Fertile,intermediate hybrids between Phaseolus vulgaris and P. acutifolius from congruity backcrossing

Summary Recurrent or introgressive backcrossing of Phaseolus vulgaris — P. acutifolius hybrids with either P. vulgaris or P. acutifolius increased fertility, as measured by pollen stainability and seed per pod from non-manipulated flowers, while invariably resulting in loss of traits from the non-recurrent parent. When hybrids were backcrossed with each of the parent species in alternate generations (congruity backcrossing), fertility decreased in early generations but gradually increased in later generations. By the fourth or fifth generation, congruity-backcross hybrids produced numbers of seeds per pod from non-manipulated flowers comparable to those of parent species, although the percent of stainable pollen tended to be lower. Congruity-backcross hybrids were intermediate to parent species when pedigrees contained equal representation of parents but favored the majority parent when pedigrees were unbalanced. Individuals exhibiting symptoms of developmental incongruity, such as abnormal leaflet number, foliar variagation, or unusual growth patterns, occurred in each generation. However, completely new characteristics appeared after the second backcross generation, presumably due to recombination. Backcrossing to both parent species in alternate generation reversed incongruity, allowing selection for fertility without loss of traits from one of the parent species.Scientific Journal Series Paper Number 15, 671 of the Minnesota Agricultural Experimental Station     

Interspecific hybridization of phaseolus vulgaris with P. lunatus and P. acutifolius

Summary The influence of genotypic combinations on the growth of hybrid embryos between Phaseolus vulgaris and P. lunatus, and between P. vulgaris and P. acutifolius was examined. All embryos obtained from P. vulgaris × P. lunatus crosses developed only to a stage which appears to be comparable to the pre-heart-shape stage of selfed embryos. Reciprocal crosses were attempted, but pods abscised at a very early stage. Embryos derived from P. vulgaris × P. acutifolius and reciprocal crosses attained the cotyledon stage although no mature seeds were formed. A distinct characteristic of these embryos was the uneven development of the two cotyledons. The rate of growth and final size of these hybrid embryos seemed to be influenced by the genotypes of both parents.Immature embryos were cultured on defined medium and the effects of glutamine and gibberellin (GA₃) were examined. Glutamine was effective in increasing the survival rate; gibberellin had no apparent effect. Plants derived from cultured embryos of P. vulgaris × P. lunatus, P. vulgaris × P. acutifolius and P. acutifolius × P. vulgaris were obtained.Technical paper No. 00 of the Oregon Agricultural Experiment Station. Research was supported by the Oregon Agricultural Experiment Station, the Research Council of Oregon State University (National Institute of Health Biomedical Research Support Grant RR07079) and the Processor Research Council of Oregon. A.R. is supported by an African Graduate Fellowship from the African-American Institute     

Root metaxylem and architecture phenotypes integrate to regulate water use under drought stress

At the genus and species level, variation in root anatomy and architecture may interact to affect strategies of drought avoidance. To investigate this idea, root anatomy and architecture of the drought‐sensitive common bean (Phaseolus vulgaris) and drought‐adapted tepary bean (Phaseolus acutifolius) were analyzed in relation to water use under terminal drought. Intraspecific variation for metaxylem anatomy and axial conductance was found in the roots of both species. Genotypes with high‐conductance root metaxylem phenotypes acquired and transpired more water per unit leaf area, shoot mass, and root mass than genotypes with low‐conductance metaxylem phenotypes. Interspecific variation in root architecture and root depth was observed where P. acutifolius has a deeper distribution of root length than P. vulgaris. In the deeper‐rooted P. acutifolius, genotypes with high root conductance were better able to exploit deep soil water than genotypes with low root axial conductance. Contrastingly, in the shallower‐rooted P. vulgaris, genotypes with low root axial conductance had improved water status through conservation of soil moisture for sustained water capture later in the season. These results indicate that metaxylem morphology interacts with root system depth to determine a strategy of drought avoidance and illustrate synergism among architectural and anatomical phenotypes for root function.     

Molecular and morphological evidence of natural interspecific hybridization between the uncommon Eucalyptus aggregata and the widespread E. rubida and E. viminalis

Human activities can promote increased hybridization in the genus Eucalyptus with potentially detrimental consequences for the persistence of rare species. However, many hybrid combinations have not been investigated with combined use of genetic markers and morphology. We assessed the efficiency of the STRUCTURE program and morphological intermediacy for identifying hybrids between the uncommon tree, Eucalyptus aggregata, which putatively hybridizes with the common congeners, E. rubida and E. viminalis in south-eastern Australia. We sampled 1,005 seedlings across 27 populations, all seedlings were genotyped at 6 allozyme loci and scored for 22 stem and leaf characters. Both marker sets confirmed that E. aggregata is hybridizing with both E. rubida and E. viminalis. Allozymes revealed hybrids from E. aggregata trees in 88% of populations and hybrids comprised 7.3% of all seedlings. Both genetics and morphology indicated that ~50% were likely to be F₁ hybrids, and both simulations and morphological characteristics indicated that the remainder were mostly backcrosses. Morphological analysis correctly distinguished 71% of F₁ hybrids from parentals and was least accurate when dealing with potential backcrosses (50% success). Hence, techniques using genetic data (no prior information) and the assessment of appropriate admixture thresholds through simulations provided the most accurate estimates of hybrid frequency. In this study, potential introgression and the high frequency of hybrids in small populations (~30%), suggests that hybridization should be considered in the management and conservation of E. aggregata.     

Dehydration-induced alterations in growth and osmotic potential of callus from six tepary bean lines varying in drought resistance

Growth and osmotic potential of calli induced from leaf- and root-derived tissues of six tepary bean lines (Phaseolus acutifolius) varying in drought resistance were assessed in vitro after polyethylene glycol-induced (10%, PEG-10,000) dehydration. Calli of resistant teparies were characterized by low initial osmotic potential (ψ_s) and relative growth rate (RGR) on medium lacking PEG (−0.30 MPa). However, calli of both resistant and sensitive lines were similar in dry matter percent (DM). Presence of PEG in the medium (−0.58 MPa) elevated DM in all teparies except one resistant line. Both leaf- and root-derived calli of sensitive teparies exhibited osmotic adjustment (OA) but reduced RGR that remained after rehydration in one line. We concluded that preexisting force of low cellular ψ_s rather than induced OA plays an important role in buffering adverse effects of dehydration and conditioning drought resistance of tepary beans. This information may aid Phaseolus breeders in screening for drought resistance among large number of accessions.     

Effect of seaweed concentrate on yield of nutrient-stressed tepary bean (Phaseolus acutifolius gray)

The effect of the seaweed concentrate Kelpak on the yield of the tepary bean (Phaseolus acutifolius L.) grown under conditions of varying nutrient supply was investigated. Kelpak significantly increased the yield of plants growing at all concentrations of nutrient supply by increasing bean weight rather than bean number. Kelpak also tended to increase the N concentration of the beans. The results suggest that Kelpak did not act simply as a fertilizer, but as some kind of biostimulant.     

Cellular double-stranded RNA in Phaseolus vulgaris

Summary High molecular weight double-stranded (ds) RNAs have been detected in apparently virus-free French (common) bean Phaseolus vulgaris cv. Black Turtle Soup (BTS). Several other bean cultivars were free of detectable high molecular weight dsRNAs. The dsRNAs have been partially characterized and have homology to the BTS genome as well as to the genomes of other bean cultivars. The T _m of hybrids formed between BTS DNA and denatured dsRNA have been estimated.     

Cytological localization of thePGIP genes in the embryo suspensor cells ofPhaseolus vulgavis L

Polygalacturonase-inhibiting protein (PGIP) is a cell wall protein which inhibits fungalendopolygalacturonases. A small gene family encodesPGIP in the genome of common bean, as indicated by Southernblot experiments performed at high-stringency conditions. Southern-blot analysis of DNA extracted from different cultivars ofPhaseolus vulgaris and fromPhaseolus coccineus showed length polymorphism of the hybridizing restriction fragments. The cytological localization of thePGIP genes was determined in polytene chromosomes of theP. vulgaris embryo suspensor cells. In-situ hybridization experiments using the clonedPGIP gene revealed labelling over a single region of the pericentromeric heterochromatin of chromosome pair X, next to the euchromatin, suggesting thatPGIP gene family may be clustered in one chromosomal region.     

Isolation and Partial Characterization of a Seed Lectin from Tepary Bean that Delays Bruchid Beetle Development

Four isolectin forms of a seed lectin from mature seed of tepary bean (Phaseolus acutifolius) were isolated using solubility fractionation, affinity chromatography, and high performance liquid chromatography. The subunits are polypeptides with an apparent molecular mass of 30,000 daltons. The 30 kilodalton subunits are produced starting approximately 13 days after flowering and subsequently comprise a major fraction of the proteins found in the mature seed. The amino terminus of each isolectin fraction was determined to be highly homologous with that of the subunits of common bean (Phaseolus vulgaris L.) phytohemagglutinin (PHA). The tepary isolectin cross-reacts with both erythroagglutinating and leucoagglutinating subunits of PHA antibodies, although differential cross-reactivity was noted. A seed protein fraction enriched in tepary bean lectin was found to be toxic to bean bruchid beetles (Acanthoscelides obtectus), when incorporated into their diets at incremental concentrations from (1-5% w/w) above that of PHA concentrations in mature seeds of the susceptible common bean variety “Red Kidney.”     

Embryo development in reciprocal crosses of Phaseolus vulgaris L. and P. coccineus Lam.

Summary Embryo development was examined in reciprocal crosses of Phaseolus vulgaris cv. Great Northern and P. coccineus cv. Scarlet Runner. The formation of abnormal (shrunken and underdeveloped) embryos constituted the primary crossing barrier between the two species when P. coccineus was the female parent. Plants of P. coccineus X P. vulgaris were obtained by embryo culture. Although the P. vulgaris X P. coccineus cross resulted in normal seed development, the fertility of the resulting hybrids was much lower (27%) than that of the reciprocal hybrids (81%). Three classes of F₂ embryos, normal, shrunken, and underdeveloped were formed on reciprocal F₁s and the frequencies did not differ between reciprocal populations. Thus, the interactions between embryo and endosperm and/or maternal parent rather than cytoplasmic-nuclear effects seem to be important in the determination of the extent of embryo growth. The examination of pollen fertility of F₂ plants and the development of F₂ and F₃ embryos suggests that the formation of abnormal embryos and reduced male fertility are independent events. The P. vulgaris — P. coccineus crosses may be useful in studying the possible involvement of interspecific differences in hormonal metabolism in the development of hybrid embryos.     

Effect of drought on phytyl wax esters in Phaseolus leaves

The small amount of phytol which is bound as wax ester in mature bean leaves is increased 10–20 fold by drought. Watering the plants before permanent wilt reverses this trend. Maximum amounts of phytyl wax esters in plants still viable are higher in the drought resistant tepary bean (Phaseolus acutifolius) than in the less resistant garden bean (P. vulgaris).     

Susceptibility of dry bean (Phaseolus vulgaris L.) to Agrobacterium infection: Transformation of cotyledonary and hypocotyl tissues

A germinating-seed assay was developed to determine the susceptibility of dry bean (Phaseolus vulgaris L.) to infection by Agrobacterium tumefaciens. Seedlings infected one to three days after germination were more susceptible to A. tumefaciens infection than seedlings germinated for five to seven days and the galls that formed on the one to three day seedlings were significantly larger. Nineteen genotypes of dry bean were screened with this assay and all were equally susceptible to nopaline, octopine and agropine biotypes of A. tumefaciens. In addition, cotyledonary nodes and hypocotyls of P. vulgaris were inoculated with disarmed strain A. tumefaciens strain C58Z707 and the avirulent A. rhizogenes strain A4RS (pRiB278b), respectively. Both strains contain the binary plasmid pGA482 which has the neomycin phosphotransferase II (NPT II) gene nested between T-DNA borders. From these infected tissues, callus and root tissues, respectively capable of growing in the presence of kanamycin were obtained. These tissues displayed NPT II activity and integrated copies of the NPT II gene were detected from putative transformed root cultures by genomic blot hybridization.     

Short-term responses of photosynthetic membrane lipids and photochemical efficiency in plants of <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> and <Emphasis Type="Italic">Vigna unguiculata</Emphasis> submitted to high irradiance

Primary leaves of young plants of common bean (Phaseolus vulgaris cv. Carioca and Negro Huasteco) and cowpea (Vigna unguiculata Walp cv. Epace 10) were exposed to high irradiance (HI) of 2 000 μmol m⁻² s⁻¹ for 10, 20, and 30 min. The initial fluorescence (F₀) was nearly constant in response to HI in each genotype except for Carioca. A distinct reduction of maximum fluorescence (F_m) was clearly observed in stressed genotypes of beans after 20 min followed by a slight recovery for the longer stress times. In common bean, the maximum quantum yield (F_v/F_m) was reduced slowly from 10 to 30 min of HI. In cowpea, only a slight reduction of F_v/F_m was observed at 20 min followed by recovery to normal values at 30 min. HI resulted in changes in the photochemical (q_P) and non-photochemical (q_N) quenching in both species, but to a different extent. In cowpea plants, more efficiency in the use of the absorbed energy under photoinhibitory conditions was related to increase in q_P and decrease in q_N. In addition, lipid peroxidation changed significantly in common bean genotypes with an evident increase after 20 min of HI. Hence the photosynthetic apparatus of cowpea was more tolerant to HI than that of common bean and the integrity of cowpea cell membranes was apparently maintained under HI.     

Utilizing the potential for increased nitrogen fixation in common bean

Many variables affect the amount of N₂ fixation that occurs in field-grown common beans (Phaseolus vulgaris L.). When environmental conditions are optimized, genetically superior plants that are nodulated with efficient rhizobia are able to fix enough N₂ to support grain yields of up to 2000 kg ha^–1. All of the required components are available for common bean to fulfill its potential as a nitrogen-fixing food crop. However, these components must be assembled and presented to growers in a usable package that is economically attractive.     

Thermotolerance of the photosynthetic light reactions in two <Emphasis Type="Italic">Phaseolus</Emphasis> species: a comparative study

The common bean (Phaseolus vulgaris L.) is sensitive to high temperature, while an ecologically contrasting species (Phaseolus acutifolius A. Gray) is cultivated successfully in hot environments. In this study, the two bean species were respectively acclimated to a control temperature of 25 °C and a moderately elevated temperature of 35 °C in order to compare the thermotolerance capabilities of their photosynthetic light reactions. Growth at 35 °C appeared to have no obvious adverse effect on the photosynthetic activities of the two beans, but changed their thermotolerance. After a short period of heat shock (40 °C for up to 4 h), the photosynthetic activities of 25 °C-grown P. vulgaris declined more severely than those of P. acutifolius grown at 25 °C, implying that the basal thermotolerance of P. vulgaris is inferior to that of P. acutifolius. But after acclimating to 35 °C, the thermotolerances of the two species were both greatly enhanced to about the same level, clearly demonstrating the induction of acquired thermotolerance in their chloroplasts, and P. vulgaris could be as good as P. acutifolius. Temperature acclimation also changed plants’ resistance to photoinhibition in a manner similar to those toward heat stress. In addition, acquisition of tolerance to heat and strong irradiance would reduce the dependency of the two beans on xanthophyll pigments to dissipate heat, and also seemed irrelevant to the agents with antioxidant activities such as SOD.     

Chlorophyll fluorescence and leaf chlorophyll content of bean leaves injured by spider mites (Acari: Tetranychidae)

The use of chlorophyll fluorescence as a method for detecting and monitoring plant stress arising from Tetranychus urticae (Koch) feeding injury was investigated. The effect of mite density (1–32 mites per 1.5 cm² of leaf) and the duration of the feeding period (1–5 days) on the chlorophyll fluorescence parameters of bean (Phaseolus vulgaris) leaves were examined. Changes in chlorophyll fluorescence parameters were dependent both on mite density and duration of feeding. Decreases in F _o, the initial fluorescence and F _m, the maximum fluorescence led to a decrease in the ratio of variable to maximum fluorescence, F _v/F _m. The decrease in F _v/F _m is typical of the response of many plants to a wide range of environmental stresses and indicates a reduced efficiency of photosystem II (PSII) photochemistry. T _1/2, which is proportional to the pool size of electron acceptors on the reducing side of PSII, was also reduced in response to mite-feeding injury. The leaf chlorophyll content decreased with increasing mite density and duration of feeding but did not appear to contribute to the decrease in F _v/F _m. Chlorophyll fluorescence is an effective method for detecting and monitoring stress in T. urticae-injured bean leaves.     

Coupling- and repulsion-phase RAPDs for marker-assisted selection of PI 181996 rust resistance in common bean

The Guatemalan black bean (Phaseolus vulgaris L.) plant introduction (PI) 181996 is resistant to all known US races of the bean rust fungus Uromyces appendiculatus (Pers. ex Pers.) Unger var. appendiculatus [syn. U. phaseoli (Reben) Wint.]. We report on two random amplified polymorphic DNA (RAPD) markers OAC20₄₉₀ tightly linked (no recombinants) in coupling phase and OAE19₈₉₀ linked in repulsion phase (at 6.2±2.8 cM) to PI 181996 rust resistance. These RAPDs, generated by single decamer primers in the polymerase chain reaction, were identified in near-isogenic bulks of non-segregating resistant and susceptible BC₄F₂ (NX-040*4/PI 181996) lines. Linkage of the RAPD markers was confirmed by screening 19 BC₄F₂ and 57 BC₄F₃ individuals segregating for PI 181996 resistance. Utility of the RAPDs OAC20₄₉₀ and OAE19₈₉₀ was investigated in a diverse group of common bean cultivars and lines. All cultivars into which the PI 181996 resistance was introgressed had the RAPD OAC20₄₉₀. A RAPD similar in size to OAC20₄₉₀, observed in some susceptible common bean lines, was confirmed by Southern blotting to be homologous to the RAPD OAC20₄₉₀. Use of the RAPDs OAC20₄₉₀ and OAE19₈₉₀ in marker-assisted selection (MAS) is proposed. The coupling-phase RAPD is most useful for MAS of resistant BC_nF₁individuals during traditional backcross breeding. The repulsion-phase RAPD has greatest utility in MAS of homozygous-resistant individuals in F₂ or later-segregating generations.Mention of a trademark or a proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable.     

Interspecific hybridization of cultivated rice, Oryza sativa L. with the wild rice, O. minuta Presl.

Crosses were made between four varieties (Mahsuri, Setanjung, MR84 and MR103) of Oryza sativa L. (2n=24, AA) and one accession of O. minuta (2n= 8, BBCC). The seed set obtained ranged between 9.5% and 25.1% depending on the rice variety used. By rescuing 14-day-old embryos and culturing them on 25%-strength MS medium we obtained a total of 414 F₁ hybrids. The F₁s were vigorous, tillered profusely, were perennial and male-sterile. The hybrids were triploid (ABC) with 36 chromosomes and showed irregular meiosis. The average frequency and range of chromosome associations at metaphase I or early anaphase I pollen mother cells of F₁ plants were 29.31(16–36) Is +3.32(0–10) IIs+0.016(0–1) IIIs+0.002(0–1) IVs. Upon backcrossing the original triploid hybrids and colchicine-treated hybrids to their respective recurrent parents, and further embryo rescue, 17 backcross-1 (BC₁) plants were obtained. Of all the crosses using MR84, no BC₁ plant was obtained even after pollinating 13 894 spikelets of the triploid hybrid. The BC₁s were similar in appearence to the F₁s and were male-sterile, their chromosome number ranged from 44 to 48. By backcrossing these BC₁s and nurturing them through embryo rescue, we obtained 32 BC₂ plants. Of these, however, only 18 plants grew vigorously. One of these plants has 24 chromosomes and the other 17 have chromosome numbers ranging between 30 and 37. The 24-chromosome plant was morphologically similar to the O. sativa parent and was partially fertile with a pollen and spikelet fertility of 58.8% and 12.5% respectively. All of the F₁ and BC₁ plants were found to be resistant to five Malaysian isolates (XO66, XO99, XO100, XO257 and XO319) of Xanthomonas campestris pv oryzae. Amongst the BC₂s, the reaction varied from resistant to moderately susceptible. The 24-chromosome BC₂ plant was resistant to the four isolates and moderately resistant to isolate XO100 to which the O. sativa parent was susceptible.Part of PhD thesis submitted by first author to Universiti Kebangsaan Malaysia, Bangi     

Molecular genetic data reveal hybridization between Typha angustifolia and Typha latifolia across a broad spatial scale in eastern North America

A recent increase in the abundance of cattails (Typha spp.) in North American wetlands has been anecdotally linked with hybridization between Typha latifolia and Typha angustifolia. In this study, we used molecular genetic markers (microsatellites) to investigate whether the hybrid lineage (Typha × glauca) is restricted to The Great Lakes region, or exists across a much broader spatial scale. We also investigated the possibility of backcrossing and genetic introgression in natural populations. Parental species could be distinguished from one another based on the distribution of alleles at six microsatellite loci. Species identification based on genetic data corresponded well with species identifications based on leaf width, a key morphological trait that can distinguish the two parental species. We found that hybrids occur in Ontario, Quebec, New Brunswick, and Nova Scotia, but we did not detect hybrids in Maine. F₁s are more abundant than backcrossed or intercrossed hybrids, although we also found evidence of backcrossing, particularly in Ontario. This indicates that hybrids are fertile, and are therefore potential conduits of gene flow between the parental species. Further work is needed to determine whether T. × glauca is particularly successful in the Great Lakes region relative to other areas in which the two parental species co-exist, and to assess whether introgression may lead to increased invasiveness in the species complex.     

Interspecific hybridization of Phaseolus vulgaris L. and Phaseolus angustissimus A. Gray using in vitro embryo culture

The introgression of new desirable characters is very necessary in common bean (Phaseolus vulgaris L.)Interspecific hybridization of P. vulgaris L. with P. angustissimus A. Gray, a wild species with narrow leaves, could be successfully achieved for the first time using embryo culture. Sixteen to twenty-three-day old embryos could grow to plantlets when they were cultivated on modified Monnier's medium.The leaf shape of the hybrid plants obtained showed intermediary traits between the two parents.A chromosome stock doubling could be achieved for one embryo.