Off-type Plants Research Articles

Influence of Genetic Drift of Restoring Gene ( Rf) on Seed Purity of Yuetai A, a Honglian-Type Cytoplasmic Male Sterile Line in Hybrid Rice

The seed samples of Yuetai A, a Honglian (HL) type cytoplasmic male sterile (CMS) line in hybrid rice were investigated to assess the seed purity and to analyze the cause of off-type plants by imitating the biological contaminant to Yuetai A in Nanjing, Jiangsu Province and Lingshui, Hainan Province during 2004–2006. The seed impurity of Yuetai A mainly resulted from the genetic drift of restoring fertility gene ( Rf) after biological contamination but not from its sterility unstability. All of the ten maintainer lines, five restorer lines and three thermo-sensitive genic male sterile lines used in the study could pollinate Yuetai A and Yuetai B to produce F 1 plants, directly or indirectly resulting in Rf-gene drifting into Yuetai A and generating ‘iso-cytoplasm restoring-generations’. Furthermore, high outcrossing rate and similar heading date of Yuetai A with many varieties used in rice production might easily result in the biological contamination. After removing all plants with Rf-gene mixed in Yuetai A and preventing Rf-gene drifting into Yuetai A, the seed purity of Yuetai A and Yuetai B had been raised to 100%.

Natural hybrids between cultivated and wild sunflowers (Helianthus spp.) in Argentina

Two introduced wild species Helianthus annuus L. and H. petiolaris Nutt. have become widespread in central Argentina and overlap the sunflower crop region. Intermediate off-type plants between the wild and cultivated species are often found, which is of concern because of the recent release of imidazolinone resistant varieties and the likely use of genetically modified sunflower cultivars. The progeny of 33 off-type plants obtained from 14 representative sites of the diffusion area were studied to confirm hybrid origin. Germination, survival, morphological traits and days to flowering confirmed hybridization between crop and both wild species, when compared to eight accessions of typical wild plants. Some progenies were presumably crop–wild H. annuus hybrids, some originated from the cross of cultivated plants and H. petiolaris, and two were the advanced generation of a cultivated hybrid. Hence, morphological traits are a good clue for the identification of spontaneous hybrid plants at field. The results indicate that crop–wild hybridization and introgression occur at various places in central Argentina. This fact may represent a way to herbicide resistance escape and future transgene escape if GM sunflower cultivars are released for commercial use.

FRUIT SET FAILURE IN TISSUE CULTURE-DERIVED DATE PALM TREES (PHOENIX DACTYLIFERA L.) CV. 'NABT SAIF' AS AFFECTED BY POLLINATOR TYPE AND POLLINATION DENSITY

There is a special interest in date palm plants regenerated by tissue culture. However, one of the major weaknesses of mass tissue culture propagation is the appearance of undesired off-type plants, such as poor fertility and delayed flowering. During the 2004 and 2005 seasons, the effect of five date palm pollinators, namely ‘Ahmar’, ‘Akhdar’, ‘Fard’, ‘Khenizy’ and ‘Maghool’ as well as sugar palm (Phoenix sylvestris), each with five different pollination densities (10, 20, 30, 40 or 50 strands/female spathe), was studied on fruit set, multi-carpel fruit formation, fruit drop, and fruit quality of eight-year tissue culture derived ‘Nabt Saif’ palm trees growing at Al-Ain oasis, United Arab Emirates, The results showed different degrees of compatibility among the pollinators on ‘Nabt Saif’. The pollinator ‘Khenizy’ resulted in the highest (34.3% and 28.7%, for 2004 and 2005, respectively) and ‘Fard’ the lowest (11. 7% and 20 % for 2004 and 2005, respectively) fruit set level. The pollinator ‘Sugar palm’ (Phoenix sylvestris) was as effective as or better than the other pollinators that belong to the species Phoenix dactlifera. There were no significant differences between the different pollination densities on fruit set and fruit quality during both seasons. Generally, neither the pollinators nor the pollination density resulted in a satisfactory level of fruit set. These results may suggest that other endogenous factors are responsible for such abnormality in the tissue culture derived ‘Nabt Saif’ palms. Some metaxenia effects of the different pollinators on fruit quality characteristics were recorded both at Bisir and Tamr stages. In this respect, the ‘Sugar palm’ pollinator significantly increased fruit and flesh weight, fruit length and diameter and seed weight percentages at Bisir stage, but decreased the concentration of total soluble solids, acidity and vitamin C at both Bisir and Tamr stages compared to other pollinators. More research work is needed on tissue culture derived date palms to understand more clearly the nature of abnormalities that appear in some cultivars.

Variability and structure of natural populations of Elymus caninus (L.) L. and their possible relationship with Hordelymus europaeus (L.) Jess. ex Harz as revealed by AFLP analysis

The AFLP method was used to study the inter-population variability of eight populations of Elymus caninus (L.) L. as well as three populations of Hordelymus europaeus (L.) Jess. ex Harz. In these studies a clear distinction was found between two phenotypes of E. caninus collected in the same locality. It also appeared that two populations of E. caninus representing the “pauciflorum” morphotype were clustered together, similarly as two populations of E. caninus exhibiting morphotype “caninus”. Additionally, the populations of the “pauciflorum” type were clustered together with all samples of H. europaeus. Furthermore, the same approach was applied to analyze the intra-population variability of E. caninus. The populations ranged from nearly uniform to as diverse as the samples collected from different localities. In some populations of this species the presence of off-type plants was revealed. Our data indicate the predominantly self-pollinating character of E. caninus and the possible genetic relationship between of E. caninus and H. europaeus.

Effect of pollination timing on the rate of apomictic reproduction revealed by RAPD markers in paspalum notatum.

Progeny tests employing molecular markers allow the identification of individuals originated by sexual means among the offspring of a facultative apomict. The objective of this work was to evaluate the effect of the pollination timing on the proportion of sexually formed individuals in progenies of a facultative apomictic Paspalum notatum genotype. Progeny families of approx. 30 plants each were generated at five different pollination times: 1-3 d pre-anthesis; at anthesis; and 2, 4 and 6 d post-anthesis. Cytoembryological analyses indicated that approx. 17% of the ovules carried a meiotic cytologically reduced embryo sac in florets formed simultaneously with those used for crosses. The parental plants and the five F1 families were analysed using RAPD molecular markers. Ninety-five oligonucleotides were assayed on the progenitors in order to search for male-specific bands. Eight primers presenting clear polymorphic bands were selected for use in the progeny tests. The proportion of sexually produced progeny reached 3.4% before anthesis and 20 % at anthesis, while pollination after anthesis generated only maternal plants. A second progeny of 97 plants obtained from pollination at anthesis produced 16 off-type plants (16.5%), of which only one was a B(III) hybrid (2n + n). Our results indicate that pollination at anthesis allows the greatest potential for sexuality to be expressed in this facultative apomictic genotype. When pollination is delayed as soon as 2 d after anthesis, only the aposporous sacs develop endosperm through pseudogamy to set seed.

A broad exploration of a transgenic population of citrus: stability of gene expression and phenotype

A collection of 70 transgenic citrus plants for the uidA and nptII genes have been maintained under screenhouse conditions over a period of 4–5 years. A detailed scanning of the plants allowed us to detect four phenotypic off-type plants and a large variation of transgene integration and expression patterns among the population. Off-type plants were analysed and characterised as nucellar tetraploids, probably originating from tetraploid starting tissues rather than from somaclonal variation events. Transgene integration and expression analyses revealed that: (1) a significant negative correlation was found between copy number and GUS activity; (2) rearrangements of the T-DNA inserts did not imply low expression levels; and (3) stability of integration and expression of the transgenes was confirmed for all the transformants grown under natural environmental conditions. These combined features validate transformation as a tool for the genetic improvement of citrus.

Characterisation and early detection of an offtype from micropropagated Lady Finger bananas

Summary. An offtype has been identified from micropropagated Lady Finger bananas (Musa spp., AAB group, Pome subgroup) that is characterised by its slow growth and poor bunch size. Bunch weights were approximately 25% those of normal Lady Finger plants and all of the fruit produced was unmarketable. This particular offtype is the most commonly encountered from micropropagated Lady Finger plants and, in 2 instances, blocks of 3000 and 1500 plants were entirely comprised of this single offtype. Detection of offtype plants was possible during establishment and growth of plants in the glasshouse by the presence of chlorotic streaks in the leaves. In more severe cases the streaks coalesced into chlorotic patches that developed thin, necrotic areas that eventually produced holes or splits in the leaves. Symptom expression was not ameliorated by the addition of fertiliser and even though symptoms were similar to severe Ca and B deficiency, both normal and offtype plants had similar levels of these elements in the leaves. The offtype plants were also slow growing in the glasshouse and produced significantly (P<0.05) smaller pseudostems and leaves than normal plants. Offtype plants could be readily detected after 4 weeks deflasking using the presence of chlorotic streaks in the leaves as the main selection criterion. Maximum discrimination was possible between weeks 5–7 and at the 6-leaf stage when all of the offtypes could be detected.

Fast resolution of identification problems in seed production and plant breeding using molecular markers

Polymerase chain reaction (PCR) analysis with specific and arbitrary primers was used to identify germplasm from a barley breeding program. Through practical application of the technology, an F1 plant's identity was confirmed, the correct pedigrees 'of 2 incorrectly labelled F2 populations were determined, confusion in the identity of seed lots of an advanced breeding line was resolved and off-type barley plants were identified in a seed increase block. This illustrated the value of PCR-based genotype analysis in plant breeding programs.

Registration of Pearl Millet Parental Lines ICMA 88004 and ICMB 88004

The pearl millet (Pennisetum glaucum) line ICMB 88004 (PI583799) is a maintainer line of male sterile ICMA 88004 (PI583798), which is the seed parent of the single-cross grain hybrid ICMH 356. ICMA 88004 derives its A1 cytoplasm from 81A (ICMA 1); ICMB 88004 was developed by 10 generations of selfing in a half-sib progeny (Togo-11) of the same early maturing, large-seeded landrace from northern Togo that was the source of the commercial open-pollinated cv. ICTP 8203. In yield trials conducted in 11 year × location environments, ICMA 88044 gave a mean seed yield of 1.91 t/ha, required 49 days to 50% flowering and had a mean plant height of 1.4 m, which were similar to the highest-yielding commercial male-sterile line ICMA 841. ICMA 88004 is highly resistant to downy mildew (Sclerospora graminicola). ICMB 88004 is a prolific pollen producer, and is similar to ICMA 88004 in the above characters, except that it flowers 1-2 days later. Both lines express yellowish seedling foliage colour under daily maximum temperatures of <40°C. Recessive inheritance of this trait permits early detection and removal of offtype plants from seed production plots. These lines were released in 1993.

Louisiana's Sweetpotato Foundation Seed Program

Foundation sweetpotato [Ipomoea batatas (L.) Lam] seedstock has been produced annually at the Sweet Potato Research Station since 1949. Breeder seedstock is selected from superior hills and used for the following year's foundation seedstock. Fields are intensely monitored after planting until harvest to remove off-type plants, mutations, etc. Seedstock is harvested from August through October, stored, graded, and repacked beginning in late January, and then made available to the growers during the early spring.

Field evaluation of tissue-cultured papaw clones in Queensland

Field performance of tissue-cultured clones of papaws established either from adult tissue of a high-yielding female plant or from juvenile tissue of seedlings (2 females and 2 hermaphrodites) was compared with seedling controls. All tissue-cultured plants had strong root systems and established more quickly than seedlings. Plants from adult tissue (TCA) had a reduced juvenile phase, as evidenced by increased circumference, lower height of first flower, reduced time to harvest, and higher fruit numbers per metre of stem. Planting date affected node number of first flower for TCA plants but not seedlings. TCA plants had higher yields than seedlings when planted in spring, and this could lead to improved commercial practice. Differences between clones established from juvenile tissue and their respective seedling controls varied and were not consistent with a reduced juvenile phase. Four dwarf off-type plants (&lt;1% of population) originated from a single bud explant.

Effects of gamma-irradiation of seed potatoes on numbers of stems and tubers.

In field trials with potatoes cv. Bintje, Jaerla and Spunta in which the seed tubers had been treated with gamma -rays from a 60Co source with doses varying from 0.5 to 27 Gy, tuber yield, harvest index and number of stems and tubers were determined. A dose of 3 Gy increased the number of tubers by 30% in Spunta in 2 out of 3 trials and by 17% in one trial in Jaerla, but it did not increase the number of tubers in Bintje. Doses of 9 or 10 Gy did not influence the number of tubers nor stems, and decreased harvest index. A dose of 27 Gy yielded off-type plants with reduced yield and number of tubers. gamma -Radiation affected the growth of the sprout apex, allowing lateral buds or divisions of the affected apex to develop into stems. To achieve larger numbers of tuber-bearing stems, tubers should preferably be irradiated at the start of sprout growth, about 5 months before planting. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Meiotic spindle disturbances in a commercial bread wheat cultivar.

Magnif 41, a bread wheat cultivar shows very abnormal microsporogenesis, apparently as a consequence of spindle disturbances giving a chaotic picture at the tetrad stage producing pollen grains of different size and frequently showing the presence of micronuclei. Female meiosis seems also to be affected but to a lesser extent than that observed on the male side. High aneuploidy frequency is observed in this cultivar, some of them with very atypical chromosome number or structure. Apparently mitotic spindles are not affected, however in the archesporial cells some disturbances have been detected. The origin of this behaviour seems to be a chromosome mutation inherited like a recessive factor, because it has also been observed in some off-type plants of Sinvalocho M. A., ancestor of this cultivar.

Morphology, origin and cytogenetics of a 48-chromosome Panicum maximum.

Chromosome behavior, method of reproduction, fertility and morphological characteristics were studied in 48-chromosome plants derived from a 32-chromosome accession (PI 298996) of guineagrass (Panicum maximum Jacq.). Multivalent associations were found at diakinesis and metaphase I which resulted in 33% of the microsporocytes having one or more laggards at anaphase I. Pollen stainability in I2KI ranged from 65% to 85%. Embryo sac analyses indicated that plants reproduced by a high level of apomixis with some sexual embryo sac development which probably accounts for the occasional off-type plants produced. The 48-chromosome plants apparently originated from the fertilization of a 32-chromosome unreduced egg from an apomictic plant by a reduced 16-chromosome male gamete. The 32- and 48-chromosome plants were morphologically simlar. A 40-chromosome plant resulting from a reduced 24-chromosome egg fertilized by a 16-chromosome male gamete was also found among the open-pollinated offspring from a 48-chromosome plant. The discovery of a 48-chromosome plant in a 32-chromosome accession and a 40-chromosome plant in a 48-chromosome offspring are other examples of the influence of apomixis in formation and maintenance of new cytoypes in nature.

In vitro propagation of green-foliaged Dracaena fragrans Ker.

Callus tissue was induced in young stem segments cultured on MS based media supplemented with 0.25–0.5 mg l-1 2, 4-D. Shoots were differentiated on media containing 0.5–1.0 mg l-1 BA and 0.5–2.0 mg l-1 IBA or 0.1–0.2 mg l-1 NAA. The same media were suitable for shoot multiplication. Shoot elongation and rooting were strongly inhibited by BA and stimulated by auxins IBA and NAA. Medium containing 0.5 mg l-1 IBA was optimal for rooting. Root elongation was stimulated by light and inhibited in darkness. Transfer of rooted plantlets to outdoor conditions was feasible and special hardening procedures were not required. Among more than 5000 plants produced by this procedure only 9 off-type plants with variegated leaves were found.

Natural Crossing of Peanut in Virginia1

Abstract Pedigreed natural crossing has been suggested as a technique for increasing the number of hybrids in peanut (Arachis hypogaea L.) breeding programs, when used in conjunction with the conventional crossing procedure. Since the success of this technique is dependent upon the natural crossing frequencies, a study was conducted from 1984-1986 to determine the current natural crossing frequency in Virginia peanut breeding plots. The cultivar Florigiant was used as the female parent, and the genetic line Krinkle was used as the male parent in a field plot each year. Krinkle has a dominant leaf characteristic easily identified in the hybrid progeny. Seed harvested from the Florigiant parent were planted in subsequent years, and the percentage of Krinkle plants determined for calculating the frequency of outcrossing. The frequency varied with environment from 2.8% in 1984 to 0.0% in 1986. The rate in 1984 was about four times the amount of natural crossing previously reported in Virginia. These results indicate that isolation distances between cultivars in seed fields may need to be greater than in current regulations, and cultivars need to be closely rogued for off-type plants during seed increase.

Production of 27-, 28-, and 56-chromosome apomictic hybrid derivatives between pearl millet (2n=14) and Pennisetum squamulatum (2n=54)

An interspecific hybridization program designed to transfer gene(s) controlling apomixis from Pennisetum squamulatum Fresen. (2n=6x=54) to induced tetraploid (2n=4x=28) cultivated pearl millet, Pennisetum americanum (L.) Leeke resulted in four offtype plants, two with 27 chromosomes and two with 28 chromosomes. These plants were found among 217 spaced plants established from open-pollinated seed of an apomictic 21-chromosome polyhaploid (2n=21) plant derived from an apomictic interspecific hybrid (2n=41) between tetraploid pearl millet and Pennisetum squamulatum. It appeared that a 21- (or 20-) chromosome unreduced egg from the apomictic polyhaploid united with a 7-chromosome pearl millet (2n=2x=14) gamete to produce a 28- (or 27-) chromosome offspring. Meiotic chromosome behavior was irregular averaging from 3.60 to 4.05 bivalents per microsporocyte in the 27- and 28-chromosome hybrids. The 27- or 28-chromosome hybrids, like the 21-chromosome female parent, shed no pollen, but set from 1.8 to 28 seed per panicle when allowed to outcross with pearl millet. Progeny of the 28-chromosome hybrids were uniform and identical to their respective female parents, indicating that apomixis had been effectively transferred through the egg. In addition, a 56-chromosome plant resulting from chromosome doubling of a 28-chromosome hybrid was identified. Pollen was 68 per cent stainable and the plant averaged 2.3 selfed seeds per panicle. Chromosomes of the 56-chromosome plant paired as bivalents (x=10.67) or associated in multivalents. Three to nine chromosomes remained unpaired at metaphase I. Multiple four-nucleate embryo sacs indicated the 56-chromosome hybrid was an obligate apomict. The production of 27-, 28-, and 56-chromosome hybrid derivatives were the results of interspecific hybridization, haploidization, fertilization of unreduced apomictic eggs, and spontaneous chromosome doubling. These mechanisms resulted in new unique genome combinations between x=7 and x=9 Pennisetum species.

Cytotaxonomy and evolutionary significance of two offtype millet plants

Cytotaxonomy and evolutionary significance of two offtype millet plants

Induction of B Chromosomes Formation in Androgenetic Lines ofNicotiana Sylvestris

SUMMARYThe production of DH plants in Nicotiana sylvestris from pollen culture shows that androgenesis induces chromosomal variability in 2 phenotypic off-type plants (38 DH plants are standard). Cytogenetic studies reveals that these off-types possess real B chromosomes: morphological differences with respect to A chromosomes, heterochromatic nature and transmission in the progeny with elimination mechanism (meiotic abnormalities, reduction in pollen viability, reduction in the rate of seed germination). The influence of the B chromosomes upon the external phenotype is discussed with respect to their origin.

Tetrasomy and quadruple trisomy in pea

Two off-type plants, morphologically distinguishable from each other and from their respective sister euploid, were isolated in the M3 generation of pea interchange heterozygotes. Pollen sterility was very high, ranging from 63.0 to 90.0%. Cytologically one of them was tetrasomic (2n+2=16) and the other one was quadruple trisomic (2n+1+1+1+1=18). In the tetrasomic plant 1IV+6II was the most frequent (46.7%) chromosome configuration, while cells with 4III+3II were predominant (40.0% cells) in the quadruple trisomic plant.