Morphological and cytological characters for defining Stevia ‘Honeyleaf’ tetraploids

Abstract

Purpose. Determination of peculiarities of anatomical and morphological characters of stevia plants to accelerate the identification of tetraploid forms. Methods. Field, laboratory and analysis-of-variance methods. Results. It was established that larger leaf area index (19–38%), fewer stomata per unit area (by 39–48%), larger diameter of pollen grains (by 42–92%) is a characteristic feature of anatomical and morphological characters of stevia tetraploid forms as compared to diploid ones. Conclusions. The parameters of leaf plate, the size of stomata and diameter of pollen grains are auxiliary selection criteria (rapid test). For tetraploid forms of stevia, leaf area index (the ratio of leaf blade length to width), size of stomata and diameter of pollen grains is truly larger as compared to diploid forms. Chromosomes number determination based on cytological analysis is the major and the most accurate criterion for selection of tetraploid forms, that seems advisable to use it at later stages of selection.

Keywords

• stevia
• polyploids
• tetraploids
• hexaploids
• leaf area index
• chromosomes