GENETICS OF SUICIDAL GERMINATION OF Striga hermonthica (Del.) Benth, BY COTTON (Gossypium hirsutum L.)

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GENETICS OF SUICIDAL GERMINATION OF Striga hermonthica (Del.) Benth, BY COTTON (Gossypium hirsutum L.)

Abstract:

The germination of “giant witchweeds” (Striga hermonthica (Del.) Benth), a noxious root parasite of many cereal crops, is stimulated by exudates from the roots of both host and non-host (“trap”) plants. Forty genotypes of cotton (Gossypium spp.), a “trap” crop, were screened in the laboratory, using the cut root technique, to investigate the variability among these genotypes for their ability to stimulate the suicidal germination of S. hermonthica and to select materials for a genetic study. The genotypes exhibited significant differences for the trait. Striga germination percentages ranged from 13.33 to 50.00% for the cotton genotypes compared with 47.33% for the sorghum variety CK60B, the susceptible control. Three cotton genotypes were selected based on their Striga seed germination stimulation and used as parents in crosses of the combination; low x high Striga germination stimulation. The F1s, F2 s and parents for these crosses, (RASA(78)11b x SAMCOT-10 and RASA(78)11b x TX-CABS-1-83) were evaluated in separate experiments. Broadsense heritability estimates for the trait from both crosses ranged from 71.8 to 78.5% indicating a high genetic influence for the trait. Gene number estimates gave values of less than 1. This was reflected by a discrete frequency distribution of the F2 populations into two classes of high and low Striga seed germination stimulation, fitting into classical phenotypic ratio of 3:1. These results tend to suggest that Striga germination stimulation by cotton (G. hirsutum L.) is a qualitative trait, and that the gene controlling this trait is monogenic and simply inherited, with high Striga germination stimulation dominant over low Striga germination stimulation. It should be possible to select and breed cotton genotypes that produce highly active germination stimulants in large amounts, while incorporating other good agronomic attributes.

GENETICS OF SUICIDAL GERMINATION OF Striga hermonthica (Del.) Benth, BY COTTON (Gossypium hirsutum L.)

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