Breeding of Fruit and Plantation Crops

Hybridization between clones

1. Generally, clonal crops are cross-pollinated and they may show self incompatibility. The selected parents may be used to produce single crosses involving two parents or an equivalent of a polycross involving more than two parents (rubber).

Selection among F1 families

• When the breeding value of parents is not known, and when the relative contribution of general combining ability and specific combining ability is not available, then a large number of crosses have to be made in order to ensure that at least some of the crosses would produce outstanding progenies in F1. This is particularly true in a species where crop improvement has not been done or has been done at a small scale.
  
• In such cases, it would be cumbersome to evaluate a large number of F1 progenies generally in detail. To avoid this, small samples of several F1 populations are generally grown. The general value of individual F1 families or populations is estimated noted. Inferior families are eliminated. Promising families with outstanding individuals are then grown at a much larger scale for selection. The procedure is designed to save time, space and labor by planting only small populations of a large number of crosses at the preliminary stage.

Selection within F1 families:

• The selection procedure within F1 families is essentially the same as that in the case of clonal selection.
• But in the case of fruit and plantation crops like cashew, it is difficult to follow the above steps. In these perennial crops, the steps given below may be followed:
• Step I: Select two parents of desirable characters and hybridize them to produce sufficient crossed fruits.
• Step II: Raise the F1 seedling populations and evaluate the individual progenies for yield and quality.
• Step III: Select few superior progenies and propagate them vegetatively to produce grafts/budding on standard rootstocks.
• Step IV: Evaluate the selected clonal seedling progenies (in sufficient number / clone usually minimum of 5-10) along with the parents and standard varieties.
• Step V: Outstanding clones may be released as new variety.
• As step I to V takes at least 20-25 years, some breeders avoid step I and IV. Instead, best performing F1 progenies are assessed and the scion collected from them is multiplied as grafts / budlings for further use as next varieties.

Achievements

• Clone No.51 from Dashehari, MA-1 from Alphanso, Tommy Atkin from Haden. Pusa Surya from Elden in mango, Pusa Seedless from Thompson Seedless of grape etc.