Physiological, cellular and molecular aspects of the desiccation tolerance in Anadenanthera colubrina seeds during germination

During germination, orthodox seeds become gradually intolerant to desiccation, and for this reason, they are a good model for recalcitrance studies. In the present work, physiological, biochemical, and ultrastructural aspects of the desiccation tolerance were characterized during the germination process of Anadenanthera colubrina seeds. The seeds were imbibed during zero (control), 2, 8, 12 (no germinated seeds), and 18 hours (germinated seeds with 1 mm protruded radicle); then they were dried for 72 hours, rehydrated and evaluated for survivorship. Along the imbibition, cytometric and ultrastructural analysis were performed, besides the extraction of the heat-stable proteins. Posteriorly to imbibition and drying, the evaluation of ultrastructural damages was performed. Desiccation tolerance was fully lost after root protrusion. There was no increase in 4C DNA content after the loss of desiccation tolerance. Ultrastructural characteristics of cells from 1mm roots resembled those found in the recalcitrant seeds, in both hydrated and dehydrated states. The loss of desiccation tolerance coincided with the reduction of heat-stable proteins.

Genetic variation of Indian potato (Solanum tuberosum L.) genotypes using chromosomal and RAPD markers

Genetic diversity in thirty Indian potatoes were analyzed employing karyotype, genome size and RAPD markers. Chromosome analysis revealed 2n = 4x = 48 except cv. K. Chandramukhi (2n = 4x + 2 = 50). Total genomic chromosome length and chromosome volume varied from 21.14µm in cv. K. Pukhraj to 31.91µm in cv. MS/89-60 and 14.31µm³ in cv. MS/92-1090 to 33.16µm³ in cv. JW-160 respectively. 4C DNA content was significantly varied from 3.640 pg (~891 Mbp) in cv. MS/92-1090 to 11.12 pg (~2747 Mbp) in cv. K. Chandramukhi. RAPD revealed 131 amplified DNA fragments (300 to 2200 bp) with 79 unique bands (7 to 71% polymorphism) among the genotypes. Similarity coefficients (ranged from 0.29 to 0.93) and cluster analysis reflected the expected trends in relationships of the full and half-sib potato genotypes. Genetic distances obtained from a dendrogram could help breeders to choose the diverse parents for a breeding program aimed at varietal improvement.