Segregation for Resistance to Trifluralin Toxicity in Progeny from Crosses of Susceptible Cucurbita moschata Parents

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Cucurbit Genetics Cooperative Report 4:35 (article 17) 1981

Adeoye A. Adeniji and Dermot P. Coyne
University of Nebraska, Lincoln, NE 68583

Several herbicides are reported to be selective in cucurbits when soil-incorporated (1, 2). Among these are the dinitroanilines, for example, trifluralin (treflan). A recent finding by us on the response of progeny derived from crosses of susceptible cultivars of Cucurbita moschata to trifluralin indicated physiological variation in response to this herbicide.

The three susceptible parental cultivars used in the study were two butternut squash types, ‘Ponca’ and ‘Waltham’ and a calabash type, ‘La Primera’. The parents, F1 and F2 generations of each cross, ‘Ponca’ x ‘La Primera’ and ‘Waltham’ x ‘La Primera’, were grown in separate replicated (randomized complete block) experiments in the field, Lincoln, Nebraska (1980). Trifluralin was incorporated into the soil at the rate of 1 lb. a.i./acre (1.12 kilos a.i./ha) a day prior to transplanting the squash seedlings.

‘Ponca’ and ‘Waltham’ showed high susceptibility to trifluralin injury while ‘La Primera’ was slightly less susceptible than these. The F1s of both crosses were highly susceptible. The F2 segregation for both crosses suggested that the cultivars possessed different genes for susceptibility to trifluralin toxicity since a number of transgressive segregates for high tolerance to trifluralin injury were observed.

We observed that injured plants had restricted root development and a subsequent poor vegetative growth. Most of these eventually died while a few that recovered did not fruit before frost.

The occurrence of resistant transgressive segregates indicated that there is potential in these squashes to breed for resistance to a family of herbicides, such as the dinitroanilines, and this could possibly permit the use of these herbicides for weed control to overcome some of our present control problems.

Literature Cited

  1. Lange, A., D. May, B. Fisher and F. Ashton. 1968. Weed control in cucurbits. Cal. Agr. 22: 8-9.
  2. Talbert, R. E. 1969. Evaluation of herbicides for weed control in cucurbits. Weed Sci. Soc. Amer. (Abstr.) 45.