Cassava Seedlings Research Articles

Integrated transcriptomics and metabolomics analyses provide new insights into cassava in response to nitrogen deficiency

Nitrogen deficiency is a key constraint on crop yield. Cassava, the world’s sixth-largest food crop and a crucial source of feed and industrial materials, can thrive in marginal soils, yet its yield is still significantly affected by limited nitrogen availability. Investigating cassava’s response mechanisms to nitrogen scarcity is therefore essential for advancing molecular breeding and identifying nitrogen-efficient varieties. This research undertook a comprehensive analysis of cassava seedlings’ physiological, gene expression, and metabolite responses under low nitrogen stress. Findings revealed that nitrogen deficiency drastically suppressed seedling growth, significantly reduced nitrate and ammonium transport to aerial parts, and led to a marked increase in carbohydrate, reactive oxygen species, and ammonium ion levels in the leaves. Transcriptomic and metabolomic analyses further demonstrated notable alterations in genes and metabolites linked to carbon and nitrogen metabolism, flavonoid biosynthesis, and the purine metabolic pathway. Additionally, several transcription factors associated with cassava flavonoid biosynthesis under nitrogen-deficient conditions were identified. Overall, this study offers fresh insights and valuable genetic resources for unraveling cassava’s adaptive mechanisms to nitrogen deprivation.

Comparative analysis of infected cassava root transcriptomics reveals candidate genes for root rot disease resistance

Cassava root-rot incited by soil-borne pathogens is one of the major diseases that reduces root yield. Although the use of resistant cultivars is the most effective method of management, the genetic basis for root-rot resistance remains poorly understood. Therefore, our work analyzed the transcriptome of two contrasting genotypes (BRS Kiriris/resistant and BGM-1345/susceptible) using RNA-Seq to understand the molecular response and identify candidate genes for resistance. Cassava seedlings (resistant and susceptible to root-rot) were both planted in infested and sterilized soil and samples from Initial-time and Final-time periods, pooled. Two controls were used: (i) seedlings collected before planting in infested soil (absolute control) and, (ii) plants grown in sterilized soil (mock treatments). For the differentially expressed genes (DEGs) analysis 23.912 were expressed in the resistant genotype, where 10.307 were differentially expressed in the control treatment, 15 DEGs in the Initial Time-period and 366 DEGs in the Final Time-period. Eighteen candidate genes from the resistant genotype were related to plant defense, such as the MLP-like protein 31 and the peroxidase A2-like gene. This is the first model of resistance at the transcriptional level proposed for the cassava × root-rot pathosystem. Gene validation will contribute to screening for resistance of germplasm, segregating populations and/or use in gene editing in the pursuit to develop most promising cassava clones with resistance to root-rot.

Predictors of Agricultural Technology Adoption Among the Cassava Farmers in the North- Central Nigeria

This research paper delves into the underexplored realm of agricultural technology adoption behaviour among cassava farmers in North Central Nigeria, with a focus on elucidating the predictors of technology adoption within the region. Leveraging a quantitative survey research design, data was collected from 377 cassava farmers through structured questionnaires. Findings reveal significant relationships between various factors such as performance expectancy, effort expectancy, social influence, facilitating conditions, price value, hedonic motivation, prior experience, and the adoption of agricultural technology. Through multiple linear regression analyses, it was established that these factors exert substantial influences on technology adoption behaviour among cassava farmers. Based on empirical evidence, policy recommendations were formulated to enhance the adoption of agricultural technologies among cassava farmers, aiming to foster a transition from subsistence to commercial farming, thereby bolstering agricultural productivity and socio-economic development in the region. These recommendations encompass governmental support for improved cassava seedlings, duty-free importation of agricultural implements, procurement and distribution of tractors, expansion of extension services, fertilizer production facilities, subsidized procurement of agricultural machinery, and enhanced importation policies for agro-chemicals. This research contributes to a deeper understanding of the complex dynamics underlying technology adoption in agricultural contexts, offering insights for policymakers, practitioners, and researchers alike.

Cocoa, Palm Tree, and Cassava Plantations among Smallholder Farmers: Toward Policy and Technological Efficiencies for Sustainable Socio-Economic Development in Southern Nigeria

This study is basically and centrally focused on the review of the extant literature in exploring the challenge of the under-utilization of natural fertile land for the cultivation and farming of different crops such as cocoa, palm tree, and cassava, which remain an important sector of the economy for sustainable socio-economic development in the southern part of Nigeria. The review of the cursory literature is necessary to bridge the gap in the existing body of knowledge, especially by addressing the less attention paid to exploring the non-oil sector of the economy such as cocoa, palm tree, and cassava as well as connecting policy and agro-technology to maximize agricultural productivity for the purpose of sustainable socio-economic development. The primary objective of this study is to explore cocoa, palm tree, and cassava plantations among smallholder farmers in order to enhance sustainable socio-economic development in the country. The methodology used in this study is a systematic literature review (SLR) cum content analysis (CA) of secondary sources or relevant literature whereby six themes were generated and analyzed. A consistent approach was used in order to establish exhaustive searching strategies and single-line search strategies such as using field codes and parentheses as part of a systematic literature review. The results indicated that smallholder farmers have been actively partaking in cocoa plantation, and the government has been supportive of them in this regard in order to achieve sustainable socio-economic development. In addition, agricultural transformation contributes to economic diversification through innovative policy and capacity building among cocoa, palm tree, and cassava farmers in the country, which culminates in improving the overall welfare of the smallholder farmers in attaining sustainable socio-economic development. In conclusion, it is noteworthy to say that giving support, especially cocoa, palm tree, and cassava seedlings, to smallholder farmers can be instrumental in bridging the vacuum created by poverty and unemployment which could be regarded as mechanisms for attaining sustainable development. The importance of the study was manifested in the practical aspect of giving concrete support to the smallholder farmers, and the innovativeness of the study is reflected in the advocacy for the efficiencies and effectiveness of agricultural policy and technology integration into the sector. It is therefore suggested that interventions of individual philanthropists, government, and international communities will boost the morale and resilience of the farmers toward enhancing cocoa, palm tree, and cassava production in order to enhance sustainable socio-economic development among smallholder farmers in particular and to maximize national economy growth in general.

Methods for overcoming dormancy in cassava seeds

The propagation of cassava via seminal is an option but faces problems due to dormancy and slow germination. Therefore, the objective was to evaluate the effect of pre-germination treatments, on overcoming Manihot esculenta seed dormancy, clone Gabriela, cultivated in Roraima, Brazil. The experiment was a completely randomized design, with four replicates of 25 seeds, each in seven treatments: intact seeds (CONTROL); lateral scarification the seed (LS); removal of the caruncle (RC); scarification of the caruncle (SC); immersion of the seeds in sulphuric acid for 10 minutes (SA10); for 20 minutes (SA20) and for 30 minutes (SA30). The seeds were sown in trays containing river sand, washed and passed through a 2 mm mesh sieve. The following variables were analyzed: seedling emergence (SE), average emergence time (MET), emergence speed index (ESI), percentage of firm seeds (PFS), percentage of hard seeds (PHS) and percentage of deteriorated seeds (PSDET). The LS (89±7%) and SC (82±5%) treatments were superior to the others, obtaining the shortest MET (11.7±0.38 and 12.8±0.69 days, respectively) and consequently the highest IVE (1.55±0.22 and 1.74±0.22). Sexual propagation of cassava is possible. Lateral scafifying the seeds until the inside of the tegument with exposure of the endosperm with the caruncle intact (LS) and Scarifying the of caruncle until the inside of the tegument (SC) were more efficient seedling emergence and in counting normal cassava seedlings. Soaking seeds in sulphuric acid (AS10; AS20 and AS30) does not overcome the dormancy of cassava seeds.

Integrated Analysis of Morphological, Physiological, Anatomical and Molecular Responses of Cassava Seedlings to Different Light Qualities.

Light quality is highly important for growth control of in vitro plant cultures. Here, we investigated the effect of blue light (BL), red light (RL) and combined red and blue light (RBL) on in vitro cassava growth. Our results indicate that RL facilitated radial elongation of cassava and increased stomatal conductance as well as glucose, sucrose, fructose and starch content in leaves and cellulose content in the stem. It also enhanced SOD and POD activities but decreased the stomatal density and chlorophyll and carotenoid content in leaves. In addition, RL leads to shorter palisade cells, denser chloroplasts and more starch granules. These phenotypic changes were inverted following BL treatment. The expression levels of photosynthesis-related genes MeLHCA1, MeLHCA3, MePSB27-2, MePSBY, MePETE1 and MePNSL2 in leaves were at their lowest following RL treatment, while the expression levels of MePSB27-2, MePSBY, MePETE1 and MePNSL2 were at their highest after BL treatment. The phenotypic changes after RBL treatment were between the values observed for the RL and BL treatments alone. Moreover, the responses of SC8 and SC9 cassava varieties to light quality were largely conserved. As such, we believe that the results of this study lay the foundation for controlling the in vitro growth of cassava seedlings by light quality.

Whole-genome assembly of A02 bacteria involved in nitrogen fixation within cassava leaves.

The endophytic nitrogen (N)-fixing bacterium A02 belongs to the genus Curtobacterium (Curtobacterium sp.) and is crucial for the N metabolism of cassava ( Manihot esculenta Crantz). We isolated the A02 strain from cassava cultivar SC205 and used the 15N isotope dilution method to study the impacts of A02 on growth and accumulation of N in cassava seedlings. Furthermore, the whole genome was sequenced to determine the N-fixation mechanism of A02. Compared with low N control (T1), inoculation with the A02 strain (T2) showed the highest increase in leaf and root dry weight of cassava seedlings, and 120.3 nmol/(mL·h) was the highest nitrogenase activity recorded in leaves, which were considered the main site for colonization and N-fixation. The genome of A02 was 3,555,568 bp in size and contained a circular chromosome and a plasmid. Comparison with the genomes of other short bacilli revealed that strain A02 showed evolutionary proximity to the endophytic bacterium NS330 (Curtobacterium citreum) isolated from rice (Oryza sativa) in India. The genome of A02 contained 13 nitrogen fixation (nif) genes, including 4 nifB, 1 nifR3, 2 nifH, 1 nifU, 1 nifD, 1 nifK, 1 nifE, 1 nifN, and 1 nifC, and formed a relatively complete N fixation gene cluster 8-kb long that accounted for 0.22% of the whole genome length. The nifHDK of strain A02 (Curtobacterium sp.) is identical to the Frankia alignment. Function prediction showed high copy number of the nifB gene was related to the oxygen protection mechanism. Our findings provide exciting information about the bacterial genome in relation to N support for transcriptomic and functional studies for increasing N use efficiency in cassava.

Novel SNP Markers and Their Application in Low-Cyanide Cassava (Manihot esculenta crantz) Breeding Program

The major flaw of cassava is its indigenous cyanide. Traditional breeding program for diminishing cyanide in cassava take a long waiting time for harvesting cassava tubers to assess cyanide content. Genetic markers are useful for selection of good agricultural traits, which also applied in low-cyanide cassava breeding programs by detecting gene associate with cyanide content in cassava. Therefore, the objective of this study was to develop SNP markers to detect low cyanide trait in cassava. Genotype analysis was carried out using Genotyping by Sequencing (GBS) technology assembling with phenotype analysis. Then, the SNP markers associated with cyanide content were found. Afterward, the primers of SNP marker associated with cyanide content 2 positions were developed using tetra-primer ARMS-PCR techniques. S16_640082 and S16_735381 SNP markers on chromosome 16 showed potential ability of the selection of cassava varieties with cyanide content less than 250 mg HCN/kg fresh weight. The selection accuracy of S16_640082 and S16_735381 SNP markers was 73.33 and 76.64 %, respectively. These markers could be used in marker assisted selection (MAS) in cassava seedling. It substantially reduces cassava breeding programs cost and time. HIGHLIGHTS The major flaw of cassava is its indigenous cyanide. Up to our knowledge, there is rarely report on SNP marker related to cyanide content in Thai cassava population By performing genome wide association mapping (GWAS) to characterize the genome position related to HCN, 2 novel SNP markers associated with cyanide content were found The primers to detect the SNP markers were developed using tetra-primer ARMS-PCR techniques The markers showed ability of the selection of cassava varieties with cyanide content less than 250 mg HCN/kg fresh weight GRAPHICAL ABSTRACT

The cassava (Manihot-esculenta Crantz)'s nitrate transporter NPF4.5, expressed in seedling roots, involved in nitrate flux and osmotic stress

AtNPF4.5/AIT2, which was predicted to be a low-affinity transporter capable for nitrate uptake, was screened by ABA receptor complex in Arabidopsis ten years ago. However, the molecular and biochemical characterizations of AtNPF4.5 in plants remained largely unclear. In this study, the function of a plasma-membrane-localized and root-specifically-expressed gene MeNPF4.5 (Manihot-esculenta NITRATE TRANSPORTER 1 PTR FAMILY4.5), an ortholog of the Arabidopsis thaliana NPF4.5, was investigated in cassava roots as a nitrate efflux transporter on low nitrate medium and an influx transporter following exposure to high concentration of external nitrates. Moreover, RNA interference (RNAi) of MeNPF4.5 reduced the nitrate efflux capacity but the overexpressing cassava seedlings increased the ability of efflux from the elongation to the mature zone of root under low nitrate treatments. Besides, MeNPF4.5-RNAi expression reduced the nitrate influx capacity but enhanced nitrate absorption in parts of overexpressing plants from the meristem, elongation to mature zone of roots under high nitrate conditions. Furthermore, MeNPF4.5-RNAi seedlings survived owing to roots that could grow normally, but the MeNPF4.5-over-expressors showed adverse growth under 7% PEG6000 stress, suggesting that MeNPF4.5 negatively regulated the osmotic stress and was involved in nitrate flux through cassava seedlings.

Performance Test of Cassava Cutting Machine Type of Double Block Cutter

Preparation of cassava seeds using a machete or hand saw takes a long time, the results are not uniform, and there is a potential for damage to cassava seedlings. The double block cutter type cassava stem cutting machine has been designed to produce high capacity and good quality cassava seeds. This study aims to test the performance of the cassava stem cutting machine with the double block cutter type. Performance tests include measuring machine working capacity, fuel consumption, seed uniformity, and planting test. The cutting test was carried out using 3 varieties of cassava seedlings. The machine works at a rotational speed of 3800 rpm and the test was carried out with various feeding loads, namely 3 rods, 4 rods, and 5 rods with. Each test was repeated 3 times. Cassava stem cutting machine (Petokong) is suitable for producing cassava stems with an average working capacity of 16275 seeds/hour. The results of the Anova test showed that the number of baits and varieties of cassava seeds and their interaction had a significant effect on the working capacity of the Petokong machine. Variations in fuel consumption are thought to be influenced by the variety of cassava stem used, which is influenced by the stem diameter of each variety. The Petokong machine is far superior to manual cutting using a machete or saw which can only produce 815 and 3005 seeds/hour per hour. The average fuel consumption is 1.82 liters per hour. Seed uniformity is about 98% and seedling damage can be minimized to 2%. The seeds produced by the Petokong machine can grow well, which is indicated by the appearance of shoots and an even distribution of roots. Keywords: Cassava seeds, Cassava stem cutter, Double block cutter, Petokong

High-Throughput Virus Screening in Crosses of South American and African Cassava Germplasm Reveals Broad-Spectrum Resistance against Viruses Causing Cassava Brown Streak Disease and Cassava Mosaic Virus Disease

Screening cassava lines for resistance against viruses causing cassava brown streak disease (CBSD) is cumbersome because of the unpredictable and erratic virus infections in the slow plant infection processes that are frequently not associated with distinct leaf symptoms and because of the reliance on the assessment of root necrosis as an indicator of plant resistance/tolerance. The selection of resistant candidates thus extends over several growing cycles and is still associated with uncertainties about the stage of virus infection. To reduce the time for selection of resistant crosses and the uncertainties associated with field screening, we have developed a fast-forward virus screening workflow to assess cassava seedlings from crosses of cassava brown streak- and cassava mosaic virus-resistant parents. After passing through an intensive and precise virus infection routine, cassava seedlings that carried resistance against cassava brown streak and mosaic viruses were identified. Taking the results of 195 seedlings from 18 crossing families together, it became evident that resistance against the viruses causing CBSD is a dominant trait. The protocol developed for virus resistance screening in cassava can be readily adopted. It shifts resistance evaluation from the field to the nursery and replaces the erroneous and lengthy virus infection and screening process with a method of precision and speed.

Cassava Brown Streak Disease Response and Association With Agronomic Traits in Elite Nigerian Cassava Cultivars.

Cassava mosaic geminiviruses (CMGs) and cassava brown streak viruses (CBSVs) cause the highest yield losses in cassava production in Africa. In particular, cassava brown streak disease (CBSD) is and continues to be a significant constraint to optimal cassava production in Eastern and Southern Africa. While CBSD has not been reported in West Africa, its recent rapid spread and damage to cassava productivity in Eastern, and Southern Africa is alarming. The aim of this study was to evaluate Nigerian cassava genotypes in order to determine their responses to CBSD, in the event that it invades Nigeria, the world’s largest cassava producer. The study gathered information on whether useful CBSD resistance alleles are present in the elite Nigerian cassava accessions. A total of 1,980 full-sib cassava seedlings from 106 families were assessed in the field at the seedling stage for a year. A subset of 569 clones were selected and assessed for another year at the clonal stage in Namulonge, central Uganda, a known hotspot for CBSD screening. Results indicated that foliar and root incidences and severities varied significantly (p ≤ 0.01, p ≤ 0.001) except for CBSD foliar incidence at 6 months (CBSD6i). Highest and lowest plot-based heritability estimates for CBSD were registered for CBSD root severity (CBSDrs) (0.71) and CBSD6i (0.5). Positive and highly significant correlations were noted between CBSD root incidence (CBSDri) and CBSDrs (r = 0.90***). Significant positive correlations were also noted between CBSD foliar severity at 3 months (CBSD3s) and CBSD foliar incidence at 6 months (CBSD6i) (r = 0.77***), CBSD3s and CBSDrs (r = 0.35***). Fresh root weight (FreshRW) negatively correlated with CBSDri and CBSDrs, respectively (r = −0.21*** and r = −0.22***). Similarly, CBSD3s correlated negatively with cassava mosaic disease severity at 3 (CMD3s) and 6 months (CMD6s), respectively (r = −0.25*** and r = −0.21***). Fifteen clones were selected using a non-weighted summation selection index for further screening. In conclusion, results revealed that the elite Nigerian accessions exhibited significant susceptibility to CBSD within 2 years of evaluation period. It is expected that this information will aid future breeding decisions for the improvement of CBSD resistance among the Nigerian cassava varieties.

Anti-osmotic Response of ‘F200’ and ‘SC8’ Cassava Seedlings under Low Temperature Stress

Anti-osmotic Response of ‘F200’ and ‘SC8’ Cassava Seedlings under Low Temperature Stress

Production of cassava seedlings on substrates based on decomposed buriti stem

ABSTRACT In the cassava (Manihot esculenta Crantz) cultivation system, planting seedlings directly in the field is widely used. However, establishment of plants by this method is slow, taking about 15 days to start the formation of shoots and roots. The plant in this phase is not very competitive, which leads to the formation of uneven and low-productivity areas. Production of seedlings on substrates is an alternative that can improve the uniformity of the plant stand, as well as allow more careful selection of the best propagules. Viability of this propagation method depends on the substrate, which must have ideal physical and chemical properties to meet the needs of the crop. The objective of this work was to evaluate the use of decomposed buriti stem (Mauritia flexuosa L. f) as a substrate in the propagation of cassava seedlings. The substrates were composed of decomposed buriti stems and soil in the following proportions: 0:100; 20:80; 40:60; 60:40; 80:20; and 100:0 (volume). The addition of decomposed buriti stem improved development of the aerial part, provided greater survival for cassava seedlings in an increasing linear fashion, and promoted increases in the levels of N, P, K, Ca, and Mg of cassava seedlings. It was determined that there is agronomic efficiency in the use of buriti residue for the production of cassava seedlings.

Adaptation of the rapid multiplication method: selecting stem cuttings based on their number of leaves for cassava seedling production

A study was conducted during four growing seasons to investigate the rooting capacity and survival percentage of cassava seedlings from stem cuttings selected based on their number of leaves. The experimental design was a randomized block design with five replications in a factorial scheme (4 × 2 × 2), totalling 16 treatments. Treatments consisted of combinations of growing season (September 22, October 7 and 19, and November 25), stem cuttings smaller (15 to 19.99 mm) and larger (20 to 25 mm) than 20 mm in diameter, and number of leaves on the stem cuttings (3 to 5 and 6 to 8 leaves). The experiment was carried out during the four growing seasons in a Van der Hoeven greenhouse. The greenhouse, as well as the benches on which the treatments were placed, had a north-south orientation. The greenhouse has an automatic mist irrigation system, and the mean temperature was 25 °C. The plant height at planting, number of leaves at planting, and number of leaves at 7 days after planting were measured. The final number of leaves, final plant height, shoot dry matter, root dry matter, and total dry matter were measured after acclimatization. Stem cuttings between 20 and 25 mm in diameter should be used to produce cassava seedlings with the rapid multiplication method. Cuttings with 6 to 8 visible leaves should be collected, and the cuttings should be planted at the end of September.

Decomposed babassu biomass residue enhances the initial development of cassava (Manihot esculenta Crantz)

Cassava is a tuber of significant cultural and economic importance for family farming. However, cultivation in the northeastern region of Brazil is characterized by low productivity, resulting from cultivation in naturally marginal soil, which can cause food insecurity to farmers in the region. The objective was to evaluate the initial development of cassava using substrates derived from decomposed residue from babassu biomass, as a supplement to the soils with low natural fertility. The experiment was carried out in a greenhouse in the municipality of Chapadinha, state of Maranhão, Brazil. The treatments consisted of six inclusion levels of babassu biomass (BB) in the substrates: S0, 100% soil; S20, 20% BB + 80% soil; S40, 40% BB + 60% soil; S60, 60% BB + 40% soil; S80, 80% BB + 20% soil; and S100, 100% BB. The treatments were arranged in a completely randomized design, with four replications. The soil used in the experiment is classified as dystrophic Yellow Oxisol. At the end of the experiment, the following were evaluated: percentage of cuttings survival, leaf area, shoot length, shoot diameter, root length, root volume, aerial part dry mass and root dry mass. With the exception of the sprout diameter, the inclusion of BB in the substrates provided a significant positive effect for all analyzed variables, which demonstrates the early response capacity of cassava seedlings to the use of organic waste associated with the soil low fertility. The use of babassu biomass as an organic fertilizer improves soil fertility, stimulating the growth and development of cassava seedlings in a sustainable production system

Taro Colocasia esculenta as an alternative host plant for rearing cassava mealybug (Hemiptera: Pseudococcidae) and its parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae)

So far, Phenacoccis manihoti (Hemiptera: Pseudococcidae) has been reared mainly with cassava. To explore alternative host plant for rearing of P. manihoti and its parasitoid Anagyrus lopezi De Santis (Hymenoptera: Encyrtidae), we examined suitability of taro Colocasia esculenta (L.) (Alismatales: Araceae) for rearing them in the laboratory, which was compared with that of cassava seedling. Either 50 newly hatched mealybug nymphs or parasitized third-instar mealybugs were reared on taro or cassava seedlings to examine immature development, fecundity and longevity of adults. Nearly 90% of P. manihoti reared on taro successfully developed to adults and they produced 230 eggs on average in their lifetime, while insects reared on cassava showed 95% survival and 250 eggs of lifetime fecundity. For A. lopezi, immature survival was 86% and they laid 140 eggs on average on taro, while it was 88% and 140 eggs on cassava. The results suggested that taro can be used for rearing of P. manihoti and its parasitoid A. lopezi.

Genome-wide identification of miRNAs targets involved in cold response in cassava

MicroRNAs (miRNAs) are recognized as essential transcriptional or post-transcriptional regulators, and play versatile roles in plants growth, development and stress responses. Cassava (Manihot esculenta) is a major root crop widely grown worldwide. Cold stress seriously affects cassava plants growth, development and yield. MiRNAs and their targets have been extensively studied in model plants, but a genome-wide identification of miRNAs’ targets is still lacking in cassava. In this study, two degradome libraries were constructed using cold-treated and control cassava seedlings to identify the roles of miRNAs and their targets in response to cold stress. Following high-throughput sequencing and comparing with miRNA database, degradome data allowed us to identify a total of 151 non-redundant miRNA-target pairs. We revealed that ~ 42% of miRNA targets are conserved across plant species. However, 83 novel miRNA targets were identified in the two libraries. Gene ontology analyses showed that many target genes involved in cellular and metabolic process. In addition, 12 miRNAs and 31 corresponding targets of them were further found to be involved in cold stress response. Particularly, miR159, 164 and 396 participated in cold stress response by up-regulating certain transcription factors that were involved in the regulation of downstream gene expression. The work helps identifing cold-responsive miRNA targets in cassava and increases the number of novel targets involved in cold stress response. Furthermore, the findings of this study might provide valuable reference and new insights for understanding the functions of miRNA in stress response in plants.

Sample size for estimation of averages of agronomic traits in cassava seedlings

O método de multiplicação rápida melhora o uso de material de propagação. No entanto, melhorar o gerenciamento e as técnicas experimentais é crucial para avaliar a produção e a qualidade da planta. Este estudo calculou o tamanho da amostra para estimar médias de caracteres agronômicos em mudas de mandioca originárias de estacas de caule com um número diferente de folhas e diâmetros diferentes. Um total de 600 mudas (cada uma com duas gemas) com um diâmetro de 15,00 a 19,99 mm (N = 300) ou 20,00 a 25,00 mm (N = 300) da cultivar Apronta Mesa foram plantadas em diferentes épocas de cultivo (julho, agosto, Setembro e outubro). Em cada estação de plantio (22 de setembro, 7 de outubro, 19 de outubro e 25 de novembro), 300 estacas, com três a cinco ou até mais de cinco folhas visíveis, foram coletadas. As seguintes estatísticas foram analisadas: mínimo, máximo, intervalo, média, mediana, variação, desvio padrão e coeficiente de variação. O tamanho da amostra foi determinado por reamostragem usando 2.000 reamostragens, com substituição, e foi definido pelo número de plantas a partir das quais o intervalo de confiança de 95% foi de 10%, 15% e 20% da estimativa média. O uso de estacas de caule com diâmetro superior a 20 mm e com mais de cinco folhas foi adequado para a produção de mudas de mandioca. Independentemente da faixa no diâmetro de corte e número de folhas, 87 plantas foram suficientes para estimar as médias das características quando a faixa do intervalo de confiança foi de 20% da estimativa média. e 20% da estimativa média. O uso de estacas de caule com diâmetro superior a 20 mm e com mais de cinco folhas foi adequado para a produção de mudas de mandioca. Independentemente da faixa no diâmetro de corte e número de folhas, 87 plantas foram suficientes para estimar as médias das características quando a faixa do intervalo de confiança foi de 20% da estimativa média. e 20% da estimativa média. O uso de estacas de caule com diâmetro superior a 20 mm e com mais de cinco folhas foi adequado para a produção de mudas de mandioca. Independentemente da faixa no diâmetro de corte e número de folhas, 87 plantas foram suficientes para estimar as médias das características quando a faixa do intervalo de confiança foi de 20% da estimativa média.

IN VITRO MULTIPLICATION OF CASSAVA VARIETIES

The implantation of a model of sustainable development for agriculture can happen with the contribution of the mandiocultura. But for this, culture needs to be strengthened. In vitro propagation is an instrument for this purpose. Micropropagation can provide growers with large quantities of vigorous and healthy cassava seedlings in a short time. The objective of this study was to evaluate the in vitro establishment of four varieties of cassava cultivated in the municipality of Colorado do Oeste, State of Rondônia, popularly known as Arara, Caturra, Cacau Vermelha and Roxinha. For that, an experiment was carried out in the Laboratory of In Vitro Cultivation at the Pole of Technological Innovation of the University of Cruz Alta (UNICRUZ), with a completely randomized design in a 4 x 2 factorial scheme, with 6 replications. The treatments consisted of explants grown in Murashige and Skoog (MS) medium without the presence of growth regulator and MS medium supplemented with of 6-benzylaminopurine (BAP). The results indicate that the average contamination percentage of the explants was 47.19%, differing among the varieties. The best growth response in culture media, in the multiple comparison of means (Scott-Knott's test, 5%), was obtained with MS medium without BAP addition, with significant difference between varieties. Under the conditions of this experiment, it was evidenced that micropropagation is a viable tool for obtaining varieties of interest, with desired phytosanitary qualities, with varietal and large scale authenticity.