IDENTIFICACIÓN DE MICROORGANISMOS PATÓGENOS EN EL CULTIVO DE (Stevia Rebaudiana Bertoni)

En campos comerciales de Stevia rebaudiana localizados en los centro poblados Las Palmas y Esperanza la se determinó la incidencia y severidad de enfermedades ocasionales por microorganismos patógenos. La investigación se desarrolló en fases de reconocimiento de la sintomatología, identificación de agentes causales y determinación de pruebas de patogenicidad. Se encontraron 8 hongos, como agentes causales de los marchitamientos, necrosis de la raíz, manchas foliares y necróticas. 8 hongos, Fusarium sp., Rhizoctonia sp., Sclerotinia sclerotiorum, Sclerotium rolfsii. Cuyos daños ocasionan en los tallos y raíces, Septoria sp., Cercospora sp., Alternaria sp., Oidium. La Esperanza se ha encontrado más plantas infestadas por una mayor diversidad de microorganismos. Los microorganismos no mostraron preferencias entre hojas y tallos y raíz. Para ambas zonas los microorganismos con mayor presencia fueron. Fusarium, Septoria y Sclerotinia sclerotiorum, Sclerotium rolfsii.

Lelliottia Rebaudianalis Sp. Nov. Isolated From Wild Stevia Rebaudiana Bertoni

A Gram-stain-negative, aerobic, chemoheterotrophic bacterium, characterized with rod shape and mobility, designated as LST-1T, was isolated from wild Stevia rebaudiana Bertoni and subjected to polyphasic taxonomic analysis. The LST-1T strain grew optimally at 37 °C and pH 6.0–7.0 in the presence of 0.5 % (w/v) NaCl. Phylogenetic sequence analysis based on 16S rDNA from LST-1 indicated that it is close to Lelliottia jeotgali (99.85%), Lelliottia nimipressuralis (98.82%), and Lelliottia amnigena (98.54%). Multi-locus sequence typing analysis of concatenated partial recA, atpD, and infB was performed to improve resolution, and clear distinctions between the closest related type strains were exhibited. Meanwhile, the results from average nucleotide identify analyses and DNA–DNA hybridization with four species (16S rDNA similarity > 98.65%) were less than 90% and 40% respectively, verifying the distinct characteristics from other species of Lelliottia, The cellular fatty acid profile of the strain consisted of C16:0, Summed Feature3, and Summed Feature8 (may be 16:1 w6c/16:1 w7c and 18:1 w6c) as major components. The major polar lipids included phosphatidylethanolamine, phosphatidylglycerol, aminophospholipid, three non-characteristic phospholipids, and a non-characteristic lipid. The genome of LST-1T is 4,611,055 bp, with a DNA G + C content of 55.02%. Combination of several phenotypic, chemotaxonomic, and genomic characteristics proved that the LST-1T strain does represent a novel genus, for which the name Lelliottia sp. LST-1 was proposed. The type strain is LST-1T (= CGMCC 1.19175T = JCM 34938T).

The Role of Growth Regulators in The Multiplication of Stevia Rebaudiana Bertoni Shoot and Callus Induction in Vitro

The research was conducted to investigate the effect of plant growth regulators on the vegetative multiplication of the Stevia plant shoot and the induction of callus from it. The results indicated that the interaction between 2.0 mg. L-1 BA with 0.5 mg. L -1 Kin gave the highest rate number of shoot with 6.32 branches and the highest average of leaves number Were 9.60 leaves compared to the lowest average for the number of shoot and leaves Were 1.40 shoot and 3.80 leaves respectively. As for the length of the shoot, the interaction between (1.0 mg. L-1 BA and 0.5 mg. L-1 Kin) gave the highest average shoot length 4.31 cm compared to the control which gave 2.20 cm. in connection with the callus induction, the concentration 3 mg. L-1 of NAA gave the highest percentage of callus induction from leaves 100%, and the lowest mean of days that for callus initiation was 9 days compared to the control which reached to 20 days. As for the wet and dry weights of callus tissue, the interaction between 2.0 mg. L-1 NAA and 0.5 mg. L -1BA gave the highest wet weight rate 3.68 g and the average dry weight was 0.31 g compared to the control which gave the lowest rate 0.95 g, 0.08 g respectively.

A fast and effective protocol for obtaining genetically diverse stevia (Stevia rebaudiana Bertoni) regenerants through indirect organogenesis

Plant regeneration through indirect organogenesis allows obtaining genetic variability that can be used in the creation of new cultivars. The study presents a fast and effective protocol of one-step preparation of stevia (Stevia rebaudiana Bertoni) regenerants. To obtain callus tissue and shoot regeneration, leaves and nodal segments were used as primary explants, which were placed on MS (Murashige and Skoog) medium supplemented with plant growth regulators (PGRs): NAA (1-naphthaleneacetic acid – 2.0 mg·dm–3, BA (6-benzylaminopurine – 4.0 mg·dm–3), 2,4‑D (2,4-dichlorophenoxyacetic – 2.0 mg·dm–3). Callus tissue was formed on both types of explants, however, only those derived from nodal segments were proliferating. An average of 3.92 shoots per explant were obtained from leaf explants on the applied medium after 6 weeks of culture. The analysis of the morphogenetic capacity of the obtained regenerants was carried out on MS medium supplemented with PGRs – kinetin (0.25 mg·dm–3), BA (0.5 mg·dm–3). The evaluation of the mean number of shoots, mean shoot length (cm), and the mean number of nodes per shoot indicated phenotypic variability of regenerants. The use of RAPD (randomly amplified polymorphic DNA) markers confirmed the differences also at the DNA level. The proposed one-step indirect organogenesis regeneration protocol induced somaclonal variation of Stevia rebaudiana Bertoni and the obtained regenerants, after selection, could be used in the breeding of this species.

Stevia rebaudiana Bertoni: The Interaction of Night Interruption on Gas Exchange, Flowering Delay, and Steviol Glycosides Synthesis

The Stevia market is estimated to be USD 1.14 billion in 2028 due to its acceptance in the food and beverage industry. Stevia rebaudiana and its two more relevant edulcorants: stevioside (St) and rebaudioside A (Reb-A) can reach 450-fold sweeter than sucrose. The species is considered a long night plant, promoting flowering and shortening vegetative growth. Thus, to increase the leaf area and St and Reb-A increase, we broke the long night with a short light pulse, here called night interruption (NI). In this study, three NI times and two S. rebaudiana genotypes were tested to promote larger vegetative growth, flowering delay, and higher synthesis of steviol glycosides (SvGly). The main goal of this study was to demonstrate that NI increased net photosynthesis (9% to 20%), the internode length (59%), the leaf area (25%), while delays in 4 to 10 days of the flowering phase, impacting in 17% to 25% more St and Reb-A, respectively. Here we describe an inexpensive flowering delay, elongation of vegetative growth, allowing extended harvesting, which could yield four to five annual harvesting of leaves, increasing the production in 21% to 24% more St and Reb-A yield (kg ha−1).

Karakteristik Fisikokimia dan Sensoris Es Krim Ubi Jalar Ungu (Ipomoea Batatas L.) Dengan Subtitusi Pemanis Ekstrak Daun Stevia (Stevia Rebaudiana Bertoni M.) dan Berbagai Jenis Stabilizer

This study aims to determine the effect of sweetener concentration, various types of stabilizers and their interactions on proximate, antioxidant and sensory content of ice cream. The study was conducted using a Factorial Completely Randomized Design (CRD) consisting of two factors. The first factor is the comparison of sweetener concentration with 3 levels of 100% sugar sweetener (D1), 50% sugar sweetener: 50% stevia extract sweetener (D2) and 100% stevia extract sweetener (D3) while the second factor is the type of stabilizer with 3 levels namely, agar. - agar (S1), Gelatin (S2) and CMC (S3). The results obtained were analyzed using the F test and followed by the DMRT test with a confidence level of 95%. The results showed that the comparison of sweetener concentration (D) and treatment interaction (DxS) had a significant effect. While the sensory analysis has a significant effect on the texture, taste, overall variables and does not significantly affect the aroma variable. The best treatment in the proximate analysis of sensory analysis is the treatment of using 50% sugar and 50% stevia and agar-agar (D2S1) stabilizer with the organoleptic score of fragrance, texture, taste and preference respectively were 3.80 (normal); 3.60 (slightly soft); 3.80 (good); 4.10 (liked), and the Physicochemical value of overrun, melting time, fibre content, viscosity, antioxidant, and sugar content respectively were 42,5%; 14,06 minutes; 0,3107%; 1,217 cP; 11,65%; 20,33%.