Inheritance of male fertility restoration of the cytoplasmic-nuclear male-sterile line NJCMS1A of soybean [Glycine max (L) Merr.]

At present, no report on inheritance of male fertility restoration has been released, yet more than 10 cytoplasmic-nuclear male-sterile soybean lines as well as their maintainers and restorers have been developed. Based on our previous work, 25 restorers for the male-sterile line NJCMS1A were identified and the inheritance of male fertility restoration for these restorers was studied. The results showed that F₁s between NJCMS1A and its restorers were completely male-fertile. The numbers of fertile and sterile plants in the F₂ population of Cross I (NJCMS1A × N23601) and Cross II (NJCMS1A × N23683) corresponded to a segregation ratio of 15:1, and the numbers of non-segregation lines, 3:1 segregation lines and 15:1 segregation lines in F_2:3 of the same two crosses fitted a 7:4:4 genotypic segregation ratio. The testcross BC₁F₁s between the F₁s of the above two crosses and NJCMS1A, NJCMS1B showed a 3:1 segregation ratio. Accordingly, it was inferred that two pairs of duplicate dominant genes controlled the male fertility restoration of NJCMS1A in both crosses. Meanwhile, F₂ of other 23 crosses between NJCMS1A and its 23 restorers showed a fertility segregation ratio of 3:1 or 15:1. The F₁s of the five testcrosses between NJCMS1A and the F₁s of five crosses selected from the above 23 crosses showed that fertility segregation was 3:1 in BC₁F₁s between NJCMS1A and F₁s of the crosses of which fertility segregation fitted 15:1 in F₂ population, while fertility segregation in BC₁F₁s was 1:1 for those fertility segregation fitted 3:1 in F₂ population. Allelism tests showed that restore genes of all restorers in the experiment were allelic to two pairs of dominant genes. All results showed that some restorers bore one pair of dominant restore gene and the others bore two pairs of duplicate dominant gene. The mechanism of F₁ male sterility of the cross N8855 × N2899 was discussed.     

Inheritance and gene tagging of male fertility restoration of cytoplasmic-nuclear male-sterile line NJCMS1A in soybean

The F₁, F₂ and F_2:3 of the NJCMS1A × 'Zhongdou 5' cross were used to analyse the inheritance of the male fertility restoration of the cytoplasmic-nuclear male-sterile line NJCMS1A in soybean. The results of genetic analysis showed two pairs of dominant genes conferring the male fertility restoration of NJCMS1A, which further confirmed previous results. The F₂ population from the NJCMS1A × 'Zhongdou 5' cross was used for tagging the restorer genes for NJCMS1A with 664 pairs of simple sequence repeat primers selected randomly from the genetic linkage map of soybean published by Cregan et al. (1999) . Satt626 on linkage group M and Satt300 on linkage group A1 of the integrated linkage map by Song et al. (2004) were found to link to the two restorer genes of NJCMS1A. The maximum-likelihood estimates of the genetic distance between the two markers, Satt626 and Satt300, and the two restorer genes of 'Zhongdou 5' were 9.75 and 11.18 cM, respectively.     

Development of a cytoplasmic male‐sterile line NJCMS4A for hybrid soybean production

Cytoplasmic male‐sterile (CMS) lines are being used to produce hybrid seeds. Thus far, four CMS sources in soybean [Glycine max (L.) Merr.] have been reported in China. However, they are not sufficient or efficient in meeting the requirements of commercial soybean hybrid seed production. In this study, 33 varieties were tested for CMS using 45 crosses among 37 landraces and 17 annual wild soybean accessions (Glycine soja Sieb. et Zucc.). The cross of N23661 × N23658 showed partial to complete male sterility in backcross generations, while the corresponding reciprocal cross showed normal male fertility. Thus, the cytoplasm of N23661 is male‐sterile, the continuously backcrossed line is a male‐sterile line (designated NJCMS4A), and N23658 is its maintainer (designated NJCM4B). The male fertility of NJCMS4A was restored by another accession, Nansheng9403. Accordingly, NJCMS4A along with its maintainer and restorer composes a complete set of three lines for producing hybrid soybean. Using mitochondrial markers and sequence analyses, NJCMS4A is a CMS line with its cytoplasm not identical to the four previously reported CMS sources in soybean.     

大豆质核互作雄性不育系NJCMS3A双亲雄性育性基因的SSR标记

利用大豆质核互作雄性不育系NJMCS3A的质、核供体亲本N21566和N21249构建F₂和BC₁F₁育性分离群体进行雄性育性的遗传分析与基因定位。结果表明, F₁正反交可育,F₂和BC₁F₁的可育株与不育株分离比例经χ²测验分别符合3∶1和1∶1,表明NJCMS3A供体亲本雄性育性由一对基因控制,可育等位基因为显性。该基因可能是NJCMS3A的一个恢复基因。选用793对SSR引物对F₂和BC₁F₁群体分别进行育性基因定位,发现该育性基因位于O连锁群上,在Satt331和Satt477标记之间,与Satt331、CSSR133和Satt477标记距离的次序一致,分别为8.1~10.4 cM、11.4~16.4 cM、13.3~19.2 cM。     

Feasibility of selection for high weed suppressive ability in soybean: Absence of tradeoffs between rapid initial growth and sustained later growth

In ecology, tradeoff theory has been used to understand differences among plant species in their competitive abilities. In efforts to develop weed-suppressive soybean, we found evidence of a tradeoff between the ability for rapid initial growth and the ability for sustained growth later in the season: early maturing lines displayed more rapid initial growth but ceased growth sooner. Such a tradeoff would increase the difficulty of obtaining a full-season weed-suppressive variety. To determine this tradeoff's existence and severity we examined two possible mechanisms that could lead to it. We tested whether early maturing soybean lines attain higher early relative growth rate than late-maturing soybean lines and whether early maturing soybean lines produce larger seeds by an environmentally-dependent or -independent mechanism. Early maturing lines had higher relative stem elongation rates than late lines but not higher relative dry weight or leaf area increase rates. In more northern locations and in years with shorter growing seasons, early maturity lines produced larger seeds than late maturing lines, implicating an environmentally-dependent rather than -independent mechanism causing seed size differences. Relative to early lines, when late lines mature, temperature and photoperiod are in greater decline, leading to a risk of incomplete seed fill. Resulting seed size decreases could lead to lower initial growth in late maturity lines and thus to an environmental rather than genetic or physiological cause of tradeoff between initial growth and sustained growth later in the season. This revised version was published online in July 2006 with corrections to the Cover Date.     

Further cytological characteristics of a male-sterile mutant in soybean affecting cytokinesis and microspore development

A spontaneous male‐sterile mutation affecting microspore development has been found in BR97‐13509H line of the official Brazilian soybean breeding programme. Slightly abnormal and irregular chromosome segregation occurred in both meiotic divisions, albeit insufficient to explain total pollen sterility. The main cause of male sterility was the absence of cytokinesis after telophase II. Instead of the typical tetrads of microspores, four‐nucleate coenocytic microspores were formed. Coenocytic microspores resulting from the absence of cytokinesis have also been described in ms1 and ms4 male‐sterile soybean mutants, although with certain differential characteristics. In the BR97‐13509H mutant line, after interphase the four nuclei were rejoined in one or two metaphase plates and progressed through the first pollen mitosis. Pollen then underwent a progressive process of degeneration characterized by continuous cytoplasmic shrinkage. The second pollen mitosis failed to occur, and pollen sterility became total.     

Inheritance of resistance to pendimethalin herbicide induced stem damage in soybean

Selective herbicides are valuable weed control tools; however, selectivity is not always complete, resulting in crop damage. Stem breakage, lodging, and enlarged hypocotyls (brittle bean syndrome) limit yields of soybean [Glycine max (L.) Merr.] genotypes treated with pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine]. Developing genotypes with resistance to pendimethalin injury would eliminate or reduce this problem. Genetic studies were conducted to determine the inheritance of resistance to pendimethalin induced stem damage. The F_2:3 progeny of crosses involving resistant ('Asgrow A4715' and 'Flyer') and susceptible (`Essex' and K87-7-95) genotypes were screened in a greenhouse. Each genotype was treated with 1.68 kg ha^-1 pendimethalin preemergence and irrigated as needed. Plants were scored at V4 for stem breakage. Progeny distributions indicated that resistance to brittle bean syndrome damage behaved as a quantitative trait. Dominance for stem breakage was expressed in the population of A4715 × Essex. Flyer was more sensitive to herbicide damage than Asgrow A4715 because it has fewer genes for resistance or different alleles. The F_2:3 variance component heritability estimates ranged from 0.19 to 0.52. Gain from selection for resistance to pendimethalin injury is possible, and resistant progeny can be recovered from segregating populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

A partially male-sterile mutant line of soybeans,Glycine max (L.) Merr.: inheritance

Summary A partial male sterility system in the soybean (Glycine max (L.) Merr.) germplasm population AP6(SI)CI was found to be controlled monogenically by a recessive allele, msp. Observations of msp msp plants in different environments suggested that environmental conditions significantly affect expressivity of the msp allele with respect to male sterility. We obtained no experimental evidence of cytoplasmic effects on msp expression. Background genotypes, however, seem to affect msp expressivity through their determination of flowering dates and resultant interactions with varying environmental conditions.Homogeneous populations of partially male-sterile plants can be generated by increasing families of msp msp plants in fertility-inducing environments, if measures are implemented to prevent the introduction and/or build-up of fertile genotypes that arise from natural cross-pollinations.Joint contribution: North Central Region, Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-9596 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011; Project 2107.     

Establishment of Chinese soybean Glycine max core collections with agronomic traits and SSR markers

It is very important to efficiently study and use genetic diversity resources in crop breeding and sustainable agriculture. In this study, different sampling methods and sample sizes were compared in order to optimize the strategies for building a rationally sized core collection of Chinese soybean (Glycine max). The diversity in the core collection captured more than 70% of that in the pre-core collection, no matter what sampling methods were used, at a sampling proportion of 1%. Core collections established with both simple sequence repeat (SSR) marker data and agronomic traits were more representative than those chosen on an independent basis. An optimal sampling method for a soybean core collection was determined, in which strategy ‘S’ (allocating accessions to clusters according to the proportion of square root of the original sample size within each ecotype) was used based on SSR and agronomic data. Curve estimation was used to estimate the allelic richness of the entire Chinese soybean germplasm and a minimum sample size for a core collection, on which a sampling proportion of about 2% was determined to be optimal for a core collection. Further analysis on the core collection with fourteen agronomic traits and allelic constitution at 60 SSR loci suggested that it highly represented the entire collections both on genetic structure and diversity distribution. This core collection would provide an effective platform in proper exploitation of soybean germplasm resources for the study of complex traits and discovering important novel traits for crop genetic development.     

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.     

Screening and genetic analysis of resistance to peanut stunt virus in soybean: identification of the putative Rpsv1 resistance gene

The peanut stunt virus (PSV) causes yield losses in soybean and reduced seed quality due to seed mottling. The objectives of this study were to determine the phenotypic reactions of soybean germplasms to inoculation with two PSV isolates (PSV-K, PSV-T), the inheritance of PSV resistance in soybean cultivars, and the locus of the PSV resistance gene. We investigated the PSV resistance of 132 soybean cultivars to both PSV isolates; of these, 73 cultivars exhibited resistance to both PSV isolates. Three resistant cultivars (Harosoy, Tsurunotamago 1 and Hyuga) were crossed with the susceptible cultivar Enrei. The crosses were evaluated in the F₁, F₂ and F_2:3 generations for their reactions to inoculation with the two PSV isolates. In an allelism test, we crossed Harosoy and Tsurunotamago 1 with the resistant cultivar Hyuga. The results revealed that PSV resistance in these cultivars is controlled by a single dominant gene at the same locus. We have proposed Rpsv1, as the name of the resistance gene in Hyuga. We also constructed a linkage map using recombinant inbred lines between Hyuga × Enrei using 176 SSR markers. We mapped Rpsv1 near the Satt435 locus on soybean chromosome 7.     

Effect of Ogura male-sterile cytoplasm on the performance of cabbage hybrid variety

Summary Cabbage hybrid seeds are commercially produced by means of self-incompatibility. This system may show some instability mainly under tropical conditions, where cytoplasmic male sterility can be an alternative approach for hybrid seeds production. However, cabbage hybrids holding Ogura male-sterile cytoplasm show some irregularities during development. By assessing some characteristics during the growing cycle of male-sterile cabbage hybrids and comparing them to genomic similar male-fertile ones and to the most common cabbage hybrid cultivated in Brazil, it was observed that the male-sterile hybrids had the same vigour, uniformity, number of leaves, resistance to Xanthomonas campestris pv. campestris, and earliness as their male-fertile counterparts and performed better than the commercial check hybrid for some of these characteristics. Although male-sterile hybrids showed yellowing of leaves, some parental combinations succeeded in overcoming or strongly reducing this cytoplasmic effect.Abbreviations dat days after transplanting - CMS Cytoplasmic Male Sterility - CNPH National Centre for Vegetable Crops Research     

大豆不育细胞质资源的发掘与鉴定

利用质核互作雄性不育系NJCMS1A的4个保持系为核背景测验种（父本）从大豆资源中筛选新不育细胞质,发现与71个不同来源的栽培大豆和17个野生大豆资源杂交所获得的103个杂交组合中有8个组合的后代出现不育株,经进一步的正反交和回交试验,发现来源于山西的野生材料N23168和来源于湖北的栽培品种N21566具不育细胞质。另一方面     

Development of a new cytoplasmic-nuclear male-sterility line of soybean and inheritance of its male-fertility restorability

Based on previous work, a new cytoplasmic‐nuclear male‐sterile line NJCMS2A along with its maintainer NJCMS2B of soybean was released through four episodes of nuclear substitution backcrossing with male‐sterile plants of (N8855 × N1628)F₂ as donor parent and N1628 as recurrent parent. The male sterility of NJCMS2A was complete and female fertility was normal. A series of restorers from different sources were screened out and evaluated. It was found that from the crosses between NJCMS2A and its restorers, two pairs of duplicate dominant genes, allelic to those of NJCMS1A, controlled the inheritance of fertility restorability of NJCMS2A.     

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.     

Resistance to soybean cyst nematode and molecular polymorphism in various sources of Peking soybean

Summary Cultivar Peking has been extensively used as a source of resistance to Race 3 and Race 5 of soybean cyst nematode, Heterodera glycines I., and Peking genes for resistance are present in a wide range of resistant soybean cultivars. Peking is also used as a host differential in the soybean cyst nematode race classification system. Thirteen Peking lines maintained in the USDA Soybean Germplasm Collection and in several breeding programs were surveyed using RFLP and RAPD markers for genetic characterization. Based on the molecular diversity combined with reaction to soybean cyst nematode, Peking genotypes from a common original source were identified. Peking lines PI 297543 (introduction from Hungary), and PI 438496A, PI 438496B and PI 438496C (introductions from Russia) represented unrelated germplasms. Identified molecular polymorphism can be used to validate the genetic purity of Peking lines used as host differentials for soybean cyst nematode classification system as well as utilization of an individual germplasm line in genetic-breeding programs.     

Inheritance of resistance in soybean PI 567516C to LY1 nematode population infecting cv. Hartwig

Worldwide, cyst nematode (SCN) Heterodera glycines is the most destructive pathogen on cultivated soybean (Glycine max (L.) Merr.). In the USA yield losses in 2001 were estimated to be nearly 60 million dollars. Crop losses are primarily reduced by the use of resistant cultivars. Nematode populations are variable and have adapted to reproduce on resistant cultivars overtime because resistance primarily traces to two soybean accessions. Recently cv. Hartwig was released which has comprehensive resistance to most SCN populations. A virulent nematode population LY1 was recently selected for its reproduction on Hartwig. LY1 population originated from a mass mating of Race 2 (HG Type 1.2.5-) females with Race 5 (HG Type 1.2-) males. LY1 nematode population infects currently known sources of resistance except PI 567516C. The female indices obtained on PI 567516C and Hartwig were 7% (resistant) and 155% (susceptible), respectively. However, the genetic basis of LY1 resistance in soybean PI 567516C is not known. Resistant PI line 567516C was crossed to susceptible cultivar Hartwig to generate 105 F_2:5 families. These families together with parents, seven indicator lines and a susceptible control cv. Lee-74 were evaluated for response to LY1 nematode population in the greenhouse. Chi-square analysis showed resistance in PI567516C to LY1 was conditioned by one dominant and two recessive genes (Rhg, rhg, rhg). Chi-square value was 0.15 and P = 0.70. This information will be useful to soybean researchers for developing resistant cultivars to nematode population that infects Hartwig.     

Morphological and cytological study in a new type of cytoplasmic male-sterile line CMS-GIG2 in sunflower (Helianthus annuus)

Cytoplasmic male sterility (CMS) is essential for sunflower hybrid production. CMS-GIG2, a new sunflower CMS type, was further confirmed by crossing with the maintainer and restorer lines for the CMS-PET1, both of which maintain the male sterility of CMS-GIG2. Meiotic division in CMS-GIG2 was observed with 4'6-diamidino-2-phenylindole dihydrochloride staining, indicating that microspore formation was disrupted before the meiotic cytokinesis was completed. Light microscopy observation showed that both middle layer and tapetal cells expand radially rather than degrade over time, followed by failure to form tetrads and normal microspores. This morphological defect leading to male sterility in CMS-GIG2 differs from that observed in the PET1 CMS type. CMS-GIG2 will certainly provide additional genetic diversity for sunflower hybrid breeding programmes.