A partially male-sterile mutant line of soybeans,Glycine max (L.) Merr.: Characterization of the msp phenotype variation

Summary Investigations of variable expression of msp partial male sterility in soybeans (Glycine max (L.) Merr.) showed that higher temperatures promote male fertility in msp homozygotes and showed that infectious agents are not intrinsic to the sterility system. Exchange grafts failed to modify fertility levels of msp msp rootstocks, Msp Msp scions, and their self-progeny. Tests for soybean mosaic virus and tobacco ringspot virus were negative in partially male-sterile plants, in control fertile plants, and in self-progeny of grafted plants. Growth-chamber experiments and field observations manifested that male fertility of msp msp plants is higher in hot environments than in cooler ones. The unexpected aberrant ratios of fertile to partially male-sterile plants observed in 1977 (Stelly & Palmer, 1980) are explainable on the basis of msp temperature sensitivity.Our observations suggest that homogeneous msp msp populations may be increased in hot environments.Research Geneticist, SEA-AR, USDA, Iowa State University, Ames, Iowa 50011, USA.     

Agronomic characteristics and genetics of a chromosome interchange in soybean

Summary A chromosome interchange in soybean (Glycine max (L.) Merr.) was studied agronomically and genetically, and comparisons of seed or abortion position within the pod were related to chromosome structure. Comparisons were among plants heterozygous for a chromosome interchange (N/T), plants homozygous for the interchange (T/T), and homozygous normal-chromosome plants (N/N). The latter two genotypes were male fertile and female fertile. Heterozygous interchange plants, which are about 50% pollen sterile and ovule sterile, are typical of a large number of plants that have equally frequent alternate and adjacent chromosome segregation. Yield, lodging, plant height, and seed oil and protein percentages among all three genotypes were similar even though significant differences existed for seed weight, seed number, and pod number per plant. Seed abortions were more frequent in the basal position of the pod than in either the middle or apical positions in N/N and T/T genotypes. Ovule abortions in N/T plants were equally frequent among all positions both in two- and three-ovule pods. The middle seed in a three-ovule pod was heavier than the basal or apical seed among all three genotypes.Joint contribution: USDA ARS, and Journal Paper No. J-11300 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011, USA, Project 2471.USDA ARS, Department of Agronomy and Genetics, Iowa State University, Ames, Iowa 50011, USA.Department of Agronomy, Iowa State University, Ames, Iowa 50001, USA.     

Pollen production in soybeans with respect to genotype,environment, and stamen position

Summary Our objective was to determine the average numbers of pollen grains from fertile plants (Ms ₁) and the average numbers of coenocytic microspores from genetic male sterile plants (ms ₁ ms ₁) in soybeans, Glycine max L. Merr. Comparisons were made between the average numbers of pollen grains and the average numbers of coenocytic microspores with respect to environment where plants were grown and to stamen position in the flower. Five male sterile lines were used. They included the North Carolina ms ₁ mutant, the cultivar Hark with the ms ₁ gene, and mutants identified as the Urbana, Tonica, and Ames male steriles. Three environments used were the Agronomy Farm, University of Georgia, Athens, Georgia; the Agronomy and Agricultural Engineering Research Center, Iowa State University, Ames, Iowa; and the Agronomy Greenhouse, Iowa State University, Ames, Iowa.Pollen production from fertile plants varied from 374 to 760 pollen grains per anther among genetic lines and environments. This variation may be an important consideration in selecting a male parent to use as a pollinator for hybrid seed production.Among fertile plants, the average numbers of pollen grains per anther of the separate stamen and and of the lower whorl of stamens were significantly different only in greenhouse-grown plants. Among male sterile plants, the average numbers of coenocytic microspores per anther of the separate stamen and of the lower whorl of stamens were significantly different in three genotype x environment combinations. These three exceptions did not conform to any genetic or environmental pattern. Deviations from the expected ratio of 4 pollen grains from fertile plants: 1 coenocytic microspore from sterile plants were attributed to initial differences in the average number of microspore mother cells between the two genotypes.Joint contribution: Agricultural Research Service, USDA, North Central Region, and Journal Paper No. J-8910 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

Analysis of genic male sterility in Brassica oleracea

Summary The male sterility system MS-1 of Brassica oleracea was studied in order to elucidate if nucleo-cytoplasmic interactions determine this system. Crosses of male sterile MS-1 genotypes with heterozygous MS-5 genotypes gave fully fertile F₁ progenies. Selfing of seven F₁ plants resulted in five F₂ populations showing a 9:7 segregation ratio and two a 3:1 ratio for fertile and male sterile plants. Two F₂ progenies deviated from the expected 9:7 or 3:1 segregation ratios for fertile and male sterile plants. Thermosensitivity and distortion of the meiosis are suggested as the causal factors underlying the deviation of the segregation ratios. It was concluded that nuclear factors determine the male sterility in the MS-1 system, because the presence of a nucleocytoplasmic interaction in this system should have given only a 3:1 segregation ratio for fertile and male sterile plants in the F₂ generation.     

Inheritance of functional male sterility in Streptocarpus Constant Nymph and its mutants

Summary A study was made of the inheritance of functional male sterility of Streptocarpus Constant Nymph and its mutants. It was concluded that plants with genotypes Da. are male sterile although in rare cases a fruit may be produced. Plants with genotype data are fertile although the degree of fruit set greatly varies. This may have been caused by many factors including physiological abortion, as it was often observed that only one or two flowers of an inflorescence grow into fruits, the other remaining undeveloped.Some thoughts about the origin of this unfavourable allele and its survival in nature are presented.It is suggested that when sterility is observed, the cause of this sterility may be functional male sterility.     

Pollen germination and pollen tube growth following self-pollination and intra- and interspecific pollination of Medicago species

Summary Pollen germination and pollen tube growth after self- and intra- and interspecific pollinations of annual [M. scutellata (L.) Mill., M. disciformis DC., and M. rigidula (L.) All.] and perennial (M. sativa L.) Medicago species were studied using a Carl Zeiss microscope with a fluorescence filter attachment.Self-pollination of self-fertile annual and intraspecific pollination of cross-fertile perennials were characterized by high pollen germination and rapid normal pollen tube growth. In contrast pollen germination percentages were very low and many pollen tube growth abnormalities occurred following interspecific pollination and self-pollination of self-sterile plants. The time period from pollination to fertilization for interspecific crosses was about double that following self-pollination of the annual species. However, fertilization occurred frequently following interspecific pollinations. Much of the sterility was due to factor(s) operating after fertilization.Cooperative investigations of the Kansas Agricultural Experiment Station, Dept. of Agronomy and the U.S. Department of Agriculture, Agricultural Research Service. Contribution No. 82-582-J- Mention of a trademark name or proprietary product does not constitute a guarantee or warranty by the U.S. Department of Agriculture, and does not imply its approval over other products that also may be suitable.     

Chloroplast-DNA variation in the wild and cultivated olives (Olea europaea L.) of Morocco

The male sterile plants that segregated in a BC₅F₂ of `C. sericeus × C. cajan var. TT-5' population were maintained by sib mating. The male sterile plants were crossed with ICPL-85012.Approximately 50% of the F₁ plants were sterile. F₂ plants derived from the fertile F₁ plants did not segregate for male sterility. The reciprocal hybrid i.e. ICPL-85012 × Fertile derivatives from C. sericeus × TT-5, did not express male sterility. However, among the 12 F₂ plant to row progenies, two segregated 25% male sterile plants and remaining 10 did not segregate. The segregation pattern in subsequent progenies revealed that the sterility was under control of a single recessive allele. Studies on the backcross and their BC₁F₂ and BC₁F₃progenies revealed another sterility gene which was found to be dominant in inheritance. This paper shows that what was thought to be cytoplasmic male sterility from C. sericeus cytoplasm is actually a single dominant gene possibly acting in concert with a single recessive gene to mimic cytoplasmic male sterility. This revised version was published online in July 2006 with corrections to the Cover Date.     

A cluster analysis of wild and domesticated soybean phenotypes

Summary Cluster analysis techniques were used to examine phenotypic variation within the USDA Soybean Germplasm Collection. This study included ten Plant Introductions each of the domesticated soybean, Glycine max (L). Merr., the wild soybean, G. soja Sieb. & Zucc., and a disputed species, G. gracilis Skvortz. G. max and G. soja were found to be morphologically distinct entities and G. gracilis was found to be conspecific with G. max. Because G. gracilis probably represents weedy races associated with the cultivated soybean and because gracilis phenotypes can be distinguished from G. max, the designation, G. max forma gracilis, is recommended.Joint contribution: North Central Region, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-9389 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

Methods of overcoming interspecific barriers in Trifolium

Summary Barriers to interspecific hybridization in Trifolium were investigated by manipulation of mentor pollen treatments, ploidy levels, and compatibility and male sterility systems. Crosses involving the addition of mentor pollen produced fewer seeds and hybrids than crosses involving normal pollination. Lower seed set with mentor pollen was deduced to result from the use of less viable pollen, approximately half the pollen having been killed by alcohol. Pollinations at the diploid level resulted in more hybrids than at the tetraploid level, perhaps because genes for male sterility produced higher female sterility in the tetraploids. The self-compatible stock produced more seeds, mostly selfs, than the self-incompatible stock, but produced more hybrids only in one cross, T. pratense L. × T. diffusum Ehrh. The use of male-sterile female parents reduced selfing but produced fewer hybrids than male-fertile female parents. Techniques of this study were designed to affect prefertilization barriers, but the lack of effect may indicate that postfertilization barriers in Trifolium are of greater importance.Journal Article No. 98-3-208 of Kentucky Agricultural Experiment Station. Published with approval of the Director.     

Inheritance of genetic malesterility in Pennisetum americanum (L.) Leeke

Summary A spontaneously occurring male sterile condition was located in an inbred line Vg 272 of Pennisetum americanum. Male sterility was inherited as a monogenic recessive condition and showed independent assortment with hairy leaf surface phenotype. Transfer of male sterile allele to inbreds Vg 212 and IP 482 revealed no cytoplasmic effects on the expression of male sterility. Stigmas of the male sterile plants were found to possess the same amount of receptivity upto three days with normal seed set, upto six days with reduced seed set and almost with nil receptivity on the seventh day.     

Chromosomal monogenic dominant male sterility in chinese cabbage (Brassica rapa supbs. pekinensis (Lour.) hanelt)

Summary Strong indication was found for the existence of a chromosal monogenic dominant male sterility-gene in chenese cabbage. This source of male sterility can be of practical use for the production of hybrid varieties. A pronounced drawback is the required removal, in the breeding and seed production stage, of the approximately 50% male fertile plants from each offspring of male sterile plants. Fortunately this removal is facilitated by the penomenon of apical dominace in the flowering process in the whole Brassica rapa taxon. Moreover an advantage of dominant monogenic male sterility is its easy and rapid introduction into all available genotypes of chinese cabbage.     

Gametocidal properties of RH-531, RH-532, RH-2956, and RH-4667 on spring wheat (Triticum aestivum L.)

Summary Several chemicals were evaluated for their gametocidal properties to control pollination in hybrid wheat (Triticum aestivum L. em Thell.) seed production. In a preliminary study, four chemicals were applied to three cultivars of spring wheat at two application times. RH-532 was the most effective of the four gametocides, reducing fertility to a 0 10% level for all three cultivars.In a second experiment, RH-532 was applied to one cytoplasmic male-sterile and three normal spring wheats at four rates (0.56, 1.12, 2.24, and 4.48 kg/ha) and at two times of application. Alternate strips of pollinator were planted throughout the experiment. All treatments decreased fertility. plant height, and spike length of the three normal wheats. RH-532 did not inhibit spike emergence of two semidwarf cultivars or one of conventional height. Cultivars did not respond similarly to treatments.Yields of cross-pollinated seed were only 1 21% of the normal yield when fertility levels on treated plants reached 0 10%. Hybrid seed content of the harvested seed ranged from 2 55%. On the treated male-sterile line, yield was significantly reduced in comparison with the open-pollinated check. Inhibitory properties of this chemical suppressed the fertilization potential of the female as well as inducing male sterility.The differential response of genotypes to treatments indicates that cultivars should be screened for male and female sensitivity to this chemical. If differential sensitivity is found, breeding and selection to improve this trait may be possible. Different environmental conditions may alter the response of cultivars to this chemical, with less effect on the female structures.Published with the approval of the Director, North Dakota Agricultural Experiment Station, as journal article No 71a.     

Chromosome behavior and sterility of hybrids between the common onion,Allium cepa,and the related wild A. oschaninii

Summary Four hybrid plants were obtained when cytoplasmic male-sterile onion inbreds, Allium cepa L., were pollinated with a wild cepa-like allium introduced from northeastern Iran and identified as A. oschaninii O. Fedtsch. It has been proposed on morphological grounds that A. oschaninii is wild A. cepa or the ancestor of A. cepa. Nevertheless, chromosome irregularities and complete sterility in the hybrids suggest that there may be a greater sterility barrier between A. cepa and A. oschaninii than between A. cepa and 3 other species reported to cross with A. cepa, namely A. fistulosum L., A. galanthum Kar. et Kir., and A. pskemense B. Fedtsch.Cooperative investigation of the U.S. Department of Agriculture and the Idaho Agricultura Experiment Station, Parma Branch Station.     

Identification and Genetic Studies of the Inhibition of Dominant Male Sterility in Brassica napus

By transferring dominant male sterility (DMS), caused by the gene Ms, to genotypes with various types of cytoplasm 12 DMS lines were developed and a number of crosses made between the DMS lines and other genotypes of Brassica napus. During the course of this population improvement programme, 16 genotypes were identified as having the capacity to restore the fertility of F₁ plants with the Ms gene. According to pedigree analysis, the inhibitory gene in those lines probably originated from a few genotypes from Australia and Germany. In further studies the inheritance of the sterility inhibition was determined, providing definite evidence that dominant male sterility and its inhibition in B. napus are controlled by two dominant interacting genes rather than by multiple alleles.     

Introgression of resistance to late blight (Phytophthora infestans) from Solanum pinnatisectum into S. tuberosum using embryo rescue and double pollination

In order to investigate the agricultural potential of the genus Vicia, and identify traits associated with productivity and responsiveness to environment, 34 undomesticated Mediterranean accessions representing Section Narbonensis (V. johannis, V. narbonensis) and V. sativa were grown in five contrasting environments in northern Syria (growing season rainfall: 76–290 mm).Highly significant genotype × environment interactions were observed for all traits. For most of the components of yield, accession mean performance (productivity)was highly correlated with responsiveness across environments (r = 0.59–0.96), as defined by joint linear regressions. Thus high yielding genotypes tended to be relatively more productive than low yielding genotypes under conditions that favoured high yields. Regression analysis revealed that mean site yields were positively correlated to rainfall (r = 0.85) and its attendant effect on growing season length as measured by cumulative season temperature and phenology (r = 0.59–0.81).In order to examine yield related traits independently of taxonomy, genotypes were grouped into three categories using K-means clustering based on productivity and responsiveness of seed, hay and biological yield. Highly productive/responsive genotypes were tall with high harvest index, large seeds and low fecundity (seeds and pods per plant), whereas unproductive/unresponsive plants tended to be short, highly fecund, with small seeds and low harvest index. Principal components analysis showed that responsiveness, in terms of seed, hay and biological yields, was closely related to phenological plasticity. Thus highly productive/responsive genotypes were able to start flowering earlier than unproductive/unresponsive genotypes in early environments, but significantly later in late, higher rainfall environments. Plant growth habit was also related to yield responsiveness. In environments with little biomass production the proportion of erect plants was high in all three categories. In more favourable, high biomass environments, the proportion of erect plants in unproductive/unresponsive genotypes fell dramatically, but was unchanged among productive/responsive genotypes. We suggest that for unproductive/unresponsive genotypes competition for light is increased under optimal growth conditions. We argue that the optimal combination of fixed and responsive traits in high yielding genotypes results in a `compound interest-type' response to more favourable environments. Highly productive and responsive genotypes can capture resources more effectively than their low yielding counterparts, leading to a positive relationship between performance and responsiveness for most components of yield. Differences in productivity and responsiveness for seed, hay and biological yield reflected Vicia taxonomy, increasing in the following order from low to high: V. johannis, V. sativa, the small seeded V. narbonensis (salmonea, jordanica, affinis) V. n. var. narbonensis, and finally V. n. var.aegyptiaca. V. n. var. aegyptiaca showed the most agricultural potential, since the taxon contained all the properties of productive/responsive genotypes listed above, yielding >1 t/ha under extremely arid conditions (104 mm),and >2.5 t/ha on 290 mm rainfall, confirming its potential for dry environments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of the frequencies of restorer- and maintainer-alleles involved in CMS1 and CMS2 in German chive varieties

There are two cytoplasmic male sterility (CMS)‐systems in chives (Allium schoenoprasum L.), which can be employed in hybrid breeding. However, the probability for selection of maintainer genotypes from German open pollinated varieties is not known. Therefore, the allelic frequencies of the restorer genes X and T involved in CMS¹ were determined in 12 German commercial chive varieties by test crossing single plants to male sterile, temperature‐insensitive genotypes [(S₁)xxT] for segregation analyses of offspring. Temperature sensitive genotypes [(S₁)xxT_] are able to produce pollen at higher temperatures, and should therefore be excluded from hybrid breeding to avoid self‐pollination of the maternal parent. The mean value of the frequency of the non‐restoring allele x in the populations examined was 0.62. The mean value of the allele t, which is responsible for the temperature insensitivity, was 0.9. As a consequence of these allelic frequencies about one‐third of all plants of the chive varieties examined were designated CMS₁ maintainer genotypes, leading to the production of temperature insensitive male sterile lines. The incidence of CMS₂ maintainers in the German varieties examined was nearly four times lower than CMS₁ maintainers. The mean value of the frequency of the non‐restoring allele _st2 involved in the CMS₂‐system was 0.29.     

Repeatability of regression stability indexes for grain yield of oats (Avena sativa L.)

Summary Two lines of descent were established from an F₃ bulk lot of oats (Avena sativa L.) initiated by mixing seeds from approximately 250 crosses. For one line of descent, seeds were radiated with thermal neutrons or X-rays from F₃ through F₆, followed by five generations of bulk propagation. The second was propagated for 10 generations. No artificial selection was practiced in either line of descent. Grain yield data from 20 random strains from each of four generations from the radiated (F₇, F₈, F₉, and F₁₁) and five from the nonradiated (F₃, F₆, F₇, F₈, and F₁₂) line of descent and 20 check cultivars tested in 14 environments were used for estimating regression stability indexes of oat strains.The 14 environments were assigned randomly to two sets of seven, and regression stability indexes were computed for the 180 experimental oat strains for both sets. Intrageneration correlations between regression stability indexes from the two sets of environments ranged from –0.35 to 0.64 (18 d.f.), and only one of nine was significant, indicating poor repeatability for estimates of this statistic computed from different sets of environments.Correlations between regression stability indexes from two sets of environments, one in which the environments varied by soil nitrogen levels and a second in which they varied by soil phosphorus levels, ranged from –0.01 to 0.28, none of which was significant.The relative magnitudes and ranking of the regression stability index values for the oat genotypes were nearly identical when environmental productivity indexes were assessed with any number of check cultivars from 2 to 20.Journal paper No. J-8080 of the Iowa Agriculture and Home Economics Experiment Station. Ames. Iowa. USA 50010. Project 1752.     

Breeding cassava for resistance to cassava mosaic disease

Summary Cassava mosaic disease (CMD) is one of the most serious and widespread diseases throughout cassava growing areas in Africa, causing yield reductions of up to 90%. Early research on breeding of cassava (Manihot esculenta Crantz) for resistance to CMD in Africa is reviewed. Changes in population size and in activity of the white-fly vector to CMD (Bemisia tabaci Genn.) in relation to changes in environmental conditions such as amount and distribution of rainfall, light intensity and temperature are discussed in relation to screening for resistance to CMD. Over the past eight years, significant progress has been made at the International Institute of Tropical Agriculture (IITA). Resistance to CMD has been successfully incorporated into high yielding cultivars of acceptable quality. The CMD resistant material has been evaluated and many promising clones have been selected in various countries in tropical Africa and India. The resistance has been effective in those countries.     

A new source of cytoplasmic male sterility in sunflower

Summary Interspecific substitutions of the nucleus of Helianthus annuus (2n=34) cv. Saturn into the cytoplasm of H. petiolaris (2n=34) by successive backcrossing, resulted in progenies with indehiscent anthers containing white, rather than normal yellow, pollen. Further backcrossing by cv. Saturn failed to restore pollen shed, suggesting that the male sterility was cytoplasmic. In vivo germination tests of pollen from 23 such plants from eight BC₅ lines, indicated complete pollen sterility for 14 plants, but normal seed set, suggesting that female fertility was not affected. Meiosis in all plants examined was normal.Crosses between seven sources of pollen-fertility restorer, one collection of wild H. annuus, and an existing source of cytoplasmic male sterility, resulted in a high frequency of plants with normal pollen shed in all F₁ progenies. However, no normal pollen shed was evident in F₁ progenies for similar crosses between BC₅ male-steriles and three of the seven restorer sources, nor for the single wild H. annuus evaluated. The foregoing suggests that the backcross substitution lines are a new source of cytoplasmic male sterility. The inheritance of restoration of pollen shed was complex and not fully elucidated. Some data suggested that two independent, complementary, dominant genes were required, but others indicated two to three independent, dominant genes.     

Enarthrocarpus lyratus-based cytoplasmic male sterility and fertility restorer system in Brassica rapa

Substituting the nuclear genome of Brassica rapa into the cytoplasmic background of Enarthrocarpus lyratus through backcross substitution helped in developing cytoplasmic male sterility (CMS). Alloplasmic male sterile plants had pale green leaves, small flowers with narrow petals and rudimentary anthers. Female fertility, low initially, improved considerably with advanced backcross generations. Male sterility expression was stable throughout the growing season. Except for EC 339014, all B. rapa accessions (38) evaluated were partial maintainers of the male sterility. Introgression of gene(s) for fertility restoration from the cytoplasm donor species was facilitated by homoeologous pairing between B. rapa and E. lyratus genomes, as was apparent from the very frequent occurrence of a trivalent in the monosomic addition plants (2n = 10 II + 1 I). Backcrossing of fertile monosomic addition plants with B. rapa led to the recovery of male fertile plants possessing the stable euploid chromosome number (2n = 20). These plants restored male fertility in crosses with different (lyr) CMS B. rapa genotypes, confirming the introgression of fertility restorer gene(s) from E. lyratus, the cytoplasm donor species.