Effect of crop plant density on critical period of weed competition in potato

A field study was conducted in Hamedan western Iran in 2006 to establish the critical period of weed competition (CPWC) in potato (Solanum tuberosum L.) for commercial and seed production plant densities. A quantitative series of treatments concerned with both increasing duration of interference and length of weed-free period were imposed within each commercial and seed potato production plant density. The beginning and end of the CPWC based on a 10% loss of tuber yield was determined by fitting logistic and Gompertz equations to the relative tuber yield data representing increasing duration of weed interference and weed-free period, respectively. At a 10% tuber yield loss level, the duration of weed interference for 571 and 676 growing degree days (GDDs) from crop emergence, corresponding to 40% and 50% canopy closure, marked out the beginning of the CPWC for commercial and seed production plant densities, respectively. When maintained weed-free for 1163 and 1014 (GDD), corresponding to 100% and 80% canopy closure, weed emerging later caused tuber yield losses of less than 10% for commercial and seed production plant densities, respectively. Practical implications of this study are that post-emergence herbicides or other weed control methods should be used in western Iran to eliminate weeds from 19–24 days post-crop emergence up to 43–51 days. Such an approach would keep yield loss levels below 10%. Interactions between plant density and weed competition durations indicated that weed management in commercial plant density of potato could be less intensive than that of seed production plant density, reducing herbicide use and risk of herbicide carryover to sensitive rotation crops.     

我国高类黄酮(红皮与红肉)苹果育种取得突破性进展

“医食同源,吃营养,吃健康”已经成为人们的共识。针对我国苹果产业品种单一、特色多样化品种严重不足、主栽品种’红富士'果实着色、风味品质及结果习性等性状需要进一步改良、苹果育种特别是红肉苹果育种周期长、缺乏优异种质等问题,系统介绍了以“高类黄酮(红皮与红肉)”为主线,以新疆红肉苹果挖掘与创新利用为研究重点,在品质形成与芽变机理、红肉苹果优异种质创制、高效育种技术创建、特色多样化新品种培育及其配套高效栽培技术创新等方面取得的最新研究进展及其成果,旨在为其他野生果树资源的评价挖掘与创新利用提供参考。     

Exploring the limits of crop productivity: beyond the limits of tipburn in lettuce.

The productivity of lettuce in a combination of high light, high temperature, and elevated CO2 has not been commonly studied because rapid growth usually causes a calcium deficiency in meristems called tipburn, which greatly reduces quality and marketability. We eliminated tipburn by blowing air directly onto the meristem, which allowed us to increase the photosynthetic photon flux (PPF) to 1000 micromoles m-2 s-1 (57.6 mol m-2 d-1); two to three times higher than normally used for lettuce. Eliminating tipburn doubled edible yield at the highest PPF level. In addition to high PPF, CO2 was elevated to 1200 micromoles m-2 mol-1, which increased the temperature optimum from 25 to 30 degrees C. The higher temperature increased leaf expansion rate, which improved radiation capture and more than doubled yield. Photosynthetic efficiency, measured as canopy quantum yield in a whole-plant gas exchange system, steadily increased up to the highest temperature of 32 degrees C in high CO2. The highest productivity was 19 g m-2 d-1 of dry biomass (380 g d-1 fresh mass) averaged over the 23 days the plants received light. Without the limitation of tipburn, the combination of high PPF, high temperature, and elevated CO2 resulted in a 4-fold increase in growth rate over productivity in conventional environments.     

河北二季作区马铃薯节水灌溉研究初报

为研究河北二季作区马铃薯整个生育期不同灌水量对其生长发育的影响,以该地主栽品种为材料,根据不同生育期需水规律,设定5个不同水量梯度的滴灌处理和1个常规沟灌处理(CK);调查分析了不同处理间物候期、重要农艺性状、病害发生情况和产量等相关指标。结果表明,处理3(采用滴灌模式,水量为110 m3)与常规沟灌相比,马铃薯生长势、总产量和商品薯产量无显著差异,生育期提前,病害较轻,商品薯率提高7.2%,节水35.41%,综合表现优于其他处理,为试验地区最佳灌水量。     

丛枝菌根真菌对酸枣水分状况影响

在塑料盆栽条件下,研究了丛枝菌根真菌对酸枣(Zizyphus spinosus Hu．)苗生长和水分状况的影响。结果表明,接种丛枝菌根真菌显著促进了植株生长,接种处理的苗高、叶数、地径、单株叶面积、茎和叶鲜重、干重、叶绿素含量都显著高于对照,苗高提高了21．9％～28．5％,叶干重增加了53．0％～73．2％。同时,接种后也提高了苗木的抗旱性,束缚水含量提高了17．2％～23．7％,显著提高了离体叶片的保水力;在干旱胁迫下,酸枣叶片推迟13～27．5h出现萎蔫,重新复水后,提前0．8～1h恢复正常。     

持效型油菜素内酯(Ts-303)对葡萄花粉活力的影响

以3年生巨峰、藤稔葡萄为试材，于花前7～8天喷布0.01mg·L-1和0.05mg·L-。的油菜素内酯，盛花期采花取花粉，用蔗糖琼脂培养基置不同温度条件下做花粉发芽试验。结果表明油菜素内酯能明显促进花粉发芽和花粉管伸长，0.05mg·.L-1处理效果更显著。     

丛枝菌根菌对连作草莓生长及抗重茬能力的影响

将丛枝菌根接种于日光温室连作草莓,分析了丛枝菌根菌对连作草莓营养生长、产量及重茬病的影响。结果表明,在甲醛与高锰酸钾混合消毒和在太阳热消毒土壤中,丛枝菌根菌均可显著增加连作草莓叶绿素含量,促进草莓营养生长,提高单株产量;显著提高SOD酶活性,降低MDA含量,增加细胞膜相对透性,增强根系活力,大大降低了连作草莓的植株死亡率,提高了相对防效。其中以在太阳热消毒土壤后接种G．mosseae效果最好。     

Effects of pavements on diversity and activity of mycorrhizal symbionts associated with urban trees

This study investigated the impact of different types of soil sealing on the communities of a group of beneficial plant symbionts, arbuscular mycorrhizal fungi (AMF), colonizing the roots of two shade trees, Celtis australis and Fraxinus ornus, frequently grown in urbanized sites. Such plants were grown in an experimental site, in northern Italy, established in November 2011 and subjected to four different pavement treatments: impermeable monolithic asphalt, permeable pavers, permeable concrete and unpaved soil. The diversity and composition of root AMF communities were assessed by PCR denaturating gradient gel electrophoresis of partial 18S rRNA gene, AMF taxa were identified by amplicon sequencing and mycorrhizal colonization was evaluated after root clearing and staining. For the first time, our molecular work revealed that impermeable pavements induced shifts in the composition of AMF communities associated to the roots of C. australis and F. ornus and impacted on the percentage of mycorrhizal root length. When the root-zone was covered with permeable pavements, a similar AMF community as that observed in the unpaved soil was detected, providing novel information to be utilised for reducing the disturbance caused by specific types of soil sealing on AMF symbionts, which play a key role in plant nutrition and health. A total of 45 AMF sequence types were detected, with Sclerocystis and Septoglomus as the most abundant phylotypes, accounting for 84% of the sequences. The predominance of Sclerocystis species in the roots of both tree species under impermeable pavements indicated their high and unforeseen tolerance towards harsh environmental conditions. Such species could be utilized as AMF inocula specifically selected for their proven resilience in paved sites, in order to exploit their ability to boost biogeochemical processes fundamental for energy fluxes and plant nutrition and health.     

Flowering in six clones of the Andean root crop arracacha (Arracacia xanthorrhiza Bancroft)

Summary

The effect of dehydration on arracacha (Arracacia xanthorrhiza Bancroft) cormels was investigated and found to have a positive effect on flowering for some accessions and a negative or negligible effect on others. The clear difference in flowering response between accessions is attributed to genetic variation and suboptimal growth conditions. The unclear results indicate that the treatments used were suboptimal and that factors other than drought stress are involved in flower induction. However, the dehydration treatments had a positive effect on the production of hermaphrodite flowers in all accessions, and dehydration is therefore considered an important factor in the flower-inducing treatment. The high temperatures and low humidity during the current experiment had a negative effect on pollen release and thus seed production, indicating that a moderate temperature is needed during the arracacha growth period. There are clear morphological differences between the accessions, with ABS 5516 as the most vigorous and with the highest measured values in all variables except percentage of hermaphrodite flowers.     

Influence of ventilation and sucrose on growth and leaf anatomy of micropropagated potato plantlets

Potato single nodes were cultured in vessels containing MS medium supplemented with 10, 20 and 30 g/l of sucrose. Vessels were closed with a clear polypropylene lid with or without 10 mm microporous polypropylene membrane. Sucrose concentration significantly increased plantlet height, shoot fresh weight and chlorophyll a content. Plantlets grown in ventilated vessels were significantly shorter, had lower shoot fresh weight and higher shoot dry weight than those in non-ventilated vessels. The highest leaf chlorophyll a content (21.83 mg/g fresh weight) was found in plantlets grown in ventilated vessels using MS medium with 20 g/l of sucrose, whereas those grown on medium with 10 g/l of sucrose had the highest chlorophyll b content (24.00 mg/g fresh weight). Total chlorophyll content was significantly higher when plantlets were grown in ventilated vessels containing medium with 10 or 30 g/l sucrose than in non-ventilated vessels. There was no significant difference in total chlorophyll content among plantlets grown in ventilated vessels with different concentrations of sucrose. Stomatal density was significantly lower when plants were grown under ventilated conditions. Leaf replica examination showed that stomata under non-ventilated condition were spherical with wide openings whereas, those in ventilated vessels were elliptical with narrow openings. Plantlets grown in non-ventilated vessels had thinner leaves and failed to build up a distinct defined upper epidermis, palisade parenchyma layer and spongy cells. On the other hand, leaves under ventilated conditions showed comparatively well organized layers with small intercellular space. The vascular system of leaves under the ventilated conditions demonstrated very well developed xylem unlike leaves under non-ventilated conditions. Thus, ventilated vessels with the 20 g/l of sucrose under ambient CO₂ in the growth room could successfully promote photomixotrophic culture and produce healthy plantlets.     

Triacontanol stimulates nitrogen-fixation,enzyme activities,photosynthesis, crop productivity and quality of hyacinth bean (Lablab purpureus L.)

Hyacinth bean (Lablab purpureus L.) serves as a good source of vegetable proteins in human diet, and its seeds and pods contain as much as 20–28% protein. The bean contains tyrosinase enzyme, which has potential use for the treatment of hypertension. However, plant biological yield appears to be comparatively low in Aligarh soil in this region of India (Western Uttar Pradesh). A hypothesis was designed to address whether foliar application of triacontanol (TRIA) could enhance the crop productivity as well as crop quality. TRIA is known to be a potent plant growth promoting substance for many agricultural and horticultural crops. The hyacinth bean plants grown in soil containing pots, were sprayed with five concentrations of TRIA (10⁻⁰ (Control), 10⁻⁸, 10⁻⁷, 10⁻⁶ and 10⁻⁵ M) at 15-day intervals. The plant fresh and dry weights, leaf-area, number and dry weight of nodules per plant, total chlorophyll and carotenoid content, nitrate reductase activity, carbonic anhydrase activity, nodule-nitrogen content, leghemoglobin content and leaf N, P, K and Ca contents were analyzed at 60, 90 and 120 days after sowing (DAS). Net photosynthetic rate, transpiration rate and stomatal conductance were measured only at 90 DAS. The protein content plus carbohydrate and tyrosinase activity were analyzed in the seeds. Foliar spray of 10⁻⁶ M TRIA significantly stimulated most of the studied attributes. At the highest concentration (10⁻⁵ M TRIA), values of all attributes were significantly decreased at all three stages. For example, 10⁻⁶ M TRIA increased seed-yield and -protein content by 56.3 and 14.5%, respectively when compared to unsprayed plants. TRIA also stimulated the activity of tyrosinase when compared to the control plants.     

丛枝菌根真菌修复设施蔬菜连作障碍机制

连作障碍问题严重制约着我国蔬菜产业的发展,造成连作障碍的原因主要有土壤理化性状恶化、植物自毒作用、土壤微生物区系变化等。解决连作障碍的措施有很多种,生物防治是其中之一。丛枝菌根真菌能与植物形成共生体,研究表明,丛枝菌根真菌能够改善连作土壤的生物环境问题、减少作物连作产生的自毒物质、改变土壤微生物区系等,在一定程度上能有效地防治连作障碍。笔者分析了丛枝菌根真菌缓解蔬菜连作障碍的作用机制,合理评价AM真菌克服蔬菜连作障碍的潜力,为解决蔬菜连作障碍问题提供新的研究方向和生物技术依据。     

Influence of flower bud density,flower bud drop and fruit set on apricot productivity

Flower bud density, flower bud drop and fruit set were studied for nine apricot cultivars in order to understand the influence of these variables on apricot biology and productivity. Cultivars in southern Spain were chosen as representatives of different flowering times and productivity. Results indicate differences among cultivars in the studied parameters. Low flower bud production, high flower bud drop and low fruit set were often recorded in mid- to late flowering cultivars. These traits subsequently led to poor yields. Early blooming varieties, which are frequently good producers, generally showed the highest flower bud density, medium flower bud drop and high percentage of fruit set. The influence of the cultivar was more determinant than the seasonal effect on fruit yield. This information should be useful to breeders for choosing the best parents for productivity.     

Differences of hyphal and soil phosphatase activities in drought-stressed mycorrhizal trifoliate orange (Poncirus trifoliata) seedlings

Differences of hyphal and soil phosphatase activities between mycorrhizal and non-mycorrhizal plants were less studied under drought-stressed (DS) conditions. In a pot experiment, fungal alkaline phosphatase (FALP), and succinate dehydrogenase (FSDH), soil phosphatase activity, both soil and plant P contents were compared in 6.5-month-old trifoliate orange (Poncirus trifoliata) seedlings under 80 days of DS with or without inoculations by arbuscular mycorrhizal fungi (AMF, Glomus diaphanum, Glomus mosseae or Glomus versiforme). Plant growth and biomass production under DS were significantly higher in mycorrhizal than in non-mycorrhizal seedlings. Both the FALP and the FSDH activities under DS were significantly reduced in these three Glomus inoculated seedlings. In general, similar soil neutral and alkaline phosphatase activities, but significantly higher soil acid and total phosphatase activities, were exhibited in mycorrhizal than in non-mycorrhizal seedlings under both the well-watered (WW) and the DS. Both leaf and root P contents were significantly higher in the AM colonized seedlings, but soil available P contents were lower in the growth media with AM seedlings. Our results showed that higher hyphal enzymes’ activities, soil acid and total phosphatase activities, and plant P contents in AM colonized seedlings, particularly in Glomus mosseae-colonized seedlings and/or under DS, would result in a better growth of the host plants, which might be the basis for enhancing drought tolerance in plants.     

Responses of fruit growth,quality, and productivity to crop load in apple cv. Ultra Red Gala/MM111

The effects of three crop load densities (4, 6 and 8 fruit per cm² of the cross-section of each tree branch, BCSA) on fruit growth, yield, fruit quality and vegetative growth were studied in apples (Malus × domestica Borkh) Ultrared Gala/MM111, from the fourth leaf (2006–2007 season) to the sixth (2008–2009 season). The maximum fruit growth rate was reached between 90 and 108 days after full bloom (DAFB), with values above 2.6 g day⁻¹. Accumulated yields to the sixth leaf reached 181, 157 and 123 Mg ha⁻¹ in the high, medium and low crop loads, respectively. Mean fruit weight decreased with increasing fruit crop load but the yields of fruit weight over 194 g were similar in all crop loads; the highest crop load exceeded the lowest crop load by 18.8 and 27.5 Mg ha⁻¹ of fruit weight of more than 172 and 154 g, respectively. The yields of harvested fruit exceeding 75% with red coloring did not show major differences, while fruit classified as 50–75% with red coloring were less common in the low crop load. No major differences were found at the end of the study in vegetative growth in the different seasons, nor in plant size. The reduction in mean fruit weight and in the percentage of fruit with good coloring was compensated by the increase in yields, thus not resulting in an effective reduction in the quality of the harvested fruit. The level of plant development reached with a semi-vigorous rootstock and high fruit loads allowed obtaining high fruit yield earlier and of good quality.     

Influence of nitrogen nutrition management on biomass partitioning and nitrogen use efficiency indices in hydroponically grown potato.

The National Aeronautics and Space Administration (NASA) has been conducting controlled environment research with potatoes (Solanum tuberosum L.) in recirculating nutrient film technique (NFT)-hydroponic systems as a human life support component during long-duration spaceflight. Standard nutrient solution management approaches include constant pH regulation with nitric acid (HNO3) and daily adjustment of electrical conductivity (EC) equivalent to half-strength modified Hoagland's solution, where nitrate (NO3-) is the sole nitrogen (N) source. Although tuber yields have been excellent with such an approach, N use efficiency indices are expected to be low relative to tuber biomass production. Furthermore, the high amount of N used in NFT-hydroponics, typically results in high inedible biomass, which conflicts with the need to minimize system mass, volume, and expenditure of resources for long-duration missions. More effective strategies of N fertilization need to be developed to more closely match N supply with demand of the crop. Hence, the primary objective of this study was to identify the optimal N management regime and plant N requirement to achieve high yields and to avoid inefficient use of N and excess inedible biomass production. In separate 84-day cropping experiments, three N management protocols were tested. Treatments which decreased NO3(-)-N supply indirectly through lowering nutrient solution EC (Expt. I), or disabling pH control, and/or supplying NH4(+)-N (Expt. III) did not significantly benefit tuber yield, but did influence N use efficiency indices. When supplied with an external 7.5 mM NO3(-)-N for the first 42 days after planting (DAP), lowered to 1.0 mM NO3(-)-N during the final 42 days (Expt. II), plants were able to achieve yields on par with plants which received constant 7.5 mM NO3(-)-N (control). By abruptly decreasing N supply at tuber initiation in Expt. II, less N was taken up and accumulated by plants compared to those which received high constant N (control). However, proportionately more plant accumulated N was used (N use efficiency) to produce tuber biomass when N supply was abruptly lowered at tuber initiation in Expt. II. Hence, a hydroponic nutrient solution N management system may be modified to elicit greater plant N-use while maintaining overall high tuber yield as opposed to achieving high tuber yields through excess N supply and shoot growth.     

Influence of sulfur supply,ammonium nitrate ratio,and arbuscular mycorrhizal colonization on growth and composition of Chinese chive

Tissue concentrations of phytochemicals formed by Allium species may be influenced by plant nutrient supply or rhizosphere microorganism activity. To test these relations, three plant nutritional factors were varied in two experiments with Chinese chive [Allium tuberosum]: (a) increasing sulfur concentrations in the substrate, (b) two ratios of ammonium to nitrate in supply, and (c) inoculation with arbuscular mycorrhizal (AM) fungi. Shoot dry weight, nutrient composition (nitrate, N, P, S), and organosulfur compounds (measured indirectly as pyruvic acid) were determined.     

Low seed/nut productivity in cashew (Anacardium occidentale): Effects of self-incompatibility and honey bee (Apis mellifera) foraging behaviour

Summary

The roles of self- versus cross-pollination and honey bee (Apis mellifera L.) foraging behaviour in low nut yield of cashew (Anacardium occidentale L.) were studied in NE Brazil in 1997 and 1998. It was shown that both self- and cross-pollination can set fruits in cashew, but most of fruits originating from self-pollination are shed 9–15 d after pollination, and fruits harvested are primarily from cross-pollination. Honey bees display foraging behaviour in cashew orchards conducive to cross-pollination, but in plantations originating from clonal material they failed to increase fruit yield despite cashew's dependence on insect pollination. It is concluded that cashew has a mechanism of selective abortion through which it discards self-pollinated fruits and that honey bees can contribute to increased fruit yield only when cashew trees of genetically diverse origin are found in the same orchard.     

Influence of storage and mixing factors on the biological activity of silver thiosulfate

Silver thiosulfate (STS) complex stability and degradation during formulation and storage were monitored indirectly by determining the effectiveness of treatment solutions in retarding flower petal abscission in geraniums (Pelargonium hortorum Baily). Freshly prepared solutions composed of Ag⁺:S₂O₃^2? ratios from 1:1 to 1:16 at constant silver concentration were all equally effective. There were no differences in effectiveness when a Ag⁺:S₂O₃^2? solution of ratio 1:4 was formulated at 5, 25 or 50°C, when prepared at pH 4.01, 7.0 or 10.0, or when prepared in the presence of 10 mM KCl, Na₂CO₃, Ca(NO₃)₂ or MgSO₄. The ability of solutions to retard abscission was reduced when Ag⁺ was substantially in excess of S₂O₃^2?. Rapid mixing of AgNO₃ and Na₂S₂O₃ solutions yielded effective solutions, independent of mixing order. Complete loss of activity was observed when solutions were stored in contact with either tin or galvanized metal for 5 days, whereas there was no loss in activity after 3 months' storage in plastic or glass at 2°C. These results indicate that currently recommended formulation procedures are unnecessarily stringent, and that long-term cold storage of prepared STS solutions is feasible.     

The role of Chinese cabbage as a trap crop for flea beetles (Coleoptera: Chrysomelidae) in production of white cabbage

During the years 2002 and 2003, preference of flea beetles, Phyllotreta spp., to white and Chinese cabbage, grown in monoculture and in mixed crop, was tested. The aim of the research was to determine if Chinese cabbage is an appropriate trap crop for this pest in the production of white cabbage, an important vegetable in Europe and in North America. The number of beetles on Chinese cabbage in monoculture and in mixed crop did not differ significantly. In both treatments the number of adults of flea beetles on Chinese cabbage and the percentage of damaged leaf area they caused, were significantly higher than that on white cabbage. Statistically significant and positive correlation was established between leaf damage and number of flea beetles. It was stronger in 2003, which was less favorable for the crop with regards to the weather conditions (drought and high air temperatures). No significant differences were found in the number of adults and in most evaluations also in the damage assessments on white cabbage when grown in monoculture and in mixed culture. Therefore, we concluded that Chinese cabbage grown in mixed crop with white cabbage is not a suitable control measure for reducing the damage caused by flea beetles.