Anther Extrusion Research Articles

Selection Procedures for Developing Fertility Restorer Lines in Wheat1

The effectiveness of selection for anther extrusion in fertility restorer lines of wheat (Triticum aestivum L. em Thell.) to improve cross‐pollination potential and the relationship between the self‐fertility of the restorer lines and the fertility of their testcrosses were examined in six R/B (restorer/conventional line) crosses and one R/R (restorer/restorer) cross. A common restorer parent, R109, was used in all crosses. One hundred and fifty‐two F6 R‐lines, selected from 722 F5 lines, were evaluated in yield trials at three locations in North Dakota in 1979. All F6 lines were testcrossed to male steriles with Triticum timopheevi Zhuk. cytoplasm, and fertility of testcross progeny was used as the criterion for fertility restoration potential. The effect of restorer genes on several agronomic and quality traits also was investigated.Regressions of the F6 on F5 generations indicated that selection for anther extrusion in the F5 was effective although somewhat less effective than selection for heading date and plant height. Forty percent of the variation in the F6 for anther extrusion was determined by variation in the F5 compared to 64 % for heading date and 72 % for plant height. R‐line anther extrusion was only slightly indicative of fertility restoration potential; the R2 for testcross F1 seed set vs. F6 R‐llne anther extrusion was 10%.Among the 152 R‐lines, there was a low negative association between anther extrusion and 200‐kernel weight and a low positive association between R‐line test weight and testcross seed set, When lines were grouped by testcross fertility, no differences among testcross fertile, testcross partially fertile, and testcross male‐sterile lines were found for any trait except R‐line anther extrusion and testcross anther extrusion. The R109‐derived restorer genes and their associated linkage blocks had no deleterious effects on agronomic traits.

Agronomic and Male‐Fertility Restoration Characteristics of Wheat Restorer Lines with Aegilops speltoides and Triticum timopheevi Cytoplasms1

The use of Aegilops speltoides Tausch cytoplasm in fertility restorer line breeding was evaluated by comparing the male fertility restoration and agronomic performance of segregating population pairs in Ae. speltoides and Triticum timopheevi Zhuk. cytoplasms. Each of 15 restorer/restorer (R/R), eight restorer/cultivar (R/B), and two male‐sterile/restorer (A/R) F1's was crossed onto ms(timopheevi)‘Butte’ and ms(speltoides)Butte or ms(timopheevi)ND537 sib and ms(speltoides)ND537 sib to obtain populations with comparable nuclear gene segregation in the two cytoplasms. There was no significant difference between F1 seed set of populations with T. timopheevi cytoplasm and those with Ae. speltoides cytoplasm (82% vs. 76%). F3 bulks from fertile plants in each population were evaluated in replicated yield trials. Populations in the two cytoplasms performed similarly for all agronomic and seed quality traits except anther extrusion. Populations with T. timopheevi cytoplasm had 10% higher mean anther extrusion than populations with Ae. speltoides cytoplasm. We believe Ae. speltoides cytoplasm can be used interchangeably with T. timopheevi cytoplasm in hybrid wheat breeding and provides an alternative which can effectively broaden cytoplasmic variability.

Mass Selection for Anther Extrusion and Seed Set in Fertility Restorer Bulks of Wheat 1

Response to natural selection and to visual mass selection for anther extrusion and seed set and their possible effects on several agronomic and seed quality traits of wheat (Triticum aestivum L.) were evaluated in F3 to F7 bulk populations from six R/B (restorer/cultivar) crosses, one R/R (restorer/restorer) cross, and one A/R (male sterile/restorer) cross. All populations had a male sterility inducing cytoplasm, either Aegilops speltoides Tausch, Triticum zhukovskyi Men. & Er. or Triticum timopheevi Zhuk., and were segregating and heterogeneous for fertility restorer genes. Visual mass selection for anther extrusion in F3 and F5 generation bulks effectively increased the mean anther extrusion of successive generations. Relative to the original F3 bulk mean, this increase was 19% per cycle of mass selection. Neither natural selection nor mass selection for seed set increased anther extrusion. Two cycles of mass selection for anther extrusion or seed set did not cause significant adverse effects on heading date, plant height, grain yield, test weight, and grain protein percentage. A slight decrease in 200-kernel weight was noted.

Investigation of possible associations between partial fertility restoration and agronomic traits in Triticum aestivum L.

Many conventional hard red spring wheat (Triticum aestivum L. em Thell) lines, including several North Dakota cultivars, carry a gene (or genes) which restore partial male fertility to male sterile plants with Triticum timopheeviZhuk. cytoplasm. Since this gene has no fertility restoration function in T. aestivum cytoplasm, the postulation can be made that it is being retained in conventional lines because of pleiotropic effects, favorable linkages or chance. The research reported in this paper examined these possibilities. Forty F6 lines, derived from a single F2 plant which was heterozygous for a gene (or genes) for partial fertility restoration, were evaluated for two years in a yield trial planted at Fargo, North Dakota. The 40 lines were testcrossed to a male sterile line having T. timopheevi cytoplasm, and the mean seed set of testcrosses was used as a measure of a line's fertility restoration potential. Twenty-seven lines had the gene for partial fertility, and 13 lines apparently lacked this gene. The 40 lines differed for heading date, anther extrusion, plant height, grain yield, 200-kernel weight, test weight, and grain protein percentage. However, comparisons of lines having the restorer gene with those lacking the gene did not provide any obvious explanation for the retention of the partial fertility restorer gene in the breeding stocks of the North Dakota conventional hard red spring wheat breeding program. The possibility that the restorer gene was linked with genes for resistance to stem rust or leaf rust also was evaluated by testing lines for their reaction to several races of rust. No conclusive association was found.

Influence of Triticum timopheevii Cytoplasm on Pollen Production and Dispersal in Common Wheat1

Breeders of hybrid hexaploid wheat (Triticum aestivum L. aestivum group) are developing R‐lines (pollinators) with cytoplasm and male‐fertility restorer genes derived from Triticum timopheevii (Zhuk.) Zhuk. var. timopheevii. It is important to determine if such R‐lines have reduced pollen production and dispersal compared to their respective B‐lines.The soft wheat cultivar ‘Monon’ was compared to three recovered backcross Monon‐type R‐lines with both cytoplasm and nuclear male‐fertility restorer factors derived from T. timopheevii. Pollen production and dispersal were measured by pollen collection in automatic spore traps, percent anther extrusion, and percent seed set on A‐lines.In spore trap comparisons A‐line 68846L2 dispersed significantly fewer total pollen grains than Monon, 1559 vs. 1975. The patterns of daily dispersal over the 7‐day period were generally similar for the R‐line and Monon although a significant day × pollinator interaction occurred.The three R‐lines were equal to Monon in anther extrusion with an average of 92% of the anthers extruded. The R‐lines and Monon were equally effective as pollinators in effecting seed set on three A‐lines (mean=60%). The small reduction in pollen dispersal of R‐lines was not great enough to reduce the effectiveness of the R‐lines as pollinators when compared to Monon at the 60% level of seed set for A‐lines in these experiments.

Single-gene inheritance of anther extrusion in barley

Single-gene inheritance of anther extrusion in barley

Variability, Combining Ability, and Interrelationships of Anther Length, Anther Extrusion, Glume Tenacity, and Shattering in Spring Wheat1

Thirty spring wheat (Triticum aestivum L., T. aestivum with T. timopheevi Zhuk. cytoplasm, and T. turgidum L. var. durum) cultivars and lines, both normal (B‐line) and restorer (R.line) genotypes, were grown at Fargo, N.Dak. in 1968 to assess variability and intercharacter associations for four floral traits: anther length, anther extrusion, glume tenacity, and shattering. In a second experiment the following year, 36 B‐line/R‐line (B/R) hybrids and their six B‐line and six R‐line parents were grown to further evaluate variability and intercharacter associations and to obtain estimates of the relative magnitude of general and specific combining ability effects for anther length, anther extrusion, and glume tenacity.Substantial variation among genotypes was found for each of the four traits in both experiments. Significant differences for both general and specific combining ability effects of parents were obtained for anther length, anther extrusion, and glume tenacity. The general combining ability to specific combining ability variance component ratio was approximately 5:1 for anther length, 1:1 for anther extrusion, and 8:1 for glume tenacity. Narrowsense heritabilities on a per spike basis were 0.61, 0.19, and 0.54 for the three respective traits. Correlations between F1's and each parent or mid‐parent were relatively high for anther length and glume tenacity but low or nonsignificant for anther extrusion. Selection to alter anther length and glume tenacity should be effective in this group of wheats. Selection in stress environments was suggested as a possible means of improving and stabilizing anther extrusion.All intercharacter associations were nonsignificant except for a low positive correlation between anther extrusion and shattering, and a low negative correlation between glume tenacity and shattering, both in the second experiment. Thus, adverse associations with glume tenacity or shattering should not seriously impede progress in improving anther length and anther extrusion.

Exclusive Preferential Transmission of an Alien Chromosome in Common Wheat1

AbstractAegilops longissima S. & M. and Ae. sharonenis Eig were crossed with Triticum dicoccum Schrank ‘Khapli’ pollen, and F1 hybrids were crossed several times with T. aestivum L. em. Thell. pollen to substitute the T. aestivum nucleus into the cytoplasm of these Aegilops species. Partially male and female‐sterile plants having a monosomic substitution (20″+2′) or a monosomic addition (21″+1′) were obtained from these nuclear‐substitution backcrosses. These plants had normal anther extrusion, abundant pollen, and incomplete scattered seed set on bagged or crossed heads, and the reciprocal cross with euploid T. aestivum as a female gave complete seed set. Euploid, 21” plants were not obtained from crosses in either direction, most offspring having again 20″+2′ or 20″+1′, and having abundant pollen but partial seed set on bagged heads. All the selfed progeny of plants with a monosomic substitution or monosomic addition had a disomic substitution or disomic addition, respectively, and were fertile. Evidently, male and female gametes with one Aegilops chromosome were functional, and those without the Aegilops chromosome did not function.There was thus an apparent gametocidal action of the sporophyte having an Aegilops chromosome, on the gametes lacking this chromosome. Occasionally malesterile euploid T. aestivum plants with Ae. sharonensis cytoplasm were obtained as a result of rare functional female gametes without the critical Ae. sharonensis chromosome.

Cross‐Pollination of Awned and Awnleted Isogenic Lines of Soft Red Winter Wheat1

Five pairs of lines of soft red winter wheat (Triticum aestivum L. em Thell.) nearly isogenic except for awns vs awnlets were compared to determine which type would serve as the best pollinator or best female in a hybrid seed production field. Pollen dispersal was measured in the field by pollen collected with adhesive coated slides mounted on wind vanes and by percent seed set on male‐sterile lines. Although the differences were small, awnleted pollinators produced greater pollen loads than the awned, 142 vs 121 pollen grains/10 mm2 in 1968 and 154 vs 120 in 1969; percent seed set from the two pollinator types was not significantly different, 42 vs 40 and 66 vs 63 in the two respective years.Pollen dispersal of awnleted and awned types was also studied in the laboratory by using individual excised spikes placed over pollen traps. Significantly more pollen was collected from the awnleted lines. The 55.2% anther extrusion for the awnleted lines was not significantly greater than the 52.6% for the awned lines. The correlation of percent anther extrusion with number of pollen grains collected gave a coefficient of 0.74 which with 248 degrees of freedom was highly significant.Male‐sterile lines which were segregating for awns vs awnlets were studied to determine which type would serve as the best female. The awned male‐steriles gave 4% higher seed sets.In all phases of this study the differences between the isogenic lines were small or nonsignificant. There seemed to be a tendency for the awnleted type to be the best pollinator and the awned type to be the best female. Cross‐pollination potential is likely to be affected more by other morphological features.

The inheritance of anther extrusion in two spring wheat varieties

Anther extrusion was observed on two occasions under glasshouse conditions in two spring wheat varieties which showed different levels of expression of this character, and on F1 and F2 generations of reciprocal crosses between them. The results indicated that anther extrusion was controlled by few, possibly only two, genes with additive effects but had a low heritability. The association of pronounced anther extrusion and particular patterns of extrusion in the ear are suggested as the basis for rapid selection in glasshouse conditions for anther extrusion.

Some aspects of cross-pollination in wheat (Triticum aestivum L.) 2. Anther extrusion and ear and plant flowering pattern and duration

In the glasshouse the five spring wheat varieties Gaby, Jufy I, Opal, Orca and Peko were investigated for differences in number of anthers extruding during florescence. A maximum of 4 ears per plant was maintained. The mean of the absolute number of extruding anthers per ear varied from 105 (Peko) to 170 (Gaby). Also, significant differences were established in the absolute number of extruding anthers divided by the number of seeds set in each ear; this value ranged on an average of 2.27 (Opal) to 3.58 (Gaby). It is remarkable that a variety-ear number interaction manifests itself for both mentioned data: as far as Jufy is concerned the first developing ear produces least, whereas in Orca and Peko it produces most. No significant differences in this respect occur between the first 4 ears of a plant of the varieties Gaby and Opal. A simple relationship between number of extruding anthers and pollen donor capacity on the field could not be demonstrated.

Intra‐Plant Variation for Pollen Production in Male‐sterile and Fertile Alfalfa1

In Medicago saliva L. intra‐plant variation in pollen production occurred in partially male‐sterile clones, but it was not associated with either flower position on the plant or sampling date. The variation occurred at random throughout the plant. Anthers within the same flower varied for both number of pollen grains and percentage of normal pollen grains.The average number of pollen grains per anther varied among clones from about 440 to 850. The free anther had only about two‐thirds as many pollen grains as each of the remaining nine anthers. The number of normal pollen grains correlated with visual estimates of the amount of dehisced pollen, r = .854**, 11 d.f. Pollen abortion in male‐sterile plants apparently reduced internal pressure sufficiently to prevent rupture of the anther wall and extrusion of pollen.

Pollen Production of Fertility Restored Lines of Soft Red Winter Wheats1

Pollen production and seed set were compared for cultivars and derived homozygous pollinator “R” lines with cytoplasm and genetic restorers from Triticum timopheevi. Pollen production and anther extrusion were determined in the laboratory on excised spikes from greenhouse and field‐grown plants. Some restored “R” lines were as good as their parent cultivars for pollen dispersal. In diverse controlled environments restored “R” lines were somewhat more sensitive to temperature and photoperiod than were normal cultivars. Apparently “R” lines developed with T. timopheevi cytoplasm will be satisfactory for most environments.

POLLEN PRODUCTION AND DISSEMINATING PROPERTIES OF TRITICALE RELATIVE TO WHEAT

A study of the pollen production properties of three hexaploid triticale strains (Triticale hexaploide Lart.) showed that their anther length was significantly greater than that of wheat anthers (Triticum aestivum L. em Thell.) and the estimated number of pollen grains per anther ranged from 15,000 to 21,000. In comparison, a total of 8000 grains per anther was estimated for wheat, cult Manitou. Eighty-nine percent anther extrusion occurred in triticale cult Rosner, while Manitou averaged 70% anther extrusion. The period of anthesis of triticale varied according to strain but generally was of longer duration than in Manitou and thereby promoted outcrossing. Using a triticale strain carrying a dominant marker gene, 50% seed-set was obtained at a distance of 12 m leeward of the pollen source; however, a small percentage was still obtained at a distance of 30 m. It would appear from the limited number of triticales used in this study that a wide range of variability exists within this species in its pollen production and disseminating properties. With appropriate selection pressures, strains with an outbreeding habit could be developed for the purpose of hybrid seed production.

Pollen Production and Pollen Shedding of Hard Red Spring (Triticum aestivum L. em Thell.) and Durum (T. durum Desf.) Wheats1

We have investigated the relative pollen‐shedding abilities of 11 hard red spring and 3 durum wheat varieties and the relationships between pollen‐shedding and other varietal characteristics.The varieties differed in amount of pollen shed, number of pollen grains/anther, percent anthers extruded, tillers/plot, fertile florets/plot, fertile florets/tiller, yield, and kernel weight. Anther extrusion varied from 72% for ‘Thatcher’ spring wheat to 22% for ‘Lakota’ durum wheat. Number of pollen grains/anther varied from 3,867 for ‘Rescue’ to 2,687 for ‘Fortuna’ spring wheat.The amount of pollen shed was positively correlated with percent anthers extruded and tillers/plot but negatively correlated with fertile florets/tiller. Path coefficient analysis indicated that percent anther extrusion had the largest direct effect on pollen shedding. Pollen shedding ability of a variety was predicted on the basis of percent anther extrusion, pollen grains/anther and fertile florets/plot.