CHLOROPLAST NUMBER IN GUARD-CELLS AS PLOIDY INDICATOR OF IN VITRO-GROWN ANDROGENIC PEPPER PLANTLETS

The number of chloroplasts per guard cell pair and the stomatal length of seventeen anther-derived plants obtained from three pepper donor g enotypes were recorded. The haploid plants showed significantly fewer chloroplasts and shorter stomatal length than the diploid plants. Alth ough both characters were positively correlated with the ploidy level, chloroplast number resulted a more reliable method compared to stomat al length to distinguish haploid from diploid in vitro-grown plantlets . The stomatal length values showed either significant variation among androgenic plants with the same ploidy or overlapping values between haploid and diploid individuals. On the contrary, the values for chlor oplast number were more stable permitting discrimination of haploid fr om diploid plantlets regardless of their genetic background. Early plo idy estimation based on chloroplast counts of in vitro-grown plantlets may hasten pepper breeding programs utilizing anther-derived doubled haploids.