Cytoplasmic relatedness of apple landraces and cultivars: a molecular analysis

Summary Mitochondrial DNA (mtDNA) diversity has been determined in apple landraces and cultivars, based upon restriction fragment length polymorphisms (RFLPs) for several mitochondrial genes. Our analysis includes three cultivars, Golden Delicious, McIntosh and Delicious, which represent the various patterns of mtDNA polymorphisms previously described (Ishikawa et al., 1992). A total of five RFLPs were detected, allowing classification of the apple genotypes into four cytoplasmic groups: GroupI, Golden Delicious-type; GroupII, McIntosh-type; GroupIII, Delicious-type; and Group IV, Dolgo Crab-type. European landraces and cultivars were assigned to Groups I, II, and III, while chinese crab apples were placed in either Group III or IV.     

用AFLP技术构建棉花雄性不育三系及其杂种F1的DNA指纹图谱

实验应用AFLP同位素标记法,获得了棉花细胞质雄性不育系、保持系、恢复系及其杂种F1的DNA指纹图谱.较为详尽地介绍了有关AFLP的技术核心及注意点,并探讨了其适用于棉花研究的方法.结果表明,AFLP是一种十分有效的DNA指纹技术,它具有多态性丰富、稳定性高、重复性好等优点.     

Large yield differences between reciprocal families of Solanum tuberosum

Summary A number of reports have indicated differences in reciprocal families of Solanum tuberosum when intergroup hybrids were studied. Questions have been raised concerning the potential magnitude, frequency, and genetic basis for such differences. In this study, exact reciprocal crosses were made using parents characterized by different maturities and having different cytoplasmic sources within Solanum tuberosum in order to substantiate previous claims of reciprocal differences and to clarify the nature of such differences.Field trials revealed reciprocal differences which were large and highly significant. Reciprocal yield differences of up to 115% were observed when parents of opposite maturities were used. In seven crosses, the higher-yielding reciprocal always had the higher-yielding parent as the maternal parent. Significant reciprocal differences for flowering and vine maturity were also observed between some families. The F₂ populations were generated for one set of reciprocals and the reciprocal differences in the F₂ generation seemed to be substantially reduced relative to the F₁ generation.It is concluded that the occurrence of large reciprocal differences seems to depend more upon having parents of opposite maturity than upon the taxonomic origin of the parent's cytoplasm. This, in conjunction with the reduced F₂ reciprocal differences, suggests that observed differences may be due to very persistent maternal effects or a type of dauermodification, rather than true cytoplasmic inheritance.Cooperative Investigation of U.S. Department of Agriculture, Science and Education Administration. Agricultural Research and the Wisconsin Agricultural Experiment Station.     

Mitochondrial genome variation in Allium ampeloprasum and its wild relatives

Limitation in mitochondrial genome diversity of leek, revealed by restriction fragment length polymorphism (RFLP) analyses with mitochondrial gene probes, prevent a cytoplasmic male sterility (CMS) system in elite populations. However, mitochondrial genome diversity was detected in Allium ampeloprasum L. wild accession and landraces, as well as in pearl onion. Within this plant material, nine mitotypes were distinguished and could be used in order to broaden the genetic basis of leek. A chimeric mitochondrial gene configuration is usable as a marker for the sterility inducing cytoplasms (S₁) in chives (Allium schoenoprasum L.) and in onion (Allium cepa L.) for (S) and (T) cytoplasm. This chimeric mitochondrial gene configuration is also present in the subgenus Allium, revealed by polymerase chain reaction (PCR). However, only a faint amplicon was observed in a few accessions investigated herein, suggesting that this fragment might be present to a lesser level in mitochondrial DNA, as a sublimon.     

A simple method to control the seed purity of japonica hybrid rice varieties using PCR-based markers

Cytoplasmic male sterility (CMS) by the cms‐bo cytoplasm and its restoration by the nuclear restorer gene, Rf‐1, are used for seed production of japonica hybrid rice varieties. To produce pure hybrid seeds, a prerequisite is to properly manage the seed purity of parental lines, especially CMS lines. In this study, three dominant polymerase chain reaction (PCR)‐based markers (M1, M2 and M3) were developed to detect mutual contamination in seed batches of CMS lines, maintainer lines, restorer lines and hybrids. M1 detected the mitochondrial sequence that was present in the cytoplasm of common japonica varieties and absent in the cms‐bo cytoplasm. M2 and M3 detected the chromosomal sequence related to the Rf‐1 allele in restorer lines and the rf‐1 allele in common japonica varieties, respectively. By the strategic use of these markers, japonica hybrids and their parental lines could be efficiently distinguished from each other. Furthermore, sensitivity tests for the three markers with a series of crude DNA samples prepared from polished grains demonstrated that these markers could detect one contaminating grain among 500 or 1000 grains. Therefore, the bulk PCR analyses with the markers developed here probably make it possible to control the seed purity of japonica hybrids properly by selecting appropriate seed batches of their parental lines quickly and efficiently.     

Development of new sources of cytoplasmic male-sterile lines in rice

Two male-sterile lines, KalashreeA and PadminiA, with a Miz.21 cytoplasm source were developed through indica/indica hybridization followed by repeated backcrossing with their respective recurrent male parents (Kalashree and Padmini) up to the BC₆ generation. These two cytoplasmic male-sterile lines are suitable for use in the development of hybrids for lowland situations owing to their intermediate to semi-tall stature, late flowering duration, good grain quality and easy fertility restoration ability.     

Effect of cytoplasmic male-sterility in sorghum on host plant interaction with sorghum midge,Contarinia sorghicola

Summary Sorghum midge, Contarinia sorghicola Coq. (Diptera: Cecidomyiidae) is one of the most important pests of grain sorghum worldwide. We studied the reaction of midge-resistant and midge-susceptible genic-cytoplasmic male-sterile (A-lines) and their maintainers (B-lines), and the effect of resistant and susceptible restorers on sorghum midge. Midge damage and adult emergence were significantly lower on the B-lines of midge-resistant genotypes (PM 7061 and PM 7068) than their corresponding A-lines, while the reverse was true for the midge-susceptible genotypes (296A and ICSA 42). Differences in midge damage and the number of midges emerged were not significant between the midge-resistant and midge-susceptible A-lines when infested without pollination (except midge emergence on PM 7061A). Pollination with a midge-resistant restorer (DJ6541) reduced midge emergence significantly in one of two seasons. Source of pollen did not influence midge emergence on the highly-resistant A-line, PM 7061A. The implications of these observations in the development of midge-resistant hybrids were discussed.     

Identification of the Putative Cytoplasmic Donor of a CMS System in Brassica juncea

Chloroplast (cp) and mitochondrial (mt) DNA restriction profiles of a cytoplasmic male sterile (CMS) line of Brassica juncea and its maintainer line were compared and found to be markedly different. Comparison of cpDNA restriction profiles of fifty different species of genus Brassica and some allied genera showed that the cpDNA profiles of CMS lines were similar to that of B. tournefortii for twenty different restriction endonucleases. This CMS system is thus not of spontaneous origin as reported earlier, but is alloplasmic in nature. Comparison of restriction profiles of mtDNA of B. tournefortii and CMS lines revealed some differences which might either be due to changes in DNA pattern during the transfer, or, due to the cytoplasm coming from a B. tournefortii line different from the one used in this study.     

Genetic studies on the interspecific cytoplasm substitution lines of an Asian perennial strain of Oryza rufipogon Griff. and O. glaberrima Steud.

Summary It is shown that the restorer gene Rf _j extracted from the Japanese rice variety Akebono is effective on pollen restoration in the cytoplasm substitution line having the nucleus of Oryza glaberrima and japonica or indica cytoplasm of O. sativa, and is of the sporophytic type.The Asian perennial type of the wild rice species O. rufipogon is considered to be the progenitor of O. sativa. Two substitution lines having the cytoplasm of a perennial strain of O. rufipogon from Sri Lanka and the nucleus of O. glaberrima with or without the gene Rf _j in homozygous condition have been bred by means of successive backcrosses. These lines have now reached the BC₅ generation. Plants of the lines resemble morphologically the recurrent parent, but do not show pollen restoration, indicating that the cytoplasm of the rufipogon strain induced male sterility and that the gene Rf _j does not act as the restorer.     

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.