Inheritance of Resistance to Sclerotinia minor in Selected Spanish Peanut Crosses1

Abstract

Abstract TxAG-5, a sclerotinia resistant Spanish germplasm line released jointly by the Texas Agricultural Experiment Station, USDA, and the Oklahoma Agricultural Experiment Station, was crossed in reciprocal to two Spanish lines, Tx851856 and Sn73–30. Parent, F1, F2, BC1F1, and F3 populations were evaluated under high natural inoculum for resistance to Sclerotinia minor using a disease rating scale of 1 (no disease) to 5 (severely diseased), and the number of days from first appearance of the fungus until plant death was recorded. F2:3 families were compared for disease the following year for genotypic assessment of the F2 parents. F1 generation plants of the Sn73–30 cross were susceptible, but F1 plants from Tx851856 were intermediate. Some TxAG-5 succumbed to the disease. F2 distributions were continuous. F2 genotypic frequency distributions based on F3 and BC1F3 families were near continuous. Broadsense heritability estimates for disease ratings for TxAG5/Tx851856 and TxAG-5/Sn73–30 were 14 and 23%, respectively. Narrowsense heritabilities based on parent offspring regression of F3 families on F2 plants were 11% for Tx851856/TxAG-5 and 1% for Sn73–30/TxAG-5. Selection for resistance among the F2 plants to increase the frequency of resistant F3 families would have been ineffective.