Variation in osmotic adjustment (OA) among chickpea (Cicer arietinum L.) cultivars has been observed when exposed to terminal drought, but some studies suggest that this benefits yield while others suggest it does not benefit yield in water-limited environments. In the present study, parents differing in OA were crossed and a set of advanced breeding lines (ABLs) developed for yield testing. The variation in OA during podding was measured under terminal drought in the F(2), F(3), F(7), and F(8) progeny and in the parents by either rehydrating the leaves before sampling for osmotic potential (OP) or by measuring the relative water content (RWC) and OP on adjacent leaves for the calculation of the OP at full turgor. Yields were measured in the F(8) progeny under terminal drought in Australia and India. While differences in OA were measured in the chickpea lines and parents, OA varied from year to year and did not consistently benefit yield when measured in the field under terminal drought. In Australia, differences in OA were not associated with any yield benefit in any year, while in India early flowering resulted in higher yields at three of the four sites, and OA had an inconsistent effect on seed yields. A comparison of OP at full turgor measured after rehydration and from measurements of RWC and OP showed that the rehydration technique underestimated OA. The lack of contribution of OA to yield of chickpea is discussed.

No abstract

To investigate wild and domesticated Mediterranean annual reproductive strategies, common garden comparisons of Old World lupins collected along aridity gradients were initiated. These are excellent candidates for ecophysiology, being widely distributed across contrasting environments, having distinct domestication histories, from ancient Lupinus albus to recently domesticated Lupinus angustifolius and Lupinus luteus, facilitating the study of both natural and human selection. Strong trade-offs between seed size, early vigor and phenology were observed: vigor increasing, and flowering becoming earlier with increasing seed size. Despite large specific differences in all these traits, natural and human selection have operated in very similar ways in all 3 species. In wild material, as collection environments became drier and hotter, phenology became earlier, while seed size, early vigor and reproductive investment increased. Wild and domesticated germplasm separated along similar lines. Within similar habitats, domesticated material was consistently earlier, with larger seeds, greater early vigor and higher reproductive investment than wild, suggesting selection for both early establishment and timely maturity/drought escape in both domesticated and wild low rainfall ecotypes. Species differences reflected their distribution. Small and soft-seeded, low vigor L. luteus had a late, rainfall-responsive phenology specifically adapted to long season environments, and a narrow coastal distribution. L. angustifolius was much more conservative; more hard-seeded, flowering and maturing much earlier, with a wide Mediterranean distribution. L. albus flowered earlier but matured much later, with longer reproductive phases supporting much larger seed sizes and early vigor than either L. luteus or L. angustifolius. This ruderal/competitive combination appears to give L. albus a broad adaptive capacity, reflected in its relatively wider Mediterranean/North African distribution.

SummaryRainfall gradients select for contrasting, integrated, adaptive strategies in the Mediterranean legume, Lupinus luteus, where phenology, productivity, fecundity, and water-use are matched to seasonal rainfall. Profligate high-rainfall ecotypes have developed drought tolerance that is redundant in drought-avoiding low-rainfall ecotypes.

The carbon isotope discrimination (δ13C) of leaves has been shown to be correlated with the transpiration efficiency of leaves in a wide range of species. This has led to δ13C being used in breeding programs to select for improved transpiration efficiency. The correlation between δ13C and transpiration efficiency was determined under well‐watered conditions during the vegetative phase in six genotypes of lentil (Lens culinaris Medikus), six genotypes of chickpea (Cicer arietinum L.) and 10 cultivars of narrow‐leafed lupin (Lupinus angustifolius L.). Biomass (dry matter) accumulation and water use (transpiration) varied among the genotypes in all three species and transpiration efficiency was 40% to 75% higher in the most efficient compared with the least efficient genotypes. However, δ13C and transpiration efficiency were not significantly correlated in any of the species. This suggests that the δ13C technique cannot be used in selection for transpiration efficiency in the three grain legumes (pulses) studied.

No abstract

Indeterminate narrow-leafed lupin (Lupinus angustifolius L. cv. Merrit) was exposed to enriched atmospheric CO2 during pod-filling to enhance the availability of carbon resources for pod-filling in order to determine whether or not seed-filling, yield, and harvest index are limited by the availability of photosynthetic assimilate. Plants were grown in a glasshouse and the flowers painted with an aqueous solution containing either N6-benzylaminopurine (BAP) or no BAP to generate 2 different numbers of pods per plant. From the time when pods began to fill seeds (≥5 mg/seed) until maturity, plants were exposed to either ambient (350–360 L/L) or enriched (700 L/L) CO2 by enclosing them in 2 transparent, box-shaped tunnels with similar temperatures, light, and water conditions. Whether or not BAP was applied to flowers, CO2 enrichment increased the final number of pods and the number of pods that filled large seeds (≥150 mg) by 20–22 pods/plant. Enriched CO2 reduced to zero the number of pods that had small seeds (≥30–80 mg) and reduced the number of pods with unfilled seeds from 16 to 1 pod/plant. This increased seed yield per plant by 44–66%, but did not affect the harvest index. Harvest index was unchanged because enriched CO2, while increasing pod-filling, also increased pod set and dry matter accumulation on the developing branches. This indicates that an increased availability of carbon resources during-pod filling changed the allocation of assimilates by filling small seeds and producing new branches. The 47–56% increase in dry matter per plant was reflected in the increase in seed yield, which occurred largely through an increased number of pods and seeds per plant. These data support the idea that seed-filling and hence seed yield in well-nodulated, indeterminate narrow-leafed lupin is limited by carbon resources at the stage when the plant is most source-limited, which is during podset and pod-filling.

An individual flower-painting technique that utilises N6-benzylaminopurine (BAP) to increase pod set was used on an indeterminate cultivar of narrow-leafed lupin (Lupinus angustifolius L. cv. Merrit) and on a breeding line with restricted branching (84A/241) to examine the interaction between pod set, water deficit, and seed yield. Petals and sepals of each flower on each inflorescence were painted with a 0·002 M solution of BAP every day from the first day the flower opened to the day it senesced. A water deficit was induced, after flowering on the first-order apical branch, in half of the plants. The other half were maintained at a soil water content close to field capacity. Leaf water potential and leaf conductance declined and remained at about –1·25 MPa and 300 mmol/m2· s, respectively, in the treatments in which a terminal water deficit was induced. Application of BAP to flowers had no effect on plant-water relations. The water deficit reduced the number of pods that reached maturity (mature pods) when no BAP was applied and increased seed yield in pods that filled seeds. Application of BAP increased the number of pods that reached maturity. However, the additional pods that reached maturity produced unfilled seeds. Seed yield and harvest index were reduced in the BAP treatments, mainly as a result of a reduction in seed number. An increase in seed abortion during seed filling probably caused the reduction in seed number. We conclude that the reduction in seed number and pod filling resulted from a shortage of assimilates to fill all the mature pods produced.