Genomic groups of PNG bananas

Nari, Normal


PAPUA New Guinea has a rich diversity in edible and wild banana species.
It is important that PNG rural farmers, who are the owners of these valuable resources, are encouraged to properly conserve, manage and sustainably utilise this diversity to sustain their household food and nutritional status.
Once their food and nutritional status is secured, their livelihood will be enhanced and elevated and surplus production can provide income-earning opportunities for the farmers and their families.
PNG has a rich genetic diversity of edible banana species and a home to 10 wild bananas of which one species, Musa ingens, which has its “centre of origin” in the highlands. It is the largest herb in the world and is only found in PNG.
The bananas belonged to the family Musaceae, and PNG has two Musaceae genera – the Ensete and the Musa. 
The genus Ensete is wild and has one species, the Ensete glaucum.
Genus Musa has three sections –  the Eumusa, Australimusa and Ingentimusa. 
The section Eumusa is where edible bananas are evolved from and it has three species in PNG – Musa acuminate, M balbisiana and M schizocarpa. 
The Australimusa section contributes the edible Fei’i group of bananas that have bunches growing erect or sideways (eg cultivar Sar, found in the mainland of Manus Island and in Madang).  
Five wild species are classified under this section (Musa maclayi, M boman, M peekelii, M bukensis, and M lolodensis) and one introduced species of Musa textalis or commonly known as Abacca.
The genus Musa has 10 species and they are found throughout the country, mostly in wild rainforest habitats.
Some of these rich habitats are at high risk of being disturbed due to lumbering activities, large clearing for agricultural developments and the construction of roads and bridges. 
The edible cooking bananas of PNG are natural crosses, mostly between Musa accuminata x Musa balbisiana. There are some cultivars that evolved from natural crosses between M accuminata x M schizocarpa and examples of such cultivars are Vunamami (PNG 144), Ato (PNG 187) and Kokor (PNG 123).
In the natural crosses, Musa acuminate provides the A chromosome while Musa balbisiana provides the B chromosome.
A natural cross where M schizocarpa is involved, it provides the S chromosome and, where Australimusa is involved, it provides the T chromosome. 
Most of the cooking bananas of PNG are categorised into genomic groups of Diploid AA, Triploid ABB and AAB and few Tetraploids AAAA or ABBT.
There are very few edible diploid AS such as cultivar Ato from Madang and cultivar Vunamami from East New Britain.  
There are also very few edible triploids AAT such as cultivar Sar found in the Erima area of Madang and in the mainland of Manus Island. 
The only two ABBT tetraploid cultivars that were collected during the collecting expeditions were Yawa 2 from Rabaul and Giant Kalapua from Madang.
Some common diploid AA cultivars includes Babi (Vudu Papua), Kurisa, Kekiau, Maleb, Manameg Red and Gonub.  The popular cultivars of ABB are the Kalapuas. 
The triploid AAB are mostly found in the highlands of PNG and some common cultivars include Rukumamb, Rukumamb Tambey, Yaurie and Kerua. 
The internationally important dessert banana variety, Cavendish, belongs to the triploid AAA genome. 
Cultivar Buka from the island of Bougainville is a common AABB tetraploid.
Over the years, staff from the Department of Agriculture and Livestock (DAL) and NARI have collected around 500 farmer cultivars/landraces or accessions of bananas from all the genomic groups (AA, AS, ABB, AAB, AAT, AABB & ABBT).
The PNG national banana germplasm collection, or Gene-bank, is housed at the NARI Southern regional centre, Laloki, and currently holds 217 accessions/landraces and 10 international varieties and hybrids that were introduced specifically for their resistance to Sigatoka (Mycosphaerella fijiensis) leaf disease complex. 
Some 500 accessions were collected from farmers’ fields and gardens throughout the country through national and international governments-sponsored collecting expeditions in the past. During the collecting expeditions, both wild and landraces were collected.
Wild species and some diploid AA accessions did not survive the ex situ field conditions at Laloki, which contributed to the decline in the number of the current collection. 
The PNG national gene-bank holds accessions or farmer cultivars collected from all over the country. There are in total 79 accessions of diploid AAs, 42 of triploids AAAs, 37 of ABBs, 33 of AABs and 4 accessions of tetraploid AAAAs. 
The work on banana research and development (R&D), in relation to genetic resources collection, conservation, management and use, was initiated by DAL in the late seventies.
The banana R&D work is now under NARI and is managed and coordinated by the genetic resources team based at NARI Laloki.
The accessions in the collection are being preliminary assessed
for their agronomic potential as well as selection for tolerance
and resistance to biotic and
abiotic condition, especially
adaptation to climatic changes including drought and salinity conditions. 
Each accession in the collection is described morphologically through the use of a standard descriptor list developed by the predecessor of Bioversity International, the International Plant Genetic Resource Institute (IPGRI).
A study is currently underway to screen PNG bananas for their high carotene (pVACs) contents.
Preliminary findings so far revealed some PNG diploid AA cultivars having high pVACs contents, ranging from 1,276-3,428 µg/100g.  Carotene is rich in Vitamin A and C and is responsible for reducing and controlling “night blindness”, diabetes and heart and kidney problems.