R.G. Gardner and P.B. Shoemaker
A.B. Herriott, F.L. Haynes Jr. and P.B. Shoemaker
Heritability of resistance to early blight disease in potatoes (Solarium tuberosum L.) incited by Alternaria solani (En. & Martin) Ser. was estimated in tetraploid × diploid crosses. Susceptible tetraploid cultivars and breeding lines were the female parents. Diploids that produced a high proportion of first-division restitution (FDR) gametes and possessed different levels of early blight resistance were the male parents. Tubers from seedlings that resulted from the tetraploid × diploid crosses were planted in a field and artificially inoculated with spores of Alternaria solani. Resistance was measured as the slope (r) of the regression of the logit of the percent defoliation of each plant vs. time. Higher r values indicated lower resistance. Mean r values ranged from 0.123 to 0.157 for the tetraploid parents, and from 0.054 to 0.116 for the diploid parents. Mean r values for the tetraploid × diploid crosses were intermediate, ranging from 0.077 to 0.143. Narrow-sense heritability (h2) was 0.815. The partial correlation coefficient between r and mean maturity values was – 0.2086.
G.D. Hoyt, J.E. Walgenbach and P.B. Shoemaker
This experiment was designed to compare best management practices for conventional and conservation tillage systems, chemical IPM vs. organic vegetable production, and rotation effect on tomatoes. Three vegetables were grown under these management practices with sweet corn (1st year) and fall cabbage or cucumber (2nd year), and fall cabbage on half of the field plots and tomatoes on the other half. The treatments were: 1) conventional-tillage with chemical-based IPM; 2) conventional-tillage with organic-based IPM; 3) conservation-tillage with chemical-based IPM; 4) conservation-tillage with organic-based IPM; and 5) conventional-tillage with no fertilizer or pest management (control). This poster describes sweet corn, cabbage, and cucumber yields from the various treatments over two 3-year rotations. Sweet corn yields were 34% higher in treatments with chemical fertilizer and pest control than with organic methods. Ear worm damage was high (58%) in the organic treatment compared to the chemical IPM program (14%). Fall cabbage was planted after sweet corn and cucumber harvest (all treatments were reapplied). Marketable cabbage yields were in the order: conventional-tilled-organic > strip-tilled-chemical > conventional-tilled-chemical > strip-till-organic > control for both years. Percent culls (< .9 kg heads) were in reverse order of marketable heads. Cabbage insect control was similar in chemical IPM and organic management. Cucumber yields were in the order: conventional-tilled-chemical > conventional-tilled-organic = strip-till-chemical > strip-tilled-organic > control for both years. Insect damage on cucumber fruit was 51% for organic systems and 1% for chemical methods of production. No differences were seen between tillage system within the same production system (chemical vs organic).