Development of techniques for wide hybridisation of the genus Lupinus L.

Shah, Azad Hussain (2002) Development of techniques for wide hybridisation of the genus Lupinus L. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

In the genus Lupinus, L. mutabilis has been recognised as potential breeding material to improve the quality and quantity of widely grown L. albus, through interspecific hybridisation. These species remain under-utilised due to the presence of certain undesirable characteristics such as alkaloids, indeterminate growth habit and susceptibility to diseases and pathogens. However, introgression of useful traits between the two species is difficult due to incompatibility barriers at the post-fertilisation level. The objective of this work was therefore, to develop appropriate technique(s) for hybridisation between L. albus and L. mutabilis species.

Interspecific compatibility between L. albus and L. mutabilis was investigated using a wide range of parental genotypes with equal number of somatic chromosomes (2n = 48). Comparative analysis of species on the basis of their morphological characteristics was carried out. The pollen viability of both species was also investigated. Following self and interspecific pollination it was observed that germination of pollen grains on the stigma and pollen tube growth in the styles were not inhibited. However, isolating mechanisms due to post-fertilisation barriers resulted in zygotic failure and thus hybrid embryo abortion at an early stage of development, which subsequently caused pod abortion within two weeks of pollination. Pod/seed development studies were carried out in the species and their reciprocal crosses and the time of embryo abortion was determined. In interspecific crosses it was observed that the period between 4^th and 5^th day after pollination was crucial for both pod and seed development. The normal development of hybrid pods and seeds for the first three days after pollination indicated fertilisation and early development of the hybrid embryos. The possible reason of embryo degeneration may be due to disharmonious interaction between embryo, suspensor, endosperm and maternal tissues. Growth regulators were applied to enhance pod development and to prevent early embryo abortion. The growth regulators were found not to be as effective in encouraging hybrid embryo development as in pod growth. Regardless of the genotype and growth regulator applicator, interspecific crosses resulted in pod abortion.

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