Ex-situ Performance Evaluation of Coffee (Coffea arabica) Seedlings under Different Management Conditions: II. Root Growth Characteristics of Accessions

Abstract

Root characteristics of coffee seedlings were studied with the main objective to compare the variations among twelve Coffea arabica germplasm accessions under contrasting nursery environments at Jimma Research Center, southwest Ethiopia. Coffee seedlings from four wild coffee populations,   namely, Harenna, Bonga, Berhane-Kontir and Yayu were ex-situ established under common nursery settings. The treatments included coffee germplasm  accessions, shadings (moderate shade and full sunlight) and irrigation levels (well-watered and water-stressed). One-year-old coffee seedlings were used  to record root growth traits from five central seedlings per plot and the data were analyzed using SAS software. Coffee accessions significantly differed in  most root characteristics. The longest and shortest lateral roots were obtained from Yayu and Harenna seedlings, respectively. Berhane-Kontir accessions  had significantly the lowest root volume as opposed to the highest value for the Harenna seedlings. Significantly higher root dry biomass was  obtained from unshaded than from shaded seedlings. The difference between watering regimes was also significant for root dry biomass and it was  higher for water-stressed than for well-irrigated seedlings. Coffee accessions were significantly differed in root proliferation and dry biomass and  consequently, the lowest and highest average values were obtained from Berhane-Kontir and Harenna seedlings, respectively. The Harenna seedlings  had a higher root mass than the others, particularly the Berhane-Kontir accessions. The ratios of root to shoot dry biomass of the seedlings were  significantly differed among coffee accessions, but not between shade and irrigation levels. The significantly lowest and highest root to shoot values was  determined for the Berhane-Kontir and Harenna accessions, respectively. Hence, Harenna genotypes can be considered as parents in coffee  improvement programs under limiting water conditions.