An understanding of the relationship between N assimilation and grain yield and protein, and the measurement of genetic variation in preanthesis and postanthesis N assimilation in wheat (Triticum aestivum L.) are necessary to achieve additional gains in selecting for both high grain yield and high grain protein. Thus, total N assimilation in the spring wheat cultivars ‘Anza’ and ‘Cajeme 71’ and 96 F5‐lines from the cross of these cultivars was studied in field experiments. Freanthesis N assimilation was similar for the two cultivars, but by maturity Anza had assimilated 9% (P < 0.01) more N than Cajeme 71 in both high and low N fertility levels. This difference was mainly due to greater postanthesis assimilation by Anza (22% of total) than Cajeme 71 (10%). Significant genetic variation among F5 lines in N assimilation prior to anthesis occurred in two of three experiments, but no relationships were found between this trait and grain yield, grain protein concentration, or grain protein yield. Significant genetic variability in N assimilation after anthesis was detected, although estimates of heritabilities were low. Nitrogen assimilation after anthesis strongly influenced grain and grain protein yields, explaining 27 to 39% of the variation, but no relationship was found with grain protein concentration. The residuals from the regression of N assimilation after anthesis on biomass at anthesis were also strongly related to grain and grain N yield in a stagewise regression analysis, indicating variation other than random error was involved. Grain protein concentration was also positively associated with these residuals in one experiment. Possible sources of this variation, particularly with relation to roots are discussed. Total N assimilation showed broad‐sense heritabilities of 21 to 27% and was correlated (r = 0.68 to 0.86; P < 0.01) with grain and grain protein yields. Thus genetic variation in N assimilation has a role in determining grain yield and protein concentration in wheat. Further work to determine the genetic and physiological basis of factors influencing N assimilation is needed, especially with regard to roots.

This study was conducted to provide basic information on the accumulation of dry matter and N in spring wheat (Triticum aestivum L.) and to develop data necessary for an understanding of the physiological and genetic relationships between N movement and grain yield and protein concentration. ‘Anza’ and ‘Cajeme 71’ and 96 random F4 and F5 lines derived from the hybrid of these two cultivars were studied in field experiments at high and low N fertility regimes. Anza, the high yielding, low grain protein parent, continued to accumulate vegetative dry matter after anthesis, suggesting utilization of postanthesis photosynthates in grain filling. Anza also assimilated more N during the reproductive stage than Cajeme 71, the lower yielding, high protein parent.A considerable loss of vegetative dry matter between anthesis and maturity was observed in Cajeme 71 suggesting a greater reliance on photosynthates formed prior to anthesis for grain filling in this cultivar than in Anza. Significant but low negative correlations between yield and grain protein concentration for 96 F5 lines indicated that simultaneous increases in grain yield and protein concentration could be achieved by selection. Grain yield was positively and grain protein concentration was negatively correlated with time of maturity. However, lines combining both high grain yield and high grain protein concentration (e.g., 8.4 Mg ha‐1, 14.8% protein) were identified over the range of maturity of the majority of lines. Genotypic variation among the F5 lines was significant for all measured traits except one. In that exception total N yield at anthesis in the low N experiment did not show significant genotypic variation in the F5 lines. The genotype ✕ environment interaction variance components were, on the whole, of much less importance than the genotypic components in this small sample of environments.

Postemergence herbicide options for mature goosegrass [Eleusine indica (L.) Gaertn.] control in bermudagrass (Cynodon spp. Rich.) turf are lacking. Greenhouse and field trials were conducted to determine the lowest rate at which topramezone, with or without triclopyr, controls goosegrass while maintaining acceptable bermudagrass quality. Greenhouse dose–response studies determined herbicide rates for field trials. In field trials, topramezone at 6.13 to 12.3 g a.i. ha−1 applied twice at a 3‐wk interval eliminated 8‐ to 18‐tiller goosegrass at three of four locations. The same topramezone treatments did not reduce smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.] cover more than 53% when applied alone and not more than 84% when applied with triclopyr at 140 g acid equivalent ha−1. The number of days over a threshold of 30% injury or stunting (DOT30) within the 28‐d period following each of two herbicide treatments was calculated for 31 bermudagrass varieties. Bermudagrass injury DOT30 following the first treatment ranged from 11.1 to 17.8 d, depending on variety. The addition of triclopyr increased injury DOT30 but reduced the severity of discoloration by eliminating white tissue discoloration. All varieties were severely injured but completely or near completely recovered by 28 d after each treatment. Generally, topramezone at 6.13 or 12.3 g a.i. ha−1 applied twice controls goosegrass in bermudagrass. Addition of triclopyr improves smooth crabgrass control and decreases severity of bermudagrass injury but increases suprathreshold‐injury duration.

To determine the extent and type of resistance to sugarcane whitegrubs in clones of sugarcane and some of their wild relatives, pot trials and field trials were carried out. The pot trials tested 405 clones and estimated tolerance effects by differences in the yields of tops, roots, and stubble of infested and uninfested plants and estimated antibiosis effects by differences in the survival and final weights of larvae placed into the pots. Two field trials used a split-plot design, insecticide treated or untreated, to determine tolerance effects on yields of commercial cane and antibiosis/antixenosis effects through differences in the number of larvae in untreated plots. Comparison of pot trials and field trials allowed an estimate of the usefulness of pot trials in estimating resistance to whitegrubs under commercial farming conditions. Both pot and field trials showed that a range of tolerance and antibiosis resistance mechanisms to whitegrub feeding exists within the current sugarcane germplasm and close relatives. Tolerance effects were apparent in the growth of tops, roots, and stubble. Antibiosis effects were apparent on grub survival and grub growth. Some of these tolerance effects are partially correlated with the general vigour of clones, but there are a number of clones that depart from the general relationships for tolerance and antibiosis. These clones would be especially important in any future program to increase the levels of resistance within the breeding gene pool. There was reasonable repeatability of pot-based tolerance levels between pot trials and with results derived from field trials. These results would be best incorporated into the current sugarcane-breeding program through a specific subprogram targetting grub resistance and using recurrent selection with rapid generation turnover. This would require the development of an appropriate screening system and may require 2 stages. The first would need to handle large numbers of clones to discard the least resistant. This could be followed by a more intensive screening (e.g. our pot technique) to identify the most resistant clones. Those identified after the first cycle of selection would then be recombined to produce more progeny and the process repeated. It is likely that several cycles would be necessary to increase resistance to a level that provides an economic protection.

The mating system of Western Australian sandalwood (Santalum spicatum) was investigated in seed collections from a family trial. The mean outcrossing rate was high (95.2%) although there was variation among families and one family showed particularly low outcrossing, high bi-parental inbreeding and high correlated paternity. Variation in flowering time between this family and others in the trial was the most likely cause of the high inbreeding and low number of fathers contributing to the seed crop in trees from this family. The high level of outcrossing in the rest of the families indicated that S. spicatum has a preferentially outcrossed mating system, but that it is capable of selfing when conditions are unsuitable for outcrossing. The seedling progeny showed no influence of inbreeding on seedling height at 4 months. Analysis of genetic diversity revealed high levels of genetic diversity have been captured in the seed crop from the trial, and this diversity is comparable to that identified in a previous study of natural populations from throughout the range of the species. These results indicated that production of seed through seed orchards will be a successful means of deployment of breeding gains in the species, however it is essential to ensure overlap in flowering times among different families planted in a seed orchard.