By Katie Ferro, Jeff Daniells and Ashley Balsom, Queensland DAF 

The first ratoon crop is now completed in the variety trial at South Johnstone, and the results are encouraging with:

• The TBRI Cavendish selection Asia Pacific #3 showing comparable yields and fruit length to Williams over the two crop cycles, combined with Panama disease TR4 resistance much better than Formosana in the NT trials.

• Continued good performance of the four Cavendish selections from Rahan Meristem with yields and finger length equivalent to Williams, with at least two of the selections being significantly shorter in stature.

• The Dwarf Cavendish selection Brier, from the Canary Islands, having yields and fruit length equivalent to Williams, while being significantly shorter in stature.

Ratoon 1 observations

Most of these selections originate from international breeding programs (Taiwan, Israel, and Guadeloupe) and are being grown for the first time in Australia after clearing quarantine. Some have so far demonstrated promise, whilst the agronomic characteristics of others have been less desirable. A notable spread of cycle time between varieties was already observed in the plant crop. This meant that some of the early second ratoon bunches of the quicker cycling varieties had already begun to be harvested before all the first ratoon bunches had been completed for the much slower cycling ones. As a result of this, some varieties were experiencing quite different seasonal conditions during the period of bunch development compared to others. The preliminary results from this investigation are a useful first look, but pre-commercialisation trials for any of the better varieties will tell more accurately how these results reflect their broader performance. The data discussed next is displayed in Table 1.

Taiwanese Cavendish selections

The nine TR4 resistant selections from Taiwan took between 19.6 and 23.7 months to reach ratoon one harvest from planting, which was considerably slower than the 17 months taken by the industry standard Williams. The slower cycle times and lower bunch weights resulted in cumulative yields (plant + ratoon 1) 63- 82% of that of Williams. The only exception was Asia Pacific #3, which had a comparable yield to Williams. The high cumulative yield of AP #3 combined with TR4 resistance, which was much better than Formosana in the NT trials, is very encouraging. This makes it a contender for inclusion in future pre-commercialisation trials. The varieties GCTCV 119, 215, 217 and 247, along with AP #3, were all significantly taller than Williams. However, rather than breaking over from wind damage, losses were typified by snapping at the point of connection of the prop to the pseudostem. It was a particular issue for AP #3, where just over half the datum plants snapped at the prop or the bunch fell out at the throat. The same fate occurred to 38 and 31% of the GCTCV 217 and 119 plants, respectively. GCTCV 247 and 215 had very few bunches affected in this way. Perhaps if the varieties were grown in double rows supported by twine then losses would have been lessened (for the current single-row configuration, propping is done using metal wire affixed to wooden stakes inserted towards the top of the pseudostem).

Israeli Cavendish selections

As was the case in the plant crop, the four Rahan Meristem Cavendish selections (Jaffa, Gal, Adi 9001 and Adi 9168) have continued to perform well in all respects compared to Williams in the first ratoon. It is noteworthy that Adi 9001 (2.7 m) and Adi 9168 (2.3 m) were both significantly shorter than Williams (3.1 m) but there were no issues with choking. Several commercial farms have begun growing these varieties on a small-scale due to their promising agronomic qualities.

Guadeloupe CIRAD hybrids

It took around five months longer than the other three hybrids for CIRAD 04 to reach first ratoon harvest. The cumulative yields of the CIRAD hybrids were slightly better than for the plant crop but were still only 57 – 66% of that of Williams. Plants remained significantly taller (11 – 31%) than Williams. Their brittle pseudostems were prone to snapping, and their long, narrow leaf stalks readily bent over leading to much reduced leaf area. Like some of the Taiwanese selections, these too were prone to snapping at the prop.

Other varieties

The two dwarf selections of Cavendish, Brier and Dwarf Cavendish, had comparable cycle times and bunch weights to Williams. And as was the case in the plant crop, Dwarf Cavendish had shorter fruit than both Brier and Williams (indicated by the percentage of fruit in the 22 – 26 cm size category).

What’s next?

Harvest of second ratoon bunches has already begun for many of the faster cycling varieties, however around 10% of the data plants were damaged in early March due to the strong winds brought on by the tropical low (which later developed into Cyclone Niran). Due to the development stage of the Taiwanese Cavendish varieties, these suffered the highest losses. Towards the end of this year, when harvest of all varieties in ratoon two is completed, the block will be nurse suckered to synchronize development for leaf spot resistance assessment in the 2022 wet season. In addition, a new trial was planted at South Johnstone in October 2020. We are evaluating some new varieties which have cleared quarantine since the present trial was established in 2018, along with some improved selections which have been identified in Australia.