Cultural Variation and Mycorrhizal Status of Blueberry Plants in NW Oregon Commercial Production Fields

ABSTRACT

Ericoid mycorrhizal fungi (EMF) form symbiotic relationships with roots of blueberry plants providing increased access to nutrients from fertilizers and soil. In August of 2001, we sampled 55 fields in Oregon to assess the mycorrhizal status of blueberry plants under production conditions and to determine whether any relationships exist between field characteristics, root distribution, soil characteristics and level of colonization by mycorrhizal fungi. Variation in measured soil characteristics, root type, root distribution and mycorrhizal colonization occurred with cultivar, field age, bed type, rate of nitrogen fertilization, irrigation type, and mulch. Root biomass was lower in the upper 15 cm of soil compared to 15-30 cm depth. Distribution of roots between the two sampled depths varied significantly with field age, nitrogen fertilization rate, and the time of 50% harvest for the different cultivars sampled. Root length was generally greatest in the upper 15 cm of the soil than at the 15-30 cm depth. Root colonization by ericoid mycorrhizal fungi (EMF) ranged from 0.5 to 44% of total root length with higher colonization generally occurring in the upper 15 cm of the soil where the majority of smaller, finer roots were found. Colonization generally increased with increasing plant age. In young plants the highest levels of colonization were found in roots from the upper 15 cm of soil while in older plants the highest levels of colonization were found in roots at the 15-30 cm depth. Colonization of roots by EMF in the upper 15 cm of the soil tended to decrease with increasing N fertilization rate, while root colonization at the 15-30 cm depth was unaffected by rate of N fertilization. Roots on cultivars that fruited early in the season tended to have higher levels of colonization than cultivars that fruited later in the growing season. Root biomass and root length were negatively correlated with soil pH and available Ca in soil, while root colonization by EMF was negatively correlated with ammonium levels in the soil. Differences in soil characteristics, root type and distribution, and mycorrhizal colonization found in this study need to be investigated in terms of production efficiency of blueberry in Oregon.     

Effects of AMF inoculation on growth of Panax ginseng C.A. Meyer seedlings and on soil structures in mycorrhizosphere

We aimed to investigate the effects of inoculating Panax ginseng C.A. Meyer seedlings with arbuscular mycorrhizal fungi (AMF) by examining the root colonization, plant nutrition uptake, growth characteristics, and soil aggregation of P. ginseng seedlings inoculated at the time of transplantation. At 16 weeks, the AMF spore density per 30 g of fresh mycorrhizosphere in seedlings inoculated with AMF (AMF+ seedlings) was 256.8 and that in seedlings not inoculated with AMF (AMF− seedlings) was 186.3, respectively. The colonization rate of AMF in the lateral roots of AMF+ seedlings was approximately 19% higher than that in the lateral roots of AMF− seedlings. The patterns of AMF colonization in ginseng roots were similar to those of the Paris-type mycorrhizal association. Plant growth characteristics, such as plant height, root length, leaf area, number of lateral roots, fresh weight of shoots and roots, and chlorophyll content, were significantly enhanced in AMF+ seedlings compared to AMF− seedlings. The macronutrient content (P, K, and Ca) and micronutrient content (Cu, Fe, and Zn) of both shoots and roots were also significantly higher in AMF+ seedlings compared to AMF− seedlings. Furthermore, glomalin content and soil aggregation were significantly enhanced in AMF inoculated areas. Our results indicate that AMF inoculation may enhance the growth of ginseng seedlings by improving the uptake of mineral nutrients and the soil structure in mycorrhizosphere.     

Beneficial roles of arbuscular mycorrhizas in citrus seedlings at temperature stress

Citrus, a cold-sensitive plant, often suffers from low temperature, which seriously affects citrus productivity. The objective of the study was to elevate the roles of an arbuscular mycorrhizal fungus, Glomus mosseae, in growth, photosynthesis, root morphology and nutrient uptake of citrus (Citrus tangerine) seedlings under temperature stress conditions. Three-month-old seedlings with or without G. mosseae were grown for 55 days at moderate temperature (25 °C) and low temperature (15 °C). Low temperature severely restrained symbiotic development including mycorrhizal colonization, entry point, vesicle and arbuscule relative to moderate temperature. Mycorrhizal seedlings grown at 25 °C maintained better stem diameter, plant height, leaf area, root and total dry weights, higher photosynthetic rate, transpiration rate and stomatal conductance, higher root volume, and more uptake of P, Ca and Mg relative to corresponding non-mycorrhizal control. However, mycorrhizal inoculation significantly increased only the root length and the Ca content of the seedlings grown at 15 °C. The results indicated that mycorrhizal formation had the beneficial effects on growth, photosynthesis, root morphology and part nutrient uptake of citrus seedlings grown at moderate temperature, but the beneficial roles of arbuscular mycorrhizas were almost lost at low temperature.     

Morphology,yield and quality of ashwagandha (Withania somnifera L. Dunal) roots and its cultivation economics as influenced by tillage depth and plant population density

Summary

Ashwagandha (Withania somnifera L. Dunal; Solanaceae) is being cultivated around the world mainly for its root which has rejuvenative properties. Field experiments during 1999–2001 under semi-arid tropical conditions of Hyderabad, India studied the effect of tillage depths (15 and 30 cm) and plant population densities (20, 40, 60 and 80 plants m^–2) on root morphology, yield and quality and cultivation economics of ashwagandha. Preparatory tillage to 30 cm depth in combination with a density of 60 plants m^–2 gave the highest root yield of 1.2 t ha^–1 which was 50% higher than that following 15 cm tillage depth and the same density. This is attributed to the favourable effect of the former treatment leading to 33, 37 and 21% increases in plant height, number of branches per plant and shoot biomass yield, respectively. Further, this treatment produced most (68%) best quality root pieces. Main root length, length of lateral roots and diameter of lateral roots were significantly increased, while the diameter of main root and the number of laterals decreased. Furthermore, increase in plant density from 20–80 plants m^–2 increased production of best quality roots from 42% to 59% under shallow tillage and from 53% to 71% of root yield under deep tillage. The implications of change in root morphology are discussed in the light of production of different grades of roots, their market preferences and economics. Deep tillage was equally advantageous for seed production, but plant population density for maximum seed yield (211 kg ha^–1) was lower at 40 than at 60 plants m^–2 for maximum root yield. Maximum gross and net returns and benefit-cost ratio occurred following the highest root yield.     

Growth responses and endogenous IAA and iPAs changes of litchi (Litchi chinensis Sonn.) seedlings induced by arbuscular mycorrhizal fungal inoculation

Seedlings of litchi (Litchi chinensis Sonn.) were inoculated with two arbuscular mycorrhizal (AM) fungal species, Glomus intraradices and Gigaspora margarita. Plant growth response and morphological changes induced by AM inoculation were investigated. Plant endogenous indoleacetic acid (IAA) and isopentenyl adenosines (iPAs) concentrations were determined. With mycorrhizal infection rate of 9.0–18.8%, plant biomasses increased by 13.5–30.1%. Leaf number, leaflet number, total leaf area and first order lateral root number were significantly increased by AM inoculation. Although G. margarita significantly increased plant P content and uptake, no significant difference in N nutrition was observed between mycorrhizal and non-mycorrhizal plants. Enzyme-linked immunosorbent assay (ELISA) indicated the changes in IAA and iPAs induced by AM inoculation. IAA concentrations in shoots and in roots were 5–7 times and 2–5 times higher in mycorrhizal than in non-mycorrhizal plants, respectively. The iPAs concentrations increased by 1.7 times in shoots and by 1.9–2.5 times in roots, due to mycorrhizal inoculation. We suggest that the changes in endogenous phytohormone level may be responsible for morphological alteration induced by AM inoculation.     

丛枝菌根真菌对香蕉试管苗植株生长和矿质营养吸收的影响

以Williams香蕉(MusaAAA)试管苗为材料,在温室盆栽条件下研究丛枝菌根真菌(AM真菌)对香蕉植株矿质营养和营养生长的影响。试验设3个处理,不接种对照和2个菌根接种处理:接种单一菌种Glomusversiform、接种混合菌种G.versiform、G.epigaeam、G.cadedonium。结果表明,香蕉植株的菌根侵染率为22.8%～32.9%;接种AM真菌促进了香蕉植株的营养生长,显著地增加地上部和根系的干重,其菌根依赖性达到30.8%～37.8%,植株的株高、叶片数和叶片长度略有提高;接种单一菌种增加了须根的数量,但2个接种处理均降低须根的长度,使得总根长减少;单一接种剂和混合接种剂分别显著提高植株的P和K含量,2个接种处理都显著地促进了植株对N、P、K的吸收,P增幅最大,为70%～120%,K的增幅次之,为80%左右,N的增幅最小,为40%～60%。结果还表明,混合接种剂的生长促进效果略好于单一接种剂。     

Responses of field grown tomato plants to arbuscular mycorrhizal fungal colonization under varying intensities of drought stress

The effects of root colonization by the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck and Smith on growth, flower and fruit production, and fruit quality were studied in field-grown tomato plants exposed to varying intensities of drought stress. Inoculated (M+) and non-inoculated (M−) tomato seedlings were exposed to varying intensities of drought stress by adjusting irrigation intervals. Mycorrhizal plants had significantly higher uptake of N and P in both roots and shoots regardless of intensities of drought stress. AM inoculation also significantly increased shoot dry matter and the number of flowers and fruits. The fruit yields of M+ plants under severe, moderate, mild drought-stressed conditions were higher than M− plants by 24.7%, 23.1%, 16.2% and 12.3%, respectively. Furthermore, M+ plants produced tomato fruits that contain significantly higher quantities of ascorbic acid and total soluble solids (TSS) than M− plants. Mycorrhizal effects increased with increasing intensity of drought. The overall results suggest that mycorrhizal colonization affects host plant nutritional status, water stratus and growth under field conditions and thereby alters reproductive behaviour, fruit production and quality of fruits under both well-watered and drought-stressed conditions.     

土壤未灭菌条件下丛枝菌根对枳实生苗生长和抗旱性的影响

在温室盆栽土壤未灭菌条件下,以枳实生苗[Poncirus trifoliate(L.)Raf.]为试材,研究水分胁迫下丛枝菌根真菌Glomus mosseae对其生长、可溶性糖含量、水分利用效率和制造1 g干物质用水量的影响。结果表明,在正常水分和水分胁迫条件下,丛枝菌根增加或显著增加枳实生苗的生长量,显著或极显著地提高植株的水分利用效率和叶片、根系内的可溶性糖含量,菌根和水分交互影响根系可溶性糖含量,显著降低制造1 g干物质用水量,节约用水28.4％-31.1％,增强了枳实生苗的抗旱性。     

Vesicular-arbuscular mycorrhizal inoculation of micropropagated fruit trees

Micropropagated plantlets of OH x F 51 and GF 677, respectively pear (Pyrus communis L.) and peach (Prunus persica x Prunus amygdalus) clonal rootstocks were inoculated during an early weaning stage of acclimatization with Glomus sp. Both rootstocks were well colonized, although the infection of OH x F 51 spread more slowly. At the end of initial vegetative growth, mycorrhizal plants of both rootstocks showed a three-fold increase in shoot length over control plants. Mycorrhizal plants also had longer internode and greater fresh mass. The root/shoot ratio was especially altered by arbuscular mycorrhizal inoculation in OH x F 51 plants, which showed a greater increase in shoot rather than in root biomass. The growth-promoting ability of endomycorrhizal fungus persisted throughout the experimental period: Glomus sp. induced a greater development of both rootstocks in the second growing year, after overwintering. Colonization of micropropagated plants by arbuscular mycorrhizal fungus appears to alter the carbohydrate status in stems and roots. Mycorrhizal plants always had a higher content of total soluble sugar, although there were no differences in soluble carbohydrate concentration between inoculated and uninoculated plants. Starch accumulation was found only in mycorrhizal plants of the peach rootstock.     

Cytokinins in citrus. II. Fluctuations during growth in juvenile and adult plants

Juvenile and adult plants of ‘Pickstone Valencia’ orange (Citrus sinensis (L.) Osbeck) were compared for differences in shoot and root growth and for endogenous cytokinins in a synchronized growth flush. Dry-mass accumulation in both shoots and roots of juvenile-budded plants was significantly greater than in adult plants. Cytokinins extracted from leaves and roots of plants removed from the dormancy-induction environment, and subsequently during active growth, were mostly of the non-polar type. Buds of juvenile scions appeared to accumulate higher levels of polar cytokinins during dormancy than adult scion buds. In both plant categories, the level of polar cytokinins decreased once growth was stimulated by higher temperatures. However, cytokinin levels in buds were markedly higher than in new shoot, leaf or root material. Polar cytokinins were present in particularly low concentrations in the developing new shoots, and non-polar cytokinins only increased after the extent of shoot enlargement reached a maximum at about 50 days after warm-temperature incubation.The possible involvement of cytokinins in growth differences between adult and juvenile plants seems to be at the stage of bud activation, prior to breaking of dormancy. At this stage, polar cytokinins reached a much higher level of activity in juvenile buds, and this may have resulted in the greater scion growth of juvenile plants.     

Effect of arbuscular mycorrhizal fungal inoculation on root system architecture of trifoliate orange (Poncirus trifoliata L. Raf.) seedlings

Plant root system architecture is essential characteristics in relation to nutrient acquisition by root system from soil volume. Many environmental factors can affect the establishment of root system architecture, e.g. arbuscular mycorrhizal (AM) fungi. We inoculated the trifoliate orange (Poncirus trifoliata L. Raf.) seedlings with four AM fungal species in rhizoboxes, with non-inoculated seedlings as control. Using the WinRHIZO^® image analysis system, the root system architecture of seedlings was characterized. Results indicated that AM colonization did not affect the tap root length, the average root diameter, the basal root growth angle in spite that four AM fungal species exerted differential influence on the plant growth. Contrastingly, AM colonization significantly reduced the total root length, the root volume, the root surface area, but promoted the formation of lateral roots of high order. In addition, AM colonization induced more fine roots and less coarse roots. To our knowledge, it is the first report on the influence of AM fungi on the distribution of root diameter size classes. The mechanisms and implication of AM fungi on root system architecture is discussed.     

不同供磷水平对辣椒根系形态和根际特征的影响

以辣椒品种线椒王为试验材料,采用盆栽方式,通过分析不同施磷水平下辣椒根系形态和根系生理的变化,探究辣 椒磷高效利用的主要根系及根际过程。结果表明,辣椒地上部和根系生物量随供磷水平的增加呈现先增加后下降的趋势,整 株磷浓度以及整株磷累积量呈增加趋势。随供磷水平增加,根系总根长呈先增加后下降趋势,根系平均直径、根冠比呈逐渐 降低趋势;辣椒根系菌根侵染率和土壤酸性磷酸酶活性呈现先增加后下降的趋势。相关分析结果表明,土壤有效磷浓度和整 株磷浓度与根系平均直径、菌根侵染率呈极显著负相关,与总根长可用一元二次方程拟合,表明辣椒根系适应低磷的根际特 征可能是通过增加根系生物量及总根长,同时降低根系平均直径来实现的。     

Arbuscular mycorrhizal fungi alleviate iron deficient chlorosis in Poncirus trifoliata L. Raf under calcium bicarbonate stress

Summary

The effect of the arbuscular mycorrhizal (AM) fungus Glomus versiforme on chlorosis due to iron deficiency in trifoliate orange (Poncirus trifoliata L. Raf) was studied under calcium bicarbonate stress in sand culture. Seeds were sown in a mixed substrate [1:1 (v/v), perlite:sand] with or without mycorrhizal inoculum. The test was carried out with four treatments: Hoagland and Arnon nutrient solution with normal, no added iron, or 50% normal iron at two levels of calcium bicarbonate. The results showed that the proportion of the total root length infected by the AM fungus was ≥ 83%, and was depressed under Fe deficiency. No root colonisation was found with no added AM fungus (NM plants).

Colonisation by AM fungus resulted in higher dry weights of both shoots and roots compared to NM treatments, suggesting that the AM fungus accelerated plant growth. The activities of peroxidase and catalase in NM plants were lower than in AM fungus-inoculated plants. The results indicate that AM fungus alleviated calcium bicarbonate stress on the cell membranes of host plants. The results also showed that AM fungus increased chlorophyll concentrations, iron contents, and the Fe:P ratios of whole plants, and decreased 50(10P+K):Fe ratios, which implied that the uptake and translocation of iron was strengthened. Therefore, AM fungus had a positive effect on ameliorating chlorosis due to iron deficiency in P. trifoliata L. Raf.     

非灭菌土接种AM真菌对油蒿抗旱性的影响

利用盆栽试验在正常水分和干旱胁迫条件下研究了非灭菌土接种AM真菌摩西球囊霉(Glomus mosseae)和土著AM真菌(Indigenous arbuscular mycorrhizal fungi)对油蒿(Artemisia ordosica)生长及抗旱性的影响。结果表明:干旱胁迫显著抑制了AM真菌对油蒿的侵染。无论在正常水分还是干旱胁迫条件下,接种AM真菌都增加了植株的分枝数、地上部鲜重和干重、地下部鲜重和干重,但没有明显提高株高、茎粗和改善组织水分状况;与未接种相比,干旱胁迫下接种土著AM真菌显著提高了根系氮、磷含量,提高了叶绿素、可溶性蛋白含量,增强了保护酶超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)的活性并降低了丙二醛的含量,因此增强了植物的抗旱性。     

丛枝菌根真菌与葡萄南方根结线虫的相互作用及其对寄主的影响

 在温室盆栽条件下对‘巨峰’葡萄扦插苗接种丛枝菌根(AM) 真菌(Glomus versiforme Berch、Gigaspora margarita Becker & Hall 及Glomus mosseae Nicolson & Gedermann) 和南方根结线虫(Meloidogyne incognita) 。结果表明, 供试AM真菌能不同程度地抑制南方根结线虫病害的发生发展, 降低根围土壤中二龄幼虫数量、卵块直径、平均每个卵块的卵量及平均每克葡萄根系上的卵量, 先接种AM真菌后接种南方根结线虫的处理比同时接种二者抑制线虫病害的效果更好。接种AM真菌可提高葡萄植株光合速率, 增加植株高度、茎粗、叶面积、地上部干样质量和地下部干样质量, 这在一定程度上补偿了由于线虫所造成的损害。此外, 接种南方根结线虫降低了G. mosseae 的根内泡囊和入侵点数量、G. versiforme 及Gi . margarita的侵染率;但增加了G. versiforme 及Gi . margarita 的根内泡囊数及入侵点数。因此, 对每一种AM真菌—植物—线虫组合关系不可能作出统一的概括。     

The Effect of a Substrate Containing Arbuscular Mycorrhizal Fungi and Rhizosphere Microorganisms (Trichoderma,Bacillus, Pseudomonas and Streptomyces) and Foliar Fertilization on Growth Response and Rhizosphere pH of Three Strawberry Cultivars

Abstract

Vegetatively propagated plants of three strawberry cultivars-‘Senga Sengana’, ‘Elsanta’ and ‘Kent’-were grown for 20 weeks in rhizoboxes filled with 1.85 kg of sterilized mineral soil. Ten plants were treated with an N-P-K foliar fertilizer (F, control), or inoculated with a substrate containing arbuscular mycorrhizal fungi, Trichoderma viride and rhizosphere bacteria (PGPR-Plant Growth Promoting Rhizobacteria) without any fertilization (M), or inoculated with the mixture of microorganisms and treated with the foliar fertilizer (MF). Total plant biomass was increased by the M treatment in all cultivars. M treatment resulted in higher total root length and number of root tips in ‘Senga Sengana’, whereas the other two cultivars showed different responses of root morphology. Shoot/root ratio was decreased by the M and MF treatments in comparison with control plants. Foliar fertilization of inoculated plants caused different growth responses in the three cultivars and a general decrease of root growth. After the MF treatment, the biomass of ‘Senga Sengana’ increased and the biomass of ‘Elsanta’ and ‘Kent’ decreased. Inoculation with the mycorrhiza-PGPR substrate increased rhizosphere pH irrespective of foliar fertilization. Plant mineral content was highly modified by the treatments in all the cultivars examined. In particular, changes were noted in N, P, K, Fe, B and Mn uptake. The results show an interaction between foliar fertilization and root inoculation with microorganisms, as well as genotype-dependent influences, on growth responses and rhizosphere pH of strawberry plants.     

丛枝菌根真菌对番茄渗透调节物质含量的影响

采用盆栽试验研究了不同浓度NaCl (0.5%和1% ) 胁迫下, 接种丛枝菌根真菌(AMF) 对番茄生长和渗透调节物质含量的影响。结果表明: 盐胁迫下, 与未接菌番茄相比, 接种AMF番茄能显著增加植株的生长, 促进叶片和根系可溶性糖的积累, 增加叶片可溶性蛋白含量及根系脯氨酸含量, 使植株耐盐能力增强。接菌株可溶性糖及可溶性蛋白的增加以及根系脯氨酸的大量积累在AMF提高番茄耐盐的渗透调节机制中具有重要的作用。     

Pepper (Capsicum annuum L.) root growth and its relation to shoot growth in response to nitrogen

Summary

The main objective of this work was to investigate shoot and root morphology of pepper (Capsicum annuum L.) (cvs Early Calwonder, Keystone Resistant Giant, Jupiter, Shamrock and Gator Belle) grown in sand culture at three N-levels, 56,84 and 112 mg l^?1. Shoot, root, and root components were evaluated 40, 50 and 60 days after seeding. Tap, basal and lateral root accounted for 1%, 40% and 53%, respectively, of the total root dry weight. Shoot: root ratios did not differ between cultivars. Basal root length, basal root number and first-order lateral root number increased with increasing N. Cultivars with either long lateral roots or basal roots had short basal roots or lateral roots respectively, although only small differences were observed in other root and shoot characteristics. In this greenhouse environment, shoot/root ratio was constant. Nitrogen stimulated root and shoot growth, and this effect was significantly different for the root components.     

摩西球囊霉对芦笋幼苗生长和矿质营养吸收的影响

摩西球囊霉（Glomus mosseae,GM）是球囊霉属丛枝菌根真菌（Arbuscular Mycorrhiza Fungi,AMF）,具有对环境适应力强、应用范围广的特点。为探明摩西球囊霉对芦笋育苗的应用效果,采用营养钵育苗播种对芦笋进行GM接种处理,研究GM对芦笋幼苗生长、菌根侵染及矿质营养吸收的影响。结果表明：接种GM后芦笋幼苗生物量显著提高,植株根系具有较高的菌根依赖性。GM对芦笋幼苗根系的侵染呈现“S”形变化趋势,播种10周后,GM对芦笋幼苗根系达到较高程度的侵染,且GM菌根苗的根系活力和叶绿素含量与不接种对照相比显著提高。接种GM显著促进了植株对矿质元素特别是P的吸收,其次为Mg。接种GM培育菌根苗的技术应用于芦笋栽培可以培育壮苗,缩短苗期,节省肥料,提高养分利用率。     

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.