Problems Encountered

Following are the some of the problems encountered in development of hybrid variety

  1. Farmers have to use new hybrid seed every year. They cannot produce their own seed.
  2. Hybrid seed production requires considerable technical skill. This makes hybrid seed production a tedious and costly affair.
  3. The exploitation of full potential of hybrid varieties requires an adequate supply of irrigation water and fertilizer, and control of weeds, diseases and insect pests. Many farmers are unable to ensure a timely application of these essential inputs.
  4. The large-scale production of hybrid seed depends on easy emasculation of the female parent, and on an adequate pollen dispersal from the male parent. In many species, emasculation and pollen dispersal are either unsatisfactory or not practically feasible. In such species, e.g., in most self-pollinated crops hybrid varieties cannot be produced on a commercial scale unless their floral biology is adequately modified through breeding/genetic manipulations.
  5. In most cross-pollinated species, the requirements of isolation are rigid and, ordinarily, difficult to fulfill, except on large farms. These render hybrid seed productions rather difficult in a country like India where farm holdings are generally small.
  6. The amount of hybrid seed required to cover the entire area under any crop appears to be impossible to produce with our present seed production setup. At present, the total certified seed production in the country is just enough to cover only about 4.6% of the total seed requirement of all the crops (including self-pollinated crops, where seed production is relatively much easier).

An extensive use of distant hybridization in crop improvement has been limited by several problems summarised below.

  1. Problems in creating new species

    2. Production of new crop species through allopolyploidy following distant hybridization suffers from several problems, e.g., lower economic yields, poor agronomic characteristics, sterility etc. But these characters can be improved through breeding and selection as is evident from the history of Triticale; however, for this considerable effort, resources and time are required.

  2. Dormancy

    3. In some cases, the F1 seeds of interspecific hybrid exhibit dormancy. For example, some interspecific of the treatments applied for inducing germination. Thus seed dormancy may render the use of some interspecific F1 hybrid difficult, and in some cases, it may effectively prevent their utilization in crop improvement.

  3. F1 hybrids from distant crosses generally exhibit variable sterility; rarely the F1 is fully fertile. Partial sterility of F1 may be either selfed or backcrossed to the cultivated species. Fully sterile F1’s are difficult to maintain, and in some cases doubling of the chromosome number of the F1 may not be feasible or desirable. In any case, F1 sterility confronts the breeder with a problem to overcome which he has to resort to specialised techniques demanding additional resources and time.
  4. Incompatible Crosses

    5. Although many distant crosses can be made with the aid of various techniques, several distant combinations cannot be crossed. When a cross fails, it is generally difficult and time consuming to establish the exact cause rally difficult and time consuming to establish the exact cause of the failure. When the reason for the failure of a cross is not known, one can attempt to overcome the barrier only by trial and error. Distant hybridization is the most common, and perhaps the most useful, at the interspecific level (within the same genus), but several intergeneric crosses have also been of great promise, e.g., Triticale, Raphanobrassica etc. Interfamily crosses are neither possible, and in all probability nor profitable. A technique of somatic hybridization is being developed to produce incompatible distant crosses, but this technique is yet to be standardized and refined for a practical application.

  5. Lack of Homology between Chromosomes of the Parental Species

    6. Transfer of oligogenes from related species is mainly limited by reduced pairing of the alien chromosome with that of the recipient species. Reduced recombination may be overcome by chromosome manipulation, but this is limited to polyploid species, and even there considerable cytogenetic analysis is required to make sure that only a small segment of the alien chromosome is transferred. In a vast majority of cases however, the gene transfer has to depend on spontaneous pairing and recombination.

  6. Undesirable linkages

    7. Linkage of the gene under transfer with some undesirable gene presents a major problem in using distant hybridization in crop improvement. In fact, undesirable linkages have prevented commercial exploitation of many alien gene transfers. In few cases, continued breeding has been able to break the undesirable linkages, but this demands considerable time, effort and resources.

  7. Transfer of recessive traits and of quantitative characters in many distant hybridization programmes is not feasible. In fact, monogenic dominant characters are the most easily transferred, and such transfers constitute the bulk of interspecific gene transfers.
  8. Lack of Flowering in F1 - F1’s from some interspecific hybrids fail to produce flowers. Hybrids between species belonging to the section Arachis of peanuts do not flower; all the techniques to induce flowering in these hybrids have failed.
  9. In distant hybridization programmes, it is important to use the best variety of a crop species as one of the parents. Transfer of genes from a related species into an agronomically poor type will necessitate further breeding efforts to use that gene. In many cases, the best varieties of a crop species cannot be crossed with the wild species; the wild relatives generally cross more easily with land races (old varieties) than with highly improved varieties.


Ag.
Technologies
(Hi-Tech Agriculture)