IN VITRO GERMINATION AND VEGETATIVE PROPAGATION THROUGH BUD DEVELOPMENT OF SACHA INCHI (Plukenetia volubilis) / Germinación y propagación vegetativa in vitro a través del desarrollo de yemas de Sacha Inchi (Plukenetia volubilis)

ABSTRACT This study describes the in vitro seed germination and micropropagation of Plukenetia volubilis (sacha inchi), an oilseed crop rich in omega-3 fatty acids, with health benefits and several industrial applications. Seed germination was evaluated in different culture media (MS and 1/2 MS), seed coat presence/absence and culture temperature (18 °C and 28 °C). Micropropagation was performed using axillary bud development (ABD) on nodal segments from in vitro seedlings. KIN, BAP and 2-ip were evaluated for ABD, and the effect of modified MS in 453 mg L-1 CaCl2 and 351.62 mg L-1 MgSO4 on ABD and shoot survival was assessed to improve the process. Finally, six treatments were evaluated to optimize ABD and shoot leaf formation. Seed germination of 91.6 % was achieved in MS at 28 °C when the seed coat was removed. ABD was obtained in 45 % and 40 % with 0.4 mg L-1 KIN and 0.6 mg L-1 2-ip, respectively, with the least CAL. The modification in 453 mg L-1 CaCl2 then allowed 76 % ABD and 82 % explant survival. ABD response was optimized to 95 % and 2.45 leaves with MS medium + CaCl2 modification + 10 % coconut water + 0.4 mg L-1 KIN. The same results were obtained by replacing the latter with 0.6 mg L-1 2-ip. Rooting was achieved in MS without PGR, and acclimatization was successful. The results indicate that plant production via germination and vegetative propagation is effective for commercial purposes.

RESUMEN Este estudio describe la germinación in vitro y micropropagación de Plukenetia volubilis, un cultivo oleaginoso rico en omega-3 benéfico para la salud y con múltiples aplicaciones industriales. Se evaluó en la germinación diferentes medios de cultivo (MS y 1/2 MS), presencia-ausencia de testa y temperatura de cultivo (18 ° C y 28 ° C). La micropropagación se realizó vía yemas axilares (ABD) de plántulas in vitro. Se evaluó el efecto de KIN, BAP y 2-ip sobre ABD, seguidamente, para mejorar el proceso se evaluó el efecto de MS modificado en 453 mg L-1 CaCl2 y 351.62 mg L-1 MgSO4 sobre ABD y supervivencia del brote. Finalmente, se evaluaron seis tratamientos para optimizar ABD y la formación de hojas. Se logró una germinación 91,6 % en MS a 28 °C cuando se retiró la testa. Se obtuvo 45 % y 40 % de ABD con 0,4 mg L-1 KIN y 0,6 mg L-1 2-ip respectivamente, ambos con la menor CAL. Posteriormente, la modificación de CaCl2 permitió 76 % ABD y 82 % de supervivencia. Se optimizó ABD al 95 % con 2,45 hojas por brote con el medio: MS + modificación de CaCl2 + 10 % de agua de coco + 0.4 mg L-1 KIN, los mismos resultados se obtuvieron cambiando este último con 0,6 mg L-1 2-ip, se logró enraizamiento en MS sin PGR, y la aclimatización fue exitosa. Los resultados indican que la producción de plantas vía germinación y propagación vegetativa es efectiva con fines comerciales.

Global analysis of the sugarcane microtranscriptome reveals a unique composition of small RNAs associated with axillary bud outgrowth.

Axillary bud outgrowth determines shoot architecture and is under the control of endogenous hormones and a fine-tuned gene-expression network, which probably includes small RNAs (sRNAs). Although it is well known that sRNAs act broadly in plant development, our understanding about their roles in vegetative bud outgrowth remains limited. Moreover, the expression profiles of microRNAs (miRNAs) and their targets within axillary buds are largely unknown. Here, we employed sRNA next-generation sequencing as well as computational and gene-expression analysis to identify and quantify sRNAs and their targets in vegetative axillary buds of the biofuel crop sugarcane (Saccharum spp.). Computational analysis allowed the identification of 26 conserved miRNA families and two putative novel miRNAs, as well as a number of trans-acting small interfering RNAs. sRNAs associated with transposable elements and protein-encoding genes were similarly represented in both inactive and developing bud libraries. Conversely, sequencing and quantitative reverse transcription-PCR results revealed that specific miRNAs were differentially expressed in developing buds, and some correlated negatively with the expression of their targets at specific stages of axillary bud development. For instance, the expression patterns of miR159 and its target GAMYB suggested that they may play roles in regulating abscisic acid-signalling pathways during sugarcane bud outgrowth. Our work reveals, for the first time, differences in the composition and expression profiles of diverse sRNAs and targets between inactive and developing vegetative buds that, together with the endogenous balance of specific hormones, may be important in regulating axillary bud outgrowth.

Micropropagation of Salvia guaranitica Benth. through axillary shoot proliferation

Nodal segments from greenhouse grown adult plants of Salvia guaranitica were used to evaluate the effect of culture media and growth regulators on the micropropagation and growth. The highest multiplication rate was obtained on Murashige and Skoog (MS) medium supplemented with 2.22 µM of 6-benzylaminopurine (BAP). The best condition for rooting was MS medium with 2.85 µM indole-3-acetic acid (IAA). Rooted plants were successfully acclimatized and exhibited a normal development until maturity. Using the described protocol, approximately 35 plants per explant were obtained after three months.

Segmentos nodais de plantas adultas de Salvia guaranitica cultivadas em estufa, foram utilizados para avaliar o efeito do meio de cultivo e reguladores de crescimento na micropropagação. A maior taxa de multiplicação foi obtida em meio Murashige and Skoog (MS) suplementado com 2.22 µM de 6-benzilaminopurina (BAP). A melhor condição para enraizamento foi o meio MS acrescido de 2.85 µM de ácido indol-3-acético (IAA). Plântulas enraizadas foram aclimatizadas com sucesso e exibiram desenvolvimento normal até a fase adulta. Utilizando o protocolo descrito, aproximadamente 35 plantas por explante foram obtidas após 3 meses.