Cultivar and storage effects on germination and hard seed content of alfalfa

Abstract

storage effects on germination and hard seed content of alfalfa. Can. J. Plant Sci. 79: [201][202][203][204][205][206][207][208]. The impermeable coat of alfalfa (Medicago sativa L.) seed can reduce germination to an extent unacceptable for commercial use. The usual method of increasing germination of lots with high proportion of impermeable or hard seeds, mechanical scarification, can damage seeds. Experiments were conducted to determine the effect of cultivar, year of production and storage conditions on germination and hard seed content in alfalfa. Experiments with four Canadian cultivars indicated a significant effect of cultivar on seed weight, germination and hard seed content in freshly harvested seed. Year of production had a greater influence on these seed traits than cultivar. Under uncontrolled storage conditions, germination of 35 alfalfa synthetics increased and hard seed content decreased with time, although not at the same rate for all synthetics. Storage at 20°C for up to 64 mo did not significantly decrease hard seed content. At 35°C, hard seed content decreased continuously for all cultivars (for one cultivar to <5%) after 64 mo. Over 80.5 mo storage at room temperature (22 ± 2°C), germination increased in a nonlinear fashion. Storing seed in sealed plastic bags at 35°C delayed seed dehydration and the loss of hard seeds. Levels of nonviable seed were low (<10%), even after storage at 35°C for 64 mo. Brief (1 min) exposure to liquid nitrogen increased germination of freshly harvested alfalfa seed to >90%. The results indicate that the germination percent of alfalfa can be increased and hard seed content reduced by short exposure to liquid nitrogen or storage at nonlethal high temperatures (35°C) such that mechanical scarification may be unnecessary. Key words:Medicago sativa, hard seed, stored seed, seed dehydration, high temperature treatment, liquid nitrogen treatment Acharya, S. N., Stout, D. G., Brooke, B. et Thompson, D. 1999. Effets du cultivar et des conditions de conservation sur le contenu en semence dure chez la luzerne. Can. J. Plant Sci. 79: 201-208. Le tégument imperméable qui enveloppe la graine de la luzerne (Medicago sativa L.) peut en réduire le pouvoir germinatif au point de la rendre inacceptable pour le commerce. La srarification mécanique, la méthode ordinaire d'accroître la germinabilité de lots à forte proportion de semences dures ou imperméables, risque d'endommager les graines. Nous avons réalisé des expériences pour déterminer l'effet du cultivar, de l'année de production et des conditions de stockage sur le pouvoir germinatif et sur la proportion de graines dures. Les essais effectués sur quatre cultivars canadiens ont mis en évidence un effet cultivar significatif sur le poids des graines, sur le pouvoir germinatif et sur la proportion de graines dures dans des lots de graines frais récoltées. L'année de production avait un effet plus prononcé sur ces caractères que le cultivar. En conditions de conservation non contrôlées, le pouvoir germinatif des graines de 35 var...

The History of Domestication and Selection of Lucerne: A New Perspective From the Genetic Diversity for Seed Germination in Response to Temperature and Scarification

“…The early farmers have probably selected plants that do not require scarification, by sampling the first emerged seedlings after sowing, and modern breeders proceed similarly. However, in our study as in others ( Acharya et al, 1999 ; Palfi, 2007 ; Kandil et al, 2012 ), the germination of cultivated varieties was enhanced by scarification, which means that the loss of the hardseededness trait is not yet completed. Either the genetics of lucerne (autotetraploidy and allogamy) make the removal of this trait from the breeding populations difficult, or the hardseededness is under a quantitative genetic control that implies many genes ( Finkelstein et al, 2008 ).…”

“…As many other annual and perennial legumes, in particular of the Papilionoideae subfamily ( Baskin and Baskin, 2014 ; Acosta et al, 2020 ), it has been well documented that physical dormancy due to hardseededness is present in lucerne to various degrees ( Acharya et al, 1999 ). Hardseededness is characterised by a water-impermeable seed coat that ensures a maintenance of the population in the soil and prevents its germination up to several years ( Baskin and Baskin, 2004 ; Finch-Savage and Leubner-Metzger, 2006 ).…”

Contribution of Alfalfa Hard Seed to Stand and Yield in the Field

“…All seed lots declined in hard seed from after cleaning in the fall to before spring seeding, averaging 8.4, 15.8, and 30.6% hard seed for the low, medium, and high levels, respectively, in the spring. The decline in hard seed with time has previously been reported (1). The amount of hard seed decline from fall to spring increased as the level of hard seed in the fall increased.…”

A Novel Method to Overcome Coat-Imposed Seed Dormancy in Lupinus albus L. and Trifolium pratense L.

“…The importance of the mechanical scarifying technique, however, lies not just in the possibility that it improves the germinability of seed, but also in how much it can accelerate the process and how practically it can be applied. In addition, mechanical scarification may damage other parts of the seed, including the embryo, and may reduce seed viability due to the pathogenic and saprophytic organisms to gain entry into the seed and thus reduce the shelf life of the seeds although intention of this technique is to provide a minor damage on seed coat for water permeability [44,45]. Acid scarification, on the other hand, is commonly not preferred due to its cost, safety risk and environmental precautions involved, and not reliable or lacking the requisite qualities on seeds of other important plant species [43,44,46].…”