Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage, or legumes. 5. Wheat yields, nitrogen benefits and water-use efficiency of chickpea-wheat rotation

In this study, the benefits of chickpea–wheat rotation compared with continuous wheat cropping (wheat–wheat rotation) were evaluated for their effects on soil nitrate nitrogen, wheat grain yields and grain protein concentrations, and water-use efficiency at Warra, southern Queensland from 1988 to 1996. Benefits in terms of wheat grain yields varied, from 17% in 1993 to 61% in 1990, with a mean increase in grain yield of 40% (825 kg/ha). Wheat grain protein concentration increased from 9.4% in a wheat–wheat rotation to 10.7% in a chickpea–wheat rotation, almost a 14% increase in grain protein. There was a mean increase in soil nitrate nitrogen of 35 kg N/ha.1.2 m after 6 months of fallow following chickpea (85 kg N/ha) compared with continuous wheat cropping (50 kg N/ha). This was reflected in additional nitrogen in the wheat grain (20 kg N/ha) and above-ground plant biomass (25 kg N/ha) following chickpea. Water-use efficiency by wheat increased from a mean value of 9.2 kg grain/ha. mm in a wheat–wheat rotation to 11.7 kg grain/ha.mm in a chickpea–wheat rotation. The water-use efficiency values were closely correlated with presowing nitrate nitrogen, and showed no marked distinction between the 2 cropping sequences. Although presowing available water in soil in May was similar in both the chickpea–wheat rotation and the wheat–wheat rotation in all years except 1996, wheat in the former used about 20 mm additional water and enhanced water-use efficiency. Thus, by improving soil fertility through restorative practices such as incorporating chickpea in rotation, water-use efficiency can be enhanced and consequently water runoff losses reduced. Furthermore, beneficial effects of chickpea in rotation with cereals could be enhanced by early to mid sowing (May–mid June) of chickpea, accompanied by zero tillage practice. Wheat of ‘Prime Hard’ grade protein (≥13%) could be obtained in chickpea–wheat rotation by supplementary application of fertiliser N to wheat. In this study, incidence of crown rot of wheat caused by Fusarium graminearum was negligible, and incidence and severity of common root rot of wheat caused by Bipolaris sorokiniana were essentially similar in both cropping sequences and inversely related to the available water in soil at sowing. No other soil-borne disease was observed. Therefore, beneficial effects of chickpea on wheat yields and grain protein were primarily due to additional nitrate nitrogen following the legume crop and consequently better water-use efficiency

Genotypic differences in partial resistance to crown rot caused by Fusarium pseudograminearum in relation to an osmoregulation gene in wheat

Both crown rot and osmoregulation are expressed when wheat plants undergo water stress. A possible genetic linkage between high osmoregulation and partial resistance to crown rot was investigated by using lines that had been bred for high osmoregulation (or gene) from parents with low osmoregulation and varying crown rot resistances. Analysis of the incidence and severity of the disease showed no association with the presence or absence of the or gene

Host range and particle length of passionfruit woodiness virus

Passionfruit woodiness virus (PWV) was found to have a wider natural and experimental host range than previously reported, particularly in the Leguminoseae. Additional species in the Passifloraceae and certain members of the Amaranthaceae, Chenopodiaceae, Cucurbitaceae and Solanaceae were also infected

Genotypic differences in partial resistance to crown rot caused by Fusarium pseudograminearum in relation to an osmoregulation gene in wheat

Both crown rot and osmoregulation are expressed when wheat plants undergo water stress. A possible genetic linkage between high osmoregulation and partial resistance to crown rot was investigated by using lines that had been bred for high osmoregulation (or gene) from parents with low osmoregulation and varying crown rot resistances. Analysis of the incidence and severity of the disease showed no association with the presence or absence of the or gene

Crown depth and susceptibility to crown rot in wheat

Sources of partial resistance to crown rot caused by Fusarium pseudograminearum are detected in mature plants grown in artificially inoculated soil in the field. The resistance in most but not all of these sources can also be detected in seedlings. In order to determine whether partial resistance is related to depth of crown formation, this character was measured in 13 cultivars/lines with a range of reaction to crown rot. It was also measured in doubled haploid plants from the cross, Batavia/2–49. Crown depths varied from 17.1 mm to -2.3 mm (above ground) in pots in a waterbath at 25 °C and from 43.5 mm to 20.7 mm when plants were grown in the field. The correlation coefficient between relative susceptibility to crown rot (Field test) and crown depth of 13 cultivars/lines was 0.57 (p ≤ 0.05). With the exception of the cultivars, Sunco and Pelsart, partial resistance to crown rot was inversely related to depth of crown formation. This indicates that depth of crown formation may be partly responsible for the reaction of a cultivar/line to crown rot. Depth of crown formation was also measured in susceptible and partially resistant cultivars/lines grown from seed planted at different depths. As depth of seeding increased, depth of crown formation in partially resistant and susceptible cultivars/lines increased in similar proportions

Crown rot and common root rot in wheat grown under different tillage and stubble treatments in southern Queensland, Australia

In southern Queensland, crown rot caused by Fusarium graminearum Group 1 and common root rot caused by Bipolaris sorokiniana are common soilborne diseases of wheat and barley. The incidence of these diseases was measured in the susceptible wheat (Triticum aestivum L.) cultivar, Hartog which was grown under no tillage, reduced tillage (two tillage operations plus herbicides) and where stubble was retained or removed by burning (1984-1986) or physically removed (1987-1993). Primary tillage was with blade, disc or chisel implements. The level of crown rot and common root rot was higher where stubble was retained than where it was removed. There was a significant interaction in incidence of crown rot between stubble management and some types of tillage. Where there was no tillage, incidence of crown rot was significantly higher where stubble was retained (32.2%) than where it was removed (4.7%) whereas under disc tillage, there was no significant difference in disease level between stubble treatments (12-17%). Incidence of crown rot was not affected by the type of tillage employed. The incidence of deadheads (heads without grain) caused by crown rot was lowest in the no tillage plots (4.3%) and highest in the reduced (19.3%) and conventional (12.2%) disc tillage stubble retained treatments. Available soil water (depth of 1.2 m) at sowing and anthesis was lowest in the conventional disc stubble retained plots and highest in the no tillage stubble retained plots. It is hypothesised that the high levels of deadheads were due to moderate to high levels of disease and low available soil water at planting and anthesis. Although incidence of crown rot was high under no tillage, incidence of deadheads was lower than in other treatments due to the higher availability of soil water. Severity of common root rot was lower in stubble removed, than in stubble retained, treatments and also lower in no tillage than in any of the other tillage treatments. (C) 1997 Elsevier Science B.V

Survey of Fusarium species associated with crown rot of wheat and barley in eastern Australia

Fusarium species associated with crown rot were isolated and identified from 409 wheat, barley or durum wheat crops from the eastern Australian grain belt between 1996 and 1999. Fusarium pseudograminearum was almost the only species isolated from crops in Queensland and New South Wales. F. pseudograminearum was also the most common species in Victoria and South Australia, but F. culmorum was frequently isolated in these states. F. culmorum accounted for more than 70% of isolates from the Victorian high-rainfall (> 500 mm) region and the South-East region of South Australia. F. culmorum comprised 18% of isolates from the Victorian medium-rainfall (350-500 mm) region, and 7% of isolates from each of the Victorian low-rainfall region and the Mid-North region of South Australia. F. avenaceum, F. crookwellense and F. graminearum were isolated very infrequently. The proportion of F. culmorum among isolates of Fusarium from districts in Victoria and South Australia was strongly correlated with climatic conditions around the end of the growing season, especially with rainfall in November

Sustaining productivity of a Vertosol at Warra, Queensland, with fertilisers, no-tillage or legumes. 7. Yield, nitrogen and disease-break benefits from lucerne in a two-year lucerne–wheat rotation

Continuous cultivation and cereal cropping of southern Queensland soils previously supporting native vegetation have resulted in reduced soil nitrogen supply, and consequently decreased cereal grain yields and low grain protein. To enhance yields and protein concentrations of wheat, management practices involving N fertiliser application, with no-tillage and stubble retention, grain legumes, and legume leys were evaluated from 1987 to 1998 on a fertility-depleted Vertosol at Warra, southern Queensland. The objective of this study was to examine the effect of lucerne in a 2-year lucerne–wheat rotation for its nitrogen and disease-break benefits to subsequent grain yield and protein content of wheat as compared with continuous wheat cropping. Dry matter production and nitrogen yields of lucerne were closely correlated with the total rainfall for October–September as well as March–September rainfall. Each 100 mm of total rainfall resulted in 0.97 t/ha of dry matter and 26 kg/ha of nitrogen yield. For the March–September rainfall, the corresponding values were 1.26 t/ha of dry matter and 36 kg/ha of nitrogen yield. The latter values were 10% lower than those produced by annual medics during a similar period. Compared with wheat–wheat cropping, significant increases in total soil nitrogen were observed only in 1990, 1992 and 1994 but increases in soil mineralisable nitrogen were observed in most years following lucerne. Similarly, pre-plant nitrate nitrogen in the soil profile following lucerne was higher by 74 kg/ha (9–167 kg N/ha) than that of wheat–wheat without N fertiliser in all years except 1996. Consequently, higher wheat grain protein (7 out of 9 seasons) and grain yield (4 out of 9 seasons) were produced compared with continuous wheat. There was significant depression in grain yield in 2 (1993 and 1995) out of 9 seasons attributed to soil moisture depletion and/or low growing season rainfall. Consequently, the overall responses in yield were lower than those of 50 kg/ha of fertiliser nitrogen applied to wheat–wheat crops, 2-year medic–wheat or chickpea–wheat rotation, although grain protein concentrations were higher following lucerne. The incidence and severity of the soilborne disease, common root rot of wheat caused by Bipolaris sorokiniana, was generally higher in lucerne–wheat than in continuous wheat with no nitrogen fertiliser applications, since its severity was significantly correlated with plant available water at sowing. No significant incidence of crown rot or root lesion nematode was observed. Thus, productivity, which was mainly due to nitrogen accretion in this experiment, can be maintained where short duration lucerne leys are grown in rotations with wheat