Contents - Faperta

132 Biotechnological Approaches for Pest Management and Ecological Sustainability
1992; Butron et al., 2002), and to the maize weevil, Sitophilus zeamais Motso. (Widstrom,
1989). Recurrent selection has also been used to breed for resistance to sorghum shoot fl y,
A. soccata, and sorghum midge, S. sorghicola (Agrawal and Abraham, 1985; H.C. Sharma
et al., 2005c). In potato, recurrent selection has been used to improve resistance to E. fabae.
Seven cycles of selection resulted in a major reduction in E. fabae damage (Sanford and
Ladd, 1983). Both recurrent selection and pedigree breeding have been used to breed for
resistance to E. fabae in alfalfa (Elden and Elgin, 1987). The level of resistance in red clover,
Trifolium pratense L. to Acyrthosiphon pisum (Harris) and yellow clover aphid, Therioaphis
trifolii (Monell) has also been increased by recurrent selection (Gorz, Manglitz, and Haskins,
1979). Five cycles of selection for T. trifolii and three cycles of selection for A. pisum have been
used to develop the synthetic cultivar N-2. Recurrent selection is useful for gene pyramiding
and for developing cultivars with multiple resistance to several insect pests and diseases.
Pedigree Breeding
Pedigree breeding involves selection of individual plants in segregating populations on
the basis of insect resistance with desirable agronomic plant types. The best F2 plants are
selected, and planted as F3 families. In the F3 generation, selection for resistance is made
within the family. Selected F4 resistant families are planted, and evaluated for resistance.
In the F5 and F6 generations, the material is subjected to more rigorous screening in replicated
trials, and yield tests are also conducted to eliminate the resistant families with poor
agronomic desirability. In the later generations, selections are made for families with insect
resistance, high yield, and other agronomic characters. The advantage of pedigree breeding
is that it eliminates unacceptable plant material early in the breeding program, allowing
detailed evaluation of selected lines over a period of time. The major disadvantages
are that its use is limited to self-pollinated crops, and that only a limited number of lines
can be processed due to extra time required for planting, harvesting, and data collection.
Pedigree breeding has been used for increasing the levels of resistance in rice to green
leafhopper, Nephotettix virescens (Distant), the brown plant hopper N. lugens, and the rice
gall midge, Orseolia oryzae Wood-Mason (Khush, 1980). Pedigree breeding has been used
to incorporate resistance to shoot fl y, A. Soccata, midge, S. sorghicola, and spotted stem
borer, C. partellus into elite lines in sorghum (H.C. Sharma, Singh and Nwanze, 1997), and
to H. armigera in chickpea and pigeonpea (Dua et al., 2005). The bulk breeding method is
also used to incorporate arthropod resistance into self-pollinated crops. Bulk breeding is
similar to the pedigree breeding method, but selection normally does not occur until the
F5 generation.
Backcross Breeding
It involves the use of recurring backcrosses to one of the parents (recurrent parent) of a
hybrid, accompanied by selection for resistance to the target insect species. The nonrecurrent
parent is a source with a higher level of resistance than that used in the previous
backcross. Backcross breeding can be used as a rapid way to incorporate insect resistance
into agronomically desirable cultivars that are susceptible to insects. After each cross,
selections are made for agronomically desirable insect-resistant plants. Several high-
yielding cultivars of rice and soybean with insect resistance have been developed using
backcross breeding (Khush and Brar, 1991; Smith, 2005). Backcross breeding has not been
found to be useful in breeding maize for resistance to insects. Reciprocal translocation
studies have shown that at least 12 genes are involved in European corn borer, O. nubilalis