Studies on the Rapid Methods for Evaluating Seed Vigor of sweet Corn
Since the germination test is still the main method for evaluating seed vigor of sweet corn, it is necessary to study the rapid methods for evaluating their vigor. First, two vigor levels of 9 super sweet corn and 9 sugar enhanced corn hybrids were distinguished by accelerated ageing treatment. Next, their vigor statuses were tested by rapid methods such as electrical conductivity (EC), soluble sugar (SS), volatile aldehyde (VA), dehydrogenase activity (DA) and Q2 oxygen sensing technology. Correlation relationship was analyzed between the above tested values and vigor performances. The results showed that EC, SS, VA, DA, oxygen metabolism rate (OMR), critical oxygen pressure (COP) were all suitable to evaluate seed vigor of sweet corn. Furthermore, VA was optimal for evaluating seed vigor of super sweet corn. DA was optimal for evaluating sugar enhanced corn.
Vigor Tests Used to Rank Seed Lot Quality and Predict Field Emergence in Four Forage Species
Laboratory and field tests were conducted in 1999 and 2000 in Gansu Province, China, to investigate the suitability of various laboratory vigor tests, to rank quality of commercial seed lots, and to predict seedling field emergence (FE) of four forage species. Species used included two legumes, purple vetch (Vicia benghalensis L.) and alfalfa (Medicago sativa L.), and two grasses, sudangrass [Sorghum bicolor (L.) Moench subsp. drummondii (Steud.) de Wet ex Davidse] and Siberian wild ryegrass (Elymus sibiricus L.). Results showed that among all tests, the electrical conductivity (EC) test provided the best estimate of seed vigor for the two legume species, both for ranking seed lots quality and predicting FE, but gave the worst indication of seed lot vigor for the two grass species. The EC result was not only poorly related to FE, but also poorly related to the standard germination (SG) of a wide range of seed lots of the two grass species that varied in viability. The controlled deterioration (CD) test generally better indicated seed lot vigor for test species than did SG, except that it lacked sensitivity in ranking seed lot quality of alfalfa and was not significantly related to Siberian wild ryegrass FE. The germination index (GI) better indicated seed lot quality and predicated FE than SG of sudangrass over the 2-yr results, but not consistently better than SG for other species. Initial count of standard germination (SGi) generally performed more poorly than the other vigor tests. From this study and previous work on forage species, we conclude that EC test for forage legumes and CD tests for both forage legumes and grasses have the potential to be developed as improved vigor tests for ranking seed lot quality and predicting seeding performance.
Genetics of the phenotypic evolution in sheep: a molecular look at diversity-driving genes
Background After domestication, the evolution of phenotypically-varied sheep breeds has generated rich biodiversity. This wide phenotypic variation arises as a result of hidden genomic changes that range from a single nucleotide to several thousands of nucleotides. Thus, it is of interest and significance to reveal and understand the genomic changes underlying the phenotypic variation of sheep breeds in order to drive selection towards economically important traits. Review Various traits contribute to the emergence of variation in sheep phenotypic characteristics, including coat color, horns, tail, wool, ears, udder, vertebrae, among others. The genes that determine most of these phenotypic traits have been investigated, which has generated knowledge regarding the genetic determinism of several agriculturally-relevant traits in sheep. In this review, we discuss the genomic knowledge that has emerged in the past few decades regarding the phenotypic traits in sheep, and our ultimate aim is to encourage its practical application in sheep breeding. In addition, in order to expand the current understanding of the sheep genome, we shed light on research gaps that require further investigation. Conclusions Although significant research efforts have been conducted in the past few decades, several aspects of the sheep genome remain unexplored. For the full utilization of the current knowledge of the sheep genome, a wide practical application is still required in order to boost sheep productive performance and contribute to the generation of improved sheep breeds. The accumulated knowledge on the sheep genome will help advance and strengthen sheep breeding programs to face future challenges in the sector, such as climate change, global human population growth, and the increasing demand for products of animal origin.