G. J. Mendel was born in 1822. Although, he was the first person to identify the genetic laws, he was not a well-known scientist he was an Augustinian monk (accessexcellence. org). For a long time it was thought that offspring inherit their traits from their parents, but it has never been proven until Mendel demonstrated in plants. In his 1866 paper “Experiments on Plant hybridisation” Mendel laid down the basis for the entire subject of genetics by suggesting for the first time the existence of the discrete hereditary determinants we now call genes (Griffiths et al. ,1999).
Though, his work was not fully recognized until the 20th century. Rediscovery of his work led to the foundation of genetics and that is why he is called the “father of modern genetics” (wikipedia. com). Mendel experiments started with pure-breeding lines of garden peas that showed distinct phenotypes for certain characteristics (yellow and green seeds). When he crossed these lines he obtained the offspring called “hybrid”. The hybrids were all yellow. When these hybrids were grown up and self-polinated, 75% of the offspring was yellow and 25% was green (Griffiths et al.
,1999). Of special importance to this investigation is rapid cycling B. rapa (RCBr). Williams and Hill developed RCBr in University of Wisconsin-Madison in 1986 (Williams and Hill, 1986). They discovered that these plants require very little attention and therefore were easy to grow, so they bred these rapid cycling RCBr as a research tool to be used for improving disease resistance of cruciferous plants. Cross breeding between RCBr and six related species from the family Cruciferae was tried to obtain shorter life cycles.
A new petite, quick-growing plant was developed known as Fast Plants® (fastplants. org). Development of these plants continued so the following characteristics could be obtained: i)short time from planting to flowering (about 2 weeks), ii) rapid seed maturation with no seed dormancy required, iii) ability to produce seeds at higher planting density, iv) petite plant size, v) ability to grow under continuous florescent lighting in a standard potting mix. Finally, from six month life cycle of B.
rapa, RCBr has 35-40 days life cycle from parental seed sown to offspring harvest (Williams and Hill, 1986). Compared to normal B. rapa, which can produce two generations in a year, under optimal conditions RCBr can produce 10 generations in a year. Additionally, over 150 genetics traits have been described (fastplants. org). Thus, the potential applications of RCBr to experimental botany are diverse (Musgrave, 2000). Here we investigate the patterns of Mendelian separation in two district generations of RcBr.
From this dihybrid investigation we expected four phenotypes: 1) non-purple stem (single recessive mutant anl/anl), 2) purple stem (dominant for anthocyaninless gene ANL/ANL), 3) yellow green leaves (recessive mutant ygr/ygr), 4) normal green leaves (dominant allele YGR). Under the seeds a water system was prepared containing a reservoir, water mat and CuSO4. Both the reservoir and the water mat contained water and were placed on the bottom of the system. The water mat was always wet due to the capillary action from the reservoir. CuSO4 is a preventative agent against fungal growth.
When the water system was set up F1 seeds were planted in two ‘quot’ pots, which each had 4 cells, those one support the plants. The cells were first labeled and then one wick was pressed into each cell. The wick was pulled down through the hole so around 1 cm of the wick was extending through the hole. The cells were then half filled with potting mixture and 3 fertilizing pellet per cell. Additional potting mixture was added loosely on the top of the pellets. Two depressions were created with forceps and one seed was added followed by a thin layer of potting mixture.
The cells were then watered until sufficient amount was added. Following that the cells were placed onto the water mat, which was on top of the reservoir. The system was placed under constant light source. The water level in the reservoir as well as the moisture in the water mat was maintained daily so that the seed received adequate water during germination. After germination the plants were continued to be watered daily to avoid wilting and encourage growth. All mutant plants were identified and removed. The mutants lucked purple pigment in the stem and yellow and green leaves.
To support the plants small stakes and plastic ring were used. Every 4 days a number of variables were collected such as plant height, number of leaves and number of buds. When the flowers were grown self-pollination was started using bee sticks. The plants were cross-pollinated for 4 days. On the last day of pollination, the unopened flower pods were removed. Then the plants were grown under constant light source and adequate water supply. During the following days all new flowering pods were removed so all the available plant sources were used for seed pod development.
After last pollination the seed pods were grown for 14 days. Then they were removed and dried for 7 days by placing each into an envelope. The cells were then washed allowed to dry. The seeds (F2) were harvested from the dry pods and counted. Then all the equipment, water reservoir, platform, quads and water mat, were cleaned. The F2 seeds were planted as described with the F1 generation. After germination the plants were grown for 4 days. Then the cells were removed from the cell counted and classified.