Pollination Control Research Articles

Development of self‐incompatible Brassica napus: (II) Brassica oleracea S‐allele expression in B. napus

Abstract Brassica napus var. oleifera varieties have traditionally been developed as open‐pollinated varieties. The successful introduction of several high‐yielding hybrids based on cytoplasmic male sterility or transgenic pollination control systems has generated interest in the development of new hybrid systems. Self‐incompatibility could be an additional useful pollination control system for B. napus if a sufficient number of S‐alleles could be developed in this species. The S‐alleles, S2, S5, S13, S24 and S39, were identified in five hybrids of B. oleracea var. italica and subsequently transferred to B. napus. Doubled haploid lines were produced for the self‐incompatible (SI) lines in B. napus and intercrossed to produce SI heterozygotes in order to study allele interaction. There was a greater incidence of interallelic dominance in the stigmas and pollen of B. napus than was reported for the S‐alleles in B. oleracea. Allele S24 exhibited the greatest degree of dominance over the other alleles tested, while allele S2 was generally recessive or codominant with other alleles. Self‐incompatible expression was very similar in the SI homozygotes and heterozygotes, thus no weakening of the SI trait in the heterozygote was observed. The implications of S‐allele interaction for the use of SI in B. napus are discussed.

Development of self‐incompatible Brassica napus: (III) B. napus genotype effects on S‐allele expression

AbstractUse of self‐incompatibility (SI) as a pollination control method for Brassica napus hybrid production requires the development of a sufficient number of S‐alleles that are expressed consistently in a range of B. napus lines. Self‐incompatibility (SI) alleles have been transferred from Brassica oleracea and Brassica rapa into B. napus var. oleifera. An understanding of expression of these alleles in B. napus is essential for their commercial use. Four SI B. napus doubled haploids containing the B. oleracea S‐alleles S2, S5, S13 and S24 were crossed to three B. napus cultivars to measure the B. napus genetic background effect on S‐allele expression. A line x tester analysis indicated that the largest source of variation in the expression rate of SI was the S‐allele itself. The B. napus genotypes tested contained modifier gene(s), some that enhanced SI expression and others that inhibited SI expression. The B. napus Canadian cultivar ‘Westar’ generally had a negative effect on SI expression while the European cultivar ‘Topas’ had a positive effect on the B. oleracea S‐allele expression. The B. oleracea S‐allele S24 was very similar in expression to the B. rapa allele W1. The application of these results for the use of B. oleracea S‐alleles for hybrid production in B. napus is discussed.

Development of a technology for commercial phytoextraction of nickel: economic and technical considerations

In recent R&D work, we have made progress in developing a commercial technology using hyperaccumulator plant species to phytoextract nickel (Ni) from contaminated and/or Ni-rich soils. An on-going program is being carried out to develop a genetically improved phytoextraction plant that combines favorable agronomic and Ni accumulation characteristics. Genetically diverse Ni hyperaccumulator species and ecotypes of Alyssum were collected and then evaluated in both greenhouse and field using serpentine and Ni-refinery contaminated soils. Large genetic variation was found in those studies. Mean shoot Ni concentrations in field-grown plants ranged from 4200 to 20 400 mg kg −1 . We have been studying several soil management practices that may affect the efficiency of Ni phytoextraction. Soil pH is an important factor affecting absorption of metals by plants. An unexpected result of both greenhouse and field experiments was that Ni uptake by two Alyssum species was reduced at lower soil pH and increased at higher soil pH. At higher pH, plant yield was improved also. In soil fertility management studies, we found that N application significantly increased plant biomass, but did not affect plant shoot Ni concentration. These findings indicate that soil management will be important for commercial phytoextraction. A number of field trials have been carried out to study planting methods, population density, weed control practices, harvest schedule and methods, pollination control, and seed processing. Such crop management studies have improved phytoextraction efficiency and provide a tool for farmers to conduct commercial production. We have done some work to develop efficient and cost-effective methods of Ni recovery. Recovery of energy by biomass burning or pyrolysis could help make phytoextraction more cost-effective. The progress made in our recent studies will enable us to apply this technology commercially in the near future.

Optimizing seed quality during germplasm regeneration in pearl millet

The effect of water stress during flowering and grain filling on seed longevity was studied in three pearl millet genotypes,ICTP-8202, ICTP-8203 and MBH-110. The seeds were produced by three pollination methods; open pollination, selfing(individual panicles enclosed in paper bags), and cluster bagging (panicles from 3–4 adjacent plants enclosed in a paper bag), stored in air-tight plastic bottles underambient conditions (20–40 °C,30–80%RH) and germination was tested at 12-month'sintervals. The seeds lost germination completely after six years ofstorage in all treatments. Analysis of variance of the estimates of potential seed longevity (i.e. the seed lot constantKi of the seed viabilityequation) showed significant effects of water stress andpollination method (P < 0.01). The interaction between irrigation treatment and method of pollination control was also significant (P < 0.05). Averaged over genotypes and pollination methods,potential longevity was greatest(Ki = 2.8) in theirrigated control, and averaged over genotypes and irrigationtreatments, it was greatest (Ki= 3.1) in seeds produced by open pollination. Theimplications of these results were discussed in relation to germplasmseed production.

The breeding system of Lycium cestroides : a Solanaceae with ovarian self-incompatibility

To determine the breeding system of Lycium cestroides,several treatments were performed: self-, cross-, and geitonogamous pollinations, autonomous self-pollination, and a control (flowers exposed to natural pollinators). Production and quality of fruits and seeds as well as pollen tube growth were evaluated for each treatment. Experimental pollinations indicate that L. cestroides is self-incompatible since fruits were obtained only under cross-, and open-pollination treatments. However, in self- and geitonogamous hand pollinations, as well as in autonomous self-pollination, pollen tubes developed successfully and reached the ovules. The speed of pollen tube growth did not differ significantly among the different hand-pollinated flowers (cross-, self-, and geitonogamous). These facts indicate the presence of an ovarian self-incompatibility system. Significant differences were observed in fruit set, fruit size, and seed number per fruit between cross-pollinated flowers and open pollination (control). These results could be explained in terms of quantity and quality of pollination in each case.

Participatory plant breeding with maize in Mexico and Honduras

Maize is a staple food crop in many developing countries. However, if seven major maize producing countries are excluded from this group, data indicate that only 34% of the maize area is planted with improved seed despite considerable effort invested in maize breeding. This has led researchers to investigate other options, such as farmer-participatory plant breeding, for delivering the benefits of plant breeding knowledge and technology to farmers in developing countries. This paper describes short-term results from participatory maize breeding studies in Mexico and Honduras. Results from three selection cycles in Mexico suggest that stratified mass selection without pollination control, with selections carried out by researchers in farmers' fields, may be effective at improving yield in farmers' local varieties. In Honduras, mass selection with pollination control, where selections were done by collaborating farmers in their own fields on their own varieties, showed trends (non-significant) towards yield improvement. Farmer selection seemed to offer the greatest yield benefit over experiment station selection on the farm with the lowest yield potential, suggesting that farmer-participatory approaches may be most advantageous in marginal environments where experiment station conditions differ most dramatically from farmers' conditions. These studies highlighted the importance of seed systems knowledge in designing participatory plant breeding programs. For cross-pollinated crops, they also highlighted the need to balance progress from selection and demands on farmers' time and labor in choosing breeding methods. Further work is needed to investigate farmer-participatory breeding approaches that can address post-harvest traits.

Effect of flowering phenology and habitat on pollen limitation in Erica multiflora

Pollination can be a major factor influencing reproductive success in plants. Pollination may be influenced by variability in pollen production and vector activity associated with environmental heterogeneity in time and space. These factors were addressed experimentally using hand pollinations of Erica multiflora L., a shrub occurring in the western Mediterranean Basin that exhibits a long flowering period. Variation in pollen limitation was considered three times (early, peak, and late) over the flowering season and between two habitats (shrubland and pine forest). The breeding system and the pollination vectors were also studied by hand pollination and exclusion experiments. Xenogamy and natural pollination (control) treatments produced more seed and fruit set than geitonogamy and autogamy treatments. Insect visitors were less abundant at the end of the flowering period and in the pine forest habitat. Pollen limitation was not different between habitats, but it changed over the flowering period. Fruit set was pollen limited at the early flowering time, when less flowers were available. Both seed and fruit set were pollen limited at the late flowering time, when both flower density and insect visitors were lower. Seed and fruit set were not pollen limited at the peak of the flowering period, but their low values suggest resource limitation associated with a large number of developing fruits.Key words: breeding system, fruit set, hand pollination, insect pollinator, phenology, seed production.

The utilization of heterosis for seed yield in hybrid and synthetic cultivars of summer turnip rape

Hybrids of summer turnip rape (Brassica rapa L. syn. B. campestris L.) have been shown to exhibit high levels of heterosis. This study was undertaken to determine whether the heterosis for seed yield observed in hybrids could be captured by synthetic cultivars of turnip rape. The agronomic performance of reciprocal inter-cultivar hybrids and their corresponding two-component synthetics was studied using four turnip rape cultivars. Hybrid seed was produced by hand pollination in the greenhouse and Syn1 seed was produced by mixing equal proportions of each parent to form the base seed (Syn0) of each synthetic, and planting these in isolation in the field. The seed yield of hybrids, synthetics and parents were similar in 1985 while in 1986, hybrids yielded 25% and synthetics 23% more than parents. Actual versus predicted synthetic yields were similar except for one synthetic, Echo-Torch in 1986, where the actual yield exceeded the predicted value. Hybrid yields may have been underestimated by the chosen prediction method and therefore the yield potential of hybrids would be greater than for synthetics in turnip rape. However, until a suitable pollination control system is developed in this species, synthetic cultivars are a viable alternative to hybrids. Key words: Turnip rape (summer), synthetic, hybrids, Brassica rapa, B. campestris

Yield response of two cycles of selection from a semiprolific early maize ( Zea mays L.) population to plant density, sucrose infusion and pollination control

Previous studies have demonstrated greater yield potential for prolific than for nonprolific maize cultivars. Although the number of ears per plant has been used as selection criterion by plant breeders for yield improvement, second ear growth has been shown to vary strongly with plant density, and the nature of this effect remains unclear. The objective of this study was to investigate the yield response of two cycles of selection from a semiprolific early maize population differing in prolificacy index, to high plant density, controlled timing of pollination, and to application of exogenous sugar in order to find evidence of a possible source limitation on the growth of a second ear in a prolific maize plant. No significant differences were observed in sucrose phosphate synthase (SPS) activity between prolific (C 6) and nonprolific (C 0) plants, although it was slightly higher in leaves of C 0. Yield per plant in C 6 exceeded that of C 0 by 37 and 59% at low and high density, respectively. Plant yield reduction in C 6 at high density was associated with reduction of second-ear yield. Preliminary data indicates that yield of second ears was source-limited, while that of apical and single ears on C 6 and C 0, respectively, seemed to be sink-limited. Prolificacy seems to be a highly elastic component of maize yield that results in greater stability of yield of the apical ear, and which can constitute a significant proportion of total yield per plant.

Identification of Cross‐Pollinated and Self‐Pollinated Progeny in Alfalfa through RAPD Nulliplex Loci Analysis

Alfalfa (Medicago saliva L.) is the most important forage crop in the world, but with current breeding practices improvements in yield potential have been limited during the last 40 yr. The development of hybrid alfalfa cultivars would likely improve forage yield potential, but an efficient method to estimate outcrossing rates would be needed to confirm percentage hybrid seed. The objective of this research was to demonstrate the applicability of a RAPD nulliplex analysis to estimate outcrossing/selfing rates in autotetraploid alfalfa. Marker selection is based on polymorphism between a seed parent and its bulk open‐pollination progeny. Polymorphic markers identify the seed parent as nulliplex (aaaa) for those particular loci, which allows the individual open‐pollinated progeny from that seed parent to be classified as F1 or S1 progeny based on the presence/absence of these markers. Two alfalfa genotypes served as seed parents in crossing studies which differed in pollination control and number of pollen parents. Random amplified polymorphic DNA (RAPD) nulliplex analysis was conducted on these two seed parents and their progeny. Controlled crossing and selfing provided independent control over S1s and F1s. Five polymorphic markers were identified for both seed parents and these markers were sufficient to identify S1 and F1 progeny. The percentage S1 seed was 7, 27, and 100% for crossing with emasculation, crossing without emasculation and self‐pollination, respectively. In conclusion, RAPD nulliplex loci analysis can provide accurate identification of F1 and S1 progeny and an estimation of outcrossing rates in autotetraploid alfalfa.

Genetic engineering for pollination control

The exploitation of heterosis (hybrid vigor) through the use of hybrid varieties is one of the major achievements of plant breeding. However, in many crops, an efficient method of producing hybrid seed is not available. To overcome these difficulties, several new genetic-engineering-based methods have been proposed or are being used. Genetic engineering can make a significant contribution to agricultural productivity by providing an economical alternative to the methods that are currently used for producing hybrid seed in some crops, and by extending the use of hybrid varieties to additional crops.

5356799 Antisense gene systems of pollination control for hybrid seed production : Steven F Fabijanski, Paul G Arnison, Ottawa, Canada assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Steven F Fabijanski, Paul G Arnison, Ottawa, Canada assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Fabijanski Steven F; Arnison Paul G Ottawa, Canada Assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Fabijanski Steven F; Arnison Paul G Ottawa, Canada Assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Steven F Fabijanski, Paul G Arnison, Ottawa, Canada assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Steven F Fabijanski, Paul G Arnison, Ottawa, Canada assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Fabijanski Steven F; Arnison Paul G Ottawa, Canada Assigned to Pioneer Hi-Bred International Inc

5356799 Antisense gene systems of pollination control for hybrid seed production : Fabijanski Steven F; Arnison Paul G Ottawa, Canada Assigned to Pioneer Hi-Bred International Inc

Performance of inter-cultivar summer turnip rape hybrids in Saskatchewan

The agronomic performance of inter-cultivar hybrids of Brassica rapa L. was studied in crosses between four B. rapa cultivars. Six reciprocal hybrid combinations were produced by hand pollination in the greenhouse. Hybrids and their parents were tested in replicated yield tests for 3 yr. An average, over all hybrid combinations, of 13% heterosis for seed yield was observed. Heterosis for seed yield was greatest in crosses between genetically diverse cultivars, which agrees with classical theories on heterosis. There were also significant differences in yield of reciprocal F1 combinations. Seed oil content was not heterotic. The results of this study indicated that the level of heterosis of seed yield in crosses between B. rapa cultivars adapted for production in western Canada is sufficient to warrant the development of a suitable pollination control system for hybrid B. rapa production. Key words:Brassica rapa, Brassica campestris, inter-cultivar hybrids, seed yield, heterosis

Natural Cross‐Pollination in Sesame (Sesamum indicum L.)

AbstractThree sesame genotypes with contrasting characters were grown in alternate rows to estimate the degree of natural cross‐pollination (NCP) at two locations. Capsules from the lower (first‐formed five capsules), upper (last five fully‐developed capsules) and middle portions were harvested separately and the frequency of appearance of progenies with dominant markers was used as the criterion for NCP. The degree of inter‐genotypic NCP was similar in the three genotypes and at the two locations (4.02—5.10 % NCP) when the total number of hybrid seeds per plant was considered. The lower portion of the early (1.03—1.31 % NCP) and medium (1.51—2.08%) flowering genotypes and the upper portion of the late‐flowering genotype (2.27—2.49 % NCP) recorded less NCP than the total plant. The NCP in the lower portion of the early‐flowering genotype due to pollen from the late‐flowering genotype was negligible (0—0.7 %). The results indicate the need for controlled self‐pollination for purity maintenance in sesame. However, contamination due to NCP can be reduced by sampling seeds from the lower capsules of early and medium‐flowering genotypes and from the upper capsules of late‐maturing genotypes when pollination control is not practised.

Self-incompatibility as a pollination control mechanism for spring oilseed rape, Brassica napus L.

Self-incompatibility was shown to be an effective method of pollination control in spring rapeseed (B. napus L. ssp. oleifera (Metzg.)) by comparing the yield of a Westar-Topas syn-1 produced by crossing two SI lines with the yield of the corresponding syn-1 produced by hand pollination. Although the trial showed high-parent heterosis in the syn-1s, there was insufficient replication to determine the level of heterosis.

Genetics of New Crop Genus Limnanthes I. Five Morphological Marker Loci in L. alba x L. gracilis Progenies

New crop development often depends on a few essential traits such as nonshattering of seed at maturity and pollination control. In order to domesticate Limnanthes alba (meadowfoam), as a source of industrial oil, we performed genetic analysis of crosses between L. alba and its closest relative Limnanthes gracilis var. gracilis which shows higher selfing ability and nutlet abscission. Differences in pubescence, nutlet abscission, and seedling pigmentation were each found to be governed primarily by a single locus; two interacting loci appeared to control capsule dehiscence. Segregation distortion was detected for pigmentation in F2 and F3 populations, and for pubescence in several F3 families. Loci controlling pubescence, nutlet abscission, and capsule dehiscence resided in a single linkage block which assorted independently of the locus controlling pigmentation.

Self‐Incompatibility in Two Alfalfa Populations

Self‐incompatibility provides a useful mechanism for pollination control in alfalfa, Medicago sativa L. Five hundred randomly selected seedlings from each of two well‐adapted multiple pest‐resistant alfalfa populations (W10 AC3 and BMP8 AC3) were screened for self‐incompatibility. Twenty‐eight plants were selected following three evaluations in the greenhouse. Unemasculated hand pollinations of the self‐incompatible plants, using plants with the singlegene, completely dominant red‐root character as the pollen source, resulted in the production of 98.6% hybrid seed. Plants were intercrossed in the greenhouse using honey bees, Apis melifera L. Growth chamber forage‐yield trials of half‐sib progenies indicate that certain combinations of self‐incompatible plants exist that will yield significantly better than the parent populations. Twelve elite self‐incompatible plants selected after the initial screening produced (i) &lt; 0.15 seeds floret−1 when self pollinated, (ii) =30% viable pollen, and (iii) =3 seeds floret−1 when used as the male or female in crosses with other plants. Pollen‐pistil interaction studies of the self‐incompatible plants showed that the pollen had normal viability and either failed to germinate upon self pollination or pollen tube growth was abnormal. Pollen tubes that grew near the ovules either formed bulbous structures and terminated, or formed several branches, or continued to grow past all of the ovules resulting in the failure of fertilization. However, normal fertilization and good seed set were obtained when the self‐incompatible plants were used both as male and female in crosses with other plants. The 12 elite self‐incompatible plants were shown to have the capacity to produce somatic embryos in vitro, indicating that these plants could be propagated utilizing artificial seed technology. Evidence to date indicates that the use of the self‐incompatibility system may provide a mechanism for successfully producing high‐yielding hybrid alfalfa cultivars.