Volume 6, No. 3, 1981

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(pp. 1-8)
Physiological Rupture of Soybean Hypocotyls in Germination and Vigor Tests1
Kar-Ling J. Tao2
ABSTRACT:
In rolled towel germination and seedling growth rate tests, some soybean (Glycine max. (L.) Merr.) hypocotyls became swollen and frequently were found to develop transverse  and longitudinal cracks. The occurrence of ruptured seedlings was as high as 46% for a seed lot of the 'Williams' cultivar at the seventh day of germination, while only 1% rupture was observed at the third day. The number of ruptured seedlings increased from 2 to 17% with increased moisture of the paper towels. The presence of light during germination markedly reduced the percentage of ruptured seedlings.

Seeds larger than 7.14  mm in diameter were more susceptible to the hypocotyl rupture than small seeds. A decrease in the initial seed moisture from 12.1 to 6.4% caused no significant change in the percentage of ruptured seedlings. The Williams seed lots showed a higher percentage (17-46% ) of ruptured seedlings than seed lots of the varieties 'Clark 63' (5-6% ), 'Evans' (1-2% ), and 'Essex' ( 1%) soybeans. These data indicate that the moisture level of paper towels used in the germination test should be specified and that it would be reasonable to classify seedlings with physiological rupture of hypocotyls as normal seedlings.
Additional index words: Glycine max. ( L. ) Merr., cultivar, abnormal seedlings.
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(pp. 9-22)
Effect of Storage Conditions on Viability, After-Ripening adn Induction of Secondary Dormancy of Kentucky Bluegrass Seed1
Bangalore R. Phaneendranath and C. R. Funk 2
ABSTRACT:
One of the most important factors that affects germination of Kentucky bluegrass (Poa pratensis L.) seeds is the conditions under which they are stored. The objective of this study was to store seeds at various temperature/relative humidity (RH) combinations and then germinate at sub-optimal (10-20 C ), optimal (15-25 C ), and supra-optimal (20-35 C) temperature conditions and determine their effects on viability, after-ripen ing and possible induction of secondary dormancy.

Freshly harvested 'Touchdown,' 'Victa,' 'P-143,' and 'P-154' Kentucky bluegrass seeds were used in this study.
Storage at high temperature (37.8 C ) and high humidity had a very detrimental effect on the viability of seeds. Seeds stored at 37.8 C/25% RH showed less after-ripening dormancy during the first few weeks of storage than seeds at lower temperature and relative humidity combina­tions. Touchdown Kentucky bluegrass seeds stored at most of the conditions exhibited fluctuations in germination which were possibly due to induced secondary dormancy and not endogenous germination rhythms. Endogenous germination rhythms, if present would have been expressed by similar fluctuations or oscillations in germination being unaffected by storage conditions and/ or germination temperatures.
Storage at -16.7 C, 5.6 C/25% RH, room temperature, and 21 C/ 25% RH maintained seed viability at a higher level for a longer period of time. After-ripening, however, was generally faster when the total degrees in Centigrade plus relative humidity in percentage was between 40 to 70.
Freshly harvested seeds germinated well at 10-20 and 15-25 C, and not at 20-35 C showing that they had possibly not completed their after­ ripening processes. They developed this faculty only after a period of storage at favorable conditions.
Seeds stored at -16.7 C and 5.6 C/25% RH failed to germinate at 20-35 C, even after 56 weeks of storage. The reason for Kentucky bluegrass seeds not germinating at 20-35 C, was not that they were either dead or pushed into thermodormancy, but, is a case of high-temperature­ induced inhibition of germination or "imposed inactivity." This was evident by almost complete recovery of germination of these seeds when transferred to 15-25 C.
Additional index words: Poa pratensis L., endogenous germination rhythms, seed germination, imposed inactivity.
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(pp. 23-30)
Effects of Inoculation Time and Cultivar on Internal Infection of Bean Seed by Pseudomonas phaseolicola
A.W. Saettler, S. ]. Stadt, and L. T. Pontius1
ABSTRACT:
We studied internal infection of bean seed by the halo bacterial blight pathogen Pseudomonas phaseolicola.   Plants of halo blight sus­ceptible Charlevoix and tolerant Montcalm, Seafarer, and Tuscola cul­tivars were inoculated with aqueous suspensions of cells of P. phaseoli­cola R13 (a mutant resistant to 50 ppm rifampin). Pods were collected at normal maturity and internally-borne blight bacteria were isolated in liquid rifampin-containing media.

In 1978, mutant R13 was recovered from seed in 23%, and 1%, of the pods from Charlevoix and Montcalm, respectively.   In 1979, 10% (60/615) and 3% (17/593 ) of the seed contained in visibly-diseased and symptom free Charlevoix pods, respectively, were infected. Time of plant infection appeared to influence internal seed infection; pods from Charlevoix plants inoculated earlier in the growing season yielded greater numbers of infected seed (12% and 15% vs. 3% ) than those from plants inoculated later in the growing season. Presence of internally-infected seed in symptom free pods of susceptible Charlevoix and, in one instance, in seed from tolerant Montcalm suggests that testing to detect seedborne blight bacteria should be a component of programs for production of disease-free seed of all cultivars.
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(pp. 31-37)
Effect of Relative Humidity and Temperature on Germination of Seeds of Two F1 Sorghum Hybrids and their Parents During Storage
P. K. Agrawal, R. B. Patil, M . Dadlani, and Daljit Singh
ABSTRACT:
Seeds of two Sorghum bicolor (L.) Moench F1 hybrids and their parents were stored at 20, 45 and 80% relative humidity (RH) and 20 and 33 C for 432 days. Loss of viability increased with either increased RH (from 20 to 80%) or increased temperature (from 20 to 33 C).

Seeds of hybrid CSH-5 and its parents did not store as well as seeds of hybrid CSH-1 and its parents. The female parental lines (CK-60A of hybrid CSH-1 and 2077-A of hybrid CSH-5) appeared to be genetically superior to the male parental lines with respect to storability. Seed of hybrid CSH-1 retained their viability as well as did seeds of their good storing female parent CK-60A which was dominant. However, in hybrid CSH-5 the poor storing pollen (male) parent CS-3541 was dominant. Therefore, it appeared that in these two hybrids reactions lead­ing to the loss of viability may be different.
Additional index words: Viability, inheritance.
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(pp. 38-49)
Fluid Sowing of Tomato Seed-Influence of Phosphorous Additions to Five Gels1
Wallace G. Pill2
ABSTRACT:
The effect of 0, 5, 50, and 500 ppm P addition to five gels on per­centage emergence (PE) , emergence rate index (ERI), and on shoot growth and P composition after fluid-sowing pregerminated 'Marglobe' tomato seed was investigated in the greenhouse. Pregerminated seed in gels without P addition generally showed significantly greater PE, ERI, and shoot dry weights than dry-sown seed.

Although increasing gel P concentration as a main effect reduced PE and ERI and increased dry weight and P concentration and content of shoots, gels interacted sig­nificantly with P addition on all these variables. Twenty-three days after transplanting seedlings into growth medium with sufficient P, shoot dry weight was still influenced by gels and gel P concentration. Both be fore and after transplanting, gel-induced growth differential at any gel P concentration was related to factors other than shoot P concentration. With any gel following transplanting, while shoot dry weight increased linearly and shoot P content increased quadratically, both shoot growth rate and shoot P concentration decreased linearly as a log10 function of increasing gel P concentration.
Additional index words: Lycopersicon esculentum Mill., chitted seed, pregerminated seed, fluid drilling, gel additive.
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(pp. 50-58)
A Comparative Study Between Field Soil and Perlite Infested with Pythium as Media for the Corn (Zea mays L.) Cold Test1
D.M. Garzonio and A. L. Larsen2
ABSTRACT:
A modified corn (Zea mays L.) cold test was developed utilizing per­lite infested with a pathogenic isolate of Pythium sp. as a substitute for unsterilized field soil. The procedure was evaluated by correlating soil and perlite cold test results for nine hybrid seed corn lots, both treated (captan) and untreated, with field emergence results for two planting times at each of two locations.

Significant positive correlations at the 95% level or above were obtained between both cold test results and field emergence at only one of the four plantings. Percent emergence of treated seed in both cold tests and the field plantings were similar. Emergence of nontreated seed in the perlite cold test was closer to actual field performance than emergence in the recommended cold test.
Additional index words: vigor test, fungicide effects, Pythium ulti­mum Throw. var sporangiferum.
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