Heteroploid F1 hybrids generated from Coffea canephora × C. arabica interploidy crossing

Abstract

Abstract Distant hybrids between two coffee species was considered promising for breeders to select novel genotypes highly resilient to changing global climate, despite pre- and or post-zygotic barriers. However, the different ploidy between C. arabica (2n=4x=44) and its diploid counterparts was another challenging barrier. The expected ploidy level for developed F1 hybrid was triploid. This study was aimed to identify ploidy level of F1 hybrids generated from Coffea canephora × C. arabica interploidy crossing. Ploidy determination was held using indirect methods, i.e. based on morphometric analysis of pollen and stomatal guard cells. Polar and equatorial diameter of 300 freshly collected pollen from each of six individuals of F1 hybrids were measured using ImageJ software. Stomatal frequency was measured as the number of guard cells on leaf area of 1 mm2. Pollen and stomatal guard cells of their diploid maternal and tetraploid paternal were also measured to be used as a standard for ploidy level determination. Generated datasets were immediately analysis statistically using t-Test procedure. The results shows that four of six F1 hybrid individuals had similar pollen size as well as stomatal density to diploid maternal. Meanwhile, another single individual was similar to tetraploid paternal. However, the rest of single individuals were similar to both of maternal and paternal. Based on those results, it could be inferred that there weres three different ploidy levels among F1 hybrid individuals, namely diploid, triploid, and tetraploid.