BREEDING A WHITE CLOVER ADAPTED TO SOUTHERN LOWLAND REGIONS OF NEW ZEALAND

White clover populations from Europe and New Zealand together with ecotypes collected from old pastures in Southland-Otago were evaluated as spaced plants at Gore. Plants were screened for herbage production and morphological and flowering characteristics. The Southland ecotypes and North Island hill country material are adapted to active growth in spring and summer. Their dense growth habit ensures continued production of branched stolons from nodal meristems which is necessary for high clover yield and persistence under intensive sheep grazing. In this region flowering characteristics are unimportant in relation to agronomic performance. Some largerleaved Huia and French lines have high-yielding features which are evident during autumn under lenient grazing. Hybrids between superior plants showing adaptive and high yie!ding features are being screened in order to select new types with the desired characteristics. Keywords: White clover, Trifolium repens L., plant breeding, southern region, ecotypes, growth, morphology.</jats:p

Development of GSO alsike clover for the South Island high country

A breeding programme to improve. the herbage yields and persistence of alsike clover (Trifolium hybniium L.)' for the South Island high country was initiated in 1984. A screening trial with gennplasm from the Baltic region of Russia, local types collected in the Mackenzie Basin, selected plants from high. country trials and overseas cultivars was established under grazing at Mt John, Tekapo. Material was assessed over 3 years for seasonal herbage yields, shoot density, growth habit and plant survival. Principal Component Analysis was used to order the agronomic performance of the.alsike lines. A set of superior alsike lines from the Russian and local New Zealand groups was identified. These lines were not significantly better than commercial alsike but showed a consistent pattern of higher yields in all seasons and years. Overseas cultivars had average to poor yields and many had low shoot densities. Elite plants were selected from the superior lines and combined in a polycross in 1988. A progeny test was sown to determine the lines with high breeding value to make up a cultivar. Similar parameters to the screenings, including seedling establishment, were assessed in the progeny test. Seventeen elite progeny were identified in 1991 and the best four plants removed from each progeny and isolated to form the 'G50' alsike clover selection. The selection is currently in comparative grazing trials in the high country. Keywords: high country, progeny test, screening, selection, Trifolium hybridum</jats:p

Achieving persistence and productivity in white clover

White clover (Trifolium repens) is a valuable forage and soil fertility resource whose persistence and contribution to production and profitability can be constrained by genetic, farm management, and environmental factors. Here we outline the growth stages of the plant, and factors affecting persistence at the plant and the population level in pasture. Breeding strategies that bring together new germplasm sources within white clover have improved persistence on farm. New experimental lines, including some accessing genetics from related Trifolium species, show advances in forage productivity and persistence in multi-site, mixed sward, trial systems under dairy, sheep and cattle grazing. New germplasm sources and the use of new tools for characterising and selecting superior plant material will enable increased genetic gain for traits including persistence and forage production in white clover and related forage legumes. Keywords: Lolium perenne, pasture, persistence, stolon density, Trifolium repens, white clover</jats:p

Forage potential of wild populations of perennial ryegrass collected from southern New Zealand farms

A ryegrass breeding programme to improve the cool season activity and summer quality of perennial ryegrass (Lolium perenne L,) in southern regions was initiated in 1986. One of the strategies assessed wild ryegrass populations from 50 dairy and sheep farms in Southland, West Otago and Westland. The plants were collected and evaluated as spaced plants in a high and low fertility site at DSIR Grasslands Gore in comparison with current ryegrass cultivars. Principal Component Analysis was used to order the performance of the ryegrass populations in relation to the observed characters of seasonal growth, tillering, crown rust infection, recurrent ear emergence and endophyte presence. Ihe collection consisted of many short-leaved densely tillered prostrate plants with high levels of crown rust infection and recurrent flowering. In comparison the cultivars had fewer, but larger tillers, rapid leaf extension and good rust tolerance. There were no strong distinguishing features between plants from dairy and sheep farms and 30% of plants had no endophyte. Selected ecotypes hybridised with New Zealand and European cultivars produced plants with better cool season growth and summer quality than standard cultivars. The ecotype germplasm is an important source in the development of new cultivars suited to the southern region. Keywords plant evaluation, Lolium perenne, ryegrass hybrids, southern New Zealand ecotypes</jats:p

An evaluation of lucerne for persistence under grazing in New Zealand

Abstract The on-farm use of lucerne (Medicago sativa) for grazing and conserved feed has increased in New Zealand over recent years, with new cultivars coming onto the market, including more winter-active ones. The extent to which the winter active types contribute to annual feed production, and the relationship to critical traits like persistence, has not been systematically tested. Two concurrent trials over a 4-year period were used to evaluate a range of lucerne cultivars and elite experimental populations ranging in dormancy from 2 (highly dormant) to 10 (non-dormant) under contrasting grazing regimes near Lincoln, New Zealand. More winter-active cultivars in the higher fall dormancy (FD) classes had similar growth to lower FD classes in all seasons except autumn, where they exhibited 18% greater yield than the lowest FD entry. However, these higher FD populations do not persist as well under heavy grazing, with a reduction in ground cover of up to 90% after four years, compared with only a 25% loss in lower FD classes. There was a negative correlation between FD and persistence measured as plant survival over 4 years (R2=0.73). However, one high FD entry showed increased survival under grazing, suggesting there is scope for selection of types with improved cool season growth and grazing tolerance. The concurrent lucerne trial subjected to a low-frequency grazing/ cutting regime showed faster recovery from defoliation than the adjacent hard grazed regime, suggesting stored underground reserves were more available for regrowth. We concluded that lucerne cultivars with FD ratings in the 3 to 5 range are most suitable for yield and persistence under grazing in these conditions. There is also scope for breeding to improve plant survival and dry matter yield within FD class. Keywords: Lucerne (Medicago sativa), grazing tolerance, persistence, fall dormancy</jats:p

Genetic variation for rate of establishment in caucasian clover

Slow establishment of caucasian clover (Trifolium ambiguum L.) is hindering the use of this legume in pasture mixtures. Improved genetic material is one strategy of correcting the problem. Newly harvested seed of hexaploid caucasian clover germplasm covering a range of origins, together with white and red clover and lucerne, were sown in 1 m rows in a Wakanui soil at Lincoln in November 1995. After 21 days, the caucasian clover material as a group had similar numbers of emerged seedlings as white clover and lucerne, but was inferior to red clover. There was wide variation among caucasian clover lines (48-70% seedling emergence), with the cool-season selection from cv. Monaro ranked the highest. Recurrent selection at low temperatures could be used to select material with improved rates of seedling emergence. Red clover and lucerne seedlings produced significantly greater shoot and root dry weight than caucasian and white clover seedlings. Initially, caucasian clover seedlings partitioned 1:1 shoot to root dry weight compared with 3:1 for white clover. After 2 months, caucasian clover seedlings had similar shoot growth but 3 times the root growth of white clover. Between 2 and 5 months, caucasian clover partitioned more to root and rhizome growth, resulting in a 0.3:1 shoot:root ratio compared with 2:1 for white clover. Both clover species had similar total dry weight after 5 months. Unhindered root/ rhizome devel-opment is very important to hasten the establishment phase of caucasian clover. The caucasian clover lines KZ3 and cool-season, both selections from Monaro, developed seedlings with greater shoot and root growth than cv. Monaro. KZ3 continued to produce greater root growth after 5 months, indicating the genetic potential for improvement in seedling growth rate. Different pasture estab-lishment techniques are proposed that take account of the seedling growth characteristics of caucasian clover. Keywords: establishment, genetic variation, growth, seedling emergence, Trifolium ambiguum</jats:p

Genetic variation for seed yield in Caucasian clover

Caucasian clover (Trifolium ambiguum M.Bieb) representing a range of 2x (diploid), 4x (tetraploid) and 6x (hexaploid) material together with ecotypes from the Caucasus region were established in a trial at Lincoln, Canterbury (43"38'S) in October 1993. Measurements were made from individual plants during summer 1994-95. The diploids were earliest to flower followed by the tetraploids and finally the hexaploids, which reached peak flowering in mid December. The hexaploids produced the most florets per inflorescence (115, 101, 96 from 6x, 4x, 2x respectively), the most inflorescences per plant (162, 101, 129 from 6x, 4x, 2x) and the highest seed yield(g) per plant (26, 9, 11 from 6x, 4x, 2x). There was large variation for all the seed production components within the three ploidy levels. For example, the hexaploid cultivar Endura consisted of plants that varied from 25-510 inflorescences per plant. The seed yield components of plants were associated with active spring growth. There was evidence of wide spreading plants producing lower numbers of -inflorescences-per-m2-andseed-yield-per-unit-area; The hexaploid material produced the greatest potential seed yields (1330,685, 1000 kg/ha from 6x, 4x, 2x respectively). There was a 5-fold difference between the lowest-yielding 6x cultivar, Prairie (570 kg/ha), and the highest-yielding KZ2 (2720 kg/ha), a selection from Monaro. Major gains are possible through selection but it is important to select for improved seed yield per plant (not just flowers) and to maintain a wide genetic base. Commercial crops yield approximately half that attained from research plots, whtch suggests a commercial yield of 900 kg/ha is possible from Endura. This compares favourably with other legumes but requires development of crop management practices that ensure consistently high seed yields. Keywords: Caucasian clover, genetic variation, Kura clover, seed components, seed yield, TrifIium ambiguum</jats:p

A review of red and white clovers in the dryland environment

Red and white clovers are best adapted to areas with good soil fertility and adequate soil moisture (750 mm annual rainfall), particularly over summer (150 mm), and are therefore restricted to small areas such as the more fertile valley floors and lower shady slopes in dryland environments. To extend their range and aid survival in dry environments, grazing management and cultivar selection are critical. Continual grazing (set stocking) during spring leads to a dense grass pasture, providing protection from desiccation for white clover stolons in the following summer. White clover cultivars have an inbuilt plasticity that allows morphological adaptation to changes in grazing management. For instance, set stocking in combination with a small-leafed cultivar results in a reduction of plant size but an increase in the stolon population, leading to better plant survival through drought periods. Where drought leads to stolon death, reseeding becomes a viable mechanism for clover persistence, and grazing management has a major influence on survival of new seedlings. For red clover, there is evidence that 'creeping' types survive better than 'crown' types in hill country, but the scope for extending red clover into drier areas is more limited. Key words: cultivars, drought, dryland, grazing management, morphological adaptation, persistence, red clover, reseeding, summer rainfall, Trifolium repens, T. pratense, white clover</jats:p

Response to selection for seed yield in six white clover cultivars

The successful commercialisation of agronomically superior white clover (Trifolium repens) cultivars is dependent on their seed production potential. Field trials were established in 2000 and repeated in 2003 to determine the impact of selection for increased seed yield. The seed yield of the pre-release cultivar (the base population prior to selection for seed yield and cultivar release, representing generation 0) was compared with the field Nucleus generation of the released cultivar (second generation after selection for seed yield, representing generation 2) and the Basic seed generation (the fourth generation after selection for seed yield, representing generation 4), in six recent cultivars (Grasslands Kopu II, Grasslands Challenge, NuSiral, Grasslands Sustain, Grasslands Demand and Grasslands Prestige). The Nucleus and Basic generations had consistently higher seed yield than the pre-release generation for all cultivars. These increases in seed yield were associated with increases in inflorescence density (inflorescences/m2) and to a lesser extent with increased seed yield/inflorescence. Changes were also evident in flowering pattern with four of the six cultivars having a sharper flowering peak following selection. This improved uniformity was also evident through reduced variability in leaf size of the Nucleus generation compared to the pre-release generation. Grasslands Kopu II had the highest seed yields which were associated with moderately high inflorescence density in combination with high seed yield/ inflorescence. The selection strategy used in the final phase of the development of these cultivars has proven successful in increasing seed yield through refining flowering pattern and production while maintaining the morphology and uniformity of the new cultivar. Keywords: cultivars, genetic improvement, seed production, Trifolium repens, white clover</jats:p

Development of white clover populations with higher concentrations of water soluble carbohydrate

Water soluble carbohydrate (WSC) provides readily available energy in the rumen that improves the efficiency of crude protein (CP) utilisation, partitioning of dietary N towards animal growth, and reduces the loss of N as urea.</jats:p