Significance of early maturity in improving grain yield and water use efficiency of wheat in low rainfall environments
Siddique, K.H.M. Dr; Ph: (08) 9368 3493; Fax: (08) 9367 5232; mailto:firstname.lastname@example.org
Tennant, D. Dr; Ph: (08) 9368 3287; Fax: (08) 9368 3355; email@example.com
Abrecht, D.G . Dr; Ph: (08) 9368 3499; Mobile 0417 934 648; Fax: (08) 9368 2165; firstname.lastname@example.org
Regan, K.L. Ms; Ph: (08) 9368 3508; Fax: (08) 9368 2165; email@example.com
Research organisation: Agriculture Western Australia, 3 Baron Hay Court, South Perth WA 6151
Sponsors: GRDC-WA, Grains Research and Development Corporation - WA State Committee
1. To test the hypothesis that greater and more stable wheat yields can be achieved by using cultivars with earlier maturity (relative to the present commercial cultivars) in short season environments (less than 300 mm rainfall);
2. To model the effect of maturity type on yield improvement and yield stability in the low rainfall environments by using data from field trials.
This project will assess the role of very early flowering in yield improvement and yield stability of wheat in low rainfall environments. Recent studies at DAWA suggests that improved grain yield and water use efficiency of modern cultivars (eg Gutha and Kulin) was associated with earlier flowering (100-108 days) compared to medium-to- late maturing (110-120 days) cultivars (Siddique et al. 1989a, b; 1990a, b). Detailed analysis (Siddique et al. 1990b) indicates that further improvement in yield should be possible by using even earlier flowering cultivars. Advanced generation (F5/F6) materials with very early flowering (90 to 100 days) and good agronomic type are available from projects (DAW 149W1, 147W1) and other projects on yield improvement at DAWA. Dr RA Richards, CSIRO, Canberra, is also providing suitable, very early flowering advanced lines from his breeding program.
Siddique, K. H. M., Kirby, E. J. M., and Perry, M. W. (1989a). Ear:stem ratio in old and modern wheat varieties; relationship with improvement in number of grains per ear and yield. Field Crops Research 21, 59-78.
Siddique, K. H. M., Belford, R. K., Perry, M. W., and Tennant, D. (1989b). Growth, development and light interception of old and modern wheat cultivars in a Mediterranean environment. Australian Journal of Agricultural Research 40, 473-87.
Siddique, K. H. M., Tennant, D., Perry, M. W. and Belford, R. K. (1990a). Water-use and water-use efficiency of old and modern wheat cultivars in a Mediterranean environment. Australian Journal of Agricultural Research 41, 431-47.
Siddique, K. H. M., Belford, R. K., and Tennant, D. (1990b). Root shoot ratios of old and modern, tall and semi-dwarf wheats in a Mediterranean environment. Plant and Soil 121, 89-98.
An analysis of historical rainfall records was carried out to assess the frequency of late breaks (after 1 June) in the eastern and north-eastern wheatbelt of Western Australia. We found that the break of the season occurs after June 1 in about 30 per cent of years at Merredin and 25 per cent of years at Mullewa. Given that the first sowing opportunities are often used for sowing legumes and for weed control, wheat sowing may occur even later than estimated. Therefore, the introduction of high stable yielding very early maturing cultivars was considered a relatively low cost desirable avenue for increasing enterprise profit in low rainfall, short season environments.
In our study we showed that wheat genotypes reaching anthesis up to 24 days (328oCd-1) earlier than currently grown cultivars produced similar yields and dry matter, and maintained high water use efficiencies. In general, the highest yielding early maturing genotypes had similar yields to that of the earliest maturing standard cultivars (Kulin and Wilgoyne), but were superior to Spear and Gamenya. This was mainly due to a greater partitioning of dry matter into grain yield (i.e. a higher harvest index). Early maturing genotypes did not produce less dry matter despite having a shorter period between sowing and anthesis. This suggests a better growth rate and more efficient utilization of solar radiation and water.
A concern with earlier maturity is the potential for a yield penalty compared to later maturing genotypes in seasons where there is a late wet finish to the season. To simulate a season with a late wet finish, we applied irrigation water from approximately anthesis to maturity in two experiments. The irrigation treatments increased grain yield by up to 104 per cent across all genotypes, but we were unable to show an interaction between the effect of irrigation and maturity on grain yield.
Genotypes with a shorter period between sowing and anthesis (i.e. early maturity) have been shown to have a longer grain growth duration (Loss et al. 1989; Austin et al. 1989) which can be beneficial in allowing the crop to complete grain filling under better post-anthesis water supply at lower temperatures. Although there was a trend for earlier maturing genotypes to have a longer grain growth duration at two sites in 1992 and under irrigation in 1993, there was no significant difference in grain growth duration or growth rates in our studies.
Increasing plant density did not increase grain yield for the early maturing or standard cultivars. Dry matter production and green area index increased at higher densities, but harvest index was lower resulting in little effect on grain yield. Increasing seeding rates can increase the number of ears per unit area, but reduce the number of grains ear-1 and grain weight. In this study, we observed no change in grain weight, but a reduction in spikelet numbers (suggesting a reduction in grains ear-1) at higher densities which was not compensated by the increase in ear numbers at higher plant densities. Therefore, there was no advantage of higher seeding rates on grain yield.
Wheat lines reaching anthesis quicker than the earliest standard cultivars (Kulin and Wilgoyne) were identified in material from the Australian Winter Cereals Collection and the Agriculture Western Australia breeding trials. The value of the wheat lines from the Australian Winter Cereals Collection for use as parental material in the Agriculture Western Australia breeding program requires further assessment. Frost and poor germination in our trials limited the determination of agronomic suitability and yield performance. The yields of the early maturing wheat lines selected from the Agriculture Western Australia breeding trials were promising, with many performing as well or better than Kulin. Our results showed better yield performance compared to standard cultivars at later sowing times. This suggests that yield testing for early maturing genotypes is better carried out at sowing times after 1 June.
Austin, R.B., Ford, M.A., and Morgan, C.L. (1989). Genetic improvement in the yield of winter wheat: A further evaluation. Journal of Agricultural Science 112, 295-302.
Loss, S.P., Kirby, E.J.M., Siddique, K.H.M., and Perry, M.W. (1989). Grain growth and development of old and modern Australian wheats. Field Crops Research 21, 131-146.
Keywords: early maturity, phenology, harvest index
Period: starting date 1992-07; completion date 1996-06
Regan, K.L., Siddique, K.H.M., Tennant, D. and Abrecht, D.G. (1993). Early maturity improves grain yield and water use efficiency of wheat in low rainfall regions of Western Australia. In Proceedings of the 7th Australian Agronomy Conference, Adelaide, 1993, pp. 286-89.
Regan, K.L., Siddique, K.H.M., Tennant, D. and Abrecht, D.G. (1996). Grain yield and water use efficiency of early maturing wheat in low rainfall Mediterranean environments. Australian Journal of Agricultural Research 47, 595-603.