High Temperature Inhibits Germination of Jalapeno and Cayenne Pepper by Levone


									                                                                                                  Pepper seed germination was
High Temperature Inhibits                                                                     improved        under     supra-optimal
Germination of Jalapeno and                                                                   conditions if the seeds were first
                                                                                              soaked in solutions of ethephon or
Cayenne Pepper                                                                                gibberellic acid (GA3) (Carter and
                                                                                              Stevens, 1998). However, priming
                                                                                              incurs additional costs and time
Anne K. Carter1                                                                               considerations. A knowledge of which
Department of Plant and Soil Sciences, University of Massachusetts, Amherst,                  cultivars can germinate under supra-
MA 01003-0910                                                                                 optimal conditions might be a more
                                                                                              acceptable approach for transplant
Charles S. Vavrina2                                                                           producers. Germination does not
University, of Florida, Southwest Florida Research and Education Center,                      necessarily     equate    with     stand
Immokalee, FL 33934                                                                           establishment, but defining whether
                                                                                              poor stand establishment is due to
Additional index words. Capsicum annuum, seed germination, stand
                                                                                              inhibition of germination or poor
establishment, thermodormancy, thermoinhibition
                                                                                              seedling growth is a logical first step.
Abstract. The germination of rive commercial cultivars of jalapeno and cayenne                The purpose of this study was to
pepper were tested to determine cultivar response of Capsicum annuum L. to                    survey the effect of temperature on the
supra-optimal temperatures. Two seedlots of 'Cayenne, Large Red Thick', 'Ole',                germination of different cultivars of
'Jalapeno M', 'Mitla', and 'Tam Veracruz' were evaluated on a thermogradient                  jalapeno      and    cayenne     pepper
table at temperatures of 20, 25, 30, 35, and 40 ºC. Percent germination and time              (Capsicum annuum L.) used commer-
to 50% of final germination (T50) were calculated. All cultivars exhibited                    cially in Florida.
thermodormancy, but the degree of inhibition varied within temperature and                        Seed sources. Five commercial
cultivar. No cultivar had >1.0% germination at 40 ºC. Generally, the T50 varied               cultivars of cayenne or jalapeno pepper
among cultivars, but not among temperatures within a cultivar (T50 at 40 ºC was               were chosen based on the ability to
not measured). Cultivar selection should be considered when growing fall                      obtain two seedlots of each cultivar.
transplants in Florida.                                                                       Seeds of 'Ole' (15759-27420 and
                                                                                              15759-34420; Ferry Morse Seed Co.,
    In the southern United States,               1997). Shade cloth and tray-top              Modesto, Calif.); 'Jalapeno M'
thousands of acres of peppers are                dressings of vermiculite or perlite to       (057-014-1168 and 057-014-1188;
planted commercially in the fall and             cool the germination medium may not          PetoSeed Co., Saticoy, Calif.); 'Mitla'
spring. Fall production accounts for             prevent      inhibited      or     erratic   (007-104-1515 and 007-104-1516;
much of the acreage of jalapeno                  germination.     Erratic      germination    PetoSeed Co.); 'TAM Veracruz'
peppers. However, seed for fall                  causes various production schedule           (057-674-1024 and 057-674-1027;
transplants is sown when summer                  complications and often reduces              PetoSeed Co.); and 'Cayenne, Large
greenhouse temperatures can reach 40             overall stand establishment.                 Red Thick' (1163 and 1169; PetoSeed
to 45 ºC for 6 h or more (Vavrina,                   The inability to germinate at higher     Co.) were used. 'Ole' and 'Mitla' are F1
1994). This is far above the optimum             than optimal temperatures is attributed      hybrids while 'Jalapeno M', 'TAM
temperature (29 ºC) for pepper                   to a condition called thermoinhibition.      Veracruz', and 'Cayenne, Large, Red
germination (Maynard and Hochmuth,               Tomato (L,ycopersicon esculentum             Thick' are open -pollinated.
                                                 Mill.) seeds do not germinate at high            Seed germination. Germination
                                                 temperatures (=35 ºC), but do                temperatures of 20, 25, 30, 35, or 40 ºC
                                                 germinate after temperature is reduced       were maintained on a one-dimensional,
Received for publication 7 Aug 2000.
                                                 to 25 ºC or 30 ºC (Abebe, 1993).             linear thermo-gadient table (Van dok
Accepted for publication 21 Nov. 2000.
Research was conducted at the Univ. of           Thermoinhibition also occurs in other        and De boer Machinefabriek b.v.,
Florida, Southwest Florida Research and          vegetable seeds, such as celery [Apium       Enkhuizen, The Netherlands). Four
Education Center, Immokalee. and was based       graveolens L. dulce (Mill) Pers.]            replicates of 25 seeds each were placed
upon work supported by the Cooperative
State Research, Extension, Education
                                                 (Biddington 1981), lettuce (Lactuca          on two layers of filter paper (W&R
Services, U.S. Dept. of Agriculture,             sativa L.) (Borthwick and Robbins,           Balston L. Genuine Whatman,
Massachusetts      Agricultural    Experiment    1928; Khan, 1980/1981), and spinach          England) in separate 9-cm-diameter
Station, under Project No. MAS00786. Use         (Spinacia oleracea L.) (Harrington,          petri dishes. The filter paper was
of trade names does not imply endorsement
                                                 1963; Leskovar et al., 1999). In lettuce,    wetted with 10 mL of distilled water.
of the products named nor criticism of similar
ones not named. The cost of publishing this      thermotolerance        differs    among      Evaporation rates at 35 ºC and 40 ºC
paper was defrayed in part by the payment of     cultivars (Damania, 1986; Gray, 1975;        required the addition of 4 mL H2O
page charges. Under postal regulations, this     Thompson, 1979); this has been               every 2 d for these two treatments. The
paper therefore must be hereby marked
                                                 attributed    to     the     degree     of   four replications of each of the 10
advertisement solely to indicate this fact.
  Extension Assistant Professor. E-mail          endo-ß-mannanase activity in the seeds       seedlots were completely randomized
address: akcarter@pssci.umass.edu                (Nascimento et al., 2000).                   within each temperature treatment. The
  Associate Professor.                                                                        entire experiment was repeated twice.
    Germination was recorded daily         seed quality resulted from differences               Effects of osmotic priming. Scientia Hort.
                                                                                                19:22 1 -227.
until the remaining seeds began to         in seed developmental age and storage
                                                                                             Biddington, N.L. 1981. Themiodormancy and
deteriorate (16 d). A seed was             conditions and that this could vary                  the prevention of desiccation injury in celery
considered germinated when the             from one seedlot to another.                         seeds. Ann. Appl. Biol. 98:558-562.
radicle had elongated =2 mm from the                                                         Borthwick, H.A. and W.W. Robbins. 1928. Let-
                                                                                                tuce seed and its germination. Hilgardia
seed coat. Total percentage of
germination and time to 50% of final                                                         Carter, A.K. and R. Stevens. 1998. Using
germination (T50) were calculated.                                                              ethephon      and      GA3      to    overcome
Statistical analysis and mean sepa-                                                             thermoinhibition in 'Jalapeno M' pepper seed.
ration were calculated using SAS                                                                HortScience33:1026-1027.
                                                                                             Damania, A.B. 1986. Inhibition of seed
statistical software (SAS Institute,                                                            germination in lettuce at high temperature.
Cary, N.C.).                                                                                    Seed Res. 14:177-184.
    Differences between the two                                                              Demir, 1. and R.H. Ellis. 1992. Development of
                                                                                                pepper seed quality. Ann. Appl. Biol.
experiments were nonsignificant, so
the data were combined in a pooled                                                           Elson, M.K., R.D. Morse, D.D. Wolf, and D.H.
analysis. Mean square errors were                                                               Vaughn. 1992. High temperature inhibition of
calculated by hand, then an F test was                                                          seed germination and seedling emergence of
                                                                                                broccoli. HortTechnology 2:417-419.
performed using the appropriate
                                                                                             Gray, D. 1975. Effects of temperature on the
degrees of freedom.                                                                             germination and emergence of lettuce
    Germination of Jalapeno M',                                                                 (Lactuca sativa) cultivars. HortScience
'Mitla', and 'TAM Veracruz' was nearly                                                          50:349-361.
100% from 20 to 30 ºC (Fig. 1A). At                                                          Harrington, J.F. 1963. The effect of temperature
                                                                                                on germination of several kinds of vegetable
35 ºC, germination of 'TAM Veracruz'                                                            seeds, p. 431-441. In: A. Lecrenier and P.
decreased to 48% while that of                                                                  Goessels (eds.). Proc. XVI Intl. Hort. Congr.
'Jalapeno M' and 'Mitla' dropped to                                                             vol. 2. Dulcot, Brussels.
                                                                                             Khan, A.A. 1980/1981. Hormonal regulation of
82%        and    72%,     respectively.
                                                                                                primary and secondary seed dormancy. Israel
Germination of 'Cayenne, Large, Red                                                             J. Bot. 29:207-224.
Thick' and 'Ole' was below 25% at 35           Temperature had little affect on the          Leskovar, D.I., V. Esensee, and H.
ºC. Germination of all cultivars was       time to 50% of final germination for                 Belefant-Miller. 1999. Pericarp, leachate, and
=1% % germination at 40 ºC. The                                                                 carbohydrate           involvement           on
                                           each of the five cultivars (Fig. 1B).                thermoinhibition of germinating spinach
critical maximum (Harrington, 1963)        Only in ‘TAM Veracruz’ did T50                       seeds. J. Amer. Soc. Hort. Sci. 124:301 -306.
for germination appeared to be             increase between 30 and 35 ºC. The                Maynard, D.N. and G.J. Hochmuth. 1997.
between 30 and 35 ºC. Germination of       T50 varied among cultivars from 4 to                 Knott's Handbook for Vegetable Growers. 4th
'Ebano' had 95% germination at 35 ºC,                                                           Ed. Wiley, New York.
                                           10 d at temperatures between 20 and               Nascimento, W.M., D.J. Cantliffe, and D.J.
but again germination dropped to 1%        35 ºC; the T50 was not calculated for 40             Huber. 2000. Thermotolerance in lettuce
at 40 ºC (data not shown). Cultivar        ºC, as germination percentages were                  seeds: Association with ethylene and
differences in germination response to     =1% for all cultivars. Differences                   endo-ß-mannanase. J. Amer. Soc. Hort. Sci.
temperature have been reported in          among seedlots of the same cultivar               Perkins-Veazie, P. and D.J. Cantliffe. 1984.
lettuce (Perkins-Veazie and Cantliffe,     were nonsignificant (data not shown).                Need for high quality seed for effective
1984; Prusinski and Khan, 1990;                Cultivar differences in final                    priming to overcome thermodormancy in
Thompson et al., 1979) and spinach         germination was most pronounced at                   lettuce. J. Amer. Soc. Hort. Sci. 109:368-372.
(Atherton and Farooque, 1983;                                                                Prusinski, J. and A.A. Khan. 1990. Relationship
                                           35 ºC. Therefore, growers should take                of ethylene production to stress alleviation in
Leskovar et al., 1999). Germination of     this into consideration when choosing                seeds of lettuce cultivars. J. Amer. Soc. Hort.
'Packman' broccoli (Brassica oleracea      cultivars for fall transplants. However,             Sci. 115:294-298.
L., Botrytis group) decreased from         no cultivar germinated well at                    Thompson, P.A., S.A. Cox, and R.H. Sanderson.
                                                                                                1979. Characterization of the germination re-
90% to 63% at 35 ºC when the               temperatures higher than 35 ºC Other                 sponses to temperature of lettuce (Lactuca sa-
germination of this cultivar was tested    methods of cooling the greenhouse,                   tiva L.) achenes. Ann. Bot. 43:319-334.
at a range between 5 and 40 ºC (Elson      such as shading or the use of white               Vavrina. C.S. 1994. Plastic tray inserts. Florida
et al., 1992).                             seed flats (Vavrina, 1994), should also              Veg. Transplant Growers News. 5:3.
    Germination differences were also      be considered.
evident between seedlots of the same
cultivar (data not shown); however,        Literature Cited
making generalizations about seedlot
differences is inappropriate when only     Abebe,     Y.    1993.    Improving     tomato
two seedlots of each cultivar were           (Lycopersicon escidentum Mill.) seed
                                             germination under high temperature by seed
tested. Since growers and seed               priming, scarification, heatshock, and light.
producers expect consistency within a        MS Thesis, Hort. Sci. Dept. Univ. of Florida,
cultivar from season to season, seedlot      Gainesville.
variation should be noted. Demir           Atherton, J.G. and A.M. Farooque. 1983. High
                                             temperature and germination in spinach. II.
(1992) showed that variation in pepper

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