ABSTRACT
Pollen conservation is an important tool for the maintenance of plant genetic resources and can promote improved efficiency in breeding programs and germplasm conservation and exchange. This review aims to understand the importance of pollen cryopreservation and how to use it for distinct species in order to encourage the use of this methodology in germplasm banks and plant breeding programs. Pollen from many plant species have already been successfully cryopreserved in liquid nitrogen. Analogous with other plant structures, to maintain pollen viability after storage at ultra-low temperatures it is necessary to adjust the water content so that at least the freezable is removed. Optimum pollen moisture levels for cryopreservation varies among species and different methods have been applied to control moisture content. Common methods to decrease pollen moisture content include exposure to saturated solutions of various salts (which have a well-defined relative humidity), silica gel, dry air or treatment with vitrification solutions. It is our understanding that pollen cryopreservation is a safe and practical alternative for conserving genetic material that is often neglected by potential users. The technique has the potential to overcome challenges of breeding programs, such as flowering asynchrony between different parent genotypes, and the production of insufficient pollen in nature. Generally, pollen cryopreservation techniques tend to be simple enough to be used routinely in research, plant breeding and germplasm conservation programs.
Subject(s)
Conservation of Natural Resources/methods , Cryopreservation , Plant Breeding , Pollen , Pollen/genetics , VitrificationABSTRACT
ABSTRACT Jatropha curcas L. is a plant species with many potential applications, especially medicinal uses (hypoglycemic, anti-inflammatory, haemostatic, healing, anti-tumor). The objective of this study was to test germination in moist paper rolls for whole seeds and in vitro for excised embryonic axes, in an attempt to identify the best method to assess the quality of J. curcas seed germplasm, cryopreserved with different water contents. The experimental sample with a 6.2% moisture content (MC) was divided in subsamples which were hydrated and dehydrated for 0 (control), 4, 8, 11 and 24h. The initial germination percentages were 63% for whole seeds and 81% for excised embryonic axes. After exposure to liquid nitrogen (LN), germination percentages were 48% (whole seeds) and 57% (excised embryonic axes). There was no significant difference between germination percentages in embryonic excised from seeds subjected or not subjected to freezing, with different MC. In contrast, there was a reduction of the whole seed germination percentage when exposed to LN (contrast = 0.17, standard error = 0.04, t = 4.09, p = 0.001) and not for the hydration and dehydration treatments. The methodology based on in vitro cultures of the embryonic axis isolated from seeds stored in LN with distinct MC values was more efficient than the standard germination test to evaluate the viability of J. curcas seeds before and after LN storage.
RESUMO Jatropha curcas L., é uma espécie com várias aplicações potenciais, principalmente para usos medicinais (hipoglicemina, anti-inflamatório, homeostático, cicatrizante, antitumoral). O objetivo deste estudo foi testar a germinação em rolo de papel para sementes inteiras e in vitro para eixos embrionários excisados visando identificar o melhor método para avaliar a qualidade de germoplasma semente de J. curcas, criopreservado com diferentes teores de água. A amostra experimental com 6,2% de teor de água foi dividida em subamostras que foram hidratadas e desidratadas por 0 (controle), 4, 8, 11 e 24 h. Os percentuais de germinação inicial foram de 63% para sementes inteiras e de 81% para eixos embrionários excisados. Após exposição ao nitrogênio líquido (NL) os percentuais de germinação foram de 48% (sementes inteiras) e 57% (eixos embrionários). Não houve diferença significativa entre os percentuais de germinação de eixos embrionários excisados de sementes com diferentes umidades e submetidas ou não ao congelamento. Em contraste, houve redução de percentuais de germinação das sementes inteiras expostas ao NL (contraste = 0.17, erro padrão = 0.04, t = 4.09, p = 0.001), mas não aos tratamentos de hidratação e desidratação. A metodologia baseada em cultura de eixos embrionários in vitro isolados de sementes armazenadas em NL, com distintos teores de água foi mais eficiente que a germinação padrão para avaliar a viabilidade de sementes J. curcas antes e após a armazenamento em NL.
