Total Root Number Research Articles

Inoculation of plant growth promoting bacteria from hyperaccumulator facilitated non-host root development and provided promising agents for elevated phytoremediation efficiency

Plant growth promoting bacteria (PGPB) have been reported to have the ability to promote plant growth, development and increase heavy metals (HMs) uptake. Therefore, PGPB inoculation as soil remediation agents into plants with larger biomass and potential of phytoextraction is of great importance to increase bioremediation efficiency. In this study, 12 PGPB strains isolated from a cadmium (Cd)/zinc hyperaccumulator Sedum alfredii Hance were inoculated into non-host plant Brassica juncea and their effects on plant growth and Cd uptake were determined. The results showed that inoculation of most PGPB strains promoted plant growth, boosted root development and improved chlorophyll content in the absence of Cd. Inoculation of PGPB strains promoted plant growth up to 111% in shoot and 358% in root when treated with 2 μM Cd. In addition, PGPB inoculation not only ameliorated plant root morphology including the total root length (RL), total surface area (SA), total root volume (RV) and number of root tips (RT), but also facilitated Cd uptake up to 126%. Furthermore, inoculation of PGPB strains promoted plant Cd accumulation up to 261% in shoot and up to 8.93-fold increase in root. Among all the 12 PGPB strains, Burkholdria SaMR10 and Sphingomonas SaMR12 were identified as the promising microbes for improving phytoremediation efficiency of Cd contaminated soils. These results not only provided useful findings for further investigation of interacting mechanisms between different bacterial strains and plants, but also facilitated the development of microbe-assisted phytoremediation application for HM contaminated soil.

Phenotypic variation of cassava root traits and their responses to drought.

Premise of the StudyThe key to increased cassava production is balancing the trade‐off between marketable roots and traits that drive nutrient and water uptake. However, only a small number of protocols have been developed for cassava roots. Here, we introduce a set of new variables and methods to phenotype cassava roots and enhance breeding pipelines.MethodsDifferent cassava genotypes were planted in pot and field conditions under well‐watered and drought treatments. We developed cassava shovelomics and used digital imaging of root traits (DIRT) to evaluate geometrical root traits in addition to common traits (e.g., length, number).ResultsCassava shovelomics and DIRT were successfully implemented to extract root phenotypes, and a large phenotypic variation for root traits was observed. Significant correlations were found among root traits measured manually and by DIRT. Drought significantly decreased shoot dry weight, total root number, and root length by 84%, 30%, and 25%, respectively. High adventitious root number was associated with increased shoot dry weight (r = 0.44) under drought.DiscussionOur methods allow for high‐throughput cassava root phenotyping, which makes a breeding program targeting root traits feasible. We suggest that root number is a breeding target for improved cassava production under drought.

Ectomycorrhizae of Norway spruce from its southernmost natural distribution range in Serbia

Abstract: Norway spruce (Picea abies Karst.) reaches its southernmost limit in the mountainous regions of south Serbia and Bulgaria. The species is a regionally important timber species for the wood industry and a significant host for various ectomycorrhizal fungi, including edible species. We analysed ectomycorrhizal community and fine root parameters of high continental / subalpine Norway spruce stands at three sites (Stara planina, Kopaonik, Tara) located in protected areas in Serbia. In addition, we assessed the potential effects of altitude and growing season on the ectomycorrhizal diversity and fine root parameters. Using standardised sampling in combination with morpho-anatomical and molecular identification of ectomycorrhizae, we recorded 29 different anatomorphotypes. None of the identified fungi belonged to commercial edible fungal species. Compared to other Norway spruce ectomycorrhiza studies in central Europe, sites in Serbia exhibited lower species diversity and different dominant species composition, with Cenococcum spp. and Russula spp. as the dominant ectomycorrhizal fungi. A number of ectomycorrhizal types and the value of the species richness index differed between Stara planina and Tara in the autumn, but the influence of site and season on the studied diversity indices was not significant. The total number of fine roots increased in the spring, while percentage of vital ectomycorrhizal root tips increased in the autumn. This study was the first examination of Norway spruce ectomycorrhizal communities at the edge of the natural geographical range of the species.

Use of Cone Beam Computed Tomography to Identify the Morphology of Maxillary and Mandibular Premolars in Chennai Population

Objective: The complex root canal anatomy is inherently colonised by microbial flora. Endodontic treatment success is always related to adequate disinfection of the root canal space, which ultimately affects the treatment outcome. A thorough understanding of the external and internal root canal anatomy by using adequately imaging modalities is essential before planning any treatment. The aim of this study was to investigate the number and morphology of the root canals of maxillary and mandibular premolars in Chennai population. Material and Methods: Full-size cone-beam computed tomographic images were randomly collected from 100 patients, resulting in a total of 200 first and 200 second maxillary premolars as well as 200 first and 200 second mandibular premolars. All the eight premolars were analysed in single patients, who underwent cone-beam computed tomography scanning during pre-operative assessment (before implant surgery, orthodontic treatment, diagnosis of dental-alveolar trauma or difficult root canal treatment). Total number of roots and root canals, frequency and correlations between men and women were recorded and statistically analysed by using chi-square tests. The root canal configurations were rated according to the Vertucci’s classification. Results: In the maxillary first premolar group (n = 200), 36.3% had 1 root, 56.7% had 2 roots and 7.0% had 3 roots, with most exhibiting a type IV canal configuration. In the maxillary second premolar group (n = 200), 60% had 1 root, 29.8% had 2 roots and 10.2% had 3 roots, with the majority of single-rooted second premolars exhibiting a type I canal configuration. In the mandibular first premolar group (n = 200), 80.5% had 1 root, 9.8% had 2 roots and 5% had 3 roots. In the mandibular second premolar group (n=200), 90.1% had 1 root, 6.4% had 2 roots and 3.5 % had 3 roots, with most exhibiting a type I canal configuration. No statistical correlation was found between number of roots, gender and tooth position. Conclusion: This cone-beam computed tomographic study confirmed previous anatomical and morphological investigations. Therefore, the possibility of additional root canals should be considered when treating premolars. Keywords: Cone-beam computed tomography; Mandibular; Maxillary; Premolar; Root canal; Morphology.

Combining ability, gene action and heritability of weevil resistance, storage root yield and yield related-traits in sweetpotato

The objective of this study was to determine general combining ability (GCA), specific combining ability (SCA), gene action and heritability of weevil (Cylass spp.) resistance, dry matter content (DMC), yield and yield-related components of newly developed sweetpotato clones. Six weevil resistant and six susceptible parents were crossed using a 6 × 6 factorial mating design. The resultant 36 families were evaluated at three locations using a 3 × 12 lattice design with two replications for weevil resistance and yield and related traits in western Tanzania. The GCA effect for females was significant except for percentage marketable root number (PMRN) and percentage marketable root yield (PMRY). Significant GCA effect of males were detected for all traits except PMRY. The SCA effect of families was significant for all traits. With a general predicted ratio (GPR) > 0.5, additive gene action controlled more the expression of total root number (TRN), root yield (RY), DMC, percentage infested root number (PIRN), percentage infested root yield and weevil damage score (WDS), whereas non-additive gene action controlled more the expression of PMRN and PMRY with a < 0.5 GPR. The narrow sense heritability for TRN, RY, DMC, PIRN and WDS were 0.24, 0.56, 0.84, 0.62 and 0.62, while the broad sense heritability for these traits were 0.58, 0.72, 0.93, 0.78 and 0.77, in that order. Four female parents and four male parents were identified as the best general combiners and 13 families recorded the best performance for the evaluated traits. The high heritability for most of the traits studded and presence of both additive and non-additive gene action for the traits suggests that genetic gain can be realized through hybridization and clonal selection in breeding programs. The selected parents and families are useful genetic resources for the development of sweetpotato genotypes resistant to weevils and enhanced root yield, yield components and DMC.

ВПЛИВ БІОГУМУСУ НА РІСТ, УРОЖАЙНІСТЬ І ЯКІСТЬ ЧАСНИКУ (ALLIUM SATIVUM L.) В УМОВАХ ПРАВОБЕРЕЖНОГО ЛІСОСТЕПУ УКРАЇНИ

Аннотація. Характерною ознакою сучасного землеробства є погіршення родючості ґрунтів через їх інтенсивне використання, дефіцит водних ресурсів і, як наслідок, зниження продуктивності сільськогосподарського виробництва. Дані фактори визначають необхідність відновлення й підвищення родючості ґрунтів шляхом застосування у технології вирощування сільськогосподарських культур вермикомпосту (біогумусу), який є ефективним засобом відновлення родючості ґрунту, підвищення врожайності овочів та отримання органічної продукції. Мета – встановлення оптимальної норми внесення біогумусу та його вплив на продуктивність і товарність часнику озимого. Методи. Польові, статистичні, розрахунково-аналітичні. Досліджували удобрення сортів часнику озимого Софіївський та Прометей біогумусом у нормах 1; 3; 5 т/га, який вносили локально у рядки перед висаджуванням порівняно з 30 т/га перегною, внесеного врозкид та варіанта без удобрення. Результати. Дослідження показали, що реакція сортів на біогумус є дещо різною, але в цілому вона є позитивною. За внесення вермикомпосту асиміляційна площа однієї рослини збільшувалася в період інтенсивного росту до 100 %, а з початком визрівання рослин – до 12,2 %, залежно від сорту. Установлено, що за внесення біогумусу інтенсивність росту рослин збільшувалася від 1,3 до 18,2 %. Доведено, що за застосування біогумусу рослина збільшує загальну кількість коренів на 1,0–44,0 %, при цьому зменшуючи їх середню довжину на 1,6–10,6 %. Дослідження показали, що збільшення маси цибулини прямопропорційне до збільшення норми біогумусу. Так, за застосування біогумусу даний показник зростав на 9,9–25,1 % у сорту Софіївський, та на 6,7–16,0 % у сорту Прометей. Найбільш ефективним виявилося внесення біогумусу з розрахунку 3 та 5 т/га, у цих варіантах приріст врожайності часнику сягав 2,4–3,6 т/га та 4,0–5,1 т/га відповідно до сортів часнику озимого Софіївський та Прометей. Дослідженням встановлено позитивну динаміку зміни структури врожаю. Для сорту часнику озимого Софіївський оптимальною нормою внесення біогумусу була 3 т/га, де загальна кількість зубків зменшилася та зросла частка великої фракції, зі збільшенням норми до 5 т/га паралельно зросла загальна кількість зубків з 10 шт. у контролі до 10,8 шт. у дослідному варіанті. Сорт Прометей мав кращу реакцію на збільшення норми біогумусу. У дослідних варіантах загальна кількість зубків знаходилася на одному рівні, проте, фракційний склад зубків суттєво різнився. Так, зі збільшенням норми біогумусу збільшилася частка великої фракції та зменшилася частка середньої й дрібної, а за внесення 5 т/га добрива дрібна фракція майже повністю зникла зі структури врожаю. Порівняння основного біохімічного складу часнику дослідних варіантів з контрольним показує суттєве поліпшення показників в обох сортів. Вміст абсолютно сухої речовини за застосування біогумусу збільшився на 3–5,8 %, сума цукрів зростала на 3,8–11,5 %. Відсоток аскорбінової кислоти перевищував контроль на 5,5–10,9 %, а вміст нітратів у зубках часнику зменшився на 4,5–16,4 %. Висновок. Отже, в цілому по досліду за внесення біогумусу відбулося підвищення всіх ростових і продуктивних процесів та поліпшення біохімічного складу часнику озимого

Substrates on the cuttings rooting of black pepper genotypes

The soil in the production of clonal seedlings of black pepper (Piper nigrum L.) contributes to fusarium and nematodes infestation in commercial crops, and thus the usage of alternative substrates might be a preventive control measure against these pathogens. The aim of this study was to investigate the rhizogenic behavior of the cultivars Bragantina, Iaçará and Guajarina of black pepper in different substrates. The experimental design was in randomized blocks in a 3x4 factorial design (cultivars: Bragantina, Iaçará and Guajarina x substrates: soil + organic compound (18%), vermiculite, carbonized rice hulls and commercial substrate), with four replications of 16 cuttings each. The evaluated characteristics were: survival (%); rooting (basal or nodal) (%); nodal rooting (%); basal rooting (%); number of nodal roots; number of basal roots; total number of roots; length of the largest nodal root (cm); basal root length (cm); nodal root volume (cm3); basal root volume (cm3); Total root volume (cm3); nodal root dry mass (mg); basal root dry mass (mg) and the total root dry mass (mg). There are differences within black pepper cultivars as to the characteristics related to the root system. The vermiculite substrate was the most suitable, and carbonized rice hull is not recommended for the adventitious rooting of cuttings of cultivars Bragantina, Iaçará and Guajarina.

Covariation in root traits of Leymus chinensis in response to grazing in steppe rangeland

Root traits are closely related to nutrient absorption and resource competition and can even influence plant recovery and community succession. Grazing can influence root traits directly through trampling and foraging, or indirectly by changing soil characteristics. In the present study, a grazing experiment that involved combinations of grazing season (from June to September) and intensity (rest, moderate and heavy) was conducted in steppe rangeland, Inner Mongolia, China to investigate how the root traits of Leymus chinensis respond to different grazing regimes in the case of aboveground miniaturisation after long-term overgrazing. Root traits such as root length, root surface area, specific root length, root tissue density, root links (unbranched parts of a root connecting either a tip and a branching point or two branching points) and root topological structure were scanned and analysed using Win-RHIZO image analysis software. The results showed that the size of L. chinensis plants was reduced in response to overgrazing, typically by a smaller plant height, total root length, root surface area, root volume, number of tips and number of links. However, root diameter and link length, branching angle and topological structure (herringbone or dichotomous) were unaffected by grazing. Most root traits showed strong correlations under moderate grazing intensity, but not under heavy grazing, indicating that grazing changed the relationships among root traits. Relationships between plant height and root traits (total root length and number of links) shifted from positive to negative as grazing intensity increased, and the trade-off between aboveground and belowground traits was an important adaptive strategy of L. chinensis under heavy grazing. Decreasing grazing intensity in the late grazing season could benefit plant recovery, and a rest in the early grazing season would mitigate root and shoot damage.

Exogenous Pi supplementation improved the salt tolerance of maize (Zea mays L.) by promoting Na+ exclusion

The mechanism of phosphate (Pi)-mediated salt tolerance in maize is poorly understood. In this study, the effects of Pi (H2PO4−) on the salt tolerance of two contrasting genotypes was investigated in a pot experiment. We discovered that the application of 3 mM Pi could alleviate salt injury caused by 200 mM NaCl. High amounts of compatible solutes and low amounts of reactive oxygen species (ROS) were also observed under Pi application. Consistent with the increased tolerance, the total number of roots and the growth of shoots increased to relieve salt stress. This phenomenon could be associated with the observed increased expression of nitrate transporters. Furthermore, the seedlings presented a negative relationship between sodium (Na+) and Pi (low Na+ content and high Pi content), which is related to the genes ZmNHX1, ZmPHT1;8, and ZmPHT1;9, indicating that the exclusion of Na+ was promoted by high Pi uptake. However, high Na+ and low potassium (K+) efflux were detected in the roots, and these were positively correlated with two K+ transporters. These observations indicate that Na+ exclusion was directly induced by high K+ retention rather than Pi absorption. We conclude that maize salt tolerance increased in response to Pi application by promoting Na+ exclusion.

Effect of Biochar on Root Morphological Characteristics of Wetland Plants and Purification Capacity of Constructed Wetland

A constructed wetland with Acorus calamus L. was built. Straw biochar, reed biochar, and sawdust biochar was added into the constructed wetland individually to study the effect of different biochars on the root morphology, dissolved oxygen, and purification ability of the constructed wetland. The results show that the total root length, total projection area, total volume, total surface area, root number, branch number, and root dry weight of Acorus calamus L. significantly increased when all three kinds of biochar were added into the constructed wetland (P<0.05). Similarly, adding the biochars into the constructed wetland also significantly increased dissolved oxygen content in the wetland (P<0.05). Addition of sawdust biochar into the constructed wetland increased the root length, projection area, surface area, total volume, number of root tips, number of branches, and root dry weight of Acorus calamus L. by 96.1%, 106.2%, 185.6%, 172.5%, 75.3%, 121.6%, and 84.9%, respectively. After adding biochars into the constructed wetland, the root morphology of Acorus calamus L. and dissolved oxygen content was significantly correlated with removal rate of TN, TP, and COD, respectively. Addition of sawdust biochar into the constructed wetland significantly increased the removal rates of total nitrogen, total phosphorus, and COD when the hydraulic load was 0.022 m3·(m2·d)-1 (P<0.05). These results suggested that the addition of sawdust biochar to the constructed wetland increased the root growth of Acorus calamus L. and enhanced dissolved oxygen content, resulting in purification capacity of the constructed wetland.

Estimation of genetic variability, correlation and path coefficient analysis in local landraces of rice (Oryza sativa L.) for the improvement of salinity tolerance

Twenty eight local rice landraces were assessed for eleven morphological traits for the improvement of salt tolerance ability of rice genotypes. Genotypic variance (σ2g), phenotypic variance (σ2p), phenotypic co-variance (PCV), genotypic co-variance (GCV), heritability, genetic advance, genetic advance as a percentage of mean, correlation coefficient and path coefficient were estimated. For all the traits, PCV was higher than the GCV indicating that they were controlled by non-additive gene action and selection for the improvement of these traits would be promising. Among the traits, survival rate of plant exhibited high estimates of PCV (460.72) and GCV (324.73) indicated wide range of variability for these traits where lowest phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) where low PCV and GCV were observed for root dry weight (0.17 &amp; 0.12) followed by shoot dry weight (0.31 &amp; 0.16) and total number of roots (0.61 &amp; 0.34) indicating lack of inherent variability and limited scope for improvement through selection for these traits among the genotypes. Highest heritability had observed in all traits except chlorophyll content and root length and maximum value of heritability was noticed for shoot length (75.96%). High heritability along with high genetic advance was noticed for survival rate of plant (31.14%) followed by live leaves percentage (11.98) and the lowest genetic advance was found in root dry weight (0.58) and shoot dry weight (0.58). Correlation study revealed that significant negative correlations at both phenotypic and genotypic level exist between standard evaluation score (SES) and survival rate (%), root length, shoot length, root fresh weight, root dry weight and shoot dry weight at the seedling stage further confirmed the importance of these parameters as useful selection criteria for screening for salt tolerance rice genotypes. Path analysis revealed that the root length (0.487), root dry weight (0.394) and shoot dry weight (0.047) had direct positive effect on standard evaluation score at genotypic level where live leaves (%) per plant (0.168), total number of roots (0.006), chlorophyll content (0.243) and shoot fresh weight (0.102) had direct positive effect on standard evaluation score at phenotypic level. From the correlation and path analysis it can be concluded that root length, root dry weight and shoot dry weight would be more promising for the improvement of salt tolerance in rice genotypesJ. Bangladesh Agril. Univ. 16(1): 41-46, April 2018

Algorithm 987

MANBIS is a C++ mathematical software package for tackling the problem of computing the roots of a function when the number of roots is very large (of the order of hundreds or thousands). This problem has attracted increasing attention in recent years because of the broad variety of applications in various fields of science and technology. MANBIS applies the bisection method to obtain an approximate root according to a predetermined accuracy. Thus, the only computable information required is the algebraic signs of the considered function, which is the smallest amount of information (one bit of information) necessary for the purpose needed, and not any additional information. MANBIS is able to compute very efficiently a user-given percentage of roots and draws its strength from the fact that the roots are expected to be many. Furthermore, MANBIS is capable of estimating without any additional function computational cost the total number of roots within the user-given interval. Our approach can also be efficiently applied in cases where the distribution of the roots is not known. This article is accompanied by another article where the user manual, some implementation details, and some examples are included.

인삼 하우스 직파재배 시 파종밀도 및 솎음처리가 3 년근 인삼의 생육과 수량에 미치는 영향

Background: The cultivation of ginseng (Panax ginseng C. A. Meyer) in greenhouses could reduce the use of pesticides and result in higher yield; however, construction costs are problematic. The adaptation of direct-sowing culture in greenhouses could reduce the cost of ginseng production.BRMethods and Results: To improve seedling establishment in direct-sowing culture, effects of sowing density (SD), number of seeds sown per hole (SN), and thinning (TH) treatment on the root yield were investigated after 3 years of seeding. The emergence rate was significantly influenced by SD, but not by SN or TH. Damping-off and rusty roots increased with an increase in SN with diminishing effects of SN on seedling establishment. Root weight and diameter were affected by SD, SN, and TH, however, there were no statistical significances. The total number of roots harvested per unit area increased with increasing SD and SN, and the weight of roots was affected by SD, but not by SN or TH.BRConclusions: Multi-seed sowing per hole and/or thinning might not be an efficient method for the direct-sowing culture of ginseng. The SD for direct seeding culture in greenhouses should be approximately 33 - 42 seeds/㎡ for an optimum yield of 3-year-old inseng.

Screening wheat germplasm for seedling root architectural traits under contrasting water regimes: potential sources of variability for drought adaptation

ABSTRACTIn this study, we selected 180 accessions from different wild relatives of wheat (Aegilops–Triticum species) and tested them in the presence of a tolerant and a sensitive control variety under well-watered and drought-stressed conditions. The results of analysis of variance for dry masses and all measured root traits showed that water regimes, accession and species main effects were highly significant. Drought stress significantly declined shoot dry mass (59.42%), root length (37.85%) and the total number of branch roots (36.25%), but increased the root-to-shoot ratio (75.00%), specific root length (64.19%) and root tissue density (29.46%). Principal component analysis for 182 individuals and 12 species groups identified two components that explained 75.67 and 82.39% of the total variation in dry mass and root traits under drought-stressed conditions, respectively. Taking together, our results identified 12 accessions with superior tolerance to drought stress. Remarkably, four species of wild relatives – Ae. cylindrica (DC genome), Ae. neglecta (UM genome), Ae. speltoides (B genome) and Ae. tauschii (D genome) – responded well to drought stress. The potential of these species could be used for molecular analysis such as marker assisted selection and gene mapping, ultimately aimed at breeding for root traits with improved adaptation to drought environments.

English

The objective of this study was to evaluate the effect of different growth media on rooting of stem cuttings of hybrid coffee varieties. The experiment was conducted on-station under a shade house at Tanzania Coffee Research Institute (TaCRI) from October 2013 to February 2014 using a split plot experiment in a Randomized Complete Block Design (RCBD) with four replications. The main factor consisted of five hybrid coffee varieties (KP423-1, KP423-2, N39-3, N39-2 and N39-7) and the sub-factor consisted of five types of rooting media (red soil, peat moss, decomposed saw dust, rice husk and forest soil + fine sand 2:1 (v/v) as a control). The stem cuttings were planted in each type of the media and four months after planting, the cuttings were evaluated based on number of rooted cuttings, total number of roots per cutting, number of lateral roots per cutting and root length. The data were subjected to analysis of variance using CoStat software and treatment means were separated based on Tukey’s test at P ≤ 0.05. Results indicate that coffee varieties N39-2 and N39-3 produced the highest rooted stem cuttings of 64.2 and 63.9% respectively. Results also show that red soil media provided the highest rooted stem cuttings of 77.9% followed by sawdust with 68.0%. It is recommended that propagators should use red soil as a rooting media for improving rooting percentage of stem cuttings from improved coffee varieties. Further studies are required to improve chemical and physical properties of red soil media. Key words: Hybrid coffee, mass multiplication, propagation, rooting media, stem cuttings.

Root Morphological Traits and Spatial Distribution under Different Nitrogen Treatments and Their Relationship with Grain Yield in Super Hybrid Rice

Succeeding in breeding super hybrid rice has been considered as a great progress in rice production in China. This on-farm study was conducted with Minirhizotron techniques to identify dynamic root morphological traits and distribution (0–30 cm) under different nitrogen treatments. Five elite super hybrid rice cultivars, Liangyoupeijiu (LYPJ), Yliangyou 1(YLY1), Yliangyou 2(YLY2), Yliangyou 900(YLY900) and Super 1000(S1000), were grown at four N levels: 0 kg ha−1 (N1), 210 kg ha−1 (N2), 300 kg ha−1 (N3) and 390 kg ha−1 (N4) in 2015 and 2016. Results showed these cultivars had greater root traits and higher grain yield under N3. Total root number (TRN) and total root length (TRL) of these cultivars reached maximum at 55 days after transplanting (DAT). The new released cultivars YLY900 and S1000 were featured with an improved root system among these cultivars. The percentage of root number on 10–20 cm soil was over 50% compared with other soil layer. A significant positive correlation was found between grain yield and both TRN and TRL at 10–20 cm soil layer (P < 0.01). Given this situation, the grain yield of super rice cultivars could be further improved by increasing the proportion of roots at 10–20 cm soil layer under suitable nitrogen management.

Genetic architecture of aerial and root traits in field-grown grafted grapevines is largely independent.

QTLs were identified for traits assessed on field-grown grafted grapevines. Root number and section had the largest phenotypic variance explained. Genetic control of root and aerial traits was independent. Breeding new rootstocks for perennial crops remains challenging, mainly because of the number of desirable traits which have to be combined, these traits include good rooting ability and root development. Consequently, the present study analyzes the genetic architecture of root traits in grapevine. A segregating progeny of 138 F1 genotypes issued from an inter-specific cross between Vitis vinifera cv. Cabernet-Sauvignon×V. riparia cv. Gloire de Montpellier, used as rootstock, was phenotyped in grafted plants grown for 2years in the field. Seven traits, related to aerial and root development, were quantified. Heritability ranged between 0.44 for aerial biomass to 0.7 for root number. Total root number was related to the number of fine roots, while root biomass was related to the number of coarse roots. Significant quantitative trait loci (QTLs) were identified for all the traits studied with some of them explaining approximately 20% of phenotypic variance. Only a single QTL co-localized for root and aerial biomass. Identified QTLs for aerial-to-root biomass ratio suggest that aerial and root traits are controlled independently. Genes known to be involved in auxin signaling pathways and phosphorus nutrition, whose orthologues were previously shown to regulate root development in Arabidopsis, were located in the confidence intervals of several QTLs. This study opens new perspectives for breeding rootstocks with improved root development capacities.

Root zone temperature alters storage root formation and growth of sweetpotato

AbstractLarge mounds amended with plant residues are a common cultivation method for sweetpotato (Ipomoea batatas) in the western parts of the Papua New Guinea highlands, with a suggested benefit of elevated root zone temperature (RZT) from decomposition. This study aimed to evaluate whether RZT affects the formation and growth of sweetpotato storage roots. Experiments evaluated the effects of a constant elevated RZT on the Beauregard cultivar and of a short‐term increase in RZT on the Beauregard and Northern Star cultivars. Plants were grown in 18‐L pots divided into a control compartment (constant RZT at 20°C) and a treated compartment (RZT at 30, 40 or 50°C). Constant elevated RZT was maintained until harvest, while short‐term increase in RZT occurred in weeks 2 and 3 only. Constant elevated RZT did not affect the total number of storage roots, but RZT of 30°C and above reduced the dry‐biomass of storage roots. The short‐term increase in RZT did not alter the total number or dry‐biomass of storage roots in Beauregard, while both of these attributes were reduced at RZT of 40°C or above in Northern Star. Elevated RZT inhibited dry‐biomass accumulation of storage root, with a more pronounced impact at constant elevated RZT. These results demonstrate that any benefits of the mound culture on sweetpotato yield production do not arise through the influence of temperature elevation.

Características de raízes tuberosas de clones de batata-doce por meio de técnicas multivariadas para seleção de genótipos superiores

Objetivou-se avaliar características de raízes tuberosas de clones de batata-doce por meio de técnicas multivariadas para seleção de genótipos superiores, a presente pesquisa foi realizada na área experimental do Setor de Melhoramento Genético de Plantas do Centro de Ciências Agrárias da Universidade Federal de Alagoas. Foram avaliados 44 novos clones oriundos de progênies de meios-irmãos e irmãos germanos, além do cultivar Sergipana Vermelha, em linhas de 5 m de comprimento, no espaçamento de 1,0 m x 0,5 m, totalizando uma área total de 5 m²/clone. A colheita foi efetuada aos 120 dias após o plantio das ramas, em que foram avaliadas a produção de raízes tuberosas não comerciais (PRTNC), produção de raízes tuberosas comerciais (PRTC), produção total de raízes tuberosas (PTRT), número total de raízes tuberosas (NTRT), peso médio de raízes tuberosas comerciais (PMRTC), cor predominante da pele das raízes tuberosas (CPPERT) e cor predominante da polpa das raízes tuberosas (CPPORT). Foi utilizada a estatística descritiva, técnica de correlação e análise de componentes principais. Observou-se que os clones 23, 36, 17 e 37 apresentaram características agronômicas interessantes, sendo recomendados para o cultivo e na análise de componentes principais as variáveis PTRT e PRTC apresentaram maiores importâncias, refletindo que elas discriminam satisfatoriamente os clones.

Sweetpotato Transplant Holding Duration Effects on Plant Survival and Yield

Studies were conducted in North Carolina to determine the effect of holding durations (HDs) [0, 1, 3, 5, and 7 days before planting (DBP)] of ‘Covington’ sweetpotato (Ipomoea batatas) transplants on plant stand and storage root numbers and yield in production fields. In a second field study, the effect of preplant irrigation (PI) treatments (PI and nonirrigation) were evaluated along with the transplant HD on plant stand, storage root numbers, and yield. Transplants held for 7 DBP did not survive as well as the other treatments (lower plant stands) and had lower no. 1, marketable, and total storage root numbers and yields than other holding treatments. HD of 1 or 3 DBP resulted in higher plant stands, and no. 1, marketable, and total numbers of storage roots and yields than holding for 0, 5, or 7 DBP. This study affirms the importance of soil moisture at and shortly after planting for transplant survival and yield. Holding transplants for 1–3 DBP can improve stand establishment and yields when dry conditions occur either before or soon after planting. However, holding transplants for 7 DBP can result in reduced plant stands and yields when stress/dry conditions occur soon after planting.