Genetic Diversity of White Yam (Dioscorea rotundata Poir) Accessions Maintained in Tissue Culture and Cultivated in Field using Simple Sequence Repeat (SSR) Markers and Morphological Characterization

Dioscorea rotundata is a staple food crop for millions of people in the tropical and subtropical regions. In vitro germplasm conservation is a very useful tool in yam improvement strategies but very little is known about the genetic integrity and stability of in-vitro conserved yam plants. In this study, 42 accessions from in vitro and field populations were genotyped using 11 microsatellite markers and 23 morphological descriptors to assess variability within and between accessions. Out of the 23 morphological variables used, 13 were identified as most discriminate and were used to cluster the accessions into 4 clusters using the unweighted pair group arithmetic mean average (UPGMA). Accession maintained in field as well as in in-vitro showed high genetic similarity (R2 = 0.91, p-value: 1e-04). Out of the 42 accessions analyzed, nine accessions maintained in the field and in-vitro displayed different genetic profiles. This study provided basic information on the possible somaclonal variation of yam accessions maintained through in-vitro. Further study with advanced tools such as next-generation sequencing is required to elucidate the nature of the observed variation within clones.

MICROPROPAGAÇÃO DA CANA-DE-AÇÚCAR

Sugarcane is cultivated in almost all Brazilian agricultural regions, Brazil being the world's largest producer, which requires breeding programs to create more productive and efficient varieties adapted to each region. In sugarcane breeding programs there is a need, under certain circumstances, to multiply the selected material rapidly. In this scenario, micropropagation appears as an alternative to the conventional process of vegetative propagation through stalks. The objective of this review was to describe the scenario on micropropagation research in sugarcane, such as meristem culture, sugarcane calli, somatic embryogenesis, in vitro germplasm conservation and cryopreservation. It has been observed in the literature that there is a wide spectrum of use for the numerous and well established protocols for the in vitro manipulation of sugarcane morphogenesis. The prospect of producing new features via induction of somaclonal variation and in vitro experimentation for pest and disease tolerance has not yet been extensively explored. While benefits of minimal growth are recognized in in vitro germplasm conservation of elite sugarcane cultivars, and all positive potential of this technique and cryopreservation may still 323 Colloquium Agrariae, vol. 13, n. Especial, Jan–Jun, 2017, p. 322-338 ISSN: 1809-8215. DOI: 10.5747/ca.2017.v13.nesp.000237 be expanded. On the other hand, techniques in the mass production of superior and pathogenfree genotypes have already been integrated in many sugarcane breeding programs.

In Vitro Germplasm Conservation of Habanero Pepper (Capsicum chinense Jacq.)

To determine the effect of different nitrogen sources and osmotic regulators on minimal growth of Habanero pepper (Capsicum chinense Jacq.) germplasm for in vitro conservation, different concentrations of nitrate, sucrose, mannitol, and sorbitol were evaluated. The micropropagation system based on Santana-Buzzy et al. (2006) culture medium was modified in its nitrate concentrations: reduced to 50% and increased to 150%, and osmoregulators were added to the basal culture media: sucrose (6% and 8%), mannitol (2%, 4%, and 8%), or sorbitol (2%, 4%, and 8%). The apical meristems of germinated plants were cultivated in the different treatments for 35 weeks without subculture. Results have demonstrated that mannitol at 2% had the better effect on minimal growth of the plantlets and did not affect the plant physiology and quality. The plantlets remained small in size, turgent, with green leaves and stems and looked like normal plants until to the end of the evaluation period. Changes in nitrogen media concentration did not prove to be adequate for conserving because they affected the plantlet quality (they became chlorotic). The presence of sorbitol and high osmolite concentrations induced minimal growth but reduced the plant quality. Sucrose at mid or low concentrations did not induce minimal growth.