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Interspecific hybrid, Zea mays L. x Tripsacum dactyloides L., a new fodder crop with large silage biomass production under abiotic stresses

Yuri Shavrukov1, Victor Sokolov2, Peter Langridge1 and Mark Tester1

1 Australian Centre for Plant Functional Genomics, PMB 1, Glen Osmond, SA 5064 (Australia);
Institute of Cytology and Genetics, Russian Academy of Sciences, 630090 Novosibirsk (Russia);


Interspecific hybrids between maize (Zea mays) and eastern gamagrass (Tripsacum dactyloides) showed different biomass production depending on environment and abiotic stress (salinity, drought and alkalinity). In the plot with a moderate level of salinity (Roseworthy), the silage production of hybrids 1 and 2 was 29.0 and 42.9 tonnes/ha, respectively, which was almost 11- and 16-fold higher than maize production in the same plot. Hybrid plants had a similar nutrient composition of vegetative material, energy, protein content and digestibility for feeding animals compared to that of parental maize. High alkalinity and low soil nutrition (Waite plot) reduced biomass production but hybrids grew at least twice as tall as the maize parent. Hybrids plants also survived at the Meningie plot with a combination of high salinity and strong drought stress.


Eastern gamagrass (Tripsacum dactyloides L.) is a natural grass originating from Mexico and the southern states of the USA, areas that are affected by salinity as well as drought and high temperatures. However, its distribution in Australia is limited by its slow growth. Tripsacum is a wild genetic relative of cultivated maize, but it is considered a different species and has a different number of chromosomes to its domestic relative (Comis 1997). During previous investigations, two stable interspecific hybrids between maize and Tripsacum (with 2n = 39 and 46 chromosomes) were created and tested to ensure they could reproduce and that chromosome number was stable (Kindiger et al. 1996). Initial tests in the glasshouse were encouraging, with the hybrids combining the tolerance to a range of abiotic stresses (salinity, drought and boron toxicity) and perenniality obtained from the Tripsacum parent, with the rapid growth form of the maize parent. These hybrids now are being tested for silage biomass production in the field in a range of soil conditions.


Three field trial plots with various environmental and soil conditions were set up. The first plot, at the University of Adelaide’s Roseworthy Campus, represents typical soil conditions in SA with moderate salinity (EC = 3.44 dS/m, equal about 2400 ppm). 300 plants of hybrid 1, 200 plants of hybrid 2 and 150 maize plants were transplanted into the plot in rows, with spacing of 1 m x 0.7 m with supporting irrigation system. The second experimental plot was established at the University of Adelaide’s Waite Campus. There was little soil available on this plot, only compressed rock, gravel and dolomite, with low salinity but high alkalinity (pH = 9.0-9.5). The third plot was located on the land of a commercial cattle farm near Meningie, SA. The soil (30 cm deep) was a heavy clay with high levels of salinity (EC = 6.05 dS/m, equal to about 4000 ppm). The plot had no irrigation and drought stress was very strong, there being only a few millimetres of rain during the summer growing season since the hybrids were transplanted in November, 2005. There were no plants of Tripsacum parent available in these experiments.

The level of salinity in soil was determined by Water and Soil Salinity Monitoring Kit (NSW DPI, Wagga Wagga) using EC1:5 method. pH of soil samples was determined after mixing 10 g of soil with 50 ml of water and using a pH-meter (Cyberscan, USA) in the laboratory. Feed analysis of silage quality was carried out by FeedTest Co (Hamilton, Victoria). Biomass production was measured on the field scale using the average mass for 50 randomly selected plants during harvesting and re-calculated for production in tonnes/ha.

Results and discussion

We have found that under the conditions at Roseworthy (moderate salinity), the hybrid plants grew extremely well, rapidly reaching two metres or more with very large silage biomass production that was almost 11- and 16-fold higher (hybrid 1 and 2, respectively) than maize in the same plot (Table and Figure). This phenomenon could be explained by expression of some Tripsacum genes in hybrids. Tripsacum parent is known to be tolerant for most of abiotic stresses with the combination of perenniality, very deep roots with aerenchyma and large numbers of tillers. Hybrid plants had a similar nutrient composition of vegetative material, energy, protein content and digestibility for feeding animals to that of the parental maize plants (Table).

Table. Biomass production (June, 2006) and silage quality analysis (May, 2006) of the vegetative material from Roseworthy plot (moderately saline soil)



Hybrid 1

Hybrid 2

Fresh biomass, kg/plant (average)




Fresh biomass, tonnes/ha (estimated)




Moisture, %




Dry matter, %




Crude protein, %




Digestibility, %




Energy, MJ/kg DM




Fig. Comparison of plant growth at Roseworthy plot, June 2006 (from left to right: maize, hybrid 1 and hybrid 2, single plant each)

In the second plot (Waite) the maize-Tripsacum hybrid plants are growing very well and are at least twice as tall as the maize parents. In third plot (Meningie) the hybrid plants are surviving well and, despite their slow growth, the plants are demonstrating a potential to grow under combined strong abiotic stresses.


Interspecific maize-Tripsacum hybrids produce very high silage biomass with good feed quality in moderately saline soil with irrigation (Roseworthy plot). High soil alkalinity (Waite plot), high salinity and severe drought (Meningie plot) reduced significantly the hybrid biomass production. The study of the maize-Tripsacum hybrid plants will be continued in the glasshouse, using supported hydroponics. These experiments will test quantitatively the tolerance of these hybrids to different extreme environments, and will determine critical levels of salinity, boron and other toxic elements, acidity / alkalinity in soil and water-logging.


Comis D (1997) Aerenchyma. Lifelines for living underwater. Agric Res 45 (8): 4-8.

Kindiger B, Sokolov V and Khatypova IV (1996) Evaluation of apomictic reproduction in a set of 39 chromosome maize-Tripsacum backcross hybrids. Crop Sci 36: 1108-1113.

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