Resistance to papaya fruit freckles among three breeding lines and their hybrids

Y.K. Chan and W.K. Toh

Abstract

Three backcross lines viz. . Line 7. Line 19 and line 20 in the B₂F₄ generation  and their three possible hybrids were evaluated for fruit freckle resistance at MARDI. Serdang. Data on the number of freckles/cm² . diameter of freckle and disease severity were measured over two seasons: February l985 ( wet period) and May 1985( dry_period). Fruits harvested during the wet season showed higher severity. not in terms of number of freckles but in freckles size. The six genotypes were found to be significantly different in expression of symptoms but significant genotype x season interaction complicated the selection of resistant lines or crosses . Examining the performance of the lines by each season. it was found that Line 20was consistently more susceptible than Line 7 or Line 19.Line 19 wast he most resistant. Line 19 x Line 20 crosses showed marked improvement ranting from 27% to 68% reduction of symptoms compared with the susceptible Line 20.

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