In vitro gynogenesis has been widely used for the induction of haploids and doubled haploids in many petaloid-type genotypes of marigold. The in vitro mass multiplication and rooting of gynogenically induced shoots is still the hardest part of their production. The high percentage of mortality in gynogenically induced shoots encountered during proliferation, rooting, and hardening, often limits their wider utility in the breeding of marigold. Therefore, in the present study efforts have been made to develop an efficient protocol for in vitro shoot proliferation and rooting of gynogenically induced regenerates of African marigold. Micro-shoots of 2-3 cm in length from healthy gynogenically induced shoots of genotypes ‘DAMH-24’ and ‘DAMH-55’ were cultured on modified MS medium supplemented with different concentrations of cytokinins and auxins. The minimum days required for shoot emergence and maximum increase in fresh weight of cultured shoots were observed on modified MS medium enriched with BAP (0.5 mgl-1), the longest shoot length and the number of leaf pairs per branch were recorded on MS medium fortified with 1.0 mgl-1 BAP. The maximum increase in the number of micro-shoots from gynogenically induced shoots was recorded on MS medium supplemented with KIN (0.25 mgl-1). The earliest rooting, highest rooting percent, better root growth character, and highest number of roots per micro-shoots were recorded on the treatment comprising of ½ MS medium supplemented with NAA (0.5 mgl-1). Among both the genotypes ‘DAMH-24’ responded better than ‘DAMH-55’ during in vitro proliferation and rooting of gynogenically induced shoots. This protocol is highly useful for the development of plants for further hardening after rooting with cutinized, strengthened shoots from in vitro gynogenically developed plantlets, which will further help in development of high-yielding F1 hybrids.

Tagetes erecta L., In vitro proliferation, Rooting, Gynogenesis, Growth regulators

It can be concluded that the modified MS medium supplemented with KIN (0.25 mgl-1) resulted in the maximum increase in the number of micro-shoots from gynogenically induced shoots and thus can be successfully utilized for mass proliferation. While the ½ strength MS medium supplemented with NAA (0.5 mgl-1) can be successfully utilized for early root induction, highest rooting percent, better root growth character, and induction of highest number of roots per micro-shoots. The developed protocol can be effective for in vitro maintenance of gynogenically induced haploid. Among both the varieties ‘DAMH-24’ performs best viz. days required for shoot emergence, increase in fresh weight of cultured shoots, shoot length, number of leaf pairs per branch, days to rooting, rooting percent, root growth character and no. of roots per micro-shoots. On the other hand ‘DAMH-55’, has less efficiency towards in vitro proliferation and rooting of gynogenically induced shoots. The standardized protocols can, also be effectively utilized for improving the vigor and large-scale mass multiplication of gynogenically induced shoots.

Eram Arzoo, Reeta Bhatia, Kavita Dubey, Kanwar Pal Singh, and Sapna Panwar (2022). Standardization of Protocol for Mass Proliferation and Rooting of Gynogenically induced Regenerats in African Marigolds (Tagetes erecta L.). Biological Forum – An International Journal, 14(4a): 602-607.