An epiphytotic of blast occurred in the Iowa oat crop in 1957. The blasting was atypical in that the panicles were stratified with all of the spikelets in a section being blasted. Normally blasting occurs in the spikelets near the base of the panicle and the central axis. The environmental condition which appeared to be the most likely cause of the blasting was a cold, cloudy period between May 10 and 27. This was during early spikelet development and panicle elongation. Severity of atypical blasting was associated with earliness and lateness in the oat varieties. The highest percentage of panicles with atypical blast and the highest percentage of blast on these panicles occurred in varieties which beaded on June 13 and 14. Seeds from heads with atypical blast were from 10 to 25 per cent heavier than those from normal heads. The yield losses caused by atypical blast ranged from 7 to 15 per cent depending upon the maturity of the varieties

Browning, J. A.

Frey, K. J.

English

University of Northern Iowa

Proceedings of the Iowa Academy of ScienceVolume 66 | Annual Issue Article 161959Yield Losses from Atypical Oat Blast in CentralIowa in 1957K. J. FreyIowa State UniversityJ. A. BrowningIowa State UniversityCopyright © Copyright 1959 by the Iowa Academy of Science, Inc.Follow this and additional works at: https://scholarworks.uni.edu/piasThis Research is brought to you for free and open access by UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academyof Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu.Recommended CitationFrey, K. J. and Browning, J. A. (1959) "Yield Losses from Atypical Oat Blast in Central Iowa in 1957," Proceedings of the Iowa Academyof Science: Vol. 66: No. 1 , Article 16.Available at: https://scholarworks.uni.edu/pias/vol66/iss1/16Yield Losses from Atypical Oat Blast in Central Iowa in 19571 By K. J. FREY and J. A. BROWNING Abstract. An epiphytotic of blast occurred in the Iowa oat crop in 195 7. The blasting was atypical in that the panicles were stratified with all of the spikelets in a section being blasted. Normally blasting occurs in the spikelets near the base of the panicle and the central axis. The environmental condition which appeared to be the most likely cause of the blasting was a cold, cloudy period between May 10 and 27. This was during early spikelet development and panicle elongation. Severity of atypical blasting was associated with earliness and lateness in the oat vari-eties. The highest percentage of panicles with atypical blast and the highest percentage of blast on these panicles occurred in varieties which beaded on June 13 and 14. Seeds from heads with atypical blast were from 10 to 25 per cent heavier than those from normal heads. The yield losses caused by atypical blast ranged from 7 to 15 per cent depending upon the maturity of the varieties. Blast is a condition which affects oats to a certain extent every year. Blasting, the failure of oat spikelets to develop fully, is ex-pressed variously from small white appendages hardly recognizable as having been potential spikelets, to large, light green but empty glumes (Figure 1). Blasted spikelets typically occur at the base of the panicle and near the central axis. Spikelets in this region are the last to differentiate (Bonnett, 193 7). Sheals ( 1950) found that 85 per cent of the blasted spikelets occurred in the lower third of the panicle, while only 14 and 1 per cent occurred in the middle and upper thirds, respectively. Oat blast as described above will be re-ferred to in this paper as "normal blast." Oat blast has been reported caused by any adverse environmental condition which occurred during the critical period of spikelet dif-ferentiation and panicle elongation; e.g., reduced water, cold and cloudy weather, leaf injury, insects, or any of several diseases (Derick and Forsyth, 1935; Huskins, 1931; Johnson and Brown, 1940; Rademacher, 1933, 1936; Sheals, 1950). However, blast sel-dom can be attributed precisely to a given factor. An epiphytotic of oat blast occurred in central Iowa in 19 5 7. Two distinct types of blast were clearly represented in this epiphytotic-normal blast, as described above, and an atypical type. This atypical blast differed from the normal in that all of the spikelets on the lJournal Paper No. J-3679 from the Iowa Agricultural and Home Eco-nomics Experiment Station, Ames, Iowa. Project No. 1176. In cooperation with the Crops Research Division, A.R.S., U.S.D.A. 129 1Frey and Browning: Yield Losses from Atypical Oat Blast in Central Iowa in 1957Published by UNI ScholarWorks, 1959130 IOWA ACADEMY OF SCIENCE [Vol. 66 ....... ~' 1'' '0~-/ ~-:' - / t ,', 4 ': ,, ~--,, " I /~\'\ , I ' - - I ' " '\ ~ ~ 1 ~y \_ ' I :;_. .... , p-'•£..--.\ '.) ~f' ~w \ ,\) \ ~-' ' I '/ I ' ' r -"'"-· '\ -- r Figure I. "Normal" blast of oats. panicle, or in a section of the panicle, were blasted. The upper, mid-dle, or lower portions of a given panicle would be blasted while the remainder of the panicle appeared healthy (Figure 2). The oat crop in 1957 apparently sustained an average amount of "normal" blast plus the "atypical" blast. The condition was striking in fields of lodged grain because the culms bearing atypically blasted panicles stood erect. This paper reports the yield losses from the atypical blasting and suggests a cause for the phenomenon. ETIOLOGY Long term average daily maximum and nummum temperatures for Ames, Iowa, and daily maximum and minimum temperature readings for May, 1957, are presented in Figure 3 and Table 1. Holt (1955) has shown that in spring oats grown at Ames the period of spikelet differentiation is about 30-40 days after planting, 2Proceedings of the Iowa Academy of Science, Vol. 66 [1959], No. 1, Art. 16https://scholarworks.uni.edu/pias/vol66/iss1/161959) OAT BLAST 131 Figure 2. "Atypical" blast of oats. or about 30-40 days before heading. The oat yield nurseries were planted on April 10, 1957, and varieties with the greatest atypical blast headed on June 14 (Table 2.) . Judging from the stage of spike-let development when growth was arrested and these two dates, the factor causing the blasting probably occurred approximately between May 10 and 25. This period was characterized by abnormally cold temperatures and generally cloudy weather. For instance on May 16, 36 days after planting, the maximum temperature did not reach the normal minimum, and minimum readings were below normal for the next several days. Furthermore, the minimum temperature May 2 7 was 42° F. with clear skies which would have allowed considerable radiation to occur. The temperature of the oat plants could well have been as low as 35° F. under such conditions. These observa-tions suggest that low temperature may have caused the atypical oat blast which occurred in 1957. Rademacher (1933) and Derick and Forsyth (1935) have shown cool, cloudy weather to be a cause of blast. Cloudiness may also 3Frey and Browning: Yield Losses from Atypical Oat Blast in Central Iowa in 1957Published by UNI ScholarWorks, 1959132 IOWA ACADEMY OF SCIENCE [Vol. 66 have contributed to the atypical oat blast in 1957. Mean insolation for the 5-day period beginning May 16 was only 293 gram calories per square centimeter per day (Table 1) whereas the 27th, a clear day, had a reading of 951. Oat blast has been shown to be associated with water supply by several investigators (Derick and Forsyth, 1935; Elliott, 1922; Johnson and Brown, 1940; Rademacher, 1936). Derick and For-syth ( 193 5) and Johnson and Brown ( 1940) increased blast by withholding water during critical periods. However, moisture was Date May 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Table I Weather Datal for Ames, Iowa, May, 1957 Air Temperature2 Wind °F. Wind direction movement, Max. Min. and cloud cover2 miles/day2 80 75 67 61 68 75 79 52 75 56 59 65 63 67 63 48 66 57 56 57 76 69 68 75 74 63 70 78 82 76 78 49 55 46 32 37 38 46 57 56 46 45 51 55 54 47 41 47 45 46· 46 52 48 44 45 60 53 42 46 55 61 57 SE Clear E P. c.s NE P. C. NEC NWC SW C SW P. C. SW P. C. NE P. C. NEC SE C SE C NEC SW P. C. NEC SE C WP. C. NWP. C. NE P. C. SE C SW P. C. NWP. C. NWP. C. SE P. C. SW P. C. NWP. C. NW Clear SE P. C. SW P. C. SE P. C. NWP. C. 31 72 126 77 31 45 170 235 92 129 49 64 84 140 66 126 112 33 65 117 194 81 31 88 140 99 48 '83 81 55 20 Insolation gm. cal,/cm2/ day 631 494 685 767 690 679 380 86 245 228 73 393 166 155 499 299 284 228 853 888 850 895 396 392 952 813 666 515 620 Evapora-tion, inches2 .24 .27 .34 .25 .19 .28 .43 .45 .22 .10 .04 .04 .04 .14 .08 .04 .08 .07 .05 .13 .37 .23 .19 .34 .12 .14 .17 .27 .22 .25 .10 lKindly furnished by Dr. Robert Shaw, Professor of Agricultural Climatology, Iowa State University. 2For 24-hour period ending at 7 p.m. sp, C.=partly cloudy; C=cloudy. 4Proceedings of the Iowa Academy of Science, Vol. 66 [1959], No. 1, Art. 16https://scholarworks.uni.edu/pias/vol66/iss1/161959] OAT BLAST 133 not limiting for oats at Ames in 1957. On May 2 there were 5 inches of available moisture in the top 5 feet of soil, and on May 31 this had been increased to 8 inches, indicating a more than adequate moisture supply. The May rainfall data are given in Table 1. Drought certainly did not contribute to the atypical blast that occurred in the oat crop in central Iowa in 1957. Of the components of the environment considered, low temperature and cloudiness seem most likely to have been the factors responsible. YIELD LOSSES FROM ATYPICAL BLAST Data on losses were obtained from two replications of each of three oat yield nurseries (Uniform Red Oat test, Uniform North Central Oat test, and Iowa Elite Oat test) which included a total of 114 entries. A random sample of 50 panicles in the west row of each plot was classed as having either normal or atypical blast. Five panicles with normal blast were removed and the number of healthy and 90 80 IJ... 0 70 I.LI a:: ::> 60 I-<t 0: w Q.. ~ 50 Ll.J I-40 30 Figure 3. bZ -· ./ / I ! ·-r-· I I ! . -, / ,,/ /~ ~I /': ~ 0 -15 APRIL I v / " ~ ·~ w I-(/) <l ...J m 15 MAY ""' "' I -~I--" // ~Dt ILY I I I .. • ~. ~.~l;f .. ... ~~ ,,....,. I / ----- -\_[ ~AILY Ulf\llUllllA 0 l&J 0 <l ILi :c <t -15 JUNE 1-90 80 70 60 50 40 30 Daily maximum and minimum temperatures for long term periods (diagonal lines) and for May, 1957 (vertical lines), for Ames, Iowa. 5Frey and Browning: Yield Losses from Atypical Oat Blast in Central Iowa in 1957Published by UNI ScholarWorks, 1959134 IOWA ACADEMY OF SCIENCE [Vol. 66 blasted spikelets were counted on each. The same was done for 5 panicles with atypical blast. 1'; ext_, 5 each of normally and atypically blasted panicles were tagged to be harvested when mature. From these the weight per 100 seeds was determined. The data were used to calculate (a) the percentage blasted panicles per variety; (b) the percentage blast on panicles with normal and atypical amounts of blast; (c) the compensatory effect on the weight of seed from pan-icles with atypical blast; and ( d) the effect of the atypical blast on yield. Table 2 Percentages of Blasted Panicles and Spikelets and Yield Loss Due to Atypical Blasting in Oat Varieties Grown at Ames, Iowa in 1957 -----------------Percentage of Percentage blasted Ratio of Date of No. of panicles with spikelets per panicle seed weights Percentage heading* varieties atypical blast Normal Atypical (A/N) yield loss 8-9 10-11 12 13 14 15-16 17-21 2 21 20 21 22 20 8 0 14 17 22 24 19 19 10 12 12 16 15 18 62 63 68 72 69 62 1.17 1.20 1.25 1.16 1.18 1.09 *Date in June when 50 per cent of heads were completely emrrged. 7 .2 9.3 11.5 14.6 11.2 8.7 The yield losses from atypical blasting in oats and other supple-mentary data according to heading dates are given in Table 2. The groupings of heading dates were selected to give approximately 20 varieties per group. This number was obtained except in the earliest and latest groups. The average percentage of panicles with atypical blast was zero for the earliest group. It increased steadily from 14 per cent for varieties heading on June 10 and 11 up to 24 per cent for those heading on June 14. The percentage dropped to 19 for varieties heading on June 15 and later. The mean percentage blasted spikelets on the normal panicles in-creased from 10 per cent for the varieties heading on June 10 and 11 to 18 percent for the latest group, whereas on panicles with atypical blast the percentage of blasted spikelets was highest for varieties heading on June 14. To determine whether the atypical blasting was associated with panicle size, correlation coefficients between percentage blast and number of spikelets per panicle were calculated (Table 3). All but one were negative, but none was significant. Derick and Forsyth ( 1935) found no correlation between percentage blast and total spikelet number, but Derick and Hamilton ( 1939) reported a sig-nificant negative correlation between the number of spikelets and percentage blast in the variety, Eagle. 6Proceedings of the Iowa Academy of Science, Vol. 66 [1959], No. 1, Art. 16https://scholarworks.uni.edu/pias/vol66/iss1/161959] OAT BLAST 135 Table 3 Correlation Coefficients Between Percentage of Blasting and Number of Spikelets Per Panicle Date of No spikelets Correlation heading per panicle coefficient 10-11 23 0.11 12 24 -0.27 13 27 -0.36 14 31 -0.29 15-16 31 -0.13 The ratio of weights of 100 seeds from atypically blasted panicles over the weight of l 00 seeds from normal panicles ranged from 1.09 to 1.2 5 (Table 2), indicating that where fewer seeds were produced they were heavier. This is in contrast to the results of Derick and Hamilton ( 1939), who found no increase in the weight of seeds on blasted heads. They concluded that whatever caused blast also adversely affected the remaining, fertile spikelets. The following formula was used to calculate the percentage of yield loss from atypical blasting of oats in 1957: The first two terms inside the brackets supply the correction factor for the normal amount of blasting on the panicles with atypical blast, and the ratio of seed weights corrects for the larger seed size on atypically blasted panicles. The calculated yield losses ranged from 7.2 per cent for varieties heading on June 10 and 11 to 14.6 per cent for those heading on June 14. Most of the Iowa oat acreage in 1957 was planted to varieties that headed between June 10 and 14. The mean percentage loss in yield from atypical blast for these dates was approximately 10 per cent. Since atypical blast occurred in only about one-third of the state, the loss in oat production for Iowa from this cause was estimated at 3.0 to 3.5 per cent. Literature Cited Bonnett, 0. T. 1937. The development of the oat panicle. Jour. Agr. Res. 54: 927-931. Derick, R. A. and J. L. Forsyth. 1935. A study of the causes of blast in oats. Sci. Agr. 15: '814-824. Derick, R. A. and D. G. Hamilton. 1939. Further studies on oat blast. Sci. Agr. 20: 157-165. 7Frey and Browning: Yield Losses from Atypical Oat Blast in Central Iowa in 1957Published by UNI ScholarWorks, 1959136 IOWA ACADEMY OF SCIENCE [Vol. 66 Elliott, Charlotte. 1922. Sterility of oats. U.S.D.A. Tech. Paper, Bui. 1058: 1-8. Holt, I. V. 1955. Cytohistological responses of varieties of Avena to 2,4-D. Iowa State Col. Jour. Sci. 29: 581-629. Huskins, C. L. 1931. Blindness or blast of oats. Sci. Agr. 12: 191-199. Johnson, T. and A. M. Brown. 1940. Studies on oat blast. Sci. Agr. 20: 532-550. Rademacher, B. 1933. Weitere Untersuchungen uber die Ursachen der Flissig-keit beim Hafer und deren Abhangigkeit von der Herkunft des Saatgutes. Arb. a-d Biol. Reichsanstalt Fur Land-und Forstwirtschaft 20: 587-602. Rademacher, B. 1936. Flissigkeit, Blassenfuss Schoden and Fritfliegenbefall an Hafarispen. Franke Pfanze 13: 129. Sheals, J. G. 1950. Observations on blindness in oats. Ann. Appl. Biol. 3 7: 397-406. DEPARTMENTS OF AGRONOMY AND OF BOTANY AND PLANT PATHOLOGY low A STATE UNIVERSITY AMES, IOWA 8Proceedings of the Iowa Academy of Science, Vol. 66 [1959], No. 1, Art. 16https://scholarworks.uni.edu/pias/vol66/iss1/16

Yield Losses from Atypical Oat Blast in Central Iowa in 1957

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Yield Losses from Atypical Oat Blast in Central Iowa in 1957

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