Barriers to hybridization of Solanum bulbocastanum Dun. and S. Verrucosum Schlechtd. and structural hybridity in their F1 plants

Summary Results of reciprocal crosses between Solanum verrucosum (2n=2x=24) and S. bulbocastanum (2n=2x=24) are described in terms of pollen tube behaviour in styles, of berry and seed set, of fertility and of meiotic behaviour of the F₁ hybrids. Pollen tube growth of S. verrucosum is strongly inhibited in styles of S. bulbocastanum, whereas no inhibition is observed in the reciprocal cross. Therefore S. bulbocastanum x S. verrucosum fails to set berries or seeds, whereas the reciprocal cross produces both berries (54.4% berry set) and seeds (0.3 per berry). Only 14.6% of the seeds germinate. Both the diploid and corresponding tetraploid hybrid plants are vigorous, flower abundantly, have a rather regular meiosis (mainly rod bivalents), but show a high degree of cytoplasmic-genic male sterility. Crossability of the diploid hybrid plants is nil when used as pollen parents and near to zero when used as pistillate parents. The barriers to hybridization of the parent species (unilateral inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of the parental chromosomes) are discussed and methods are suggested to overcome these barriers.     

Evaluation of proline analysis and chlorophyll fluorescence quenching measurements as drought tolerance indicators in durum wheat (Triticum turgidum L. var. durum)

Summary The possibility of using proline accumulation and fluorescence inhibition as predictive tests for drought tolerance in durum wheat has been investigated. The drought susceptibility of 25 genotypes was evaluated by comparing yields and yield components in irrigated and non irrigated conditions in the field. A drought susceptibility index (DSI) was calculated based on yields from irrigated and dry treatments and compared with the results obtained using the two physiological criteria. Proline accumulation and chlorophyll fluorescence inhibition were found to be significantly and negatively correlated with DSI of grain yield, biological yield, and thousand kernel weight, and tiller index. The use of both criteria for breeding durum wheat in Mediterranean dryland is discussed.     

中棉所45对亚洲玉米螟存活和生长的影响

以常规棉中棉所23为对照,采用饲喂法,测定了转双价(Bt CpTI)基因抗虫棉中棉所45不同器官对亚洲玉米螟幼虫的杀虫活性和对幼虫的生长抑制作用,调查了田间罩笼试验和自然为害的结果.结果表明:中棉所45对亚洲玉米螟幼虫都具有较高的抗性.室内饲喂结果还表明,对一代的抗性＞二代＞三代;对1龄抗性＞3龄;对3龄幼虫的抑制生长作用显著.     

生姜辐照抑制发芽贮藏工艺研究

本研究结果表明 ,生姜辐照抑制发芽的最适辐射剂量为 0 0 8～ 0 40kGy,最高耐受剂量为 0 40kGy。辐照时要保证产品的吸收剂量不均匀度≤ 1 5。适宜剂量的辐照处理与聚乙烯蔬菜专用保鲜膜包装相结合能够实现生姜在常温下的中长期贮藏 ,贮藏 1 2 0d保鲜率可达到 90 %以上。在 0 0 8～ 0 2 5kGy的辐照剂量范围内 ,不会引起生姜维生素C和钙质含量的损失。     

花魔芋和白魔芋褐变机理及褐变抑制研究

该文通过研究花魔芋和白魔芋球茎中酚类物质含量、多酚氧化酶(Polyphenol Oxidase, PPO)活性、褐变底物和干燥脱水过程中褐变的机理，探讨了无公害酶促褐变抑制剂植酸、抗坏血酸、柠檬酸、L-半胱氨酸对魔芋褐变的抑制效果。结果表明：从11月至次年1月，白魔芋球茎的总酚含量始终高于花魔芋，花魔芋的PPO活力始终强于白魔芋，白魔芋的褐变强度始终弱于花魔芋的褐变强度，褐变强度跟魔芋球茎PPO活力呈正相关。引起魔芋褐变的主要底物可能是多巴胺。引起白魔芋和花魔芋褐变的酶均为多酚氧化酶。对白魔芋采用0.01% L-半胱氨酸单因子抑制剂浸泡5 min，并在60℃下烘烤，所得白魔芋干片颜色白，效果最好。对花魔芋采用0.15% L-半胱氨酸+1%柠檬酸+1%植酸+0.01%抗坏血酸组合抑制剂浸泡5 min，并在60℃下烘烤，所得魔芋干片颜色白，效果最好。     

樟子松热处理材耐久性能的评价

对樟子松热处理材进行室内防霉、防蚁蛀及野外埋地检测,综合评价其耐久性能。结果表明:樟子松热处理材对霉菌、变色菌均无防治效力,不抗白蚁蛀蚀;樟子松热处理材的耐久年限约为3年。     

Kaurane-type diterpenoids from Chromoleana odorata, their X-ray diffraction studies and potent α-glucosidase inhibition of 16-kauren-19-oic acid

A new diterpenoid, 15-angeloyloxy-16,17-epoxy-19-kauronic acid (1), along with five known metabolites, 16-kauren-19-oic acid (2), 6′-hydroxy-2′,3′,4,4′-tetramethoxychalcone (3), isosakuranetin (4), acacetin (5), and kaempferide (6) was isolated from the organic extracts of the roots of Chromoleana odorata. Their structures were determined by spectroscopic evidences. The structures of 1 and 2 were further confirmed by single-crystal X-ray diffraction studies. Compound 2 exhibited significant α-glucosidase inhibitory and antibacterial activities against Escherichia coli and Bacillus subtilis.     

Response of denitrifying communities to successive soil freeze–thaw cycles

The effect of soil freeze–thaw cycles on the denitrification potential was examined based on the C₂H₂ inhibition method. The gross N₂O production curve of the soil sample (incubation with C₂H₂) showed minor changes between the freeze–thaw treatment and the unfrozen control. However, kinetics analysis revealed that the initial production rate, an indicator of the population density of denitrifying communities, decreased (P = 0.043) and the specific growth rate constant, an indicator of the activity of denitrifying communities, increased (P = 0.039) as a result of the freeze–thaw cycles in five of six soil samples examined. The increase in the specific growth rate constant suggested the stimulation of the activity of denitrifying communities that survived after the freeze–thaw cycles and may explain the minor suppression on the gross N₂O production in spite of decreasing the population density of denitrifying communities that was suggested by the initial production rate. The net N₂O production curve of the soil sample (incubation without C₂H₂) showed a remarkable change in one out of six soil samples, and in that one soil sample, N₂O release to the atmosphere was largely stimulated (7.6 times) by the freeze–thaw cycles. However, the stimulation of the N₂O release by the freeze–thaw cycles was even observed in two other selected soil samples (4.6 and 1.8 times), suggesting that an imbalance in the N₂O-producing and N₂O-reducing activities of denitrifying communities might complementally explain the N₂O release stimulated by the freeze–thaw cycles.     

Novel antibiotics as inhibitors for the selective respiratory inhibition method of measuring fungal:bacterial ratios in soil

The use of the selective inhibition (SI) method for measuring fungal:bacterial ratios may be limited due to biocide selectivity and the overlap of antibiotic activity. This study evaluated novel pairs of antibiotics for their specificity in soils of different origins and their potential reduction in inhibition of non-target organisms. Four soils selected for this study were from a semi-arid shrub-steppe, a loblolly pine forest and two grassland sites (restored and farmed prairie plots). Three bactericides were tested: oxytetracycline hydrochloride, streptomycin sulphate, and bronopol. Three fungicides were tested: captan, ketoconazole, and nystatin. The inhibitor additivity ratio and fungal:bacterial ratios were calculated from control and treated soils where inhibition was measured as CO₂ respiration reduction with biocides. We were able to minimize non-target inhibition by the antibiotics to <5% and thus calculate reliable fungal:bacterial ratios using captan to inhibit fungi in all four soils, and bronopol to inhibit bacteria in three of the four soils. The most successful bactericide in the restored prairie was oxytetracycline-HCl. Our results demonstrate that application of novel antibiotics is not uniformly successful in soils of different origin and that the SI technique requires more than just optimization of antibiotic concentration; it also requires optimization of antibiotic selection.     

Denitrification losses from an irrigated sandy-clay loam under a wheat-maize cropping system receiving different fertilizer treatments

Studies were conducted on denitrification in the plough layer of an irrigated sandy-clay loam under a wheat-maize cropping system receiving different fertilizer treatments. The treatments were: N-100 (urea-N at 100kgha^–1year^–1), N-200 (urea-N at 200kgha^–1year^–1), FYM-16 (farmyard manure at 16 tonnes ha^–1year^–1), FYM-32 (farmyard manure at 32 tonnesha^–1year^–1) and the control (unfertilized). Averaged across sampling dates during the wheat season, the denitrification rate as measured by the C₂H₂-inhibition/soil-core incubation method was highest in N-200 (83gNha^–1day^–1), followed by FYM-32 (60gNha^–1day^–1, N-100 (51gNha^–1day^–1), FYM-16 (47gNha^–1day^–1) and the control (33gNha^–1 day^–1). During the maize growing season, average denitrification rate was highest in FYM-32 (525gNha^–1day^–1), followed by FYM-16 (408gNha^–1day^–1), N-200 (372gNha^–1day^–1, N-100 (262gNha^–1day^–1) and the control (203gNha^–1day^–1). Denitrification loss integrated over the whole vegetation period was at a maximum under FYM-32 (13.9kgNha^–1), followed by N-200 (11.8kgNha^–1), FYM-16 (10.6kgNha^–1) and N-100 (8.0kgNha^–1), whereas the minimum was observed for the control (5.8kgNha^–1). Under both crops, denitrification was significantly correlated with water-filled pore space and soil NO₃ ^–-N. The best multiple regression models accounted for 52% and 70% of the variability in denitrification under wheat and maize, respectively. Results indicated that denitrification is not an important N loss mechanism in this well-drained, irrigated sandy-clay loam under a wheat-maize cropping system receiving fertilizer inputs in the range of 100–200kgNha^–1year^–1. Received: 14 January 1997