Abstract
The objective of the present study was to develop an effective protocol for optimum callus induction, duration of culture and size of explants of primordial panicle of inter-genomic hybrid of Oryza sativa/ Oryza brachyantha. It was observed that, primordial panicle at very young stage (0.5 to 1.5 cm) takes hardly 5 to 7 days for callus initiation. The two basic media tested, the Murashige and Skoog (MS) medium and Chu’s N6 medium supplemented with 2-4-D, NAA and kinetin (2 mg L-1 2 mg L-1 and 1 mg L-1) was better for callus growth and proliferation. In this medium, callus was sub-cultured continuously for 12 passages (12 months) without loss of totipotency. Plantlet regeneration in MS medium was examined using two cytokinins (KIN and BA) along with one auxin NAA at various concentrations and combinations. Tests indicated that, good plant regeneration could be best effected without BA, but with 1.5 to 2.0 mg L-1 of KIN at fixed level of NAA (at 0.5 mg L-1). Key words: Somaclonal, callus, subculture, wide cross, MS medium, N6 medium.
Highlights
Improvement in plant breeding techniques in present century have resulted in increased yields and solved many problems associated with disease, insects, harvest, and quality
Peak callusing period was delayed and proportion of embryogenic calli obtained was low in N6 medium when compared to Murashige and Skoog (MS) medium (Figures 1 and 2)
When the level of KIN was increased to 1.0 mg L-1 and 2, 4-D being tested under similar concentrations as earlier, it was observed that, 100% callusing was obtained in the MS medium (Figure 2) containing 2.0 mg I-1 of 2,4-D, while at the same concentrations, the response in N6 medium was comparatively low (74%)
Summary
Improvement in plant breeding techniques in present century have resulted in increased yields and solved many problems associated with disease, insects, harvest, and quality. The plant breeders have, historically, utilized the variability in land races for selection and improvement of crops. As modern varieties are planted on much of the cultivated acreage and as human population centres expand, many land races that were developed by our ancestors, are no longer grown and the associated wild species which coexisted with land races in their natural habitat are becoming extinct. The variability and germplasm resources available for many cultivated varieties are becoming extremely limited (Harlan, 1976). As additional genetic resources are required to enrich the germplasm, unique and imaginative procedures are required to exploit fully the potential of our crop plants. Utilization of wild species, is one method designed to introduce additional germplasm into cultivated varieties (Stalker, 1980). The reason for leaving the wild species until last decade is well enough known as listed by (Harlan, 1976) who stated that:
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