DIRECT AND INDIRECT EFFECTS OF FULL-SIB RECURRENT SELECTION FOR RESISTANCE TO COMMON RUST (PUCCINIA-SORGHI SCHW.) IN 3 SWEET CORN POPULATIONS

Common rust (Puccinia sorghi Schw.) is a major pathogen of sweet corn (Zea mays L.). Recurrent selection may be useful for improving resista nce to common rust. The objectives of this study were to (i) evaluate three sweet corn populations (Minn11, Minn14, NECDR) after three cycle s of full-sib recurrent selection for resistance to common rust evalua ted 40 d after pollination (DAP), (ii) determine if selection increase d resistance 21 DAP, and (iii) determine if selection affected agronom ic traits related to plant architecture, maturity, and yield. Cycles 0 to 3 from each population were evaluated under artificial rust infest ation in 1989, 1990, 1993, 1994, and 1995, and without infestation in 1994 and 1995. Percent leaf area infected declined linearly from 37.0 to 8.2% in Minn11 (R-2 = 0.98) and 57.0 to 9.9% in NECDR (R-2 = 0.98) evaluated 40 DAP, and from 22.5 to 7.8% in Minn11 (R-2 = 0.89) and fro m 22.8 to 10.0% in NECDR (R-2 = 0.91) evaluated 21 DAP. Population Min n14 tended to have decreased percent leaf area infected over cycles, b ut the response was not significant because of cycle x year interactio ns in each experiment. Most agronomic traits decreased linearly over c ycles except for ear weight/stover weight ratio in Minn11 and NECDR, a nd silk delay in Minn14, which increased linearly. In general, plants tended to be more compact and newer earlier over cycles. Selection for plant type, ear weight, and flowering time should accompany selection for resistance to common rust.