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A method is described for evaluating persistence and productivity of pasture species in the advanced stage of testing. Six bred lines of Macroptilium atropurpureum were compared with cv. Siratro at Samford, south-east Queensland, under stocking rates equivalent to 2.0 and 3.0 steers-ha-1. Each plot was grazed separately for 4 days every 6 weeks, without any mowing being imposed. Attributes measured over a 5-year period included presentation yield, legume density, weed invasion and soil seed reserves. One line of M. atropurpureum was superior to Siratro in yield and plant density, although it produced lower reserves of soil seed. These results were similar to those from a previous experiment under cutting. The advantages and limitations of the method are discussed.

Improvement over cv. Siratro in five advanced lines from an M. atropurpureum breeding programme was evaluated at four sites (with two soil-types at one site) during four growing seasons. On all except four of the 20 environment/season occasions all the bred lines produced a dry-matter yield markedly higher than that of Siratro. However, this increase in vegetative vigour was obtained at the expense of some reduction of viable seed addition to the soil, although it was considered that, at least under the conditions of the experiment, sufficient seed of all lines was added to soil for their persistence in pastures. Two of the lines (18 and 19) were extremely versatile, with a good performance at all sites; the others (2, 13 and 15) showed some small degree of differential environmental tolerance. It was concluded that the two most specialized environments (Beerwah and Narayen brigalow) could have been excluded from the experiment without diminishing the results. If only relative line performance had been required, a single season would have sufficed; but for a realistic estimate of yield all four seasons (one unusually wet, one unusually dry and two average) were essential. It is recommended that in future work more attention should be paid to standardizing management procedures over all sites.

The comparative effects of CaCO3 on growth, nodulation and chemical composition were determined in four Leucaena leucocephala lines (three bred), Macroptilium lathyroides and Lotononis bainesii grown in pots of an acid soil. Calcium carbonate treatments were equivalent to nil, 250, 750, 1250 and 2500 kg ha-1 (Ca0 to Ca4). L. leucocephala is a tree, well adapted to calcareous soils. M. lathyroides and L. bainesii are herbaceous species tolerant of acid soil conditions. Total dry matter production (tops+roots) of the four Leucaena lines exceeded that of M. lathyroides and L. bainesii. However, the top DM yield of the latter two species exceeded that of Leucaena due to a low top/root weight ratio in Leucaena. The Leucaena lines gave successive total DM increases up to the Ca3 treatment, the overall increase being relatively large, especially in line 3 ;at Ca4 mean DM yieldswere below those at Ca,. Both M. lathyroides and L. bainesii had significant responses particularly at the Ca1 treatment, but at the Ca4 treatment their total DM yields were reduced below those obtained with no CaCO3 addition. In all Leucaena lines there was a significant increase in nodule DM pot-1 between the Ca0 and Ca4 treatments. However, there was a decrease in nodule DM of lines 5 and 27A from the Ca3 to Ca4 treatment. Nodule DM of M. lathyroides and L. bainesii was only affected to a limited extent over the range of treatments Ca0 to Ca3, but at Ca4 a significant reduction occurred in both species. In all species CaCO3 additions progressively increased the concentration of Ca in the plant tops. The positive DM responses were considered to be primarily due to Ca, although Al may have had a confounding effect, especially in L. leucocephala. Line 3 of L. leucocephala had the highest Ca concentration as well as the greatest reduction in Al concentration.

A new perennial tropical pasture legume, that has been named Siratro, has been bred from a cross between two Mexican strains of the wild species Phaseolus atropurpureus DC. It is a composite of three high yielding selections which are transgressive segregates from the cross with a marked intensification of the stoloniferous character. The breeding method wed was to select superior recombinants in the F2 population and then subject plots of the F3 and F4 families from them to a system of heavy intermittent grazing with cattle. This mass-selected those plants able to spread and produce seed under high grazing pressure. Siratro has inherited the high resistance of the parents to root-knot nematode and the virus disease legume little leaf. These resistances are necessary in pasture legumes grown in northern Australia. Under grazing, Siratro not only outyields the parents but also all other introduced strains of P. atropurpureus available. The marked stoloniferous habit of the selections in Siratro gives greater persistence and density and high yielding ability. This in turn results in the selections maintaining the Rhodes grass sown with them. The composite nature of Siratro should give it sufficient variability for its adaptation to the spear grass zone Queensland and other coastal and sub-coastal areas of northern Australia.

In each of two years the reactions of 36 lines of Phaseolus atropurpureus to the four root-knot nematodes Meloidogyne arenaria, M. hapla, M. incognita, and M. javauica were studied. Seven of the experimental lines were common to the two years. Two known susceptible species, Phaseolus lathyroides and Lycopersicon esculentum (tomato cv. Grosse Lisse), were used as controls. Four macroscopic and four microscopic reactions were recorded on each occasion, and the results analysed. Resistance to the four nematodes was present in all lines of P. atropurpureus. Thcre was also evidence of differential resistance between lines; some showed increased resistance to all nematodes except M. hapla, and others showed both increased susceptibility to M. hapla and increased resistance to M. javanica. The severity of attack on thc controls was significantly less in the second ycar. Several explanations for this are advanced.

Two tomato hybrids bred at the Hawaiian Experiment Station for resistance to Meloidogyne incognita (Kofoid & Thite) Chitmood proved also to be resistant to M. javanica, which is dominant in the Murray Valley and subtropical areas of Australia. These hybrids also possessed resistance to a range of Australian isolates of the fusarium wilt fungus (Fusarium bulbigenum var. lycopersicli(Brushi) Wollenweber & Reinking). Both these important characters were heritable and could be recombined with agronomic quality in hybrids. Fusarium wilt resistance showed positive potence in the progenies. Root-knot nematode resistance had an irregular pattern of inheritance. The potential of varieties as parents was first gauged from simple crosses. The desirable characters were then concentrated in progenies by a modified backoross followed by selfing and successive selection. Yielding ability has been maintained and suitable agronomic characters have been achieved in the hybrids by the breeding methods used. The work has indicated that suitable crop rotation will be necessary to prevent the selection of nematode strains capable of causing severe infection.

A virus of legumes causing a disease described as "little leaf" has infected with differing degrees of severity some 40 per cent. of pasture legumes in experimental plots in subtropical Queensland. The symptoms are similar to those caused by the "big bud-witches' broom" complex of viruses of which it is probably another strain. Transmission studies have shown that the vector is the leafhopper Orosius argentatus (Evans) which also transmits tomato "big bud", lucerne "witches' broom", potato "purple top wilt", and tobacco "yellow dwar"' diseases. The O. argentatus taken direct from the field in Queensland, and its progeny reared in the laboratory, were efficient vectors of "little leaf" whereas the Canberra strain bred in the laboratory would not transmit 'little leaf' and was not an efficient vector of the other "yellows" viruses. The majority of species and strains tested in the genera Crotalaria, Desmodium, Indigofera, and Stylosanthes are susceptible to "little leaf". Within such genera there are a few resistant species or strains with promising agronomic characters. Lucerne and white clover are relatively resistant to "little leaf". The genera Arachis, Centrosema, Doliehos, Glycine, Lespedeza, Leucaena, Pueraria, Phaseolus, Vigna, and Zornia contain species and strains with marked field resistance. Most of the species and strains considered to be promising pasture legumes possess field resistance to "little leaf".

A number of varieties of subterranean clover (Trifolium subterraneum L.) were tested with a severe strain of Phaseolus virus 2 Pierce. Northam First Early, Dwalganup, and Pink Flowered gave lethal necrotic reactions while the rest developed mottles and chlorosis of different degrees of intensity. Reductions in the mean fresh weights of plants of five subterranean clover varieties ranged from 26.1 to 76.7 per cent. Epidermal cells of mottled leaves contained irregular aggregates of viroplasts stained by treatment with phloxine-trypan blue. Viroplasts in young tip leaves did not stain if the plants were held at temperatures below 44.6°F while those in mature basal leaves were not so affected. The lethal-reactors Northam First Early, Dwalganup, and Pink Flowered were resistant in the field to Phaseolus virus 2. With hand inoculation in the glass-house an average of 10 per cent. of plants of these varieties remained free from systemic infection, whereas all the plants of mottle-reacting varieties became systemically infected. The virus had a discontinous distribution in plants of lethal-reactors, compared with a continuous distribution in those of mottle-reactors such as Mount Barker. The lethal reaction is heritable in a dominant fashion in most crosses, so that the development of desirable new virus- resistant varieties is possible.

Diploid Physalis floridana has 24, and the induced autotetraploid 48 somatic chromosomes. The increased ploidy resulted in the usual increases in size of stomates, pollen, and seed, but in a decreased nitrogen content of the leaves. Dry matter production of the leaves and stems was 28.3 per cent, greater in the tetraploid than in the diploid. The percentage moisture content was not increased by tetraploidy. The increased ploidy did not affect the reaction to several mesophyll viruses, but resulted in a marked increase in the sensitivity to the phloem virus, leaf roll. Inoculation with leaf roll at the third true-leaf stage reduced the mean fresh weight per plant by 26.5 per cent. in the diploid, and 57.3 per cent. in the tetraploid. The greater sensitivity of the tetraploid followed inoculations at other growth stages, but, with both diploid and tetraploid P. floridana, the closer the plants were to the flowering stage at inoculation the less obvious the reaction.

Subterranean clover pollen germinates freely on an agar medium at relative humidities above 95 per cent. and at temperatures between 20 and 25°C. Temperature was not as critical as relative humidity, since pollen germinated freely a t 4°C. Based on these findings an improved technique for the artificial hybridization of subterranean clover varieties was developed. With this technique 35.3 per cent. of the emasculated and cross-pollinated florets set seed in 18 different intervarietal crosses. Varying degrees of compatibility exist between different varieties. The percentage of emasculated florets in Tallarook which set seed from pollinations with different male parents varied from 75 per cent. for Dwalganup to 6.5 per cent. for Wenigup. The characteristics of a number of the F1 hybrids are described. The extent to which different parental characters were dominant in the hybrids is indicated.

Studies have been made of the development of the spotted-wilt virus In the inoculated leaves and non-inoculated parts of three Lycopersicon species. At temperatures of 60°F to 87°F. L. pimpinellifolium (Porter's strain), L. peruvanum, and the L. esculentum variety Rey de los Tempranos, exhibit different degrees of resistance to virus multiplication when compared with the susceptible Bonny Best variety. Infected plants of Porter's strain and Rey de los Tempranos are able to develop new growth free from virus. Resistance appears to depend on the presence of a virus-inactivating system which functions more actively when plants are maintained at a temperature of 90°F. Although the resistance of Porter's strain can be transmitted to hybrids, Rey de los Tempranos appears more promising as a parent for the development of spotted-wilt-resistant tomato varieties. A method for the selection of the resistant phenotypes in hybrid progenies is suggested.

When the leaves of potato hybrids resistant to virus Y were inoculated, virus development was restricted and within 14 days the virus was inactivated in most instances. There was no evidence to suggest that resistance was due to hypersensitivity. Virus concentration increased gradually in susceptible varieties after inoculation. Four treatments of virus Y inocula were tried; that made with phosphate buffer of pH 7 produced the most lesions on the resistant potato hybrid 11-84. A marked reduction in lesion numbers occurred on 11-84 when sap from virus-free D. stramonium plants or X-infected N. glutinosa plants was added to inoculum of virus Y. Crossbred progenies were developed from two of the resistant hybrids and one of the varieties used to study virus development after inoculation. One progeny contained 68.3 per cent. phenotypes resistant to virus Y and the other had 29.4 per cent. In both progenies there was a strong association between resistance to virus Y and the immune reaction to virus X. The results indicate that immunity and high resistance to virus Y are governed by the nulliplex and simplex conditions of a major gene, while the quadruplex condition controls susceptibility.

Spotted-wilt-resistant and susceptible phenotypes among potato varieties and hybrids are not determined satisfactorily by hand-inoculation of leaves, but can be selected by stem-tip inoculation of vigorously growing plants at the flowering stage with a strain mixture of the virus. This glasshouse method gives a better differentiation than that obtained in field epidemics. Phloroglucinol staining of infected stems indicated that spotted wilt affects the same tissues as virus Y. Studies on the movement of spotted wilt have shown that varieties like Brownell have a high degree of tolerance, and that the tip blight and necrotic strains of a mixture take part in the early stages of systemic infection in susceptible varieties. A high percentage of the hybrids bred by the authors were resistant to spotted wilt.

By their differing reactions, Lycium halimifolium, L. rhombifolium, Physalis floridana, and Capsicum annuum distinguished between four strains of potato virus Y, P. floriduna giving the best differentiation. The avirulent strain produced no symptoms in L. rhombifolium and P. floridana, and virus development was restricted in P. floridana. The two varieties of C. annuum were immune to virus Y except for the tolerant reaction of one to a virulent strain. Nicotiana glutinosa indicated virulence of a Y strain when inoculated concurrently with virulent X strain.

A detailed field trial and other experiments were made to explore the effects of leaf roll on the growth of different varieties of potato. The shoots of a tolerant variety, Up to Date, were little changed in size by infection at emergence, but during the early vegetative stage of development the growth rate of the haulm was reduced. The shoots of an intolerant variety, Bismark, were probably smaller in size at emergence, and for a period during the vegetative stage of development the tops of the plants grew at the same reduced rate as those of Up to Date and three other varieties. These other three varieties, which were intermediate in tolerance, were intermediate in growth reaction between Up to Date and Bismark. The tolerant variety, Up to Date, during the first stages of tuberation, reacted to infection without serious changes in length of stolons or time of initiation of tubers. The intolerant variety, Bismark, reacted with a shortening of stolons and a hastening of tuber initiation. The reduction in size of various parts of the plant was greater for intolerant than for tolerant varieties. The numbers of leaves developing on the main axes of both tolerant and intolerant varieties were reduced by infection. The reduction in the proportion of leaf area contributed by axillary shoots to the total leaf area of infected plants, was similar in the tolerant and intolerant variety, in spite of the difference in the size of the plants. In the intolerant variety, Bismark, there was a change in type of axillary growth above ground as well as a change in vigour. The course of development of the foliar parts of the plant during maturity and senescence demonstrated the serious alteration in growth characteristics of the infected plants of the intolerant variety Bismark. There was relatively little alteration in the tolerant variety, Up to Date. Incomplete data suggest that losses in yield due to infection are not due to a reduction in efficiency per unit of leaf area in the production of tubers by infected plants. The reduction can be accounted for on the basis of reduced growth rate, loss in size of haulm. The repercussions of these findings on the problem of breeding for resistance against leaf roll are mentioned.

Flowering in Glycine javanica is affected by both photoperiod and temperature. All accessions studied were short day plants, and in the sensitive ones there was little effect of temperature. In others, a lowering of day and/or night temperatures caused flowering to occur in long (16 hr) days and may prevent flowering in short days. Seed formation did not occur in day temperatures above 27C.

Seven traits were studied in seven hybrids of G. javanica, and their progeny. No hybrid vigour was found in the F, for flowering time, stolon number, or per cent stolons rooted, but hybrid vigour was found for all other traits, and was followed by inbreeding depression in the F2. All traits were polygenically controlled and heritability estimates ranged from 39 to 77 per cent. Genotypic correlations indicated that early flowering, high yield and good stolon development could be combined into one variety by means of a suitable breeding program. A delay in planting date caused a delay in flowering, but mainly in those families which were normally early flowering.

The leaf-roll reactions of a number of potato hybrids and varieties have been defined by external symptoms and the extent of phloem necrosis present in stem sections. There is no constant correlation between the leaf-roll reaction and field resistance of varieties and hybrids. The variety Bismark had the highest leaf-roll resistance of any of the types tested so it should prove a useful parent for this character. The resistance of Bismark and some hybrids is apparently dependent upon a virus-inactivating mechanism, which not only reduces field infection but prevents the transmission of leaf roll to a proportion of the tubers of infected plants. The initial selection of resistant hybrids could be made by sprout inoculating them and keeping those in which a proportion of the tuber progeny was free from leaf roll.