Somatic embryogenesis and plant regeneration inpurple food yam (Dioscorea alata L.)

Jocelyn  R. Gonzales,; Marilyn  M. Belarmino,

Somatic embryogenesis and plant regeneration inpurple food yam (Dioscorea alata L.)

Marilyn M. Belarmino | Jocelyn R. Gonzales

Abstract:

A study was conducted to (1) evaluate the maintainer and restorer lines of Mestizo hybrids for resistance to Philippine Xanthomonas oryzae pv. oryzae (Xoo) races; (2) incorporate bacterial blight resistance genes into these lines via marker-aided backcrossing; and (3) confirm the presence of introgressed Xa genes in the progeny of each backcross generation through phenotyping and molecular marker analysis. Mestizo hybrids, their maintainer and restorer lines, the IRBB62 donor, and check varieties were inoculated with ten Xoo races (12 isolates). Marker-aided backcrossing from the IRBB62 donor (carrying Xa4, Xa7, and Xa21) to each line was conducted to introgress the target genes. Resistance in the advanced lines was confirmed using diagnostic Xoo races and analysis of linked DNA markers. Mestizo 1, 2, and 3, along with their maintainer and restorer lines (IR68888B, IR68897B, IR34686R, IR62161R, IR60819R)—except IR58025B—were similar to IRBB4, indicating the presence of the Xa4 resistance gene. However, these lines did not contain the Xa7 and Xa21 genes. Resistance genes Xa7 and Xa21, in addition to Xa4, were successfully incorporated into BC5F2 progeny (BC5F3 seeds) of IR34686-179-1-2-1R, IR60819-34-2R, IR62161-184-3-1-3-2R, and IR6888B. These genes were also incorporated into BC4F1 progeny (BC4F2 seeds) of IR58025B and IR68897B. The presence of the resistance genes was confirmed through analysis using linked molecular markers. Lines carrying gene pyramids exhibited increased resistance to bacterial blight and a broader resistance spectrum to Xoo races. The advanced backcross progeny were phenotypically similar to their recurrent B and R parent lines.

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