Apomicts (fwd)

From: Steve Marak samarak at arachne.uark.edu> on 2000.11.29 at 21:00:38(5724) This message was submitted by Claude Sweet to list aroid-l@mobot.org. If you forward it back to the list, it will be distributed without the paragraphs above the dashed line. You may edit the Subject: line and the text of the message before forwarding it back. If you edit the messages you receive into a digest, you will need to remove these paragraphs and the dashed line before mailing the result to the list. Finally, if you need more information from the author of this message, you should be able to do so by simply replying to this note. +More ----------------------- Message requiring your approval ---------------------- Sender: Claude Sweet Subject: Re: Apomicts Generating viable seed is not the issue, it is the genetic material that is different in a hybrid (out crossing) or selfed seed. Apomictic seed is identical to the female parent. This can be caused by duplication of genetic material of the female parent that produces a seed without male genetic input. In fact, if pollen is applied, the genetic material is not accepted. Some plants produce seed both through pollination (hybrid seed) and identical to the female parent (parthenogenesis). An example would be mangoes. I don't know if in aroids there is one dominate gene that causes apomictic seed to be produced or if it is recessive. It would depend on the source of the genetic material (1N or 2N). I can assure you that the apomictic seed has a full compliment of genes - as the seed is an exact duplicate of the 2N female parent by definition. If the trait is recessive, the pollen from an apomictic female plant could be used to pollinate a non-apomictic plant to produce hybrid seed. This is because the pollen produced by the apomictic female plant is 1N (only carrying half of the genetic code necessary to produce a viable seed). Hybridizing could be more complicated if multiple genes are involved in the expression of apomictic seed. As parthenogenetic seed and hybrid seed can be produced in the same mango fruit, the genetic transfer may also be related to external stimulus such as temperature. Oriental persimmon fruit can be seedless (a parthenogenetic process) in California, but does not seem to be observed in Florida. If you want a detailed explanation for the purpose of plant breeding, you should consult with someone in the plant science department of your local university. Claude Sweet San Diego, CA zone 10 Jay Vannini wrote: > > Keith: > > Indeed, my understanding of these plants is that they CAN generate viable > seed without manual fertilization. I am aware of at least two Anthurium spp. > that often generate seed thusly - A. clarinervium & A. papillilaminum. > Surely, there are many more. > > With regard to Claude Sweet's comment - it is worth noting that both of > these Anthuriums have been utilized by aroid hybridizers for some time, and > that the former species is suspected of being one of the parents of A. > leuconeurum. I have manually pollinated both of the above, and have > generated viable seed either way. > > Regards, > > Jay

From: Steve Marak samarak at arachne.uark.edu> on 2000.11.29 at 21:18:10(5725) This message was submitted by "Jay Vannini" to list aroid-l@mobot.org. If you forward it back to the list, it will be distributed without the paragraphs above the dashed line. You may edit the Subject: line and the text of the message before forwarding it back. If you edit the messages you receive into a digest, you will need to remove these paragraphs and the dashed line before mailing the result to the list. Finally, if you need more information from the author of this message, you should be able to do so by simply replying to this note. +More ----------------------- Message requiring your approval ---------------------- Sender: "Jay Vannini" Subject: Apomicts Dear Jim: Sorry for muddying the waters even further on this issue, but I was trying to clarify that apomicts "spontaneously" generate ovules, ergo, may generate seed without having been self-pollinated, cross-pollinated, etc. I accept that my post was less than clear on this. Again, I find it interesting that, in Anthurium papillilaminum at least, one may cross-pollinate two presumably unrelated plants and that the plant in stigmatic phase will accept pollen from its conspecific, and that, in my experience, manual pollination appears to "short-circuit" apomictic seed set further up the spadix. The morphological variation amongst individual plants suggests that this trait is far from being able to be described in absolute terms. I'm afraid one might easily fall into the "what constitutes a species" trap with this. And in another, "DUH!" yesterday, hopefully the product of sleep deprivation, I overlooked a number of well-known apomictic indigenous Anthurium, i.e. A. bakeri, A. gracile, etc. in my mail. Regards, Jay -----Original Message----- To: Multiple recipients of list AROID-L Date: Mi?rcoles, 29 de Noviembre de 2000 08:44 a.m. Subject: Re: Apomicts >In a message dated 11/28/2000 11:19:20 PM Eastern Standard Time, >interbnk@terra.com.gt writes: > ><< Indeed, my understanding of these plants is that they CAN generate viable > seed without manual fertilization. I am aware of at least two Anthurium spp. > that often generate seed thusly - A. clarinervium & A. papillilaminum. > Surely, there are many more. > > With regard to Claude Sweet's comment - it is worth noting that both of > these Anthuriums have been utilized by aroid hybridizers for some time, and > that the former species is suspected of being one of the parents of A. > leuconeurum. I have manually pollinated both of the above, and have > generated viable seed either way. >> > >Jay, > >Apomixis is a very complicated subject with many variations in natural >manifestation. Typically the subject species/clone can create viable ovules >without "outside" genetic influence. One of the best studied and classic >examples is Hosta ventricosa. The seed-grown offspring are essentially clones >of the mother. > >If I read your posting correctly, you emphasize dependency on "manual >fertilization" which has nothing to do with apomixis. Most will have heard of >"parthenogenesis" and it is typically apomixis from an unreduced gamete >identical to the mother's tissue. There are many variations and the subject >has an interesting bibliography. > >The reason the apomicts in question could in fact have been used in >hybridization is that their pollen is usually fertile and the apomict can be >used as the pollen parent. If the cross is attempted in reverse, GENERALLY >the apomict's ovule would not accept the pollen's genetic contribution (be >warned; exceptions are known!). > >Hope this slightly clears the murky water". :-) > > Jim Langhammer >

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