F₂ and F₃ segregating populations. The F₁ hybrids were produced from genotypes contrasting in their reaction to boron. The F₁ hybrids responded similarly to the tolerant parent indicating that boron tolerance was dominant trait. Segregation patterns for boron tolerance in F₂ populations and F₃ derived families were established by the measurements of primary root length and tissue boron concentrations. The segregation ratios were explained in terms of two major genes interacting in a dominant epistatic manner to govern tolerance. Evaluation of selected tolerant and susceptible F₃ families indicated that tolerant families produced significantly longer primary roots as compared to susceptible families.     

Somatic Embryogenesis in Maize and Comparison of Genetic Variability Induced by Gamma Radiation and Tissue Culture Techniques

Sixteen inbred lines and one hybrid of manse were tested for their capability of somatic embryogenesis, and fully developed plants could be regenerated, from ten inbred, lines. The highest frequency of plant regeneration was expressed in the inbred line CHI 31, and when this line was crossed with a recalcitrant, non-regenerating line, the F₁ and BC hybrids were regenerable. The results of reciprocal crosses demonstrated that dominant nuclear genes and cytoplasmic factors are primarily responsible for the heritable determination of embryogenic callus proliferation and in vitro regeneration of maize plants. Somaclonal and radiation-induced variability was studied in maize to assess their nature and potential contribution to plant breeding., The inbred line CHI 31 possessing a high in vitro capacity of somatic embryo formation was used as experiments.] material. CHI 31 plants were selfed and twelve-day old zygotic embryos irradiated with ⁶⁰Co gamma radiation in situ. Mature caryopses were harvested and assigned as M₁ material. In another series, immature zygotic embryos (size 1.2—1.5 mm) were cultured in vitro on N-6 medium supplemented with 2,4-D (2.5 μM), and somatic embryos regenerated into plants; these were transplanted into soil and self-pollinated. Regenerants from non-irradiated cultures were grown as R₁ generation, while regenerants from irradiated explants were considered as M₁R₁ generation. The genetic variability was evaluated in the M₂, R₂ and M₂R₂ generations, respectively, and compared with a non-treated seed control. Irradiation induced a variety of chlorophyll and morphological variants segregating in the M; generation; however, the frequency of deviant types obtained in the R: generation (somaclonal variation) was significantly exceeding the one derived from the M₂ populations. The combination of expert irradiation and in vitro regeneration was most effective for the manifestation of chlorophyll and morphological o if types in the M₂R₂ generation, and increased drastically the frequency of early flowering variants. Differences in the segregation patterns of mutant phenotypes amonsister somaclones in the R₃ and M₃R₃ generations indicate a different genetic basis, of plants originating from the same explant. This phenomenon suggests a mutational sectoring of the callus during culture. Radiation induced and somaclonal variation exerted a similar spectrum of chlorophyll and morphological deviants.     

Dominant gene for common bean resistance to common bacterial blight caused by <Emphasis Type="Italic">Xanthomonas</Emphasis><Emphasis Type="Italic">axonopodis</Emphasis> pv. <Emphasis Type="Italic">phaseoli</Emphasis>

The common bacterial blight pathogen [Xanthomonas axonopodis pv. phaseoli (Xap)] is a limiting factor for common bean (Phaseolus vulgaris L.) production worldwide and resistance to the pathogen in most commercial cultivars is inadequate. Variability in virulence of the bacterial pathogen has been observed in strains isolated from Puerto Rico and Central America. A few common bean lines show a differential reaction when inoculated with different Xap strains, indicating the presence of pathogenic races. In order to study the inheritance of resistance to common bacterial blight in common bean, a breeding line that showed a differential foliar reaction to Xap strains was selected and was crossed with a susceptible parent. The inheritance of resistance to one of the selected Xap races was determined by analysis of segregation patterns in the F₁, F₂, F₃ and F₄ generations from the cross between the resistant parent PR0313-58 and the susceptible parent ‘Rosada Nativa’. The F₁, F₂ and F₃ generations were tested under greenhouse conditions. Resistant and susceptible F_3:4 sister lines were tested in the field. The statistical analysis of all generations followed the model for a dominant resistance gene. The resistant phenotype was found to co-segregate with the SCAR SAP6 marker, located on LG 10. These results fit the hypothesis that resistance is controlled by a single dominant gene. The symbol proposed for the resistance gene is Xap-1 and for the bacterial race, XapV1.     

大豆质核互作雄性不育系NJCMS3A双亲雄性育性基因的SSR标记

利用大豆质核互作雄性不育系NJMCS3A的质、核供体亲本N21566和N21249构建F₂和BC₁F₁育性分离群体进行雄性育性的遗传分析与基因定位。结果表明, F₁正反交可育,F₂和BC₁F₁的可育株与不育株分离比例经χ²测验分别符合3∶1和1∶1,表明NJCMS3A供体亲本雄性育性由一对基因控制,可育等位基因为显性。该基因可能是NJCMS3A的一个恢复基因。选用793对SSR引物对F₂和BC₁F₁群体分别进行育性基因定位,发现该育性基因位于O连锁群上,在Satt331和Satt477标记之间,与Satt331、CSSR133和Satt477标记距离的次序一致,分别为8.1~10.4 cM、11.4~16.4 cM、13.3~19.2 cM。