ISSN:
1432-2145
Keywords:
Key words Tomato
;
Interspecific hybridization
;
Incongruity
;
Self incompatibility
;
Reproductive barriers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Both interspecific and intraspecific mechanisms restrict the exchange of genes between plants. Much research has focused on self incompatibility (SI), an intraspecific barrier, but research on interspecific barriers lags behind. We are using crosses between Lycopersicon esculentum and L. pennellii as a model with which to study interspecific crossing barriers. The cross L. esculentum×L. pennellii is successful, but the reciprocal cross fails. Since the cross can be successfully made in one direction but not the other, gross genomic imbalance or chromosomal abnormality are precluded as causes. We showed that the lack of seed set observed in the cross L. pennellii×L. esculentum is due to the inability of pollen tubes to grow more than 2–3 mm into the style, whereas SI crosses show continued slow pollen tube growth but, also, fail to set seed. These results indicate that the unilateral response is a barrier distinct from SI, differing from SI in the timing and location of expression in the style. We therefore suggest that this unilateral response in the L. pennellii×L. esculentum cross is more accurately referred to as ”unilateral incongruity” (UI) rather than interspecific incompatibility. Periclinal chimeras were used to determine the tissues involved in UI. The results of crosses with the available chimeras indicate that the female parent must be L. pennellii at either LI (layer 1) or both LI and LII (layer 2) and the male parent must be L. esculentum at either LII or both LI and LII to observe UI similar to that seen in the L. pennellii×L. esculentum cross. Pollinations with a mixture of pollen from L. pennellii and from transgenic L. esculentum plants harboring a pollen-specific GUS reporter gene marker were used to ascertain whether the growth of the pollen tubes of either species was modified as a possible means of overcoming UI. We found no evidence of communication between the two types of pollen tubes to either enhance or restrict all pollen tube growth.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004970050046
Permalink
