484 
In 1951, four isolates were tested for 
ability to produce rot on corms of 68 va- 
rieties. Results are shown in table 14. lso- 
late 50-27 was a vascular isolate; the 
others were brown rot isolates. All four 
isolates caused rot on all varieties used in 
this test, but the severity of rot varied with 
isolates as well as with varieties. The av- 
erage indexes in table 14+ can be consid- 
ered indicative of the relative susceptibil- 
ity of the different varieties to Fusarium 
rot. Since the test was conducted under 
conditions that favored development of 
rot, varieties with an average index of 0 
to 50 can be considered resistant and va- 
rieties with an index greater than 50 can 
be considered susceptible. 
In 1952, all 40 isolates were tested on 
seven gladiolus varieties. The indexes of 
rot severity obtained in this test are shown 
in table 15. The isolates varied greatly in 
their ability to produce rot on corms of 
different varieties. Seven of the isolates 
failed to produce rot on any of the seven 
varieties tested. Only basal dry rot iso- 
lates 47-2 and 47-3 produced rot on all 
ILtrnoris NaturaAL History Survey BULLETIN 
Vol. 26, Art. 6 
seven varieties. The average rot severity 
index for the 7 basal dry rot isolates 
was 26.5, for the 16 brown rot isolates it 
was 17.8, and for the 17 vascular isolates 
it was 6.7. Apparently vascular isolates 
are less capable of causing corm rot than 
are the brown rot and basal dry rot iso- 
lates. These results are in general agree- 
ment with those of McCulloch (1944), 
who found that the vascular isolates with 
which she worked caused only mild rot on 
corms inoculated in the laboratory, while 
isolates from corms having the disease type 
described by Massey (1926) caused severe 
rot. 
In this test the average severity in- 
dex for rot on the variety Picardy was 
59.4 while on Maid of Orleans and Rosa 
Van Lima it was only 2.5. The differ- 
ence in susceptibility indicated by these 
figures agrees well with what is observed 
in commercial stocks of these varieties. Fu- 
sarium rot is very rare in stocks of Maid 
of Orleans and Rosa Van Lima but it is 
extremely common in stocks of Picardy. 
Six of the varieties used in the 1951 
Table 16.—Severity indexes for the rots produced in 2 successive years by four isolates 
of Fusarium on six gladiolus varieties.* 
ISOLATE 
VARIETY AND YEAR 
49-8 49-17 50-22 50-27 
Ethel Cave Cole 
PST ee Se Nine Ah heh ed Somme 50.0 75.0 100.0 87.5 
(12 aEay BRS MRE aR AMR eee pee: ot Rei Ve PS 25.0 100.0 0.0 
Miss Bloomington 
TOS hae cater eisk ten Sc eae eee eee 50.0 50.0 50.0 50.0 
TOSI eres 35 Salem Sark Ceake tyne © cithe Bees 3735 62.5 0.0 
Picardyt 
12/59 (Pa Be Ve 2 See eS eel as Wl tA? 5.0 100.0 100.0 100.0 
if? OLS Daan Dok Spe Nr Ser uae val a ED KE Page tee 87.5 100.0 100.0 75.0 
Rosa Van Lima 
(15 ERS ok PS RIS Riese RR ER OON Weet 2530 75.0 62.5 37.5 
152 oi ene oe gare Ee 0.0 0.0 0.0 0.0 
Snow Princess 
DS oe eed er aa as ee nt tee 0.0 62.5 100.0 SS 
PS a ove Ninety Petre anes Ook Ar ata eee 0.0 See 100.0 0.0 
Spirit of St. Louis 
CIN LE eae Pee A OER ANE Pater, MEARNS Ae 87.5 1205 1355 IPE, 
je I Sie) mck Se gree Ne ae SSM Cs BAe Rpt SR 75.0 0.0 ES 0.0 
*The indexes used in this table are taken from tables 14 and 15. 
+In 1951, Silver Wings, a sport of Picardy, was used instead of Picardy. 
