Interaction between jasmonic and gibberellic acids on in vitro tuberization of potato plantlets

Summary A reverse of the delaying effect of gibberellic acid (GA₃) was observed in in vitro tuberization of potato plantlets when the medium contained 0.8×10⁻⁵ M jasmonic acid (JA). The promoting effect of JA seemed to be correlated with the initial absence of growing roots, probably through direct activity of JA in microtuber-producing buds in the stoloniferous shoots. This is based on the fact that JA did not inhibit root growth a posteriori. Endogenous gibberellins (GAs) synthesized by roots did not interfere with the previous activity of JA in tuberization. The absence of a JA promoting-effect on tuberization of previously-rooted plantlets could be related to the capacity of potato roots to synthesize endogenous GAs which might antagonize the JA effect on buds of stoloniferous shoots.     

Evaluation of dihaploid populations from potato varieties and breeding lines

Summary Dihaploid populations from 20 varieties and 11 breeding lines ofSolanum tuberosum differed greatly in the occurrence and frequency of mutant phenotypes, in tuberization, flowering, pollen stainability, 2n-pollen production and resistance toGlobodera rostochiensis pathotype Ro-1. One population contained up to 61.7% lethal mutants: 39.1% of the total of 5377 dihaploids obtained did not tuberize, and 32.4% of 825 vigorous dihaploids did not flower. Of 825 vigorous dihaploids, 26.9 and 3.9% respectively had a pollen stainability higher than 20 and 60%. Among 222 dihaploids with a pollen stainability higher than 20%. 23.0% produced some 2n-pollen and none of these had a stainability higher than 60%. Among the dihaploid populations investigated the proportion of resistant to susceptible dihaploids ranged from 8:26 to 62:8.     

Fertility of doubled monoploids ofSolanum phureja

Thirteen anther-derived doubled monoploids and their heterozygous diploid anther donor were evaluated in the greenhouse for flowering, fruit set, seed set and pollen fertility. Doubled monoploids varied for number of days to flower, duration of flowering, abundance of flowers and general flower quality. Fruit set on the doubled monoploids in controlled crosses with diploid male-fertile clones varied from 0 to 73% with a mean of 33% compared to the anther donor with 58%. Seed set varied from 9 to 210 seeds per fruit and was significantly lower than the anther donor (377 seeds/fruit). Five doubled monoploids that shed low quantities of pollen exhibited significantly less pollen stainability (10-30%) than the anther donor (88%). However, pollen of doubled monoploids did not germinatein vitro. 2n pollen frequencies of 20–55% were observed for the doubled monoploids compared with 22% for the anther donor. It was concluded that doubled monoploids had lower female fertility compared to the anther donor but that they produced sufficient seed to facilitate utilization in a breeding program as female parents. However, they were considered to be male-sterile for practical purposes.     

The effect of the inhibitors of protein and nucleic acid synthesis on the coumarin-induced tuberization and growth of excised axillary shoots of potato sprquts (Solanum tuberosum l.) culturedin vitro

The inhibitors of protein and nucleic acid synthesis; chloramphenicol, para-fluorophenylalanine, actinomycin D, and 5-fluorouracil were evaluated for their effectiveness in inhibiting coumarin-induced tuberization, tuber growth, and the inhibition of.root and shoot growth of excised axillary shoots of potato sprouts culturedin vitro. To date, it has been demonstrated that both kinetin and coumarin readily effect 100 percent tuberization of the shoots culturedin vitro. The results of the present study demonstrate that with the exception of 5-fluorouracil, the inhibitors significantly inhibited the coumarin-induced. tuberization, tuber growth, and root growth whereas in previously published data by Palmer and Smith (6), the inhibitors merely delayed kinetin-induced tuberization. It is suggested that both protein and nucleic acid synthesis are required for the coumarin-induced tuberization processes, and the mode of action of coumarin is distinctly different from that of kinetin.     

Wx基因对灌浆期小麦不同叶位叶片光合特性的影响

为了解Wx基因对小麦光合作用的影响,对8个小麦Wx近等基因系的不同叶位叶片光合参数进行了测定和分析。结果表明,小麦叶片净光合速率、气孔导度、胞间CO2浓度和蒸腾速率在叶位和基因型间均有极显著差异,缺失单个Wx基因使叶片光合参数下降,且降幅表现为Wx-D1Wx-A1Wx-B1;胞间CO2浓度不影响光合作用,不同叶位叶片光合参数明显呈旗叶倒二叶倒三叶,但WxABD(糯小麦)光合参数在叶位间没有显著差异;Wild type和WxABD总体光合能力和产量相对较高。以上结果说明,Wx基因的缺失会引起叶片光合能力下降,不利于小麦产量形成。     

Selection of monoploids for protoplast fusion and generation of intermonoploid somatic hybrids of potato

The union of potato monoploid genotypes (2n=1x =12) through protoplast fusion may result in vigorous somatic hybrids due to a reduction of the “genetic load” normally present in this highly heterozygous tetraploid (2n=4x=48) crop. More than 100 androgenic monoploids derived from diploid (2n=2x=24)Solanum phureja Juz. & Buk. andS. chacoense Bitt. xS. phureja clones were evaluated in field trials during 1996 and 1997 to identify the most promising genotypes for protoplast fusion experiments. Compared to the total population, the 1996 selected genotypes had higher means for tuber number (30.1 vs 11.2 tubers/plant), average tuber weight (3.0 vs 1.8 g/tuber) and total yield (66.1 vs 20.4 g/plant). Similarly, the 1997 selected genotypes had higher means for tuber number (42.8 vs 25.4 tubers/plant), average tuber weight (3.6 vs 2.5 g/tuber) and total yield (114.0 vs 63.4 g/plant) compared to the total population. The 31 selected monoploid genotypes from 1996-97 varied in their response to protoplast isolation and culture from no growth (9), cell enlargement (5), limited cellular divisions (8), callus formation (5) to plant regeneration from callus (4). Chemical fusion and electrofusion produced three groups of intermonoploid somatic hybrids. Polymorphic simple sequence repeat (SSR) loci enabled distinction of somatic hybrids from parental somaclones. Rapid DNA extraction with SSR analysis enabled screening of calluses to identify somatic hybrid tissue prior to plant regeneration. The somatic hybrids were highly polyploid, mostly hexaploid (2n=6x=72), possibly due to fusion of endopolyploid protoplasts and/or chromosomal doubling during plant regeneration.     

Tuberization in potato at high temperatures: response of physiologically young plants to disbudding and growth inhibitors

Summary In physiologically young plants (Solanum tuberosum L., cv. Sebago), abscisic acid (ABA) and chlorethyltrimethylammonium chloride (CCC) promoted tuberization at day/night temperatures of 32°/18°C, but not at 32°/28°C, in contrast to earlier experiments with physiologically old plants. Disbudding promoted tuberization at both temperatures. These results suggest that physiologically young plants have a greater capacity for increased gibberelling synthesis in the buds at high temperatures.     

Behaviour of plant material issued from in vitro tuberization

Summary In vitro bacterization of potato microplants with a pseudomonad bacterium,Pseudomonas spp. strain PsJN, induces developmental modifications which make them more hardy and more vigorous upon transplanting. The paper reviews previous experiments and presents recent data on the post-inoculation microplant generation response of genetically engineered and nonengineered clones, microplant response to CO₂ supplement, as well as the results of field experiments conducted between 1987 and 1993. Production of minitubers under greenhouse conditions and tuberization under heat stress in growth chamber are also presented. The use of the in vitro culture system for the development of microbial associations benefitting crop rotations is postulated.     

Effects of exogenous applications of cytokinin on the development of potato (Solanum tuberosum L.) cuttings

Summary Application of 6-benzylaminopurine or its riboside to potato cuttings on four successive days was very effective if the treatment started on day 4 after cutting. These cytokinis caused cuttings that were well induced to express a lower level of induction than they actually had received. There was a shift from sessile tuberization of the central bud to non-sessile tuberization of the central bud or to tuberization of ancillary buds, or a shift from ancillary-bud tuberization to swollen shoots. Effects were largest after a moderate induction. If rooting occurred, cytokinin reduced the proportion of rooted cuttings significantly. Cytokinin increased the levels of fructose and glucose in the tubers if it was applied after day 3. Dry weight of the buds was reduced by cytokinin in those cases where it caused suppression of ancillary-bud development. Paper No 836, Department of Vegetable Crops, Cornell University, Ithaca, N.Y. 14853, USA.     

Grey mould incidence is reduced on grapevines with lower vegetative and reproductive growth

The hypothesis that grey mould incidence would be positively correlated to grapevine canopy development was confirmed over a period of 3 years (2004–2006) on Aranel cultivar in an experimental vineyard near Montpellier, south France. Different levels of vine growth were generated by implementing three management schemes: (i) perennial cover crop, (ii) chemical weed control and (iii) irrigation and fertilisation. Grey mould incidence was assessed at harvest, together with various sets of variables linked with canopy microclimate, shoot vigour, vine capacity, cluster architecture, yield components and fruit composition. Significant positive correlations were observed between disease incidence and key variables of shoot vigour and vine capacity: total leaf number, leaf dry matter, leaf layer number, leaf area per metre of row, pruning mass and nitrogen accumulation. In 2004, Botrytis cinerea developed in all experimental plots because climatic and microclimatic conditions were conducive to grey mould. The climatic and microclimatic variables that significantly favoured grey mould development were: precipitation, duration of relative humidity >90% in the canopy and low potential evapotranspiration. However, in 2005 and 2006, under dry summer conditions, disease developed only in the most vigorous vines, which were both irrigated and fertilised. These vines showed a very high canopy growth, very compact clusters and a delayed fruit maturity. This evidenced that unfavourable climatic conditions for the disease development can be counterbalanced by conditions of high vine growth and associated canopy and cluster features.     

Morphogenic Response of Leaf and Petiole Explants of Broccoli Using Thidiazuron

Broccoli (Brassica oleracea var. italica) is an important nutritionally rich vegetable cole crop grown in the world. Environmental stress, pests, and diseases cause enormous yield losses because of a limited gene pool. Genetic manipulation is becoming an important method for broccoli improvement. The objective of present study was to evaluate the potency of thidiazuron (TDZ) as a plant growth regulator in evoking morphogenic responses in leaf and petiole explants of broccoli. An efficient, reproducible, and high frequency plant regeneration protocol has been standardized in broccoli cv. Solan green head. Leaf and petiole explants were cultured on Murashige-Skoog (MS) medium, supplemented with a wide range of TDZ concentrations. The following treatments were designed for efficient in vitro shoot regeneration: TDZ alone, TDZ with adenine, TDZ with naphthalene acetic acid (NAA), and TDZ with indole acetic acid (IAA). Among the 36 combinations of growth regulators used, the highest percentage of leaf explants producing shoot (89.25%) was recorded on MS medium containing 1.0 μM TDZ and 0.107 μM NAA. The multiple shoot regeneration response of petiole explant producing shoots (91.55%) was obtained on MS medium containing 2.0 μM TDZ and 0.107 μM NAA. Shoot multiplication and elongation were obtained on the same medium. For root regeneration in in vitro regenerated shoots, different concentrations of NAA were applied. High frequency (100%) root regeneration response with healthy and vigorous roots was observed on MS medium supplemented with 0.54 μM NAA. The regenerated plantlets with well-developed shoots and root system were transferred to pots containing cocopeat and successfully acclimatized. We recommend 1.0 μM TDZ with 0.107 μM NAA and 2.0 μM TDZ and 0.107 μM NAA combinations for adventitious shoot regeneration from leaf and petiole explants in broccoli cv. Solan green head respectively. This is the first report on high frequency organogenesis from leaf and petiole explants of broccoli cv. Solan green head using thidiazuron.     

Influence of bud position on the formation of tubers on multiple node cuttings of potato (Solanum tuberosum L.)

Summary Stem cuttings with variable number and position of leaves and variable number and age of buds were used to study the preference of tuberization at certain buds when several potential tuber sites were present. These cuttings were exposed to different orientations of the cuttings themselves and/or their light source. Inverting the cuttings did not affect overall tuberization, but had significant effects on individual buds, probably by the interaction between the original basipetal patterns in the cuttings and gravity effects. A smaller angle to the horizontal and lighting from below increased the overall expression of the tuberization stimulus. Leaf and bud position or age affected expression in a complicated manner, but the distance between screened bud and light-exposed leaf was crucial; buds most distant from illuminated leaves showed the strongest induction. The basic pattern of tuberization was basipetal.     

磷素水平对小麦突变体农艺性状和品质特性的影响

为丰富磷高效小麦遗传资源,分析了小麦纤维素相关基因突变体（ZC5和ZC7,为郑麦9023经EMS诱导的脆杆小麦）及其野生型（小麦品种郑麦9023）在三种磷素水平下（0、105、210 kg·hm^-2）、不同发育时期的相关生理指标和成熟期农艺和品质性状。结果表明,基因型、磷水平和基因型与磷水平互作均对旗叶叶面积、旗叶SPAD值和籽粒淀粉含量有一定影响,影响程度因生育时期而异。不同处理小麦灌浆过程符合Logistic生长规律,籽粒干物质积累均呈“慢－快－慢”的变化趋势。基因型和磷水平均对成熟期籽粒蛋白质含量和全磷含量有极显著影响;基因型对成熟期株高、有效小穗数、穗粒数及千粒重有极显著影响。相关分析表明,籽粒渐增期灌浆速率和干物质积累量、快增期干物质积累量和旗叶SPAD值均与千粒重呈极显著正相关,籽粒渐增期、快增期持续时间和淀粉含量均与千粒重呈显著正相关。ZC5为磷敏感材料,施磷能提前ZC5最大灌浆速率出现日期,提高其最大灌浆速率和平均灌浆速率,且随着施磷量的增加籽粒蛋白质和全磷含量增加。纤维素合成相关基因突变对旗叶SPAD值、叶面积、籽粒淀粉含量、蛋白质含量、全磷含量、株高、有效小穗数、穗粒数和千粒重均存在显著影响。通过化学诱变改良小麦细胞壁成分可为小麦育种提供丰富的遗传资源。     

Two β-amylase genes,OsBAM2 and OsBAM3, are involved in starch remobilization in rice leaf sheaths

To identify mechanisms of starch degradation in rice leaf sheaths at the post-heading stage, we investigated the function of OsBAM2 and OsBAM3, which encode plastid-targeted active β-amylase isoforms, in starch remobilization in leaf sheaths. The starch content in the second leaf sheaths below the flag leaf (the third leaf sheaths) peaked at the flag leaf emergence stage and gradually decreased until 15 days after heading. The mRNA levels of OsBAM2 and OsBAM3 in the third leaf sheaths increased from the flag leaf emergence stage to the heading stage when the starch content began to decrease. However, these mRNA levels did not always remain high during post-heading. Overexpression of OsBAM2 or OsBAM3 markedly repressed starch accumulation in the third leaf sheaths, showing that OsBAM2 and OsBAM3 function in starch degradation in rice leaf sheaths. In contrast, no significant differences in starch content in the third leaf sheaths were detected between knockdown plants of OsBAM2 or OsBAM3 and non-transgenic wild-type plants. Our results suggest that reduced expression of the individual genes, OsBAM2 or OsBAM3, does not result in excess accumulation of starch in the leaf sheaths, probably because of the complementary function of another gene or the action of other genes encoding starch-degrading .     

Effect of photoperiod on tuberization in the Livingstone potato (Plectranthus esculentus N.E.Br. Lamiaceae)

The Livingstone potato (Plectranthus esculentus N.E.Br.) produces a cluster of edible tubers at the base of the stem that are used as a potato substitute in many areas of Africa. No information is available on factors affecting tuberization in this species. Photoperiod is known to influence storage organ formation in a wide range of crops, and pilot trials indicated that it also played a role in tuberization in P. esculentus. The critical photoperiod for tuber induction, as well as the number of short-day cycles required to induce tubers, were investigated in glasshouse trials using in vitro plants. Nine photoperiod treatments (30-min intervals from 10 to 14 h of light) were applied in the critical photoperiod experiment. To determine the number of short-day cycles required to induce tuberization, plants were exposed to short days (10 h light) for periods ranging from 0 to 20 days at 2-day intervals. Data were collected from both intact plants and sub-apical two-node cuttings made after the experimental treatments were completed. The critical photoperiod for the specific genotype used in this study was between 12.5 and 13 h, with cuttings giving a slightly exaggerated result over that of intact plants. It was established that exposure to four short-day cycles was sufficient to induce tuberization in this species.     

Tuberization in potato at high temperatures: Responses to exogenous gibberellin,cytokinin and ethylene

Summary In potato (Solanum tuberosum L., cv. Sebago), benzyladenine (BA) promoted tuberization at high day/night temperatures (32°/18°C), while gibberrellic acid (GA) and chlorethylphosphonic acid (CEPA) reduced tuberization at low day/night temperatures (22°/18°C). These results are consistent with the hypothesis that temperature exerts its influence on tuber formation by altering the balance between endogenous gibberellins, cytokinins and inhibitors, but not ethylene.     

The effect of nitrogen on the coumarin-induced tuberization of potato axillary shoots culturedin vitro

Coumarin-induced tuberization was studied on axillary shoots excised from etiolated potato sprouts each of which was cultured in vitro. Sprouts grown on culture medium with high nitrogen concentrations produced axillary shoots which elongated and would not readily tuberize. Sprouts cultured on medium low in nitrogen produced axillary shoots which tuberized with limited elongation. Carbohydrate concentration of the culture medium for the excised axillary shoot could significantly modify the nitrogen effect of the potato sprout medium. Axillary shoots growing on high nitrogen medium did not tuberize except in cases where the carbohydrate concentration was increased.     

Physico-chemical Characteristics as Indicators of Starch Availability from Milled Rice

The hypothesis was tested that certain physico-chemical characteristics might be used as indicators of total starch availability and rate of starch availability of milled rice. Milled unparboiled (uPB) and parboiled (PB) rice samples (n=93) were characterized using standardized methods of physical tests and chemical analyses and anin vitromethod was used for measuring the rate of starch digestion on a subsample of rice (n=26). The rice varieties were dominated by medium long, bold rice grain with high amylose rice and intermediate gelatinization temperature (GT), but a wide range in all characteristics was measured. Small amounts of resistant starch (RS) were measured in the cooked rice, indicating virtually complete starch availability. The RS of PB rice (0·4 g/100 g rice as eaten) was significantly (P<0·004) higher than the RS of uPB rice (0·1 g/100 g) however. The rate of starch digestion was significantly affected by both variety and parboiling. The starch digestion index (SDI) values of the PB samples (mean value 73·7) were significantly (P<0·001) lower than those of the uPB samples (mean value 79·0). The apparent amylose content (AC) was the strongest determinant for SDI in both uPB and PB rice. The widths and shapes of the raw grains and the elongation after cooking were correlated significantly with SDI values for the uPB rice, while the relatively mild parboiling procedure followed in this study eliminated this correlation. The minimum cooking times were correlated significantly with the SDI values in the uPB samples.     

Content of starch and sugars and in vitro digestion of starch by α-amylase in five minor millets

Five varieties of minor millets were studied for their amylose, soluble amylose, amylopectin, soluble amylopectin, reducing sugar, total sugar and starch contents. Pure starch was isolated from each variety and the enzymic degradation of starch by porcine pancreatic -amylase were examined with and without gelatinisation. Gelatinised sample ofEchinochloa frumentacea (var. K2) showed minimal hydrolysis and gelatinised sample ofPanicum miliaceum (var. CO3) showed maximum hydrolysis of starch by porcine pancreatic -amylase. Gelatinised starch was highly susceptible to enzymic digestion when compared to ungelatinised starch. The extent of starch degradation varied from 71 to 85 percent in gelatinised samples and starch degradation in ungelatinised sample varied from 10 to 18 percent.