Multi-environment field testing for identification and validation of genetic resistance to Botrytis cinerea causing Botrytis grey mold in chickpea (Cicer arietinum L.)

Botrytis grey mould (BGM), caused by Botrytis cinerea Pers. Ex. Fr., is a destructive foliar disease of chickpea (Cicer arietinum L.) worldwide. Disease management through host-plant resistance is the most effective and economic option to manage this disease. The objective of this study was to identify new sources of resistance to BGM, validate their stability across environments and determine the magnitude of G × E interaction. One hundred and nine chickpea genotypes with moderate levels of resistance (BGM severity ≤5.0 on a 1–9 scale) were selected from the preliminary evaluation of 412 genotypes including germplasm and breeding lines under controlled environmental conditions in 2004–2005 at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India. In order to validate resistance stability, an ‘International Botrytis Grey Mould Nursery’ (IBGMN) was constituted with 25 genotypes and tested in multi-environments for BGM resistance at two locations (Gurdaspur and Pantnagar) in India for 4 years and two locations (Tarahara and Rampur) in Nepal for 3 years. Additive main effects and multiplicative interaction (AMMI) analysis showed significant genotype (G), environment (E) and G × E interaction (p < 0.0001) with largest contribution by environment (47.36%). The first two principal component axes were significant, and contributed 48.21% to the total G × E interaction. The AMMI biplot analysis allowed the selection of five genotypes ICCV 96859, ICCV 96853, ICCV 05604, ICCV 96852 and ICCV 05605 with low BGM severity (between 3.7 and 4.7 on 1–9 scale) and moderate stability. Genotype ICCV 96859 having least disease severity and moderate stability could be highlighted and exploited in chickpea resistance breeding programmes.     

Evaluating sustainable and profitable cropping sequences with cassava and four legume crops: Effects on soil fertility and maize yields in the forest/savannah transitional agro-ecological zone of Ghana

Rotations are important practices for managing soil fertility on smallholder farms. Six cropping sequences (cassava, pigeonpea, mucuna–maize–mucuna, cowpea–maize–cowpea, maize–maize–maize, and speargrass fallow) were evaluated during 2003–2004 in Wenchi district of Ghana for their effects on the profitability of the different rotations and the productivity of subsequent maize. Soil chemical properties were not significantly affected by cropping sequence. On the researcher-managed and farmer-managed plots maize grain yields were significantly influenced by cropping sequence. On the researcher-managed plots maize grain yield ranged from 1.0 t ha⁻¹ after speargrass fallow to 3.0 t ha⁻¹ with cassava cropping when N fertiliser was not applied to maize and from 2.1 t ha⁻¹ with continuous maize to 4.2 t ha⁻¹ with mucuna–maize–mucuna when 60 kg N ha⁻¹ was applied to maize. On the farmer-managed plots where N fertiliser was not applied to maize, maize grain yields ranged from 0.4 t ha⁻¹ on speargrass fallow to 2.2 t ha⁻¹ on plots previously cropped to pigeonpea. High maize grain yields associated with the cropping sequences involving cassava, mucuna and pigeonpea were related to the faster decomposition and N release of the biomass compared with the slower release of N by the poorer quality materials like maize stover and speargrass. Return on investment of the different rotational sequences ranged from −22% with speargrass/maize to 235% with cassava/maize when no N application was made to maize, and from 29% with continuous maize to 196% with cassava/maize when N fertiliser was applied to maize. Cassava/maize rotation was ranked by native farmers as the most preferred rotation whereas migrant farmers ranked cowpea–maize–cowpea–maize as the most preferred rotation. Among natives, male farmers ranked rotation involving cowpea as the next most preferred rotation after cassava/maize. In contrast, female farmers ranked pigeonpea/maize rotation as the second most preferred rotation, due to low labour and external input requirements of pigeonpea compared with cowpea. The choice of a particular rotational sequence is related to access to resources and the needs of the farmer. The study therefore suggests that, in a heterogeneous farming community like Wenchi, technology development should be targeted to suit the needs and resources available to each particular group of farmers.     

Tillage system effect on nitrogen rhizodeposited by faba bean and chickpea

The quantification of the below-ground N of legumes is a key to understand its effect on soil N fertility and the N economy of subsequent legume-based rotations. Significant amounts of the N fixed by legumes are incorporated into the soil as fallen leaves and stems. However, the N from roots, nodules and root exudates has rarely been quantified under field conditions, nor have the management effects been evaluated. This study measured the effects of tillage system [no-tillage (NT) and conventional tillage (CT)] on N rhizodeposition in faba bean (Vicia faba L.) and chickpea (Cicer arietinum L.) during a 3-year period (2003–2004, 2005–2006 and 2006–2007) in a Vertisol under rainfed Mediterranean conditions. Faba bean and chickpea plants were labelled in situ with ¹⁵N using stem feeding and leaf feeding, respectively. NT increased the N derived from rhizodeposition (NdfR) with respect to CT (135 vs. 68 kg N ha⁻¹ in faba bean and 115 vs. 97 kg N ha⁻¹ in chickpea). Such differences between tillage methods can be attributed to the more favourable conditions for root growth produced by NT. NdfR was significantly influenced by depth; in faba bean, the greatest amount (70%) was found in the 0–30 cm layer, whereas in chickpea, 41% of the NdfR was concentrated in the 30–60 cm depth. The 54% and 61% of total plant N was NdfR (in faba bean and chickpea, respectively) representing 90% of the below-ground plant N in both crops. Our results show that the N derived from rhizodeposition is an important source for N balance and is a key to soil fertility in rain-fed Mediterranean cropping systems.     

Combining superior agronomic performance and terminal heat tolerance with resistance to spot blotch (Bipolaris sorokiniana) of wheat in the warm humid Gangetic Plains of South Asia

Seven hundred twenty-nine lines of diverse wheat germplasm lines were evaluated in eight locations of three countries (India, Nepal and Bangladesh) of South Asia for 5 years (1999–2000 to 2003–2004) through Eastern Gangetic Plains Screening Nursery (EGPSN) organized by CIMMYT South Asia, Nepal, for agronomic performance and tolerance to spot blotch of wheat. Each year, the number of lines represented a new set of 150 lines that included six common checks and a different local check at each of the eight locations. One hundred and five lines, 21 in each year, advanced from EGPSN were also tested for 5 years (2000–2001 to 2004–2005) in five locations of South Asia through Eastern Gangetic Plains Yield Trials (EGPYT) to verify spot blotch tolerance and superior yield performance of the selected germplasm. Many lines yielded significantly more than the best check and possessed high levels of spot blotch resistance under warm humid environments of South Asia. The most promising 25 lines have been listed as sources of strong resistance, with 9 lines better yielding than the best resistant check PBW 343 in fewer days to maturity. Most of these superior lines represented elite CIMMYT germplasm and around half were derived from Kauz and Veery. The line EGPYT 67, Kauz//Kauz/Star/3/Prinia/4/Milan/Kauz, was the best for spot blotch resistance, yield, days to maturity, and 1000 grain weight (TKW). The next two lines in the order of merit were EGPYT 84 (Mrng/Buc//Blo/Pvn/3/Pjb 81) and EGPYT 69 (Chirya3/Pastor). The results demonstrate that additional spot blotch resistant wheat genotypes with high grain yield and TKW, and early maturity, have become available as a result of the regional and international collaboration in South Asia.     

On-farm evaluation of the ‘push–pull’ technology for the control of stemborers and striga weed on maize in western Kenya

The ‘push–pull’ technology is a novel pest management strategy developed for control of stemborers and striga weed, Striga hermonthica, in maize-based farming systems in eastern Africa, where maize is intercropped with desmodium, a forage legume, and Napier grass is planted as a border crop. Desmodium repels stemborer moths while Napier grass attracts them. Desmodium also suppresses the parasitic striga weed through a series of mechanisms ranging from shading to allelopathy through the root system. The technology is currently being disseminated among smallholder farmers in eastern Africa and adoption rates are rising. Our on-station studies have reported efficacy of this technology against the two pests resulting in increased grain yields. The current study was conducted between 2003 and 2006 in 14 districts in western Kenya to assess effectiveness of the technology under farmers’ own conditions. Twenty farmers from each district, who had adopted the technology, were randomly selected for the study. Each farmer had a set of two plots, a ‘push–pull’ and a maize monocrop. Seasonal data were collected on percentage of maize plants damaged by stemborers, the number of emerged striga, plant height and grain yields. Similarly, farmers’ perceptions on the benefits of the technology were assessed using a structured questionnaire. Stemborer damage and striga counts to maize plants were significantly lower in the ‘push–pull’ plots than in the maize monocrop plots. Similarly, maize plant height and grain yields were significantly higher in the former. Farmers rated the ‘push–pull’ technology significantly superior in having reduced stemborers and striga infestation rates and increased soil fertility and grain yields. These results demonstrate that the technology is equally effective in controlling both pests with concomitant yield increases under farmers’ conditions in the districts studied.     

Enhancing Productivity of Rice-Wheat System Through Integrated Crop Management in the Eastern-Gangetic Plains of South Asia

Abstract

Rice (Oryza sariva)-wheat (Triticum aestivum) rotation is the major production system in the Indo-Gangetic plains of South Asia and mid hills and is important for the food security of the region. The productivity and profitability of the rice-wheat system are very low mainly because of inappropriate nutrient input and poor crop management practices. Field experiments were conducted in 21 farmers' fields in Bara and Parsa districts in the Eastern-Gangetic plains of Nepal from May 1999 to April 2002 to evaluate site-specific nutrient management (SSNM) and integrated crop management (ICM) for improving rice-wheat productivity and profitability. Soil nutrient-supplying capacity (based on omission plot method) varied largely among farmers' fields. Rice soil had a higher N, P, and K-supplying capacity (35–76, 8–17, and 63–98 kg ha¹, compared with wheat (16–41, 6–12, and 20–104 kg ha¹, respectively). Both SSNM and ICM strategies significantly improved the grain yields of rice and wheat. Overall yield increment by ICM over farmers' practice (FP) reached up to 2.3 Mg ha¹ (66%) in rice and 2.3 Mg ha¹ (87%) in wheat, suggesting that there is a large potential for increasing rice and wheat yields in Nepal. Yield gap 1 (maximum attainable yieldaverage yield in ICM) was 1.3 to 1.4 Mg ha¹ for rice and 0.3 to 1.0 Mg ha¹ for wheat. While yield gap 2 (maximum attainable yieldaverage yield in FP) ranged from 2.8 to 3.5 Mg ha-1 for rice and 2.3 to 2.8 Mg ha-1 for wheat. Rice N-use efficiencies increased up to 50% and 70% with SSNM and ICM, respectively, over FP. In wheat, N-use efficiency increased up to 46% by ICM over SSNM. The net profit gained by applying ICM over FP was higher in wheat (US$ 217) than in rice (US$ 73). The findings suggest the urgent need to develop an effective program for wider dissemination of ICM technology in the Eastern-Gangetic plains.     

Effect of trifluralin,pronamide, haloxyfop-p methyl,propaquizafop, and isoxaben on weed control and oilseed rape yield in Iran

In order to investigate the effect of trifluralin, pronamide, haloxyfop-p methyl, propaquizafop and isoxaben on weed control and oilseed rape yield, a two year field experiment was conducted at Darab, Iran, during 2004–2005 and 2005–2006 growing seasons. Herbicides reduced weed biomass compared with the weedy check. In 2004–2005, at 16 WAP (weeks after planting), application of trifluralin plus propaquizafop plus isoxaben at 1200 + 200 + 250 g a.i./ha and trifluralin plus haloxyfop-p methyl plus isoxaben at 1200 + 100 + 500 g a.i./ha provided best control (80%) of wild mustard (Sinapis arvensis L.), compared to other treatments. At 8 and 16 WAP, wild mustard control decreased to 47 and 42%, respectively, when trifluralin was applied alone at 1400 g a.i./ha. In 2005–2006 at 16 WAP, maximum reduction in wild mustard biomass (82%) was achieved with trifluralin plus propaquizafop plus isoxaben at 1200 + 200 + 250 g a.i./ha. In both years, all herbicide treatments controlled fumitory (Fumaria officinalis L.) 64–96%. In 2004–2005, at 16 WAP, wild oat (Avena fatua L.) biomass reduction by trifluralin plus propaquizafop plus isoxaben at 1200 + 200 + 250 g a.i./ha was 95%. In 2005–2006, at 8 and 16 WAP, minimum biomass reduction of wild oat (37–53%) was observed with trifluralin at 1200 and 1400 g a.i./ha. In both years, at 8 and 16 WAP, the most effective herbicide treatments were trifluralin plus propaquizafop plus isoxaben and trifluralin plus haloxyfop-p methyl plus isoxaben regardless of the dose applied and provided maximum reduction in total weed biomass (77–89%) compared to other treatments. Results of both years showed that all herbicide treatments increased oilseed rape grain yield as compared with the weedy check but percentage of oil was not affected by various herbicide treatments. Maximum grain yield was obtained with trifluralin plus haloxyfop-p methyl plus isoxaben at 1200 + 100 + 500 g a.i./ha.     

Integrated management of Striga hermonthica, stemborers,and declining soil fertility in western Kenya

Striga hermonthica (Delile) Benth., stemborers, and declining soil fertility are serious threats to sustainable food production in the Lake Victoria zone of Kenya. To address these constraints, promising integrated crop management technologies were evaluated, using a multi-locational design in four sub-locations in Siaya and Vihiga district (western Kenya) for six cropping seasons. Technologies evaluated consisted of the traditional maize (Zea mays L.) – bean (Phaseolus vulgaris L.) intercrop, maize – Desmodium (Desmodium uncinatum (Jacq.) DC.) push–pull intercrop, Crotalaria (Crotalaria ochroleuca G. Don) – maize rotation, and soybean (Glycine max (L.) Merr) – maize rotation. Within each of these systems, imazapyr-coated herbicide-resistant maize (IR-maize) and fertilizer were super-imposed as sub-plot factors. The push–pull system was observed to significantly reduce Striga emergence and stemborer damage from the second season onwards. IR-maize reduced and delayed Striga emergence from the first cropping season. Differences in Striga emergence and stemborer damage between the other systems were not significantly different. After five cropping seasons, the Striga seedbank was significantly higher in the maize-bean intercrop system than in the push–pull system under both maize varieties while the rotational systems had intermediate values not different from the day zero values. Under IR-maize, the Striga seedbank was significantly lower than under local maize for all cropping systems. Maize yields varied between seasons, districts, and cropping systems. Yields in the push–pull system were higher than in the maize-bean intercrop after two seasons and in the absence of mid-season drought stress. Both maize and soybean responded significantly to fertilizer application for both districts and for most seasons. The various interventions did not substantially affect various soil fertility-related parameters after five seasons. In the short term, IR-maize integrated in a push–pull system is the most promising option to reduce Striga while the rotational systems may need a longer timeframe to reduce the Striga seedbank. Finally, farmer-led evaluation of the various technologies will determine which of those is really most acceptable under the prevailing farming conditions.     

Late defoliation and wheat yield: Little evidence of post-anthesis source limitation

The effect of source reduction on yield and protein content of bread wheat under well-watered and mild drought stress condition in a semi-arid climate was studied. Field experiments were conducted at the Tehran University research farm during 2003–2004 and 2004–2005 growing seasons. Mild drought stress was imposed when plants were at the second node stage by repeatedly withholding watering and re-irrigating when they showed symptoms of wilting or leaf rolling. Partial defoliations (all leaf lamina other than flag leaves were removed) were imposed at booting and anthesis; complete defoliation was imposed at anthesis (defoliation treatments were applied to all plants of each plot). Drought stress caused a significant increase in the remobilization of pre-anthesis reserves to the grain. Defoliation did not significantly affect remobilization. Grain yield and 1000-grain weight was reduced slightly by drought stress, but in most cases it was not significantly reduced by defoliation. Significant changes were not observed for grain protein content between defoliated and control plots. The results suggested that grain yield of the cultivar used under the condition tested is more controlled by sink than source strength.     

Effects of interspecific competition on the growth and competitiveness of five emergent macrophytes in a constructed lentic wetland

To evaluate the performance of new rice establishment methods viz., system of rice intensification (SRI) and integrated crop management (ICM), a field study was conducted during 2008–11 in South Garo Hills, Meghalaya, foot hills of Eastern Himalayas, India. Field demonstrations were undertaken during wet seasons of 2008–11 and socio-economic information in the context of farmer’s realities were obtained during 2010–11 using a well structured questionnaire administered to 134 farmers. The results indicated that the average higher productivity of rice under SRI and ICM demonstration was 209.9 and 185.4 %, respectively, over conventional rice culture (CRC). The SRI and ICM methods of rice cultivation could save seeds (97.56 and 60.98 %), saving water (78.05 and 63.66 %), reduce cost (70.33 %), higher yield etc. compared to CRC. The main reasons for non-adoption of SRI/ICM was related to involvement of more efforts, faith towards traditional practices, ignorance and lack of knowledge on scientific water management. The net-return of $816.69, $706.63 and $51.48/ha was realized under SRI, ICM and CRC, respectively. The co-efficient of multiple determinations (R ²) of the production function was 0.695 in SRI, 0.714 in ICM and 0.734 in CRC which indicated that about 69.5, 71.4 and 73.4 % of the variation in rice productivity under SRI, ICM and CRC, respectively were explained by the independent variable and remaining 30.5, 28.6 and 26.6 %., respectively in SRI, ICM and CRC were as a result of non-inclusion of some explanatory variables as well as other factors outside the farmers control.     

Highly client-oriented breeding,using local preferences and selection,produces widely adapted rice varieties

When explicit measures are taken to account for the needs of clients (farmers and consumers) it results in highly client-oriented breeding. This involves the participation of farmers to specify the design of desirable varieties and, once they are produced, their testing without delay with the target clients in the target environments. The term highly client-oriented breeding (COB) explains the purpose of farmer involvement – the deliberate achievement of a high degree of client orientation – rather than simply explaining the process of farmers participating in plant breeding (participatory plant breeding). Client-oriented breeding is sometimes based on the preferences of relatively few farmers in a small area, so a possible drawback is that it will produce varieties that are too locally adapted. We describe the testing of varieties in the High Barind Tract (HBT) of Bangladesh from a COB programme carried out in Chitwan district, Nepal. The two best lines, Judi 582 and Judi 567, yielded 19–50% more during the T. Aman season and 106% more during the Aus season than check varieties in the HBT. Research to determine farmers’ preferences and adoption consistently showed these varieties were preferred over all available alternatives. The new varieties were broadly adapted as they were superior in all the three rice-growing seasons over varying levels of inputs. This broad adaptation could be explained by the breeding method: the generations were advanced in two contrasting seasons and each generation was grown on a different farmer's field under different management and planting dates. Because the segregating generations were grown under moderate and fluctuating levels of nitrogen, it is to be expected that genotypes with good nitrogen use efficiency will be selected that can also respond to added nitrogen. Overall, the cost-effectiveness of COB was high as it produced widely adapted genotypes from a small breeding programme, and knowledge of farmers’ preferences increased the efficiency of targeting new germplasm.     

Effect of different soil tillage and organic fertilizers on winter triticale and spring barley stem base diseases

Multi-factor crop management field experiments were conducted in Vezaiciai, in southwestern Lithuania, from 2004 to 2006 to assess the influence of tillage and organic fertilizer management on stem base disease development. The treatments included 4-year crop rotations of continuous grass, winter triticale, winter oilseed rape and spring barley in combination with three tillage systems (shallow (8–10 cm) non-ploughing tillage, shallow (10–12 cm) tillage and deep (20–25 cm) ploughing). Eyespot prevailed both in winter triticale and spring barley crops. Winter triticale was more susceptible than spring barley. Shallow tillage decreased eyespot incidence and severity relative to deep tillage. Crop residue management exerted a weak but statistically significant effect on the disease development on triticale; in general, slightly higher numbers of affected stems were recorded in triticale plots where the straw from the previous crop had been removed prior to planting. However, complete straw removal from plots significantly decreased eyespot severity in comparison with crop residue or manure management treatments in spring barley. The highest number of affected triticale and barley plants was found in shallow (10–12 cm) tillage plots. The effects of residue management on minimising eyespot severity can be expected only after a delay of a few years.     

Increasing paddy yields and improving farm management: results from participatory experiments with good agricultural practices (GAP) in Tanzania

Rice is an increasingly important commodity in sub-Saharan Africa. In Tanzania, the rice yield gap is as high as 87%, due to a combination of production constraints and sub-optimal crop management. Reducing this yield gap may be partly achieved through the introduction and dissemination of good agricultural practices (GAP). We conducted 18 farmer-managed on-farm trials in Tanzania, to test a set of GAP components against conventional farmers’ practices (FP) for two consecutive growing seasons in 2013 and 2014. The objectives were: (1) to understand farmers’ capabilities in implementing GAP; (2) to acquire better insights into the merits, relevance and suitability of individual GAP components; and (3) to provide a case study showing that exposure to good practices combined with the farmers’ own experimentations can serve to improve and, trigger a positive change in the participating farmers’ crop management. Compared to the farmers’ own practices, average yield increases of 1 t paddy ha^?1 in 2013 and 2.7 t ha^?1 in 2014 were achieved when following GAP. These yield advantages were mainly obtained by a higher panicle number, improved harvest index and improved weed control. Farmers experienced difficulties with land levelling, planting or sowing in lines and using rotary weeders, but they were convinced that these technologies are important to boost their rice yields. The case of Tanzania shows that paddy yields can be substantially improved by GAP and that adoption of GAP by smallholder rice farmers can be triggered by stimulating experimentations with such practices on their own farms.     

Intercepted solar radiation affects oil fatty acid composition in crop species

Solar radiation intercepted during grain filling affects growth of grain crops. Its effects on oil fatty acid composition have not been investigated. The objective of this work was to investigate the effect of intercepted solar radiation per plant on oil fatty acid composition in four crops. An experiment including a cultivar of soybean, maize and sunflower was sown at Balcarce, Argentina, during two growing seasons (2001–02 and 2004–05) and two experiments with a rape cultivar were conducted during in 2004 and 2005. The amount of intercepted solar radiation during grain filling was modified by shading (50–80%) and thinning plants (50%). In addition, the same cultivars of soybean and maize were sown in the field at Paraná, Argentina, during the 2004–05 growing season and in growth chambers under different day/night temperatures during grain filling. Regardless of the species, oleic acid percentage increased as intercepted solar radiation (ISR) per plant increased. The highest difference (13%) was observed in sunflower (shading vs. thinning) and the increase in oleic acid was associated with a reduction in both linoleic and linolenic acids. Saturated fatty acid percentage was not affected by intercepted solar radiation per plant. Differences among radiation treatments were observed not only at physiological maturity but also at earlier stages of the grain filling period. In soybean and maize, increasing daily mean temperature increased oleic acid percentage (r² ≥ 0.52). Changes in fatty acid composition in radiation experiments and treatments were not accounted for by variations in temperature (differences among treatments were ≤1 °C). In sunflower and maize, the source (ISR)–sink (grain number) ratio during the grain filling period better explained changes in oleic acid percentage than per plant ISR alone. Changes in fatty acid composition due to radiation treatments were as large as variations produced by changes in temperature in soybean and maize, but not in sunflower. Based on these results, management practices that increase intercepted radiation by the plant during grain filling could contribute to obtain oils with higher oleic acid percentage.     

Dry matter and nitrogen accumulation,partitioning, and retranslocation in safflower (Carthamus tinctorius L.) as affected by nitrogen fertilization

Safflower (Carthamus tinctorius L.) is a deep-rooted crop which can tolerate water stress and can be grown in rotation with other crop species. Nitrogen is one of the most important nutrients for the growth and development of safflower; however, the effect of N level on dry matter, accumulation, partitioning, and retranslocation has not been extensively studied. A 2-year field study was therefore conducted with the objective to determine the effect of N fertilization on crop phenology, dry matter, N accumulation, partitioning and retranslocation of safflower grown under rain-fed conditions. Three rates of N were used (0, 100, and 200 kg N ha⁻¹) and two hybrids (CW9048 and CW9050) of safflower were selected. The experiment was conducted during the 2003–2004 (2004) and 2004–2005 (2005) growing seasons on a calcareous sandy loam (Entisols, Orthents, Typic Xerorthent) at the experimental farm of the Aristotle University of Thessaloniki, in Northern Greece. During 2004 spring was quite mild with significant rainfall whereas during 2005 spring was hotter with lower rainfall. Our study found that N fertilization increased biomass at anthesis by an average of 24% and at maturity by an average of 25% compared with the control. Total above ground biomass increased after anthesis in both years, in both hybrids and for all fertilizer treatments. N fertilization increased the dry matter partitioning in leaves + stems and heads at anthesis and also in leaves + stems, seeds, and head vegetative components at maturity. Dry matter translocation was not affected by N fertilization but lower values were found during the second year. N content was affected by the fertilization treatments and increased in those plants treated with fertilizer compared with the controls. In addition, N fertilization increased N retranslocation from the vegetative parts of the plant to the seed, but it did not affect N gain. During the second year, which was drier, there were significant N losses but also greater N translocation efficiency and higher contribution of pre-anthesis N to seed. Seed yield was correlated with the dry matter and N translocation indices, and was higher for the fertilized plants, compared with the control. The present study indicates that N fertilization promoted the growth of safflower and increased the dry matter yield, N accumulation, translocation and seed yield under rain-fed conditions.     

Agronomic assessment of Bt trait and seed or soil-applied insecticides on the control of corn rootworm and yield

Corn rootworm (Diabrotica spp.) has become the most concern and widespread insect pest of corn (Zea mays L.) production in North America. Two field experiments were conducted to assess the agronomic and yield performance of transgenic rootworm trait, Bacillus thuringiensis (Bt) Cry3Bb, seed-coating treatment, and a soil-applied insecticide under natural corn rootworm infestation. Experiment 1 compared a conventional corn hybrid with and without insecticide (Force 3G) with its near isoline Bt hybrid from 2003 to 2005, on a clay loam soil. Experiment 2 investigated the same treatments as in Experiment 1 plus an additional seed-coated Poncho treatment on a sandy loam in 2004 and 2005. Rootworm population before the crop anthesis, root node injury and root:shoot dry weight ratio during the early grain filling stage, and stalk lodging and grain yield were determined. Our data showed that rootworm population diminished over the 3 years owing to rootworm displacement and adverse weather conditions. At the clay loam site, both Force 3G and the Bt hybrid significantly reduced the larval populations, root injury and lodging score, and increased root:shoot ratio. Over the 3 years, grain yields of the Bt hybrid were 11–66% greater than the untreated non-Bt isoline hybrid; yield of the non-Bt hybrid treated with Force 3G was also significantly greater than the same untreated non-Bt hybrid in 2 of 3 years. Despite less root node injury in the first rows of non-Bt plants adjacent to the Bt plots was observed, yield benefit of this effect remained to be proven. On sandy loam soil, the larval population was very low and there were no differences in root node injury and plant lodging among all the four treatments in either 2004 or 2005. The yield of the Bt hybrid was up to 10% greater than its non-Bt isoline hybrid treated or not with an insecticide in 1 year. Our data showed that Bt rootworm seed technology was effective to control the rootworm larvae and protected grain yield under severe infestation. Furthermore, our data suggest that some of the gain in Bt hybrid yield may be attributed to the genetic transformation as observed in sandy loam soil experiment. In all cases, corn producers should be aware of the pest history, rootworm pressure in relation to economic threshold, soil type and the expected cost-to-benefit ratio before deciding to adopt any protective measures.     

Evaluation of CIMMYT conventional and synthetic spring wheat germplasm in rainfed sub-tropical environments. I. Grain yield

Hexaploid spring wheat (Triticum aestivum L.) germplasm from CIMMYT's breeding program in Mexico has assisted wheat improvement in Australia, particularly in the north-eastern region where terminal drought frequently reduces grain yield. A total of 273 conventional hexaploid and derived synthetic hexaploid spring wheats from CIMMYT, along with 15 locally adapted Australian cultivars (Oz lines), were evaluated for grain yield over four years in a total of 27 environments in Australia's north-eastern wheat region. The CIMMYT conventional spring wheats were from a Seri/Babax recombinant inbred line population (SB lines), elite entries from an International Adaptation Trial (IAT lines) introduced to Australia between 1999 and 2004 and from CIMMYT screening nurseries introduced to Australia in 2004–2005 (SW lines). Synthetic wheats (SYN lines) were also from these nurseries as well as from a separate program of synthetic wheat introductions to Australia over 2001–2004.     

Interaction between host plant resistance and biological activity of Bacillus thuringiensis in managing the pod borer Helicoverpa armigera in chickpea

The legume pod borer Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) has developed high levels of resistance to conventional insecticides, and therefore, efforts are being made to develop transgenic chickpea expressing toxin genes from the bacterium Bacillus thuringiensis (Bt) for controlling this pest. However, there is an apprehension that acid exudates in chickpea might interfere with the biological activity of Bt. Therefore, we studied the biological activity of Bt (Biolep^R) on four chickpea genotypes with different levels of resistance to H. armigera under field conditions, and by incorporating lyophilized leaf and pod tissue into the artificial diet with and without Bt. The pH of the acid exudates varied from 2.1 to 2.9, and malic and oxalic acids were the major components of the acid exudates in different chickpea genotypes. There was no survival of H. armigera larvae in chickpea plants sprayed with 0.1, 0.2 and 0.5% Bt. There was a significant reduction in larval survival, larval and pupal weights and fecundity, and prolongation of larval and pupal periods in chickpea plots sprayed with Bt (0.05%) as compared to the unsprayed plots. Biological activity of Bt was lower on artificial diets with leaf or pod powder of chickpea genotypes, which might be because of a low intake of Bt toxins due to the antifeedant effects of acid exudates in the chickpea or reduction in biological activity of Bt due to the interaction of biochemical constituents in chickpea with the Bt toxins. Larval survival, larval and pupal weights, pupation and adult emergence were significantly lower on diets with leaf or pod powder of the H. armigera-resistant genotypes than on the susceptible check. Chickpea genotypes with resistance to H. armigera acted in concert with Bt to cause adverse effects on the survival and development of this insect. The results suggested that development of transgenic chickpeas expressing toxin genes form Bt will be quite effective for controlling of the pod borer, H. armigera.     

On-farm soil N supply and N nutrition in the rice–wheat system of Nepal and Bangladesh

On-farm research to evaluate the productivity and nitrogen (N) nutrition of a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system was conducted with 21 farmers in the piedmont of Nepal and with 21 farmers in northwest Bangladesh. In Nepal, two levels of N-fertilizer (0–22–42 and 100–22–42 kg N–P–K ha⁻¹) and farmers’ nutrient management practices were tested in the rice season, and three levels of N (0–22–42, 70–22–42, and 100–22–42) and farmers’ practices were evaluated in the wheat season. The treatments in Bangladesh included a researchers managed minus-N plot (0–22–42) and the farmers’ practices. Rice and wheat yields were higher in all treatments than the 0–22–42 control plots, with the exception of rice with the farmers’ practices at one location in Bangladesh. The researchers’ treatment of 100–22–42 in Nepal resulted in larger yields of both rice and wheat than the farmers’ practices, indicating that farmers’ rates of N-fertilizer (mean 49 kg N ha⁻¹) were too low. Delaying wheat seeding reduced yields in the fertilized plots in both countries, especially as N-fertilizer dose increased. Soil N-supplying capacities (SNSC), measured as total N accumulation from the zero-N plots (0–22–42), and grain yields without N additions were greater for rice than for wheat in both Nepal and Bangladesh. Higher SNSC in rice was probably due to greater mineralization of soil organic N in the warm, moist conditions of the monsoon season than in the cooler, drier wheat season. However, SNSC was not correlated with total soil N, two soil N availability tests (hot KCl-extractable NH₄⁺ or 7-day anaerobic incubation), exchangeable NH₄⁺ or NO₃⁻. Wheat in Nepal had greater N-recovery efficiency, agronomic efficiency of N, and physiological efficiency of N than rice. Nitrogen internal-use efficiency of rice for all treatments in both countries was within published ranges of maximum sufficiency and maximum dilution. In wheat, the relationship between grain yield and N accumulation was linear indicating that mobilization of plant N to the grain was less affected by biotic and abiotic stresses than in rice.