Eragrostis curvula (Schrad.) Nees s. lat., a highly polymorphic polyploid complex, can be considered as one of the most important warm season perennial grasses for the semi-arid regions of central Argentina. In apomictically propagated and perennial plants such as weeping lovegrass, where successive measurements can be done across time, repeatability estimates provide an indication of the degree of influence of permanent effects on the phenotypic variation and allow prediction of future performance from past records. Analysis of variance of the experiment showed highly significant variation (P < 0·01) for the main factors in all four traits. Although there was very high variability between cuts, hybrids of E. curvula exhibited considerable inter-entry variability, in particular for those traits determining forage yield. Repeatability calculated in this experiment was highest for the crown diameter (0·86), leaf length (0·84) and dry matter (0·84), while in panicle number (0·66) it was lowest. Repeatability estimates for the vegetative characteristics indicate small effects of temporal environment. The four traits studied, including panicle number with their moderate repeatability, do not require an essentially different number of observations to obtain measures at the same level of accuracy. For vegetative characters two harvests provided 98% of the accuracy of the total obtained with four cuts, and for panicle number the same percentage was obtained for three harvests. This stability of performance is a desirable characteristic for grass cultivars. Patterns of trait associations were also described. Because leaf length is closely associated with dry matter and has high repeatability, to use leaf length as an indirect evaluation criterion should be almost as efficient as direct evaluation for aerial biomass yield. Reliable estimates of parameters such as repeatability and phenotypic correlation are needed for prediction of production values and for the design of efficient improvement programmes. For genotype evaluation additional research is required to quantify the extent of genotype × environment interaction across years and localities of semi-arid regions.

A study on the use of quebracho tannins as chemical additives was carried out at the Spanish Council for Scientific Research, León, Spain during 1998 by conducting two experiments. In the first experiment, three ruminally cannulated ewes were used to determine in situ degradability of soya bean meals (SBM) treated with different doses of quebracho tannin. Samples were prepared by spraying 100 g SBM with 100 ml distilled water containing 0, 1, 5, 10, 15 or 25 g of commercial quebracho powder (S0, SQ1, SQ2, SQ3, SQ4 and SQ5, respectively). Intestinal digestibility of non-degradable protein was estimated in vitro. The rapidly degradable protein fraction of all quebracho treated soya bean meals was different (P<0·05) from the non-treated SBM (S0: 0·154), with values ranging from 0·032 to 0·133. SQ4 and SQ5 showed lower fractional rates of degradation of the protein than S0 (0·042 and 0·046 v. 0·082, respectively). By contrast, in vitro digestibility of the non-degradable protein was not significantly affected by the treatments imposed, with the exception of treatment with the highest dose of quebracho tannin in which intestinal digestion was reduced (0·939 v. 0·826 for S0 and SQ5, respectively. P<0·05). In the second experiment, ten ruminally cannulated ewes were used to examine the effect of a daily dosing of quebracho tannin into the rumen on the degradation of the quebracho-treated SBM. Long-term dosing of quebracho tannin did not increase the ability of the rumen microbes to degrade tannin treated SBM. It was therefore concluded that quebracho tannins could be used as chemical additives for improving the digestive utilization of protein-rich feeds in sheep.

During the introduction of a new crop, it is important to study and select for resistance to pests to ensure preservation of possible natural protection in the plant material. One accession of Barbarea verna (Mill.) Asch. and one of Barbarea vulgaris R. Br. was exposed to female pollen beetles, Meligethes aeneus Fab. (Coleoptera: Nitidulidae) in a greenhouse experiment. The experiment was initiated to reveal the extent to which the plant material is accepted as a host plant to this important Brassicaceae pest. The two species, B. verna and B. vulgaris, were used for oviposition by 26% and 21% of the females, respectively. The amount of oviposition and feeding injury on either of the two species throughout the experiment did not indicate any difference in acceptance of the species by the pollen beetle. For both species a majority of the egg-laying females oviposited only once during the 5-day period and laid less than 3 eggs per clutch. The females present on the Barbarea spp. were not more disposed to accept the species as the days passed and the mean clutch size did not increase with time since previous oviposition. Females laying eggs used large and small buds of B. verna to the same extent for feeding. On B. vulgaris there was a tendency for more frequent use of large buds for feeding than small. Acceptance for oviposition by the pollen beetle on the two accessions of Barbarea is low in this experiment. Injury caused was limited to a level probably tolerated by the plant material without causing economic damage. As the oogenesis of the pollen beetle is reduced by exposure to low-quality host plants the potential natural protection would endure despite an increasing occurrence of the species.

A method that allows the effect of temperature treatments on plant quality to be quantified is described. The proposed method is based on the analysis of temperature regions for plant quality characteristics and enables an easier and more precise analysis of the influence of day and night temperature on plant growth and development. Plant quality may be evaluated by the combination of any number of plant characteristics. The proposed method can assist growers in determining what temperature regimes are necessary to produce acceptable-quality crops on specified days.

A field experiment was conducted for two years (1994–96) to evaluate three nitrogen fixing bacteria (NFBs) namely Azotobacter, Azospirillum and Beijerinckia as foliar biofertilizers on mulberry (Morus spp.). Foliar application of these bacteria in their specific culture media with half of the recommended dose of N as a basal application of chemical fertilizer were compared with the recommended dose of N (300 kg/ha per year in four equal splits) but without biofertilizer. Other controls for comparison were respective culture media with half N. All the NFBs improved leaf yield over their respective controls (specific culture media). The addition of Azotobacter resulted in significantly greater yield than that given by the recommended dose of N. The Beijerinckia treatment resulted in a leaf yield equal to that from the recommended dose of N and Azospirillum reduced leaf yield in comparison to that from the recommended N treatment although the yield from Azospirillum treatment was more than that from the culture medium treatments. A combination of NFBs where Azotobacter was one of the components improved leaf yield over single NFB treatments. NFBs also resulted in improved leaf quality as indicated by their protein content and their impact on silkworm rearing and cocoon production when treated leaves were subjected to bioassay. The use of these NFBs, particularly the Azotobacter, as a foliar biofertilizer to increase mulberry leaf production has not been investigated before.