HYBRID SEED SUCCESS OF COFFEA CANEPHORA X C. ARABICA INTERSPECIFIC HETEROPLOID CROSSING DIRECTION

Abstract

Coffea canephora × C. arabica-crossing direction has shown to have a complete post-zygotic barrier. The study sought to unravel the degree of seed failure of paternal excess interspecific hybridization of C. canephora × C. arabica. The present research was conducted at the Pakuwon Experimental Station, Indonesian Industrial and Beverage Crops Research Institute (IBCRI), from August 2019 until March 2022. The C. canephora “Sidodadi” hand pollination used freshly collected pollen from C. arabica “Mangening” and C. arabica “AGK,” as well as from C. canephora “Kriting” and C. liberica. The fruit set was observed three months after anthesis (MAP) and six MAP. Cherry fruit and seed morphometric traits were measured at harvest time, with the number of seeds with collapsed endosperm (empty seed) also recorded. The surviving healthy seeds subsequently were sown to observe germination percentage. The number of leaf pairs on developing seedlings was recorded at a 2-month interval. Results showed that paternal excess had generated larger fruit and seeds but mostly contained collapsed endosperm. Few healthy developed seeds could germinate and subsequently develop into seedlings that are more vigorous. Interestingly, the interspecific homoploid crossing of C. canephora × C. liberica also exhibited a robust post-zygotic barrier.