Coffea arabica cultivar Ruiru 11 sibs exhibit significant variation in plant regeneration through direct somatic embryogenesis.

Abstract

This experiment evaluated the response of 11 selected recalcitrant coffee ‘Ruiru 11’ sibs to plantlet regeneration through direct somatic embryogenesis. Third leaf pair explants from field-grown mother plants were harvested, sterilized and induced for up to 12 months in half-strength Murashige and Skoog basal salts medium supplemented with 1 ml/L thidiazuron, 0.2 g/L thiamine, 0.1 g/L nicotinic acid, 0.1 g/L pyridoxine, 20 g/L sucrose, 100 mg/L myoinositol, 100 mg/L cysteine and 3 g/L gelrite. Embryos were sequentially transferred to media for shooting for 8 weeks, rooting for 6 weeks and weaning for 4 weeks. The explants were effectively sterilized using 30% sodium hypochlorite (3.85 v/v) for 20 minutes. The sibs showed significant (P<0.05) genotypic variation, with sibs 11, 41, 71 and 121 from ‘Catimor 86’and those from ‘Catimor 90, 128 and 134’ regenerating somatic embryos, whereas sibs 52 and 142 from ‘Catimor 88’ failing to do so. Sib 137 had the highest 63% embryogenic rate and 3.7 average embryos per explant. Sibs 71 and 137 embryos developed longest shoots, with 84% of sib 137 embryos developing shoots. Sibs 93 and 71 embryos developed longest roots, with 91% of sib 71 embryos developing roots. About 91% of sib 71 plantlets survived acclimatization. Sibs 137, 71 and 93 were classified as highly embryogenic, whereas sibs 52 and 142 were non-embryogenic. Sib 71 best responded to plantlet regeneration through direct somatic embryogenesis. Therefore, sib 71 plantlets should be used in future as stocks for mother plants for mass propagation of ‘Ruiru 11’.