Onion Populations Research Articles

Distribution pattern of cytoplasm and restoration of male fertility (Ms) locus in short-day tropical Indian onion populations

Distribution pattern of cytoplasm and restoration of male fertility (Ms) locus in short-day tropical Indian onion populations

Genetic Analyses of the Shape and Volume of Onion Bulbs and Daylength Effects on Bulbing

The formation of onion (Allium cepa) bulbs is affected by photoperiod length and onion germplasm is commonly classified as short- (SD), intermediate-, or long-day (LD) types. The objectives of this study were to develop a segregating family from a cross between doubled haploids (DHs) of LD and SD onions and complete genetic analyses of bulb shape and volume, as well as daylength effects on bulbing. DH parents and F1 and F2 progenies were grown in a greenhouse under lengthening days. The diameters of the neck constriction and pseudostems were measured weekly and their ratio was used as the determinant of bulbing. Bulbs were harvested when the foliage collapsed and the diameters and heights of individual bulbs were measured and used to calculate a shape index (diameter divided by height) and bulb volume. Single nucleotide polymorphisms (SNPs) were genotyped and a genetic map of 112 SNPs constructed. Genetic analysis revealed two highly significant quantitative trait loci (QTL) affected bulbing under increasing daylengths, and both QTL showed significant additive effects with no dominance. One highly significant QTL was detected for bulb-shape index and explained 30% of phenotypic variation for bulb shape. Three additional QTL were slightly above the significance threshold, and together these four QTL explained over 50% of the phenotypic variation for bulb shape. No significant QTL were detected for bulb volume. These results reveal that bulb-shape and daylength effects on bulbing are relatively simply inherited, and this research should facilitate introgression of traits between onion populations of different daylength sensitivities and efforts to modify bulb shape.

A Single Nucleotide Polymorphism Unique to the Galanthum-CMS of Onion

Different sources of cytoplasmic male sterility (CMS) are used to produce hybrid onion seed. The most commonly used source of CMS in onion is S cytoplasm (S-CMS), and male fertility is restored by a dominant allele at the nuclear male-fertility restoration locus (Ms). Male-sterile plants possess S cytoplasm and have the homozygous recessive genotype at Ms; seed propagation of male-sterile plants is possible by crossing with a male-fertile maintainer plant or inbred possessing normal (N) male-fertile cytoplasm and the homozygous recessive at the Ms locus (N msms). Some commercially important onion populations possess S-CMS and high frequencies of the dominant Ms allele, eliminating the possibility to develop maintainer lines. An alloplasmic source of CMS (Gal-CMS) was developed by backcrossing the cytoplasm of Allium galanthum into the nuclear background of onion. The advantage of Gal-CMS is that the dominant allele at Ms does not restore male fertility, making this source of CMS useful for the development of male-sterile lines from populations possessing S cytoplasm and dominant allele(s) at Ms. In this research, a single nucleotide polymorphism unique to the cytoplasms of A. galanthum and Gal-CMS was identified, useful to distinguish Gal-CMS from other onion cytoplasms.

Genotyping-by-Sequencing Defines Genetic Structure within the "Acquaviva" Red Onion Landrace.

Genetic structure and distinctive features of landraces, such as adaptability to local agro-ecosystems and specific qualitative profiles, can be substantially altered by the massive introduction of allochthonous germplasm. The landrace known as “Cipolla rossa di Acquaviva” (Acquaviva red onion, further referred to as ARO) is traditionally cultivated and propagated in a small area of the Apulia region (southern Italy). However, the recent rise of its market value and cultivation area is possibly causing genetic contamination with foreign propagating material. In this work, genotyping-by-sequencing (GBS) was used to characterize genetic variation of seven onion populations commercialized as ARO, as well as one population of the landrace “Montoro” (M), which is phenotypically similar, but originates from another cultivation area and displays different qualitative features. A panel of 5011 SNP markers was used to perform parametric and non-parametric genetic structure analyses, which supported the hypothesis of genetic contamination of germplasm commercialized as ARO with a gene pool including the M landrace. Four ARO populations formed a core genetic group, homogeneous and clearly distinct from the other ARO and M populations. Conversely, the remaining three ARO populations did not display significant differences with the M population. A set of private alleles for the ARO core genetic group was identified, indicating the possibility to trace the ARO landrace by means of a SNP-based molecular barcode. Overall, the results of this study provide a framework for further breeding activities and the traceability of the ARO landrace.

Outcrossing and heterozygosity rates in tropical onion populations

Outcrossing and heterogosity rates are important for defining genetic conservation and breeding strategies, and these estimates are quite rare to onion. The aim of this study was to estimate cross-pollination and heterozygosity rates in tropical onion populations to guide development of new varieties. Eight tropical onion pairs were field isolated to be open pollination by insects. Parents vernalized bulbs were used for pair crossing, in alternate rows, 1:1. Seeds were harvested from the female parent to assess the progenies outcrossing and heterogigosity rates based on color of the red bulb, partially dominant over yellow, and four microsatellite loci. The outcrossing rates estimated with morphological marker, in the ‘BRS Rio Vale’ × ‘BRS Carrancas’, ‘Botucatu’ × ‘BRS Carrancas’, ‘IPA 11’ × ‘IPA 10’ and ‘BRS Alfa São Francisco’ × ‘IPA10’ crosses, ranged from 15% to 39%, with an average of 28.2%, while with microsatellite loci, in the ‘BRS Alfa São Francisco’×’IPA 11’, ‘Alfa SF RT’ × ‘BRS A. São Francisco’, ‘BRS Rio Vale’ × ‘Botucatu’ and ‘Cascuda T6’ × ‘Botucatu’ crosses, ranged from 33% to 71%, with an average of 42.7%, indicating a mixture of cross-pollination and self-pollination within progenies. The average values ​​of heterozygosity in the eight populations ranged from 0.82 to 1.0, indicating the possibility of developing open pollinated onion varieties with greater adaptation to biotic and abiotic stresses.

Perspectives of onion hybrid breeding in India: An overview

Onion (Allium cepa L.), a major member of monocot family Amaryllidaceae, is an important bulbous vegetable cropused in almost every Indian kitchen. Being cultivated since antiquity, farmers rely on growing open pollinated varietiessince hybrid development in this crop has not gained pace. Among important vegetables, F1 hybrid developmentremains underutilized in onion especially in India and other developing countries as compared to other onion growingcountries. Development of commercial hybrids in onion principally depends on the availability of suitable inbredlines against the backdrop of stable male sterile system. The future scope of commercial onion hybrids needs to befocused comprehensively for the identification of male sterile lines from Indian onion population by utilizing modernbiotechnological tools. Molecular markers distinguishing cytoplasm and linked to restorer of male sterility, Ms locus,are important. Release of commercial hybrids from public sector would play a great role for breaking yield barriers andsignificant enhancement of productivity of onion under changing climate scenario and increasing domestic demand.

Recurrent selection for resistance to Thrips tabaci in a tropical onion population

Recurrent selection for resistance to onion Thrips tabaci has not been well studied by breeding programmes. Onion thrips is a pest of major concern and is controlled by insecticide spraying, raising production costs and potentially damaging the environment. This study aimed to estimate onion bulb yield genetic gain through six cycles in the ‘BRS Alfa São Francisco’ developed by recurrent selection for T. tabaci resistance. Experiments were carried out in a randomised block design, with three replications, in two locations. The degree of infestation in plants was evaluated five times after transplanting, as well as plant architecture traits and bulb yield. The latest selection cycle presented bulb commercial yield of 32.1 t.ha-1, while the base population ‘Alfa Tropical’ and IPA 10 check cultivar 15.9 and 14.0 t.ha-1, respectively (p<0.01). The broad sense heritability values ranged from 0.65 to 0.74 for bulb yield. The mean genetic gain was 1.0 t.ha-1 or 6% per selection cycle, indicating the efficiency of the method to increase the frequency of favourable alleles for thrips resistance and the possibility of onion cultivation in the total absence of insecticide applications to control this pest, or a reduction in their number

Genetic Analysis of the Unique Epicuticular Wax Profile of ‘Odourless Greenleaf’ Onion

The amounts and types of epicuticular waxes on onion (Allium cepa) leaves affect the severity of feeding damage by onion thrips (Thrips tabaci), a serious insect pest of onion. Onion plants with light green leaves are referred to as “glossy” and accumulate less epicuticular wax relative to the blue–green (“waxy”) foliage of wild-type onion. The onion cultivar Odourless Greenleaf (OGL) has visually glossy foliage, shows resistance to thrips feeding damage, and has the unique profile of accumulating waxes with 28 or fewer carbons. Plants of glossy OGL were crossed with the glossy inbred B9885 and waxy inbred lines DH2107, DH066619, and B8667. Hybrid progenies from glossy OGL by waxy plants had waxy foliage, indicating recessiveness of the glossy OGL phenotype relative to the waxy phenotype. Hybrids from the cross of glossy OGL with glossy B9885 were also waxy, revealing different genetic bases for the glossy phenotype in these two onions. Hybrid plants were self-pollinated and segregations in F2 families from OGL × waxy crosses fit the expected 3:1 ratio for the single locus at which the homozygous recessive genotype conditions glossy foliage. Segregations in F2 families from crosses of glossy 9885 × glossy OGL fit the 9:7 ratio, supporting two independently segregating loci, where the recessive genotype at either locus conditions the glossy phenotype. Amounts and types of epicuticular waxes on leaves of F2 progenies from crosses of OGL × waxy B8667 and glossy B9885 × OGL were determined using gas chromatography-mass spectrometry. Single-nucleotide polymorphisms were genotyped and genetic maps were constructed. The visually glossy phenotype from OGL and its unique profile of epicuticular waxes were conditioned by one locus on chromosome 6, for which we propose the name glogl. Onion populations such as OGL with unique epicuticular wax profiles will be important germplasms for the development of onion cultivars that suffer less feeding damage from onion thrips compared with waxy onion.

Susceptibility of different plant species to two populations of Ditylenchus dipsaci Kühn, 1857 (Tylenchida: Anguinidae) from Turkey

Stem and bulb nematode, Ditylenchus dipsaci Kuhn, 1857 (Tylenchida: Anguinidae), is one of the most important plant parasitic nematodes worldwide. The host range of local populations needs to be determined for control using crop rotation. Susceptibility of 29 plant species was tested for onion and garlic populations of D. dipsaci from Central Anatolian Plateau in Turkey under growth chamber conditions in Karaman in 2019. Based on the reproduction factor of the nematodes, garlic, onion and tomato were excellent hosts for both populations of D. dipsaci . Pea and spinach were excellent hosts for the onion population, while good host for the garlic population with cucumber a good host for both populations. Eggplant, pepper and zucchini were identified as poor hosts for both nematode populations. Bean and potato were poor hosts for the onion population, and were non-hosts for the garlic population. Alfalfa, barley, carrot, chickpea, daffodil, hyacinth, kale, leek, lettuce, maize, melon, oat, rye, strawberry, sugar beet, tobacco, tulip and wheat were non-hosts for both populations of D. dipsaci . Infection with D. dipsaci significantly reduced plant weight of onion and tomato, and plant height of pepper. Rotational crops for use in areas infected with D. dipsaci in Central Anatolian Plateau in Turkey were indicated by the current study.

Identities of and Phenotypic Variation for Epicuticular Waxes among Leaves and Plants from Inbred Onion Populations

The amounts and types of epicuticular waxes on onion (Allium cepa) leaves affect feeding damage by onion thrips (Thrips tabaci). This study used gas chromatography mass spectrometry (GCMS) to establish the identities of waxes and measure over time wax amounts on leaves of inbred onion plants with glossy, semiglossy, and waxy foliage. Nine waxes were detected on leaves of all inbreds, and higher coefficients of variation (cv) were observed for less abundant waxes on foliage of doubled haploid onions. Older leaves had higher amounts of waxes compared with younger leaves on the same plant. Except for one minor wax, amounts of individual waxes on leaves were not significantly different for plants of different ages. There was a significant inbred by sampling date interaction due to lower amounts of waxes on the leaves of older plants from the semiglossy inbred. These results indicate that there is little advantage to multiple samplings of leaves over time from the same plant and resources may be better used to evaluate more plants. The relatively large cvs for amounts of specific waxes may reduce response to selection for unique epicuticular wax profiles to develop onion populations that suffer less feeding damage by onion thrips.

Are there differences in heterozygosity of strains obtained from intercrossed and self-fertilized onion plants?

ABSTRACT The commercial use of onion hybrids is preferred by producers. In contrast, the production of hybrid onion seeds is extremely inefficient. This is due to the use of lineages obtained by successive self-fertilizations assuming the effect of inbreeding depression per se. Therefore, it is necessary to understand new alternatives to reduce the effect of inbreeding depression in the strains. The objective of this study was to evaluate possible differences in polymorphism and levels of heterozygosity of strains obtained from intercrossed and self-fertilized plants. Twelve onion populations belonging to Bayer’s breeding program (Granex, IPA-1, IPA-2 and IPA-3) were used, obtained by self-fertilization of one plant, intercrossing of two plants or intercrossing of three plants. Three individuals from each strain were used in the analyzes. The amplifications were performed using 8 microsatellite primers with greater polymorphism, according to germplasm characterization studies carried out by CITA. Heterozygosity generally decreases with self-fertilization and increases as more plants are used in the cross. The SSR markers used in the present study were efficient in detecting variability in different genetic backgrounds. With the results obtained, it is suggested to carry out the obtaining of hybrids between the different combinations and to analyze the performance per se of the different modalities of obtaining strains proposed in the present research.

Genetic Mapping of Chartreuse Bulb Color in Onion

The most common bulb colors of onion (Allium cepa) are red, yellow, and white; chartreuse is a relatively rare bulb color conditioned by the homozygous recessive genotype at the G locus. In this research, plants with chartreuse bulbs were crossed with inbreds with yellow bulbs to develop segregating families for genetic mapping of the G locus. For all of 17 F2 families, segregations for yellow vs. chartreuse bulbs fit the expected 3:1 ratio (P > 0.05). DNAs were isolated from one F2 family and genotyped for single nucleotide polymorphisms (SNPs) to produce a genetic map of the G locus and 380 SNPs, of which 119 SNPs have not been previously mapped. Segregations for yellow vs. chartreuse bulbs placed the G locus at the end of chromosome 7 at 6.7 cM from the nearest SNP (isotig28625_2789). This codominant SNP marker linked to the G locus should be useful for introgression of recessive chartreuse bulb color into diverse onion populations for commercial production of this uniquely colored onion.

Research Article Genetic divergence between onion populations derived from three different crossing methods

Research Article Genetic divergence between onion populations derived from three different crossing methods

Informativeness of Single Nucleotide Polymorphisms and Relationships among Onion Populations from Important World Production Regions

Single nucleotide polymorphisms (SNPs) were genotyped using a high-density array and DNAs from individual plants of important onion (Allium cepa L.) populations from major production regions and from the likely progenitor of onion, Allium vavilovii Popov et Vved. Genotypes at 1226 SNPs were used to estimate genetic relationships among these populations and revealed close associations among onions grown in Europe and those in North America, South America, and eastern Asia, supporting paths of introduction from Europe to the Americas and Asia. ‘Nasik Red’ is a population grown on the Indian subcontinent and was divergent from onions of European origin. Frequencies of SNPs among and within populations were used as a measure of informativeness, and 199 commonly polymorphic SNPs were identified distributed across the eight chromosomes of onion. These SNPs will be useful for estimations of relatedness among broader collections of onion populations, mapping of important phenotypes, fingerprinting of inbred lines and hybrids, and quality control of seed lots.

Efficacy of Molecular Markers Jnurf13 and AcPms1 for Prediction of Genotypes at the Nuclear Ms Locus in Three Open-pollinated Populations of Onion from North America

Seed of hybrid onion (Allium cepa L.) is produced using cytoplasmic male sterility (CMS). For the most widely used source of onion CMS, male sterility is conditioned by the interaction of male sterile (S) cytoplasm and the homozygous recessive genotype at the nuclear male fertility locus Ms. Because of the biennial generation time of onion, classical crossing and segregation analyses take years to establish cytoplasms and genotypes at Ms. Numerous molecular markers have been developed to distinguish onion cytoplasms and estimate genotypes at Ms. Two nuclear markers (jnurf13 and AcPms1) have been reported to cosegregate with Ms and correctly predict genotypes in commercial breeding lines and diverse onion germplasm; however, these markers were less predictive for open-pollinated (OP) populations from India. We evaluated the efficacy of jnurf13 and AcPms1 to correctly classify genotypes at Ms using 144 random plants from three OP populations of long-day onion from North America. No recombination events were detected between AcPms1 and the Ms locus and three events occurred between jnurf13 and Ms. Our results support either marker as a useful tool to predict genotypes at Ms in North American populations of onion, with AcPms1 being the better of the two.

Genetic gain of ‘Valenciana’ onion populations developed in the Brazilian Semi-Arid region

The aim of the present study was to estimate the genetic improvement in the last recurrent selection cycles applied in two ‘Valenciana’ onion populations in Petrolina, PE. The experiments were carried out between October 2014 and January 2015, in Petrolina and Juazeiro, BA. The experiment consisted of a randomized block design, with 12 treatments and three replications. Analyses of variances were carried out separately for each population. The control population CNPH6400 was the comparison basis. Heritability and genetic gain were estimated for total (Prototal) and commercial (Procom) bulb yields. Significant differences were observed for Prototal and Procom in both populations and in both environments, except for the 25CA10 population, in Juazeiro. The highest Procom genetic gains were observed in Petrolina for 25CA10 and T811CR13 populations (510.5% and 522.1%, respectively), proving the efficiency of recurrent selection cycles. Genetic gains were nonlinear, and fluctuations may have occurred due to genetic drift.

Isolation of Male Sterile and Maintainer Lines from North-Indian Onion (Allium cepa L.) Populations with the Aid of PCR-Based Molecular Marker

Isolation of Male Sterile and Maintainer Lines from NorthIndian Onion (Allium cepa L.) Populations with the Aid of PCRBased Molecular Marker Marker assisted selection (MAS) using mitochondrial DNA based marker cytochrome b (cob) was integrated with phenotypic evaluation to isolate male sterile and maintainer lines from openpollinated onion varieties adapted to North Indian agro-climatic region. Cytotype (N/S) determination by cob marker followed by morphological and microscopic study of pollen discovered male sterile plants (Smsms) at frequencies of 0.015 in Punjab Naroya, 0.020 in Punjab Selection, and 0.006 in Punjab White. The progeny scoring of test-crosses between male sterile and N-cytoplasmic plants isolated the maintainers (Nmsms) at frequencies of 0.133 in Punjab Naroya, 0.231 in Punjab Selection and 0.182 in Punjab White. As a novel approach, Trait Recovery Programme was demonstrated to reduce the population size required to recover a male sterile plant by 91.08% in Punjab Naroya, 92.99% in Punjab Selection and 97.66% in Punjab White. For recovering a maintainer, 10% reduction in Punjab Naroya and 9.10% in Punjab Selection was calculated. However, no reduction was observed in Punjab White. This analysis also validated that in a randomly mating onion population, frequency of recessive ms allele squared is equal to the frequency of male sterile plants among S-cytotype and frequency of maintainers among N-cytotype (fms2 = fSmsms/fS = fNmsms/fN)....

Allometric Growth Dynamics of Onion (Allium Cepa) Sampled from Gilgit-Baltistan, Pakistan

Allium cepa, an Amaryllidaceous member traditionally used as anti-thrombotic, anti-platelet, anti-asthmatic, anti-biotic, anti-carcinogenic and anti-blood clotting. It also improves sleep quality, circulation, skin and hair maintenance, hair growth stimulant, heart ailments, blood pressure, lowers cholesterol. Study was aimed at growth dynamics of Onion in two districts of Gilgit-Baltistan i.e. Hunza and Gilgit. Research revealed that mean leaf length (cm), width (cm) and area (cm2) of plant collected from Hunza were 14.88 cm, 0.43 cm and 9.0 cm2 respectively. In district Hunza leaf length grows 97.1 percent faster as compared to its growth in width and width increase is only 2.9% to the increase in leaf length. Similarly, plants collected from district Gilgit showed a mean values of leaf length, width and area as 25.05 cm, 0.59 cm and 10.1 cm2 respectively. Average growth of leaf length in Gilgit is 97.64 percent (%) faster than its growth in width which is only 2.35%. this shows that growth in district Gilgit is relatively higher (12.70%) than in Hunza. Roots arising from the bulb have an average length of 0.40 cm in Hunza as compared to 0.44 cm in Gilgit. This shows minute difference between the two and samples from Gilgit show around 10% long. Adventitious roots grow almost 97.3% slow as compared to its leaves above the ground. Mean weight of bulbs collected from district Hunza was 9.62g as compared to average 16.25g in Gilgit. Bulb growth in district Gilgit is almost 60% (59.2%) faster as compared to Hunza leading to bigger and heavier bulbs in Gilgit.? Mean values of Onion populations from both the districts show leaf length (19.97cm), leaf width (0.506cm), leaf area (9.55 cm2), root length (0.42) and weight (12.936).

Adaptability and stability of ‘Valenciana’ onion populations in the Brazilian tropical semi-arid

Brown onions of the ‘Valenciana’ type are not available for short-day growing conditions in the Northeast of Brazil. The goal of this study was to estimate parameters of adaptability and stability in order to release ‘Valenciana’ onion cultivars in the Northeast of Brazil. Eight populations of onions derived from a cross between ‘Baia population’ בValcatorce INTA’ and improved by recurrent selection were associated with six commercial onion cultivars, included as controls; they were evaluated in five experiments carried out in the municipalities of Petrolina, Pernambuco, Juazeiro, Bahia and Belem do Sao Francisco, Pernambuco. The experimental design was a randomized block design with three replications. Total and commercial bulb productions were evaluated for adaptability and stability parameters according to the methodologies of Eberhart and Russell, Lin and Binns and Main Effects and Multiplicative Interaction (AMMI). Significant genotype × environment interaction was observed for the two analysed variables. Eberhart & Russell and AMMI showed similar results for the overall cultivars, while some discrepancies were observed under the Lin & Binns method. The three methodologies produced concordant results for the ‘Valenciana’ onion types. The 25CA10 and T811CR13B’Valenciana’populations demonstrated broad adaptability and stability, associated with bulb production close to some cultivars and the commercial hybrid, and will be protected and released as new cultivars in the Northeast region of Brazil.

The Study of Effect of Planting Date and Density on Marketable Yield and Bulb Characteristics of an Onion Population from Behbahan

The Study of Effect of Planting Date and Density on Marketable Yield and Bulb Characteristics of an Onion Population from Behbahan