ISHS International Symposium on Biotechnology of Tropical and Subtropical Species Part 2 IMPROVING COLD TOLERANCE AND INSECT RESISTANCE IN CHICKPEA AND THE USE OF AFLPS FOR THE IDENTIFICATION OF MOLECULAR MARKERS FOR THESE TRAITS
Optimisation of potassium (K) use efficiency in pastures on sandy soil is challenging. We characterised growth response, root carboxylate exudation and mycorrhizal colonisation in three perennial pasture grasses: tall fescue (Festuca arundinacea L.), veldt grass (Ehrharta calycina Sm.) and tall wheatgrass (Thinopyrum ponticum L.) in two glasshouse experiments with: (1) four K rates (0, 40, 80 and 120 mg K kg-1 soil), and (2) four N and K treatments (no N and K (–N–K), 81 mg N kg-1 soil but no K, 80 mg K kg-1 soil but no N, and N at 81 and K at 80 mg kg-1 soil (+N+K)) in low-K sandy soil. Veldt grass had the highest shoot dry weight and shoot P content, but the lowest mycorrhizal colonisation. Potassium fertilisation had no significant impact on exudation of citrate and oxalate. The K0 plants had significantly lower exudation of acetate and total carboxylates than K40 plants. The +N+K plants had maximum shoot growth at both harvests (30 and 60 days after sowing (DAS)) and highest N and K shoot contents at 60 DAS. The –N–K plants exuded maximum amounts of citrate and malate at 30 DAS, but at 60 DAS tall fescue had the highest rhizosphere concentrations of citrate and malate in the +N+K treatment. At 60 DAS, mycorrhizal colonisation was significantly lower with than without N and K fertilisation. We concluded that pasture grasses could yield well even in inherently low-K soil without external K fertilisation and mycorrhizal symbiosis. However, the +N+K plants had the highest yield and root carboxylate exudation.
In this chapter we review recent advances in cool-season pulse production in Australia and how rhizobial, soil, and environmental factors impact on productivity. Nationally, pulse production has continued to increase to about 2 × 106 t yr−1, but in recent years the capacity for nitrogen (N2) fixation has been limited, especially due to insufficient moisture in 2002 and through the emergence of Ascochyta blight in chickpea (Cicer arietinum L.) crops across southern Australia, in addition to abiotic factors such as extremes in soil pH (highly acidic or alkaline soils), temperature, soil moisture, nutrients, and chemical residues have a significant impact on N2 fixation and pulse production in Australia.
The problems and challenges of rapidly increasing world population, global climate change, shortages of water suitable for irrigation and degradation of agricultural land are increasing the demand to improve grain production from rainfed arable lands. Specific challenges include estimating the size and thus the value of the yield gap, identifying the factors limiting current average production and designing profitable remedial strategies for a range of agro-ecological regions. This review of the rainfall-limited potential yields and the gap between actual or average yields of cereal and legume crops and the rainfall-limited potential indicates that there is still substantial room to increase the average yield of crops in rainfed systems in both developed and developing regions. The review has indicated that (1) the size of the gap between average and potential yields varies according to the agro-ecological zone and the available technologies from about 0.5 to over 5 t/ha, leaving considerable scope for future yield improvement; (2) there is relatively less information applicable at the farm or field scale that assesses the spatial and temporal variability of the yield gap, the reasons for the gap and the possible methods to close the gap; (3) there is also limited information on the feasibility and profitability of applying various approaches to close the gap, including tactical and strategic management practices and plant breeding; (4) the evidence of the impact of the components of conservation agriculture on crop yields in a wide range of agro-ecological regions supports the adoption of zero tillage and crop rotation but is less clear in support of residue retention; (5) objective identification and testing of factors that limit production can lead to a rational sequence of amelioration that is specific to each agro-ecological or field situation and can close the yield gap in winter-dominant rainfall environments; and (6) farmer-participatory varietal selection, including breeding for specific adaptation can make a substantial contribution to closing the gap in a range of environments. A common observation from the reports reviewed here is that sustainable yield improvement will need to employ a range of methods that are appropriate to specific agro-ecological conditions—previous approaches based on single inputs, practices or genotypes can only be partial solutions.
The phenology, growth, seed yield and yield components of a number of introduced narbon bean (Vicia narbonensis L.) accessions and F9 breeding lines were compared with faba bean (Vicia faba L. cv. Fiord) or field pea (Pisum sativum L. cv. Dundale) at 3 sites in 2 seasons. All narbon bean accessions had slow development, for example all accessions reached 50% flowering 9-35 days later than faba bean or field pea depending on the accession, site and season. Dry matter production near flowering ranged from 1.0 to 2.3 tlha and the growth of the best accessions was comparable with faba bean. In general, the accession ATC 60114 collected in the Beka'a Valley, Lebanon, produced the greatest seed yield across the sites and seasons (on average 1.52 t/ha). In 1993, the best narbon bean accession produced seed yields that ranged from 59% of the faba bean seed yield at the wettest site to 121% at the driest site. In the following year, one of the driest in decades, 6 accessions produced seed yields of more than 1.0 t/ha, similar to field pea. Seed yield was negatively correlated with days to flowering, podding and maturity, suggesting that yield could be improved by selecting for more rapid development. Most accessions retained the majority of their leaves at maturity, but showed some degree of pod shattering and a moderate level of lodging at maturity. Genotypic variation in all these characters was evident. Further selection and breeding, together with appropriate agronomic packages will improve the adaptation of narbon bean to mediterranean-type environments of southern Australia. However, the adoption of narbon bean in Australian agriculture will depend on its marketability and acceptance by the stockfeed industry, and its on-farm utility.
