GRAFTING AS TOOL IN BEAN INTERSPECIES BREEDING

摘要

Attempts to introgress genes from P. angustissimus into common bean either through direct backcrossing or through bridge crossing using P. acutifolius as bridging species is hindered by many genetic and physiological problems. Major hurdles include complete pollen sterility in the FI, very early embryo abortion upon backcrossing, recalcitrant rescued backcross embryos and problems in multiplication and maintenance of F_1 hybrids through stem cuttings. Screening of these wide hybrids for specific traits or for various procedures such as colchicine dipping etc. is only possible through vegetative propagation. Stem cuttings is a common method of mass multiplication. Unfortunately rooting the stem cuttings of hybrids produced between P. acutifolius (W6 15578 and PI 430219) with P. angustissimus (PI 535272) and P. acutifolius (PI 430219) with P. vulgaris has not been successful. In general stem cuttings of dry bean varieties establish in 2 weeks with 60-75% success rate.