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EFFECTS OF GENOTYPE AND ENVIRONMENT ON GRAIN FILLING IN BARLEY GROWN IN SOUTH-EAST AUSTRALIA

N.R. Long1, S.J. Logue1, C.F. Jenner1, P. Gianquitto1, L.C. MacLeod2 and A.R. Barr1

1University of Adelaide, Waite Campus, Glen Osmond, S.A. 5064
2
Barrett Burston (International) Pty. Ltd., South Yarra, Vic. 3141

Abstract

Conditions of higher temperature and lower rainfall hasten the development of the grain and result in reduced final grain weight. The occurence of moisture stress without temperature effects (dryland trials) reduced the rate of grain filling as well as duration. Most varieties ranked consistently across all trials in terms of both rate and duration of grain filling.

Key words: Genotype, environment, grain filling, barley.

Grain filling, the stage of development during which dry matter is deposited in the grain, is initiated shortly after anthesis. The amount of dry matter deposit-ed into the grain is influenced by both the rate and duration of grain filling, which in turn can be influenced by both genotype and environment (1). Genotypic differences have been reported between cultivars particularly in the rate of grain filling (2), although other studies have found no statistically significant genotypic differences in the rate of grain filling (3). Environmental factors also have an impact on grain filling. Rising temperatures, in particular, hasten grain development by reducing grain filling duration. At the same time, rate of grain filling may be increased, but does not fully compensate for the reduction in duration (2, 3). The aim of this study was to characterise the effects of genotype (G) and environment (E) on the rate and duration of grain filling in barley grown in south-east Australia.

Materials and methods

Five barley cultivars were selected; namely, Schooner, Sloop and Galleon (SA malting and feed varieties), Arapiles (VIC malting variety), and Franklin (TAS malting variety). Trials were sown at Kingsford, SA from 1993-1994 and at Horsham, VIC from 1994-1995. Two trials were conducted at Horsham in both years: a flood irrigated trial which received 100 mm of irrigation at stem elongation and anthesis, and a dryland trial. Daily rainfall and air temperature were monitored with the use of datalogger weather stations (Unidata Australia) at each trial site. Main spikes were tagged at anthesis to ensure that all ears were at the same physiological age at sampling. Sampling of heads began 12 days after anthesis and was carried out during grain filling on a weekly basis until physiological maturity. Ten grains were removed from the central part of each head, dried at 80oC (24 hours), then weighed. Grain weight accumulation during grain filling was described by a logistic model generated using the FITCURVE directive in Genstat 5.

y = a + c/{1 + exp(-b*(x-m))} ;(i)

where y is the grain weight, a and c are the lower and upper asymptotes respectively, b is a rate parameter and maximum instantaneous rate occurs at x = m (inflection point). The fitted curves from the logistic model were used to calculate values and standard errors for max-imum rate and duration of grain filling. Duration was estimated as the time from anthesis to 95% of (a + c).

A second method for evaluating the influence of genotype and/or environment on the rate of grain filling was to calculate the rate of grain weight accumulation between sampling dates. The rates were plotted against DAA to observe the change in rate of grain filling from anthesis to physiological maturity (data shown in poster). Final grain weight (FGW) data were statistically analysed by ANOVA (data not shown).

Results and discussion

Maximum rate and duration of grain filling were well characterised for all cultivars by the logistic model, with over 98% of the variance accounted for in most cases (data not shown). The 1994 season was warmer and drier than either the 1993 or 1995 seasons at both Kingsford and Horsham (Table 1). Kingsford and Horsham were both classed as having severe drought in 1994.Under the conditions of higher temperatures and lower rainfall in 1994, FGW was reduced for all cultivars and a shorter duration was available for the deposition of dry matter (Table 1). At Kingsford, the reduction in duration was accompanied by an increase in the rate of grain filling, as has been previously reported (2, 3) in response to increasing temperature. This increased rate, however, did not fully compensate for the shortened duration, since FGW was reduced. At Horsham, the shorter durat-ion of grain filling in 1994 was accompanied by a reduct- ion in the rate of grain filling. This combination of reduc- ed rate and duration of grain filling in the dryland trial in 1994 resulted in significantly lower FGWs than in 1995 (P<0.001). In the irrigated trial at Horsham, there were no significant effect of season alone on FGW, but a significant variety*season (P<0.05) interaction was observed. Neither rate nor duration of grain filling were affected by the temperature difference of 2.8oC.

Comparison of the irrigated and dryland trials in each season showed that rate of grain filling was lower under drier conditions. Duration was also reduced in 1994 resulting in lower final grain weights in the dryland trial. In 1995, duration of grain filling and FGW did not differ markedly between the irrigated and dryland trials as rainfall was higher compared to 1994. However, the small differences in FGW was influenced by a significant variety*treatment interaction.

Ranking of varieties differed between seasons and between the irrigated and dryland treatments, suggesting there were GxE interactions influencing the rate and duration of grain filling. Galleon, Schooner, Arapiles and Sloop were fairly consistent across all environments for both rate and duration of grain filling. Arapiles was usually lower in rate of grain filling than all SA cultivars. However, duration of grain filling did not differ between these 4 cultivars across environments. Franklin seemed to be the most influenced by environment, particularly for rate of grain filling which did not rank consistently across sites. Duration of grain filling for Franklin was on average shorter than the other cultivars across all trials. This was reflected in smaller grain weight.

References

1. Jenner, C.F. 1990. Aust. J. Plant Physiol. 18, 211-226.

2. Sofield, I., Evans, L.T., Cook, M.G. and Wardlaw, I.F. 1977. Aust. J. Plant Physiol. 4,785-797.

3. Wheeler, T.R., Hong, T.D., Ellis, R.H., Batts, G.R., Morison, J.I.L. and Hadley, P. 1996. J. Exp. Botany. 47, 623-630.

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