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Who are the Parents of Hybrids?

With regard to the hybrid you identified, was it a Ld pubescens crossed with salignum or a Ld salignum X pubescens? Is there a difference? Is it possible to determine whether the seed that created the cross came from a salignum cone or a pubescens cone?

Nigel Forshaw, Bergvliet

If there is a difference, I am unaware of any evidence to the fact. Yes it should be possible to trace the "mother" parent if mitochondria or plastids are derived only from the female parent. But this is the realm of microbiology.

Of course, plant breeders may be very interested. It is often the case that certain species hybridize more than others. There are two reasons for this. Firstly, the pollen may lack chemicals that cause related species to reject them as "foreign." More likely, the stigmatic surfaces may lack "recognition" chemicals to stop germination of foreign pollen. It is thus likely that species which hybridize freely are those that produce the hybrid seeds. But even so, there are a whole range of further "screenings" that are required between the pollen landing on the stigma and the plant producing a seed. These include, the pollen tube growing down the style, its rate of growth, its penetration of the ovule, and the integration of the functioning of the pollen and ovule chromosomes. Also, it seldom happens that a single pollen grain lands on the style: there may be intense competition between pollen grains in the race down the style. Presumably grains from the correct species will be the best adapted for the long race (a pollen grain less than a mm in diam. has to grow down the 50-100 mm-long style) and negotiate hurdles at the fusion stage.

Species which frequently hybridize include Pr longifolia, Pr susannae & Ld xantho-conus. Whether these are typically the seed producing parents I am not certain. Although some work on hybridization in proteas has been done, I am not aware of any publications on the issue. Most horticultural finds from hybrids have been serendipitous and, after having been found in the wild or gardens, have been maintained by vegetative propagation. Seed production is a problem, as hybrids very rarely breed true, but result in a wide range of colours, shapes and flowering times - this variety is useless to a commercial grower who needs uniformity to satisfy his marketers. Where further crossing is done, the hybrid is usually used as the seed bearer, as the incompatibility barriers of the hybrid are more likely to allow both parents (and their parents) to fertilize the ovules - except where the hybrids are sterile! However, hybrids are so common in nature (once you start looking hard) that there has been little incentive to produce hybrids, except with the most important commercial species: Ls cordifolium, Pr magnifica and a few others. Furthermore, most of the successful hybrids are between species in the same sections of the genus.

Tony Rebelo

A comprehensive list of recorded hybrids between proteas is given in PAN 21.14. Additional hybrids detected (mainly by atlassers, but also from the literature) to date include:

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