Improvement in the haploid technique routinely used for breeding sweet and spice peppers in Hungary

Abstract

Large numbers of genetically stable, homozygous plants are needed for classical and molecular breeding programmes. In vitro anther culture has proved to be a useful tool for haploid/doubled haploid (DH) induction in pepper (Capsicum annuum L.) for more than twenty years. The present paper reports on a great improvement in the in vitro haploid induction and genome duplication methods routinely used for resistance breeding in sweet and spice peppers by two Hungarian research institutions, the Agricultural Biotechnology Center in Gödöllő and the Budapest Research Unit of the Vegetable Crops Research Institute. As a result of the colchicine-stimulated early genome induction method, the critically low (<0.1%) regeneration frequency of spice pepper types became ten times greater, reaching a value of around 1.0%, though this was still considerably lower than that achieved in pepper varieties for fresh consumption (5-10%). Moreover, the ratio of useful doubled haploids was far higher (H:DH = 1:2 or 1:4) in some cases after colchicine treatment than that of untreated control plants (H:DH = 2:1 or 3:1, depending on the genotype). An efficient method with good reproducibility, requiring less manual work, was elaborated for the in vitro genome duplication of pepper haploid regenerants using colchicine. When the haploid induction ability of plants conventionally cultured in the greenhouse was compared to that of plants raised under artificial conditions in phytotron chambers (satisfactory day and night temperatures, illumination, humidity), the responsiveness of the latter microspores (ratio of plant regeneration) was found to be almost twice as high. The application of 3% maltose for six days at 35°C resulted in a 1.45% increase in the ratio of responding anthers and a 0.34% increase in plant regeneration, averaged over all the variety types. Phenosafranin staining was used for the analysis of microspore viability. The reduction in viability during the induction period proved to be less pronounced in lines with better androgenetic responses than in those with poorer responsiveness.