Inheritance of microspore embryogenic ability in Brassica crops

Inheritance of microspore embryogenic ability in oilseed rape (Brassica napus L.) and Chinese cabbage (Brassica campestris L. ssp. pekinensis) was examined by 4 × 4 diallel crosses using cultivars showing a different response. In both species, embryo yields of most F₁ hybrids were similar to, or over, the high responsive parent and some F₁s showed intermediate embryo yields between their parents. Diallel analysis showed that both additive and dominant effects were significant at the 1% level for the genetic control of microspore embryogenic ability in both species. Dominant genes had positive effects on microspore embryogenesis. In oilseed rape, the additive effects were important, while in Chinese cabbage the dominant effects were largely contributed. The broad- and narrow-sense heritabilities were 0.972 and 0.811 in oilseed rape, and 0.959 and 0.659 in Chinese cabbage, respectively. From the results of the segregation of embryo yields in the F₂ population of ’Lisandra’×’Kamikita’, it is considered that the microspore embryogenic ability is controlled by two loci with additive effects in oilseed rape. Received: 6 September 2000 / Accepted: 24 November 2000     

Genetic studies of corn (Zea mays L.) anther culture response

Summary Anthers of two maize (Zea mays L.) inbred lines, DBTS (P₁) and B73 (P₂), their F₁, F₂ and first backcross generations — F₁ x DBTS (B₁), and F₁ x B73 (B₂) — were float cultured in YP medium to study the inheritance of corn anther culturability using generation mean analysis. Significant effects of generation were observed for the three traits measured: anther response (%), frequency of embryos (%) and anther productivity. Variation among the generations was similar for anther response and frequency of embryos: no significant differences were found among the P₁, F₁, F₂ and B₁ means, but the means of P₂ and B₂ were significantly lower than those of the other generations. For anther productivity, the F₂ generation tended to have a slightly higher tendency for multiple embryo formation. A simple additive-dominance model was adequate in explaining the inheritance of anther response and frequency of embryos, but digenic epistasis (additive x dominance) was involved in the inheritance of anther productivity. Additive genetic variance was higher than non-additive genetic variance for all the traits; however, only environmental variance was significant. Narrow-sense heritability estimates were 65% and 75% for anther response and frequency of embryos, respectively. Significant inter-plant variation was observed within generations, even for the inbred line DBTS, but isozymic analysis involving five enzyme loci did not reveal any genotypic variability within the inbred lines DBTS and B73.     

Genetic studies of rice (Oryza sativa L.) anther culture response

Anthers of two rice (Oryza sativa L.) varieties, Lunhui 422 (P₁) and Jinzao 5 (P₂), their F₁, F₂ and first backcross generation-F₁ x Lunhui 422 (B₁), and F₁ x Jinzao 5 (B₂)-were cultured in L8 medium to study the inheritance of rice anther culturability using generation mean analysis. Significant effects of generation were observed for the four traits measured: anther response (%), frequency of callus induction (%), frequency of callus differentiation (%) and culture efficiency (%). Variation among the generations was similar for all traits: significant differences were found among six generations and the means of the P₂ and B₂ were significantly lower than those of the other generations. The frequency of callus differentiation showed a nonsignificant difference among the P₁, F₁, F₂ and B₁ generations which had slightly high values than the P₂ and B₂. Additive genetic variance (V_A) was higher than non-additive genetic variance (V_D) for anther response and frequency of callus induction. However, A_V was lower than V_D for frequence of callus differentiation and culture efficiency, V_A was significant for all traits except for the culture efficiency, and V_D was nonsignificant for all traits except for the frequency of callus differentiation. On the other hand, environmental variation (V_E) was significant for the 4 traits. Narrow-sense heritability estimates were 95.52%, 82.19% and 13.54% for anther response, frequency of callus induction and culture efficiency, respectively.Abbreviations 2,4-d 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid     

Genetic analysis of salt tolerance during germination in Lycopersicon

Summary The salt-tolerant cultivated tomato (Lycopersicon esculentum) accession, PI174263, and a sensitive cv, UCT5, were crossed to develop reciprocal F₁, F₂ and BC₁ populations for genetic analysis of salt tolerance in tomatoes during seed germination. Variation was partitioned into embryo, endosperm and maternal (testa and cytoplasmic) components. Generation means analysis indicated that there were no significant embryo (additive, dominance or epistatic) effects on germination performance under salt stress. Highly significant endosperm additive and testa dominance effects were detected. The proportion of the total variance explained by the model containing these two components was R²=98.2%. Variance component analysis indicated a large genetic variance with additive gene action as the predominant component. Furhter inspection indicated that this variance was attributable to endosperm additive effects on germinability under salt stress. Narrow-sense heritability was estimated as moderately high. Implications for breeding procedures are discussed.     

REPRODUCTIVE CHARACTERISTICS OF THE FLOWER BREEDING DROSOPHILA HIBISCI BOCK (DROSOPHILIDAE) IN EASTERN AUSTRALIA: GENETIC AND ENVIRONMENTAL DETERMINANTS OF OVARIOLE NUMBER

Quantitative genetic analysis of the ovariole number of the Australian Hibiscus flower-breeding Drosophila hibisci Bock was conducted on populations from two localities along a latitudinal cline in ovariole number previously observed in the species (Starmer et al., in press). Parental strains, F₁, F_1r (reciprocal), F₂, backcross, and backcross reciprocal generations were used in a line-cross (generation means) analysis. This analysis revealed both additive and epistatic effects as important determinants of variation in ovariole number when larvae were reared at 25°C. Maternal effects and maternal-by-progeny genetic interactions were not significant. These results are comparable to previous studies that document epistatic components as genetic determinants of ovariole number in D. melanogaster. Parallel studies on ovariole number in D. hibisci parental and hybrid generations (F₁ and F_1r) reared as larvae at three temperatures (18°, 21.5°, and 25°C) showed environmental effects and genotype-by-environment interactions as significant influences on the phenotype. Maternal effects were present when temperature of larval development was considered and significant, nonlinear environmental effects were detected. Field collections of D. hibisci females showed that field conditions result in significant departure of ovariole number from comparable laboratory reared females. The significant epistatic genetic effects, genotype-by-environment interactions, and maternal effects indicate that the genetic architecture of traits, such as ovariole number, may be more complex than often acknowledged and thus may be compatible with Wright's view of a netlike relationship between the genome and complex characters (Wright 1968).     

Genetic investigation of contributions of embryo and endosperm genes to malt Kolbach index, alpha-amylase activity and wort nitrogen content in barley

 A genetic model is proposed for the analysis of embryo and endosperm effects as well as GE interaction effects. An investigation of three malting quality traits in grains of seven parents and their F₂s was undertaken in a half-diallel cross of barley (Hordeum distichum L.) over 2 years. The results indicated that the malt Kolbach index (KI), alpha-amylase activity (αAA) and wort soluble nitrogen (Wort-N) are controlled by both embryo genetic effects and endosperm genetic effects. Variance of the endosperm additive effects was obviously larger than that of the embryo additive effects. In the contribution of the embryo genetic effects to variation in malt αAA and Wort-N, the dominance effects were considerably larger than the additive effects. The endosperm dominance effects constituted a major part of the total genetic effect on the KI. Significant endosperm GE interactions were also detected in the malt traits concerned. Endosperm general heritability (h ² _e ) tended to be larger than interaction heritability (h ² _oE or h ² _eE ) for all the traits. Endosperm heterosis was observed to be significantly positive for αAA but negative for Wort-N in the F₂ seed generation. Prediction of main gene effects for seven parents showed that ‘Ganmu 2’ and ‘Supi1’ were suitable parental varieties for malt αAA and Wort-N improvement. Our genetic model for malting quality traits and its application in breeding are discussed. Received: 5 August 1997 / Accepted: 11 September 1997     

Genetic interactions between wheat and rye genomes in triticale

Summary Six primary triticale lines were produced from two advanced breeding lines of Triticum durum and three inbred genotypes of Secale cereale. The wheat and rye parents and the triticale derivatives were crossed in all possible combinations within each species group. Chiasma and univalent frequency of parents and hybrids were determined. The primary triticale lines had more univalents and less chiasmata per pollen mother cell than the corresponding wheat and rye parents together. The parental wheat F₁ exhibited negative heterosis for chiasma frequency whereas all rye hybrids had much higher chiasma frequencies than their inbred parents. Triticale F₁s generally showed lower chiasma frequencies and more univalents than their parents, but the degree of pairing failure was dependent upon which of the parental species within the triticale, wheat or rye, was in the heterozygous state. F₁s with heterozygous wheat genome only showed the least reduction in chiasma number (presumably caused by gene actions within the wheat genome), while F₁s with heterozygous rye genome showed high reduction in chiasma frequency and an increase in pairing failure (induced by negative interactions between the heterozygous rye and the wheat genome in triticale). A high correlation was found between the frequency of undisturbed pollen mother cells and the frequency of aneuploids in the subsequent generation. A higher number of aneuploids occurred in those populations which were heterozygous for the rye genome.     

Genetic analysis of Karnal bunt (Neovossia indica) resistance in wheat

Embryos excised from seeds of six generations (P₁, P₂, F₁, BC₁, BC₂ and F₂) of a cross WH 283 x WH 533 were cultured on modified MS medium already inoculated with secondary sporidia ofNeovossia indica. Significant variations for callusing response (CR) (54.55–75.55%) were observed among generations but the presence or absence ofN. indicia did not affect callusing response. A clear inhibition zone (IZ) was formed around each embryo showing callusing. The diameter of IZ varied significantly among generations and was maximum in the resistant genotype, WH 283 (3.60 cm). Fresh weight and dry weight of calli, initiated from embryo cultured and inoculated withN. indica, varied significantly among generations. Coefficient of infection as well as percentage of infection reflected the overdominance of susceptibility. Generation mean analysis showed that the three parameter model was adequate for diameter of IZ only. Six-parameter model showed that additive (in presence ofN. indica), additive and additive x dominance (in absence ofN. indica) effects were also significant. Complementary type of epistasis for fresh weight of calli and dominance, and dominance x dominance effects for dry weight of calli were observed in the presence ofN. indica. Magnitude of additive effects was higher for diameter of IZ in three parameter model. Therefore, selection might assist in improving this trait and thus indirectly help in attaining the resistance towardsN. indica.     

Genetic drift and selection effects of modified recurrent full-sib selection programs in two F2 populations of European flint maize

Selection response of a modified recurrent full-sib (FS) selection scheme conducted in two European flint F₂ maize (Zea mays L.) populations was re-evaluated. Our objectives were to (1) determine the selection response for per se and testcross performance in both populations and (2) separate genetic effects due to selection from those due to random genetic drift. Modified recurrent FS selection was conducted at three locations using an effective population size N _e = 32 and a selection rate of 25% for a selection index, based on grain yield and grain moisture. Recombination was performed according to a pseudo-factorial mating scheme. Selection response was assessed using a population diallel including the source population and advanced selection cycles, as well as testcrosses with unrelatesd inbred line testers and the parental F₁ generation. Selection response per cycle was significant for grain yield and grain moisture in both populations. Effects of random genetic drift caused only a small reduction in the selection response. No significant selection response was observed for testcrosses, suggesting that for heterotic traits, such as grain yield, a high frequency of favorable alleles in the elite tester masked the effects of genes segregating in the populations. We conclude that our modified recurrent FS selection is an alternative to other commonly applied intrapopulation recurrent selection schemes, and some of its features may also be useful for increasing the efficiency of interpopulation recurrent selection programs.     

Effect of the 1B/1R translocation on anther culture ability in wheat (Triticum aestivum L.)

Using two varieties, their reciprocal hybrids, F₈ lines and doubled haploids, results confirmed that three genetic components are involved in wheat anther culture ability, viz embryo induction frequency, regeneration ability and the frequency of albinism. In these experiments, no significant maternal effects were noticed. For embryo yields, transgressive lines were obtained from hybrids between distant genotypes. Regeneration of green plants depended upon two independent traits: regeneration ability and the frequency of albinos. F₈ lines and two doubled haploids equaled the 50% regeneration rate of the hybrids, but they only regenerated green plants. Based upon cytological examination and gliadin patterns, it is suggested that genes favoring regeneration ability could be linked to the 1BL-1RS translocated chromosome from Aurora.Abbreviations DH doubled haploids - MS Murashige and Skoog - MPG multicellular pollen grains     

Physical mapping and molecular-cytogenetic analysis of substitutions and translocations involving chromosome 1D in synthetic hexaploid triticale

 Chromosome 1D, which carries the advantageous alleles of glutenin and gliadin, attracts major interest with respect to improving the bread-making quality of triticale. Eighty-one BC₁F₄ lines from different primary and secondary hexaploid triticale crosses were selected for 1D chromatin analysis using SDS-PAGE and C-banding. In situ hybridization and RFLP-based comparative physical mapping of group 1 chromosomes revealed 20 lines with complete 1D (1A) substitutions. Nine 1D (1B) substitutions, six 1D (1R) substitutions and one 1D addition line were also selected. Three lines were pure AABBRR hexaploids without any D-genome chromosomes. For the remaining 42 lines (51.8%), a wide spectrum of 20 different recombinations between chromosomes 1A and 1D was uncovered. Altogether, they were generated without any earlier irradiation, tissue culture or genetic induction of chromosome pairing. In addition, 14 translocations between 1B/1D, 1A/1R, 1B/1R, 1D/1R and 1A/1B were detected. Considerable variability for sedimentation values was found, with the highest sedimentation values among lines with complete 1D chromosomes. The implications of using triticale as a model for generating compensating chromosome rearrangements in defined homoeologous groups and the breeding potential of D-genome chromatin introgressed into triticale with improved sedimentation values are discussed. Received: 27 July 1998 / Accepted: 5 August 1998     

Nitrogen-induced variations in leaf gas exchange of spring triticale under field conditions

Nitrogen (N) is the key factor limiting photosynthetic processes and crop yield. Little is known about the response of leaf gas exchange of spring triticale (Triticosecale Wittm.) to N supply. The effect of N fertilizers on different gas exchange variables, i.e., photosynthetic rate (A), transpiration rate (E), stomatal conductance (g _s), instantaneous water use efficiency (WUE) and maximum quantum yield of photosystem II (PSII) (F _v/F _m), chlorophyll index (SPAD, soil–plant analysis development), and the relationship of these variables with yield were studied in spring triticale grown under field conditions. Six treatments of N—0, 90, 180, 90 + 30, 90 + 30 + 30 kg ha^?1 (applied as ammonium nitrate, AN) and one treatment of N 90 + 30 + 30 kg ha^?1 (applied as urea ammonium nitrate solution, UAN) were compared. The analysis of variance showed that throughout the triticale growing season, N fertilization had significant effects on A, WUE, g _s and SPAD. On average, N fertilizer application increased A values by 14–70%. E and F _v/F _m values were not influenced by N fertilization levels. The effect of growth stage and year on gas exchange variables and F _v/F _m and SPAD was found to be significant. At different growth stages, A values varied and maximum ones were reached at BBCH 31–33 (decimal code system of growth stages) and BBCH 59. With aging, values of A decreased independently of N fertilization level. The gas exchange variables were equally affected by both fertilizer forms. The interplay among grain yield, leaf gas exchange variables, F _v/F _m and SPAD of spring triticale was estimated. The statistical analysis showed that grain yield positively and significantly correlated with A and SPAD values throughout the growing season.     

Effect of long-term drought stress on leaf gas exchange and fluorescence parameters in C<Subscript>3</Subscript> and C<Subscript>4</Subscript> plants

A field study was performed on triticale, field bean, maize and amaranth, to find differences between studied species in physiological alterations resulting from progressive response as injuries and/or acclimation to long-term soil drought during various stages of plant development. The measurements of leaf water potential, electrolyte leakage, chlorophyll a fluorescence, leaf gas exchange and yield analysis were done. A special emphasis was given to the measurements of the blue, green, red and far-red fluorescence. Beside, different ratios of the four fluorescence bands (red/far-red: F ₆₉₀/F ₇₄₀, blue/red: F ₄₄₀/F ₆₉₀, blue/far-red: F ₄₄₀/F ₇₄₀ and blue/green: F ₄₄₀/F ₅₂₀) were calculated. Based on both yield analysis and measurements of physiological processes it can be suggested that field bean and maize responded with better tolerance to the water deficit in soil due to the activation of photoprotective mechanism probably connected with synthesis of the phenolic compounds, which can play a role of photoprotectors in different stages of plant development. The photosynthetic apparatus of those two species scattered the excess of excitation energy more effectively, partially through its transfer to PS I. In this way, plants avoided irreversible and/or deep injuries to PS II. The observed changes in the red fluorescence emission and in the F _v/F _m for triticale and amaranth could have occurred due to serious and irreversible photoinhibitory injuries. Probably, field bean and maize acclimatized more effectively to soil drought through the development of effective mechanisms for utilising excitation energy in the photosynthetic conversion of light accompanied by the mechanism protecting the photosynthetic apparatus against the excess of this energy.     

The hybrid protein interactome contributes to rice heterosis as epistatic effects

Heterosis is the phenomenon in which hybrid progeny exhibits superior traits in comparison with those of their parents. Genomic variations between the two parental genomes may generate epistasis interactions, which is one of the genetic hypotheses explaining heterosis. We postulate that protein?protein interactions specific to F₁ hybrids (F₁‐specific PPIs) may occur when two parental genomes combine, as the proteome of each parent may supply novel interacting partners. To test our assumption, an inter‐subspecies hybrid interactome was simulated by in silico PPI prediction between rice japonica (cultivar Nipponbare) and indica (cultivar 9311). Four‐thousand, six‐hundred and twelve F₁‐specific PPIs accounting for 20.5% of total PPIs in the hybrid interactome were found. Genes participating in F₁‐specific PPIs tend to encode metabolic enzymes and are generally localized in genomic regions harboring metabolic gene clusters. To test the genetic effect of F₁‐specific PPIs in heterosis, genomic selection analysis was performed for trait prediction with additive, dominant and epistatic effects separately considered in the model. We found that the removal of single nucleotide polymorphisms associated with F₁‐specific PPIs reduced prediction accuracy when epistatic effects were considered in the model, but no significant changes were observed when additive or dominant effects were considered. In summary, genomic divergence widely dispersed between japonica and indica rice may generate F₁‐specific PPIs, part of which may accumulatively contribute to heterosis according to our computational analysis. These candidate F₁‐specific PPIs, especially for those involved in metabolic biosynthesis pathways, are worthy of experimental validation when large‐scale protein interactome datasets are generated in hybrid rice in the future.     

Production and characterization of alloplasmic lines of a triticale ‘Rosner’

Summary The transfer of cytoplasms of various Triticum and Aegilops species to a hexaploid triticale (Rosner) has been attempted using 30 alloplasmic lines and a euplasmic line of common wheat as cytoplasmic donors. The average rate of F₁ hybrid production (seed setting rateXgermination rate) following an ordinary method of crossing is only 0.09%, whereas this rate is increased to 3.1% by use of embryo culture. The first backcross of the F₁ plants with triticale pollen is again difficult, the hybrid production being 0.9%. Further backcrosses proceed smoothly in most cases. As a consequence, the following seven cytoplasms have been transferred to triticale: T. dicoccum, T. aestivum, Ae. squarrosa, Ae. cylindrica, Ae. juvenalis, Ae. ovata and Ae. speltoides. None of these alien cytoplasms causes more meiotic instability than does the triticale's own cytoplasm. Two cytoplasms of T. dicoccum and T. aestivum, both belonging to the B plasma type, have no effect upon any of triticale's characters. Two D type cytoplasms of Ae. squarrosa and Ae. cylindrica cause about 50% reduction of male fertility but exert no other remarkable effects. This fact suggests a partial functional compensation of the effect of a 1D chromosome upon interacting with D cytoplasm by a rye chromosome substituting for it in triticale. A D² cytoplasm of Ae. juvenalis causes earlier heading and complete male sterility, accompanied by some reduction of growth vigor. An M⁰ type cytoplasm of Ae. ovata and an S type cytoplasm of Ae. speltoides cause a great heading delay, complete male sterility, and severe reduction of vigor. From the viewpoint of triticale breeding, none of these cytoplasms appears superior to the triticale's own cytoplasm. However, from the viewpoint of genetics, the hexaploid triticale is an effective tester for differentiating the B, S, and D plasma types.Contribution No. 466 from the Laboratory of Genetics, Faculty of Agriculture, Kyoto University, Japan     

Cotton chromosome substitution lines crossed with cultivars: genetic model evaluation and seed trait analyses

Seed from upland cotton, Gossypium hirsutum L., provides a desirable and important nutrition profile. In this study, several seed traits (protein content, oil content, seed hull fiber content, seed index, seed volume, embryo percentage) for F₃ hybrids of 13 cotton chromosome substitution lines crossed with five elite cultivars over four environments were evaluated. Oil and protein were expressed both as percentage of total seed weight and as an index which is the grams of product/100 seeds. An additive and dominance (AD) genetic model with cytoplasmic effects was designed, assessed by simulations, and employed to analyze these seed traits. Simulated results showed that this model was sufficient for analyzing the data structure with F₃ and parents in multiple environments without replications. Significant cytoplasmic effects were detected for seed oil content, oil index, seed index, seed volume, and seed embryo percentage. Additive effects were significant for protein content, fiber content, protein index, oil index, fiber index, seed index, seed volume, and embryo percentage. Dominance effects were significant for oil content, oil index, seed index, and seed volume. Cytoplasmic and additive effects for parents and dominance effects in homozygous and heterozygous forms were predicted. Favorable genetic effects were predicted in this study and the results provided evidence that these seed traits can be genetically improved. In addition, chromosome associations with AD effects were detected and discussed in this study.     

Introgression of <Emphasis Type="Italic">Aegilops</Emphasis> genetic material into the genome of hexaploid triticale

Cytological analysis of different meiosis stages was performed in F₄ hybrids in comparison with the F₁ hybrids obtained through crosses between the hexaploid triticale and genome-substitution forms of Aurolata (AABBUU) and Aurosis (AABBS^shS^sh) wheat, in which D genome of common wheat Aurora was substituted for the genomes of Aegilops umbellulata and Ae. sharonensis, respectively. It was demonstrated that in F₄ the level of bivalent conjugation was substantially higher than the expected one. However, the value of meiotic index in F₄ hybrids was still small, pointing to incomplete process of the meiosis stabilization, specifically, of the stages following the metaphase I. Based on the data of morphological and biochemical analyses of the hybrids produced, the forms of triticale carrying some properties of the genus Aegilops, which were of interest for genetic and breeding studies, were isolated.     

Genetic analysis of anther culture response in wheat carrying alien translocations

A bread wheat cultivar, Saratovskaya 29, (S29), its nearly isogenic lines carrying alien translocations [Lr9 from Aegilops umbellulata (Eg29) and (Lr19) from Agropyron elongatum (Ps29)] and two F₁ hybrids between three nearly isogenic lines of S29 that differed by the Lr19+Rht1,Pro1+Pro2 and Ppd1+Ppd2 gene complexes, namely the S29 (Lr19+Rht1)/S29 (Ppd1+Ppd2) F₁ and the S29 (Pro1+Pro2)/S29 (Lr19+Rht1) F₁ were studied for their culture response with the following results. (1) Translocations with Lr9 and Lr19 decreased embryo frequency and green plant regeneration. (2) Both F₁ hybrids showed a decrease in embryo frequency. One of the F₁ hybrids, S29 (Lr19+Rht1)/S29 (Ppd1+Ppd2) showed a decrease, with respect to S29 for green plant regeneration; the other F₁ S29 (Pro1+Pro2)/S29 (Lr19+Rht1), equalled S29 for green plant regeneration. (3) The gene complex of the F₁ hybrid S29 (Pro1+Pro2)/S29 (Lr19+Rht1) was better than that of the F₁ hybrid S29 (Lr19+Rht1)/S29 (Ppd1+Ppd2) for embryo induction and green plant regeneration. This effect was possibly induced by interactions between the Pro1+Pro2 and Lr19+Rht1 genes or was the result of direct actions of the Pro1+Pro2 genes.     

Chronic boron or copper deficiency induces limb teratogenesis in Xenopus

Sets of adult male and female Xenopus laevis were administered a boron-deficient (−B) diet under low-boron culture conditions, a boron-supplemented (+B) diet under ambient boron culture conditions, a copper-deficient (−Cu) diet under low-copper culture conditions, or a copper-supplemented (+Cu) diet under ambient copper culture conditions, for 120 d. Adults from each group were subsequently bred, and the progeny were cultured and bred. Results from these studies indicated that although pronounced effects on adult reproduction and early embryo-larval development were noted in the −B F₁ generation, no effects on limb development were observed. No significant effects on reproduction, early embryogenesis, or limb development were noted in the +B group, irrespective of generation. Highly specific forelimb and hindlimb defects, including axial flexures resulting in crossed limbs and reduction deficits, were observed in −B F₂ larvae, but not in the +B F₂ larvae. As was noted in the boron-deficiency studies, significant effects on reproduction and early embryo development were observed in the −Cu F₁ generation, but not in the +Cu F₁ generation. Unlike the effects associated with boron deficiency, maldevelopment of the hindlimbs (32 responders, n=40) was found in the F₁ generation.     

The Effect of Photoautotrophy on Photosynthesis and Photoinhibition of Gardenia Plantlets during Micropropagation

We studied the relationships between the degree of photoautotrophy, photosynthetic capacity, and extent of photoinhibition of Gardenia jasminoides Ellis plantlets in vitro. Two successive micropropagation stages (shoot multiplication and root induction), and three culture conditions [tube cap closure, photosynthetic photon flux density (PPFD), and sucrose concentration] which may influence the development of photoautotrophy in vitro were assayed. The ratios of variable chlorophyll fluorescence to either maximal (F_v/F_m) or ground (F_v/F₀) values were low, irrespective of the culture stage or growing conditions. Incomplete development of the photosynthetic apparatus and permanent photoinhibition may be involved. However, F_v/F_m and F_v/F₀ increased from shoot multiplication to root induction owing to a decrease in F₀ and an increase in F_m. This suggests that photoinhibition decreases later during micropropagation, when the photoautotrophy of plantlets is more advanced. The low sucrose content and high PPFD increased the photoinhibition of plantlets, whereas growth in tubes with permeable caps showed the opposite effect. The only culture factor with a significant (positive) effect on maximum photosynthetic rate (P _max) was PPFD. At shoot multiplication net photosynthetic rate (P _N) was positively correlated with the half time of the increase from F₀ to F_m (t_1/2). Such association may be mainly due to a common response of both traits to higher PPFD in culture. Within each culture stage, no relationship was observed between P _N and the degree of photoautotrophy, which was positively correlated with F_v/F_m and F_v/F₀ during root induction. During shoot multiplication, these correlations were not significant, or were even negative. Hence during the last stage of micropropagation, plantlets with a higher degree of photoautotrophy are less photoinhibited, whereas they do not follow this pattern at the earlier stage.