Bulb Color Research Articles

Genetic Characteristics of the Indonesian White Shallot.

The bulb color of tropical shallot is commonly red, but there is a shallot with white bulb color in Indonesia. Genetic information to classify the white shallot and utilize it as breeding material is non-existent, so that we decided to genetically characterize the Indonesian white bulb shallot. Except for the colors of the bulbs, the leaves at sprouting and the anthers, the white shallot shared all morphological characters with the red bulb shallot (Allium cepa L. Aggregatum group, red shallot). The white shallot, which has eight homologous somatic chromosome pairs, possessed the same karyotype and meiotic behaviour as the red shallot. There was also a high cross compatibility between the white shallot and red shallot. Furthermore, PCR-RFLP analyses of chloroplast DNA and mitochondrial DNA showed that these cytoplasmic components were similar for both shallot types. We conclude that the white shallot belongs to the A. cepa L. Aggregatum group ; we suppose that the white shallot originated from the red shallot through natural mutation processes.

'NuMex Snowball' Onion

Additional index words. Allium cepa, vegetable breeding, Phoma terrestris dium size that are firm, pungent, and store for long periods of time. ‘White Sweet Spanish’ was selected out of ‘Utah Sweet Spanish’, which originated from selections out of ‘Spanish’, which was introduced from Spain to the United States in 1916. The reciprocal crosses were made by intercrossing all parents in a common pollination cage, using honey bees as the pollen vector. Seeds from each parent were kept separate, and selections were made within each maternal line using phenotypic recurrent selection for pink root resistance, white bulb color, whole bulb firmness, and bulb shape in 1981. Selection was done at field maturity from spring seeding near Las Cruces, N.M. The selections were made from fields that contained high inoculum levels for Phoma terrestris (Hansen), causal organism of pink root, and Fusarium oxysporum f. sp. cepae [(H.N. Hans.) W.C. Snyder & H.N. Hans], causal organism of Fusarium basal rot. Selec-

Effects of onion (Allium cepa) plant maturity at harvest and method of topping on bulb quality and incidence of rots in storage

A field study was carried out over two growing seasons to investigate the effects of physiological maturity of onions (Allium cepa L.) at harvest and different topping methods on bulb colour, skin retention, and the incidence of storage rots. Onion plants were lifted at five different stages of maturity from 0 to 4 weeks after 50% leaf collapse (top‐down). Foliage was removed from the bulbs (topped) either before or after field‐curing. The effects of time of lifting of onion plants and method of topping on the incidence of bulb storage rots were the same in both seasons. Onions that were lifted 3 weeks after 50% top‐down and topped before curing had the greatest incidence of rots in store. Increasing harvest maturity increased the mean skin colour score of onions, and decreased markedly the mean number of intact outer skins. The timing of foliage removal had no effect on mean skin colour score, but onions that were topped before curing had slightly more bulb skins than onions topped after curing. Timing of onion lifting to optimise bulb quality appears to be a trade‐off between skin retention and colour. These results confirm that traditional method of harvesting onions in New Zealand, where onions are lifted at 60–80% top‐down, the bulbs are field‐cured, and the foliage is removed after curing, is the simplest method and best compromise to ensure postharvest onion quality and successful storage.

Analysis of (Allium cepa × A. fistulosum) × A. cepa Fourth-generation Backcross Populations for A. fistulosum Introgression

(Allium cepa × A. fistulosum) × A. cepa breeding lines have been established to the fourth generation. The aim is to develop an A. cepa-like bulbing onion carrying A. fistulosum genes. Seven populations were characterized for morphological traits and three isozyme markers. Each bulb from the populations was characterized for maturity, soluble solids content, bulb shape, and bulb color. All the populations produced A. cepa-like bulbs. Significant variation was observed within each population for each morphological trait. All the bulbs were screened for the presence of A. cepa and A. fistulosum alleles of alcohol dehydrogenase (Adh-1), esterase (Est), and phosphoglucoisomerase (Pgi-1). Allium cepa Adh-1, Est, and Pgi-1 alleles were observed in all the populations. One population, 951026-8, contained plants heterozygous for A. cepa and A. fistulosum Pgi-1 alleles. Recovery of these fourth generation Allium backcross plants demonstrates introgression of the A. fistulosum genome into an A. cepa-like bulbing onion.

Insecticidal activity of ethanolic extracts of Urginea maritima (L.) Baker bulbs

Squill bulbs ( Urginea maritima (L.) Baker) have long been used as a source of natural products with pharmaceutical (cardiotonic) and biocidal (rodenticide) applications, although other biological activities remain to be studied. It has considerable crop potential for semiarid zones but product utilization is negatively affected by variations in toxicity due to genetic and environmental effects. In this paper we studied the insecticidal activity of a group of 24 ethanolic extracts of squill bulbs: 12 wild Spanish populations of different bulb colours with 3 n, 4 n or 6 n ploidy levels extracted either after harvesting or after exposure to indirect sunlight for drying during 30 days. Bioassays were performed using the stored product pest Tribolium castaneum Herbst. Extracts topically applied at 25-day-old larvae, caused a mortality of 60–100% (after 24 h) at doses over 10 μg/insect, although no differences were recorded due to bulb colour, ploidy level, sample origin or light exposure prior to extraction. When extracts were mixed at 10% in the diet, newly hatched larvae showed growth inhibition (3.0–6.2 mm in comparison with 6.5 mm of the control) after 14 days of feeding; extracts from tetra- and hexaploid white bulbs were more active ( P<0.001) than those from triploid red bulbs and an indirect sunlight exposure of the bulbs prior to extraction increased the activity as well.

Caracterização morfológica de germoplasma de alho por análises multivariada componentes principais e variáveis canônicas

O Banco Ativo de Germoplasma (BAG) de alho, mantido pela Embrapa Hortaliças, possui 89 acessos representativos da diversidade genética da cultura no país. A presença de genótipos duplicados na coleção onera os custos de manutenção e dificulta a avaliação agronômica dos materiais. A identificação de duplicatas no BAG de alho foi feita com a utilização de 27 variáveis de caracteres morfológicos. Essa metodologia possibilitou a diferenciação de treze grupos de genótipos através de análise multivariada. As variáveis que mais contribuíram para a distinção morfológica dos grupos através de análise de componentes principais foram: altura de plantas com folhas levantadas aos 60 dias; altura de plantas com folhas normais aos 60 dias; ângulo de inserção de folhas aos 90 dias; cor dos bulbos; número de bulbilhos de peneiras um, dois e quatro; peso de bulbilhos da peneira dois; peso médio de bulbos na colheita e peso médio de bulbos na debulha. Os parâmetros mais importantes na distinção de representantes de grupos de genótipos, na análise de variáveis canônicas foram: altura de plantas com folhas levantadas aos 120 dias e altura de plantas com folhas normais aos 60 dias; ângulo de inserção de folhas aos 90 dias; número de folhas aos 60 e aos 90 dias; número de bulbos na colheita; número total de bulbos; peso médio de plantas no primeiro dia e aos 60 dias da colheita e peso médio total de bulbos. Os genótipos representativos de diferentes grupos foram distintamente caracterizados com base em 34 parâmetros, complementados pela análise de variáveis canônicas.

A low-density genetic map of onion reveals a role for tandem duplication in the evolution of an extremely large diploid genome

The bulb onion, Allium cepa L., is a diploid (2n=2x=16) plant with a huge nuclear genome. Previous genetic and cytogenetic analyses have not supported a polyploid origin for onion. We developed a low-density genetic map of morphological markers, randomly amplified polymorphic DNAs (RAPD), and restriction fragment length polymorphisms (RFLP) as a tool for onion improvement and to study the genome organization of onion. A mapping population of 58 F3 families was produced from a single F1 plant from the cross of two partially inbred lines (Brigham Yellow Globe 15-23 and Alisa Craig 43). Segregations were established for restoration of male fertility in sterile cytoplasm, complementary light-red bulb color, 14 RAPDs, 110 RFLPs revealed by 90 anonymous cDNA clones, and 2 RFLPs revealed by a cDNA clone of alliinase, the enzyme responsible for the characteristic Allium flavors. Duplicated RFLP loci were detected by 21% of the clones, of which 53% were unlinked (>30 cM), 5% loosely linked (10–30 cM), and 42% tightly linked (<10 cM). This duplication frequency is less than that reported for paleopolyploids but higher than for diploid species. We observed 40% dominant RFLPs, the highest yet reported among plants. Among duplicated RFLP loci, 19% segregated as two loci each with two codominant alleles, 52% segregated as one locus with codominant alleles and one locus with only a dominant fragment, and 29% segregated as two loci with only dominant fragments. We sequenced cDNAs detecting duplicated RFLPs; 63% showed homology to known gene families (e.g., chlorophyll binding proteins, ubiquitin, or RuBISCO), and 37% were unique clones showing significant homology to known genes of low-copy number or no homology to database sequences. Duplicated RFLPs showing linkage could be due to retroviral-like sequences in adjacent coding regions or intrachromosomal, as opposed to whole genome, duplications. Previous cytological analyses and this genetic map support intrachromosomal duplication as a mechanism contributing to the huge onion genome.

Genetic Mapping in Onion: Insight to the Evolution of a Large Diploid Genome

The bulb onion (Allium cepa L.) is a diploid with an very large nuclear genome of 15300 Mbp/1C (107× arabidopsis, 16× tomato, 6× maize). We developed a low-density genetic map with morphological, RAPD, and RFLP markers to examine genome organization and to study QTL controlling phenotypically correlated bulb quality traits. A mapping population of 58 F3 families was derived from a cross of the inbreds Brigham Yellow Globe 15-23 (BYG) × Alisa Craig 43 (AC). These inbreds are distinct in solids, storability, pungency, and bulb shape. Analysis of 580 RAPD primers detected 53 (9%) polymorphisms between BYG and AC, but only 12 (2%) segregated at expected ratios among F3 families. Using probes from onion cDNA libraries and four restriction enzymes, 214 RFLPs were identified between mapping parents. A 112-point map includes 96 RFLPs, 13 RAPDs, a locus controlling complementary red bulb color, and two loci hybridizing with a clone of the enzyme alliinase (EC 4.4.1.4), which produces the flavors characteristic of Allium species. Duplicated loci were detected by ≈25% of RFLP probes and were unlinked, loosely linked (2 to 30 cM), or tightly linked (&lt;2 cM). This frequency of duplication was comparable to species with polyploid ancestors (paleopolyploids) and was higher than that found in most true diploids. However, the distribution of duplicated loci suggests that, in contrast to whole genome duplications typical of paleopolyploids, the contemporary size and structure of the onion genome may be a product of intrachromosomal duplications (cryptopolyploidy) and subsequent structural rearrangements.

Herança de coloração de bulbos em cebola (Allium cepa L.) com resistência a Colletotrichum gloeosporioides

O objetivo deste trabalho foi determinar a herança de coloração de bulbos de cebola a partir do cruzamento de bulbos brancos com resistência a Colletotrichum gloeosporioides (Mal de 7 voltas) segregantes da população Roxa do Barreiro com bulbos amarelos de linhagens endogâmicas obtidas das variedades Super Precoce e Pira Ouro. Para tal obtiveram-se as gerações F1 e F2 entre (Super Precoce x Barreiro "Branca") e entre (Pira Ouro x Barreiro "Branca"). Nas gerações F1 obtiveram-se apenas bulbos roxos, enquanto que nas gerações F2 obtiveram-se uma segregação para bulbos roxos, brancos e amarelos numa proporção aproximada de 9:4:3, o que permitiu concluir que a herança, para estes cruzamentos, foi devida a 2 pares de genes contrastantes nas populações progenitoras, cujos genótipos, com base na literatura, são: ii cc RR (Barreiro Branca) e ii CC rr (linhagens de Super Precoce e de Pira Ouro). Conclui-se, também, que é possível, a partir destes cruzamentos, obter uma variedade ou linhagem com resistência a C. gloeosporioides somente com bulbos amarelos ou com bulbos brancos com genótipo homozigoto recessivo para todos os genes, que quando cruzada com outra amarela pode-se obter uma geração F1 com bulbos amarelos e com resistência a C. gloeosporioides.

RFLP ANALYSIS OF DIVERSITY AMONG OPEN-POLLINATED POPULATIONS OF ONION (ALLIUM CEPA L.)

Restriction fragment length polymorphisms (RFLPs) in the nuclear genome were used to assess genetic diversity among cultivated open-pollinated populations (OPs) of bulb onion (Allium cepa L.). Twenty OPs of contrasting day-length responses [long (LD) and short (SD) day] were examined with 104 random cDNA probes and two to four restriction enzymes. Sixty-one probes detected polymorphisms among the OPs for at least one restriction enzyme. Parsimony and cluster analyses were completed and no distinct grouping was observed between LD and SD OPs. Parsimony analysis generated a consensus tree that grouped all but two LD OPs and their relationships to the SD OPs were not resolved. Cluster analysis grouped all but three LD OPs and the distances from that group to the others were not greater than those among LD or SD OPs. These results suggest that LD and SD onions do not represent distinct germplasm sources and LD OPs possess a more narrow genetic background. The paucity of unique fragments among OPs indicates that phenotypic variation, e.g., day-length response or bulb color or shape, does not reflect diverse sources of germplasm.

Effect of Brooder Attractant Lights on Performance of Bobwhite Quail

Two experiments were conducted using a total of 4,320 day-old bobwhite quail chicks to evaluate bird responses when exposed to different colors and intensities of brooder attractant lights. Attractant lights were operated constantly and were part of the quartz bar/radiant heat brooder installed in each brooding pen. Treatments consisted of brooder attractant lights as follows: 7.5 watt incandescent red bulb (7.5 W/R); 7.5 watt incandescent white bulb (7.5 W/W); 15.0 watt incandescent white bulb (15.0 W/W).The use of white bulbs resulted in higher 21-day body weights than the use of red bulbs in both experiments. Results for feed consumption and feed conversion indicated less feed wastage and better feed conversion by chicks brooded with 7.5 W/W and 15.0 W/W compared to 7.5 W/R attractant light bulbs. In general, white bulb color improved the effectiveness of brooder attractant lights for use with bobwhite quail.

Germination and post-germination development of Colletotrichum dematium f. circinans on Allium cepa

Spores of Colletotrichum dematium f. circinans were inoculated onto the abaxial epidermis of washed and unwashed pieces of leaf-base tissue taken from the first thru fourth layers of white, yellow and red onions. Washing tissue dramatically improved germination, less than 0.1% for unwashed versus 83% for washed. Germination capacity, and the number of germination types (16) found on washed tissue was not affected by onion bulb color or leaf-base layer inoculated. Spores with one sessile appressorium, type 001, or with one germ tube without an appressorium, type 100, or with one germ tube with an appressorium produced at the tip, type 110, made up approximately 93% of the types for those spores which germinated.

Inheritance of bulb color in the onion (Allium cepaL.)

The present study on inheritance of bulb color in onions continues work begun 10 years ago at the United States Department of Agriculture. Results obtained in F1, F2, F3, and backcross progenies of several varieties and lines are explained by assuming that five major genes, I, C, G, L, and R (each with two alleles) interact, and segregate independently of each other. The five genes act in a specific order on a biochemical pathway that leads to pigment formation. A diagram for such a pathway, showing the action of each gene, is proposed. Four of the genes, I, C, L, and R, were reported previously by other workers. (L and R are the designations given by us to the complementary genes reported by (Jones and Peterson, 1952). The fifth gene, G, is proposed in the present study. The results of several of the crosses cannot be explained without its presence. The density of golden yellow and red colors is apparently controlled by several microgenes; i.e., it is quantitatively inherited. Quantitative inheritance is not discussed in the analysis of the crosses, because this subject requires further investigation. The study also further substantiates the presence of the four genes previously reported.

INHERITANCE OF BULB COLOR IN THE ONION

INHERITANCE OF BULB COLOR IN THE ONION