Date of Award

1983

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Sugarcane seedlings, Saccharum (interspecific hybrids) from a susceptible by susceptible (S x S) cross, a moderately susceptible by susceptible (MS x S) cross, a susceptible by moderately susceptible (S x MS) cross, and a susceptible by resistant (S x R) cross were categorized with regard to mosaic resistance after inoculation with strains H and I of Sugar Cane Mosaic Virus (SCMV). No particular relationship was observed among the four crosses on the basis of seedling reactions to SCMV. All seedlings were planted in the field. All susceptible and resistant seedlings were further classified respectively as highly susceptible (HS), moderately susceptible (MS), or recovered (RC); and field resistant (FR) or field susceptible (FS). All selected clones were treated with hot-water at 57.3(DEGREES)C for 5, 20, 20 minutes in three sequential dates and single bud pieces were planted in the greenhouse. Across all crosses 85% of the susceptible and 95% of the field susceptible shoots were completely cured of mosaic. Mosaic free stubble and plant shoots were spray inoculated after five months. In every cross the percentage of infected clones in the susceptible group was higher than in the resistant group. There were significant differences among the HS, MS, RC clonal types and the S, R, FS clonal types after stubble shoot inoculations. The over all r value was .61 with regard to plant and stubble shoot comparisons. This indicates that stubble shoots can be inoculated for an estimate of mosaic reaction. Recovered seedlings were reinfected by stubble shoot inoculation. On the whole 17% of the susceptible clones and 28% of the resistant clones remained mosaic free after stubble shoot inoculation. Further research is needed to determine the actual mosaic reaction of the escaped clones of the susceptible group. If escaped clones are found susceptible during subsequent inoculations then one can introduce the sugarcane seedling screening in the greenhouse without fear of loosing good materials. This screening procedure will help to increase the frequency of mosaic resistant progenies as well as to save in effort, expense, and greenhouse and field space in the breeding program.

Pages

69

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