Hereditary changes in Capsicum annuum L. I. Induced by ordinary grafting

Summary Hereditary changes of certain Mendelian traits in red pepper after grafting are described. It is suggested that these changes are induced by a mechanism similar to that of transformation in higher organisms.The abstracts of this paper and the parts to follow have been presented at the XIII International Congress of Genetics held in August 1973 at Berkeley, California, USA as both a contributed paper and an exhibit including real herbarial specimen and color pictures of the variants genetically analyzed.     

Gibberellic acid as a gametocide for the common onion (Allium cepa L.)

Summary A high concentration of gibberellic acid (GA₃, 2%) was found to act as a gametocide for the common onion, Allium cepa L., when sprayed in the beginning of the bolting process.This technique is suggested as a possible substitute for hand emasculation, since it would greatly facilitate interspecific and intervarietal crosses, recurrent backcrosses and the selection of good B lines.     

Preventing chimerism in potato (Solanum tuberosum L.)

Summary A fast neutron irradiation experiment using two different dose rates has been performed on the potato variety Desiree in order to obtain chimera-free mutants. Both tubers and tuber parts (cross sections) were de-eyed at different moments before and after irradiation. Adventitious sprouts successively developing on the callus in the holes of excised eyes were separated from the treated tubers and planted individually. So called grouped sprouts were separated. Results indicated that (practically) chimera-free mutants can be obtained by de-eying tuber parts shortly before irradiation, by applying relatively high dose-rates and by taking adventitious sprouts which develop not earlier than three months after irradiation.Separation of the grouped sprouts demonstrated that each part originated from a single original cell.This article is dedicated to Dr F. P. Ferwerda who till September 1969 was in charge of potato mutation research at our Institute.     

Comparison of some selection procedures and objectives in faba beans (Vicia faba L.). I. direct and index selection for seed yield

Summary Starting with two heterogeneous F₂ populations, each based on 20 cross combinations, different selection procedures were applied for four consecutive selection cycles. Three of the selection procedures involved seed yield per plant (SYP): (i) direct selection for SYP (DSY); (ii) indexselection for SYP (ISY) with plant length, the ratio of the vegetative top to plant length, end of grain filling and duration of the generative stage as auxiliary characters and finally; (iii) independent culling levels selection (ICL) for the index described above and crude protein content. For ICL-selection the attention is focussed on SYP in this paper.For all three selection procedures, predicted and realized responses were calculated and expressed as percentage of a corresponding non-selected population. The intensities of selection differed over selection methods and generations, mostly due to practical constraints.As far as predicted responses are concerned, ISY-selection seemed to be slightly superior to DSY-selection and DSY-selection to ICL-selection. This order may partly be due to differences in selection intensity. However, none of the predictions was very accurate, but the predictions of ICL-selection seemed to be the most accurate. This has been ascribed also to the relative mild selection intensity applied in ICL-selection. It is concluded that a decision in favour of a complicated selection procedure like index selection based on predicted responses only cannot be defended. As far as realized responses are concerned, DSY-selection seems to be slightly superior to the other two selection procedures, as it is the only procedure that resulted in a more or less stable positive response to selection.The auxiliary characters, especially plant length, showed a marked correlated response to all three selection procedures. In case of direct selection for SYP this seemed paradoxical with the inefficiency of index selection, but, it may reflect the differences in the genuine genotypic correlations and the estimated genotypic correlations.     

Characterization of cytoplasmic male sterility in Petunia hybrida. I. Localization,composition and activity of esterases

Summary Anthers of male fertile, cytosterile and restored male fertile clones of Petunia hybrida were compared for esterase activity and composition in subsequent stages of microsporogenesis. Three methods were applied (i) ultra-thin layer isoelectric focussing on polyacryl amide gels, (ii) quantitative spectrophotometrical assay, (iii) histochemical determination of total esterase activity associated to the azo-coupling method (Pearse, 1972).In male fertile and restorer idiotypes the isozyme patterns were quite similar. Both the number and intensity of bands increased gradually till the tetrad stage. In contrast, esterase activity in cytosterile anthers remained at a low level and hardy any new bands showed up in later stages. This unvariable, low activity level in cytosterile anthers was also found in the spectrophotometric assay. Histochemical determinations revealed that in male fertile anthers esterase activity is concentrated in the outer tapetal layer at late prophase and that it accumulates there till the early microspore stage. In male sterile anthers esterase accumulation in the tapetal cells stops at the moment that tapetal breakdown becomes visible. This suggests that differences in esterase activity and composition are an effect rather than a cause of the failing pollen formation.     

Characterization of cytoplasmic male sterility in Petunia hybrida and Zea mays. Localization and activity of cytochrome c oxidase

Summary Anthers of male fertile, cytoplasmic male sterile (cms), and restored male fertile Petunia hybrida, are analyzed for cytochrome c oxidase (cox) activity in subsequent stages of microsporogenesis, and compared with anthers of male fertile, cms-S and cms-C Zea mays. The cox activity is determined in anther extracts and cytochemically. In petunia anthers, the first differences in cox activity occur from meiosis onward. However, at these stages, the initial symptoms of degeneration are already apparent. It is suggested that the decline in enzyme activity of the cms petunia anthers is the result rather than the cause of the non-formation of functional pollen.In maize anthers, the cox activity of sterile-type anthers is reduced in comparison with fertile-type anthers from premeiosis onward. There are also consistent cytochemical differences in the mitochondrial organization of cox activity between pollen of cms-S and male ferile maize anthers. In fertile-type mitochondria, the DAB reaction product indicating cox activity is localized in the cristae and within the space between the outer and inner limiting membranes of the organelles. In mitochondria of pollen of cms-S maize, cox activity is only observed between the outer and inner membranes of the mitochondria. The biochemical and cytochemical differences are observed at stages of development at which no structural signs of degeneration are apparent. The results suggest that cms in maize correlates with deviations in cytochrome c oxidase activity.Abbreviations cox cytochrome c oxidase - DAB 3,3-diaminobenzidine     

Occurrence of 2n gametes in the F1 hybrids of Oriental × Asiatic lilies (Lilium): Relevance to intergenomic recombination and backcrossing

Cytological modes of the origin of 2n gametes were investigated in six different genotypes of F₁ hybrids between Oriental and Asiatic (OA) lilies (Lilium, 2n = 2x = 24). Chromosome pairing between the parental genomes was very low, the average frequency range from 0.3 to 1.2 bivalents per cell among the genotypes. Within a genotype the frequency of bivalents varied from 0 to 6 in some cases. The normally occurring haploid pollen grains were totally sterile. In contrast, in different genotypes, variable percentages of 2n pollen were found and shown to be fertile as estimated from pollen germination. A cytological analysis of Metaphase I and subsequent stages of meiosis using genomic in situ hybridization (GISH) revealed that there was intergenomic recombination between the alien genomes. Following Metaphase I stage, three different types of abnormal cytological events led to the formation of 2n pollen: (i) Post-Metaphase I division (PMI), (ii) Post-Metaphase II division (PMII) and (iii) Asymmetric Cytokinesis of the pollen mother cell followed by chromosome division. All three cytological events led to first division restitution (FDR) gametes. Based on in vitro pollen germination it was proved for two genotypes that 2n pollen was viable only during the first day of anthesis. It was possible to use 2n pollen successfully for backcrossing. Implications of 2n pollen for intergenomic recombination in BC₁ progenies are discussed.     

Genetic linkage of QTLs for late blight resistance and foliage maturity type in six related potato progenies

A set of test crosses of diploid potatoes was used to identify QTLs for foliage resistance against Phytophthora infestans and QTLs for foliage maturity type, and to assess their genetic relationship. The most important locus for both traits was found on chromosome 5 near marker GP21: the allele of marker GP21 that is associated with resistance to late blight is also associated with late foliage maturity. An additional QTL with a small effect on foliage maturity type was identified on chromosome 3, and additional QTLs for late blight resistance were found on chromosomes 3 and 10. Another QTL was detected on chromosome 7 when resistance was adjusted for the effect of foliage maturity type. The additional QTLs for resistance against P. infestans on chromosomes 3 and 10 seem to be independent of foliage maturity type and are not affected by epistatic effects of the locus on chromosome 5. The effects of the additional QTLs for resistance are small, but early maturing genotypes that necessarily have the allele for susceptibility for late blight on chromosome 5 may benefit from the resistance that is provided by these QTLs on chromosomes 3 and 10.