Means of crosses of the GEM accessions to FR1064 and LH185 generally reflected the differences between the parents in that means of crosses to LH185 were significantly lower than means of crosses to FR1064 for GLS, SCLB, NCLB, and NCLS.
For the seven tropical populations crossed to both B73 and Mo17, average disease ratings were significantly lower for crosses to Mo17 than for crosses to B73 for GLS, SCLB, NCLS, and NCLB (Table 2).
l][Mu]' values that were negative and significantly different from zero for GLS, SCLB, and rust (Table 6).
dagger]) GLS = gray leaf spot, NCLB = northern corn leaf blight, SCLB = southern corn leaf blight, NCLS = northern corn leaf spot.
t] [Mu]' GLS 41 34 1 NCLB 35 5 28 SCLB 41 13 16 NCLS 37 2 21 Rust 41 8 1 Nonsignificant net value with significant Disease([dagger]) l[[bar] p.
l][Mu]' values for NCLB, SCLB, NCLS, and GLS suggest that it should be possible to select donors that would contribute favorable alleles for more than one disease.
dagger]) NCLB = northern corn leaf blight, GLS = gray leaf spot, SCLB = southern corn leaf blight, NCLS = northern corn leaf spot.
For SCLB, approximately equal numbers of accessions had significant negative and significant positive net value estimates.
In general, germplasm with a Stiff-Stalk Synthetic background (B73 types) has less resistance to SCLB, NCLB, and NCLS than germplasm with a Lancaster background (Mo17 types).
l][Mu]', the top 10 accessions for SCLB were population x Mo17 crosses (Table 8).
150 x Mo17 L,S Pasco 14 x Mo17 L,S DK888 x B73 F,S Puerto Rico GP3 x Mo17 L,S XL380 x Mo17 S B844 x B73 F,S NCLB DK888x B73 F,S XL380 x Mo17 B Cuba 110 x Mo17 L,B Pasco14 x Mo17 L,B B830 x Mo17 L,B Antigua 3 x Mo17 L,B DK 212 x B73 F,S Brazil 051501 x Mo17 L,B XL 380 x B73 F,S Puerto Rico GP3 x Mo17 L,B SCLB DK888 x Mo17 L,S Puerto RicoGP3 x Mo17 L,S Dom.
Abbreviations: ALB, anthracnose leaf blight; ASR, anthracnose stalk rot; AUDPC, area under disease progress curve; DSR, diploidia stalk rot; ES, eye spot; GLS, gray leaf spot; GSR, Gibberella stalk rot; IAD, percentage total internode area discolored; LAB, percentage leaf area blighted; MLD, multiple leaf diseases; MSR, multiple stalk rots; NCLB, northern corn leaf blight; NCLS, northern corn leaf spot; NID, number of internodes discolored; SCLB
, southern corn leaf blight.