Cytology and Taxonomic Description of Two Brachiarias (Congograss and Tannergrass)

Abstract

The chromosome number and microsporogenesis of two plant introductions, Congograss (Brachiaria ruziziensis) and Tannergrass (Brachiaria sp.), were determined to evaluate the possibility of utilizing these two grasses in a breeding program. Two techniques of pollen germination were utilized as a means to study pollen viability. Although germination on artificial media was successful, the in vivo technique provided a more reliable test of viability. Germination of pollen was examined in vivo with percent tube formation scored under both selfing and crossing. Both Tannergrass and Congograss were described taxonomically. The chromosome numbers of Congograss and Tannergrass were found to be 2n = 18 and 2n = 36 respectively. From observations made at metaphase I, meiosis appeared normal in Congograss and no laggards were observed. In Tannergrass, lagging univalents were observed which could account for the low pollen stainability obtained. The pollen germination on artificial media and the in vivo techniques undoubtedly can be applied to other genera.