Effect of the genotype, developmental stage and medium composition on the in vitro culture efficiency of immature zygotic embryos from genus Capsicum

Abstract

A new reliable in vitro technique for immature embryos of Capsicum spp. was developed. A collection of 10 accessions, encompassing the five cultivated species of Capsicum, and four media formulations, combining different levels of sucrose (40g/L vs. 80g/L) and MS salts (½×MS vs. 1×MS), were evaluated. In addition, the four main embryo stages (i.e. globular, heart, torpedo, early cotyledonary) were also considered. Thus, almost 2000 embryos were excised, cultured, and evaluated for germination in the present experiment. Genotype (G), media composition (M), and developmental stage (S) contributed significantly to culture efficiency. G×S and S×M interactions were also significant, although their contribution was lower than individual main factors. C. annuum accession Piquillo, C. frutescens B-144 and, particularly, C. pubescens B-61 showed the highest in vitro germination rates, while C. chinense and C. baccatum accessions showed, in general, the lowest responses. In most cases, the more advanced the embryo stage the higher the culture efficiency. However, for the first time in Capsicum globular embryos from most genotypes were germinated in vitro and also relatively high rates were achieved for heart embryos. Finally, the medium with the lowest levels of both sucrose (40g/L) and MS (½×MS) enabled, in most genotypes and stages of development, the highest in vitro germination rates. In fact, this medium allowed rates of up to 25% in globular embryos. These results provide useful information to those breeders interested on the applications of embryo culture in Capsicum peppers (e.g. shortening breeding cycles, perhaps rescue of interspecific embryos).