What are the characteristics of Tester ?

The most desirable tester is one which provides maximum information about the performance of a line in cross combinations under different environmental conditions (Allard, 1960). The important characteristics of à tester are given below:

1. Broad Genetic Base

The testers with broad genetic base include heterogeneous cultivars, populations or crosses. Such testers were considered more desirable to determine general combining ability in the early years of hybrid development programmes.

2. Wider Adaptability

The tester should have wider adaptability so that it can be used for evaluation of inbred lines for combining ability under changing environmental conditions.

3. Low Yield Potential

The best inbred line has a masking effect due to its desirable dominant alleles, therefore, it should not be used as tester. Thus in order to obtain the real expression of a line, low performing testers "should be used. An inferior synthetic developed by crossing together, poor lines may be used as a tester,

4. Low Performance for Other Traits

A tester should be poor in the trait for which lines are to be evaluated. For example, a synthetic susceptible to lodging should be used to test the capacity of lines to withstand lodging. It is difficult to have all these characteristics in a single tester, therefore, the breeder has to use several testers to meet various evaluation requirements. The testers must commonly used today for the first evaluation of contenong sbury of a line are the inbreds with which it would most likely be estesand to posduce a commercial byteid. For species in which commercial hybrids as vimpie meca, te reage is an inbred line that Line x Tester Analysis is widely used for hybrid seed production. Three-way hybrid cultivars are common in sugar beet, and the testers used to evaluate general combining ability are single cross hybrids used to produce commercial cultivars. Parents of current cultivars are used as testers because they provide good information about the general combining ability of a line with other potential parents and also provide information on specific combining ability of the line with the tester.

For the initial evaluation of combining ability, only 1 or 2 inbred testers are used because the number of test crosses increases as a multiple of the number of testers. For example, evaluation of 200 lines with one tester involves 200 test cross hybrids, and evaluation of 200 lines with two testers involves 400 hybrids. When the resources for testing are fixed, the breeder has to choose between evaluating more lines with less precision with one tester or fewer lines with more precision with two or more testers.

Lines which have good performance in the first evaluation are advanced to tests involving more testers and eventually to evaluation in specific hybrid combinations. With each year of evaluation, the number of lines decreases and the extensiveness of testing increases for the lines retained.