First report on genome size and ploidy determination of five indigenous coffee species using flow cytometry and stomatal analysis

Abstract

The nuclear 2C DNA content and ploidy level determination of five indigenous coffee species from India was carried out using flow cytometry and by assessing the stomatal characteristics. The nuclear DNA content (2C/pg) analyzed varied from 1.29 pg in Coffea wightiana Wall. ex Wight & Arn. to 1.48 pg in Coffea jenkinsii Hook.f. Based on the genome size, all five species were divided into two groups. The first group comprises Coffea travancorensis Wight & Arn and C. wightiana with lower genome size (2C DNA 1.29–1.30 pg), and the second group consists of Coffea bengalensis Roxb.ex Schult, Coffea khasiana (Korth.) Hook.f and C. jenkinsii with larger genome size (2C DNA 1.45–1.48 pg). The species included in the first group were inhabited in dry environmental conditions in contrast to the species included in the second group which was predominantly from mesic habitat. Among the stomatal characteristics, no significant variation in stomatal density was observed among the species, although stomatal guard cell length and stomatal chloroplast number recorded significant variation among some species. Based on flow cytometry and stomatal characteristics, all five endangered coffee species analyzed in the study were identified as diploids. The study revealed that stomatal guard cell length and stomatal chloroplast number could be fast, inexpensive, and reliable methods for determining the ploidy status of indigenous coffee species.