Read about Pairat Songpanich by
clicking here

The spectacular outcome of cross-pollination of intersubgeneric species, using subgenus Nymphaea (hardy waterlily) as the pod parent and subgenus Brachyceras (tropical waterlily) as the pollen parent, is Nymphaea 'Siam Blue Hardy', introduced in WGI ONLINE Journal 3.2. 

The pod that produced N. 'Siam Blue Hardy' yielded 244 seeds, of which 39 germinated. From those seedlings, 20 grew to maturity with different characteristics in the five categories described below.

< Seedlings of hybrids
between subgenus Nymphaea
x subgenus Brachyceras

1. Flower

The offspring from the pink pod parent (hardy) and purple/blue pollen parent (tropical) can be categorized into two colors.

1.1 Pink. There are 17 hybrids that have color from light pink to dark pink. We can divide these 17 pinks into 3 groups.

Group I consists of hybrids 4, 8, 12 and 14. All are light pink. The interesting point of this group is that the bloom on the first day has a light pink color and then the petals and sepals start to pale into a white color after two or three days; in contrast, the tips of the petals shade into a darker pink.

Group II consists of hybrid 1, 2, 9, 10, 11, 15, 19 and 20. All are dark pink, most lighter towards the base.

The characteristics of group I and II are rarely found in subgenus Nymphaea, but are typically found in Brachyceras.

Group III consists of hybrid 5, 6, 7, 13, and 17. All have uniform color, ranking from light to middle pink. There is no different tip color in this group.

1.2 Blue. Three hybrids have colors leaning towards the pollen parent (purple/blue) and the color at the base is usually lighter than at the tips of the petals (hybrid 3 which is N. 'Siam Blue Hardy', 16 and 18.

In all the seedlings, the traits of the tips of the anthers are received from the pollen parent which is the same color as the petals. Most of the hybrids are easy to flower like the pod and pollen parents and have many flowers like the tropical waterlily. There are a few with flowering difficulties.

Hybrid 3 (N. 'Siam Blue Hardy') >

2. Carpels

By using a razor blade to cut right through the flower ovary, we can see that, surrounding the center of the ovary, are the carpels within which the seeds are produced. We can see that a characteristic of all hardy waterlilies is that the carpels share a single common wall between adjacent carpels. This is called "syncarpous". And the characteristic of all tropical day flowering waterlilies is that each carpel has its own wall which separates it from the adjacent carpels. This is called "apocarpous" (Conard, 1905). The walls of the carpels are then an important part that botanist uses in separating the genus Nymphaea into two following groups:

Group Apocarpiae consisting of two subgenera, Anecphya and Brachyceras

Group Syncarpiae consisting of three subgenera, Hydrocallis, Lotos and Nymphaea

The result of cutting the ovaries of the 20 hybrids is that all the hybrids have syncrapous walls meaning the hybrids received genetic traits from the pod parent (subgenus Nymphaea) which is in the group Syncarpiae (Table 1)

3. Pads

The characteristic of the margin of a hardy is well known to be entire (smooth) and tropical to be dentate (toothy). All the hybrids have the entire characteristic with the flecked pattern (from the pollen parent) on 13 hybrids and plain green on the other seven (from the pod parent).

For the petiole and pedicel, all the hybrids have pubescences on both like the pod parent.

4. Rootstock

5. Proving the Hybridity

Four hybrids, along with their parents, were tested with the molecular marker and morphology marker method for proving the hybridity of the hybrids with the following results: 

Molecular Markers Method

These four hybrids were genetically confirmed, using PCR-RFLP marker specific to ITS sequence after cutting with three restriction enzymes; AluI, RsaI and MseI (Fig.1). Based on the DNA fingerprint, each parent does possess distinct alleles that were found to combine in the hybrids.  

Morphological Markers Method

The characteristics of the parents and offspring presented, it can be seen that offspring possess genetic germplasm from both pod (Nymphaea) and pollen (Brachyceras) parents. Morphological markers that characterize the parents and hybrids are investigated to confirm that these four hybrids were true hybrids. (Table 1)

 * The names of the parents of these hybrids will be disclosed at the appropriate time.

Conclusion

The result of testing four hybrids (N. 'Siam Blue Hardy', N. 'Siam Pink Tips', N. 'Siam Pink' and unnamed hybrid) with both molecular markers and morphological markers methods proves that the hybrids generated have the genetics of both parents and are indeed new intersubgeneric hybrids between subgenus Nymphaea and subgenus Brachyceras of the genus Nymphaea.

It can be seen that the important characteristics of hardy waterlilies are the syncarpous carpels, smooth edged pads and horizontal growth habit. These three characteristics are the deciding factor in determining that these hybrids are hardy waterlilies and not tropical day blooming waterlilies.  

Reference: Conard, H.S. 1905. The Waterlilies, A Monograph of the Genus Nymphaea. The Carnegie Institute of Washington. Washington D.C. p.86-87,126.