Time to Radicle Protrusion Does Not Correlate with Early Seedling Growth in Individual Seeds of Impatiens and Petunia
Impatiens (Impatiens wallerana Hooker F.) and petunia (Petunia ·hybrida Hort. Vilm.) seeds were imaged usingaflat-bedscanner interfacedwithapersonal computerprogrammed to captureimages every hour. Imageswere used to measure time to radicle protrusion and seedling growth. Time to radicle protrusion was calculated as time to 50% germination or as actual germination for each seed. Seedling growth after germination was calculated from linear regression of growth over time. Radicle protrusion and seedling growth were evaluated as indicators of seed vigor. Both were good indicators of seed vigor in impatiens seed lots. These measurements of vigor were highly correlated for each impatiens seed lot and for pooled seed lots. However, there was little or no correlation between time to radicle protrusion and seedling growth on an individual seed basis. The relationship between germination speed and seedling growth rate observed in impatiens was confirmed in two petunia seed lots. This study supports the use of time to radicle emergence and seedling growth as good indicators of seed vigor. However, it appears that different aspects of seed vigor may be measured by these indicators because there was no relationship between time to radicle protrusion and seedling growth rate on an individual seed basis.
Identification of quantitative trait loci associated with germination using chromosome segment substitution lines of rice (Oryza sativa L.)
Rapid and uniform seed germination under diverse environmental conditions is a desirable characteristic for most crop plants, such as rice, wheat, and maize. However, the genetic base of the variations in the rate of germination is not well understood. In this study, quantitative trait loci (QTL) for germination rate were mapped with a set of 143 chromosome segment substitution lines (CSSL) each contains a small genomic fragment from a japonica variety Nipponbare in the uniform genetic background of an indica variety Zhenshan97. Nine CSSL showed significantly lower germination rate than that in Zhenshan97. Four germination-related QTL were identified located on chromosomes 2, 5, 6 and 10, at which all japonica alleles decreased germination rate. By using the CSSL-derived F2 population, a major QTL (qGR2) on chromosome 2 was confirmed, and delimited to a 10.4 kb interval containing three putative candidate genes, of which OsMADS29 was only expressed preferentially in the seed. These results would facilitate cloning of the major gene that affects germination rate, and provide an insight into the genetic basis of germination.
Measurement of seedling growth rate by machine vision
Seed vigor and germination tests have traditionally been used to determine deterioration of seed samples. Vigor tests describe the seed potential to emerge and produce a mature crop under certain field conditions and one measure is seedling growth rate. A machine vision system was developed to measure root growth rate over the entire germination period. The machine vision measurement technique was compared to the manual growth rate technique. The vision system provided similar growth rate measurements as compared to the manual growth rate technique. The average error between the system and a manual measurement was -0.13 for the lettuce test and -0.07 for the sorghum test. This technique also provided an accurate representation of the growth rate as well as percent germination.