CLARK 63, HAROSOY 63, HAWKEYE 63 AND LINDARIN 63 SOYBEANS
Research Progress Report 44 January 1963
A. H. Probst, Kirk Athow and F. L. Laviolette, Departments of Agronomy and Botany and Plant Pathology; and the U. S. Department of Agriculture
Phytophthora root rot is the most destructive soybean disease in Indiana. The disease causes an estimated annual yield loss of 4 to 6 percent in Indiana and a monetary loss of $8 to $10 million. On some farms and in some areas of the state these losses are as high as 25 to 50%. The disease, caused by a soil fungus, is found throughout Indiana. Phytophthora root rot may cause pre-emergence seedling-decay, stunting, or killing throughout the active plant growth period. Stand and yield losses vary among years depending upon environmental conditions.
Through cooperative work by the Agricultural Experiment Stations of the North Central Region and the U. S, Regional Soybean Laboratory, Crops Research Division, Agricultural Research Service, USDA, Phytophthora root-rot resistant soybean varieties Lindarin 63, Harosoy 63, Hawk-eye 63, and Phytophthora and bacterial-
pustule resistant Clark 63 have been developed by backcross breeding. The retention of the names Lindarin, Harosoy, Hawkeye, and Clark with the 63 added indicate the similarity to the original variety but with disease resistance added to the 1963 release.
Data in Tables 1, 2 and 3 show comparisons of the resistant and susceptible varieties when tested under conditions where there were no visible Phytophthora effects, except as noted. Effect on yield of moderate Phytophthora infection is shown for Greenfield in Table 3. Effect on yield of severe infection is shownfor Stockwell in Tables 1 and 3.
These new varieties are recommended to replace the old varieties from which they were derived. Harosoy 63 has ranked highest in yield at most locations, Lindarin 63 second, and Hawkeye 63 lowest. This is the same order the parent varieties have ranked in Indiana tests over a period of years.
Table 1. Comparison of Clark and Clark 63 soybeans at Evansville, Stockwell and Worthington, Indiana, and Edgewood and Eldorado, Illinois, in 1961 and 1962.
No. of	Average for four locations					Average yield, bu./A., and years				
tests Acre	Matur.	Lodg-	Ht. Seeds	% pro-	%	Worth-	Evans	- Stock'	- Edge-	Eldo-
and yield	diff.	ing a/	in. /lb.	tein	oil	ington	ville	well b/ wood		raao
variety						1961-62	1961	1962	1961-	62
No. tests 7	7	7	7 3	7	7	2	1	1	2	2
VARIETY										51.3
Clark 45.6	0	2.6	45 2700	42.0	20.8	42.4	49.9	24.1	41.0	
Clark 63 45.5	0	2.6	45 2900	41.5	21.1	42.1	52.4	44.4	42.6	48.4
a/ Score (1 is erect; 5 is lodged flat).
b/ Severe Phytophthora infection. Not included in the average.
PURDUE UNIVERSITY • Agricultural Experiment Station • Lafayette, Indiana