Variation in partitioning and percentage nitrogen and phosphorus content of the leaf, stolon, and root of white clover genotypes

Abstract

As part of a programme to breed a productive white clover (Trifolium repens L.) tolerant of low soil phosphorus (P) levels, 98 white clover and 2 Lotus pedunculatus Cav. genotypes were examined for partitioning of P, nitrogen (N), and dry matter within the plant, and for concentration of P and N within leaves, stolons, and roots. Genotypes were grown in pots with either 300 or 2000 mg P per kg soil. Differences among genotypes for 0,10 P content and partitioning of P within the plant did not result in differences in dry matter response to added P fertiliser between genotypes. Genotypes that allocate a high proportion of total P to shoots and have low shoot % P were large-leaved and had high herbage yields, but a low proportion of dry matter in stolons suggested that they would be nonpersistent in grazed, low P swards. Ge~otypes collected from hill country swards had a high proportion of dry matter in stolons but were low yielding, had a high shoot % P and a low NIP ratio. There was sufficient variation among genotypes to suggest that selections of persistent plants that have a low harvest index, low shoot % P, and high NIP ratio may be successful.

Heritability of, and relationships between phosphorus and nitrogen concentration in shoot, stolon and root of white clover (Trifolium repens L.)

“…Twenty genotypes were collected from a range of soils on roadside cuttings in the North Island; 30 genotypes were from five cultivars (Kent Wild White, Kopu, Huia, S.100, and Regal)(6 genotypes from each cultivar); and 48 genotypes were from an extensive collection of hill country white clovers (Suckling and Forde, 1978). A full description of genotypes is given by Caradus (1986). Genotypes were initially grown in potting mix until sufficient stolon tips were generated to allow vegetative propagation.…”

“…Additionally, correlation analyses were used to identify characters that vary together since when selecting for a trait it is important to be aware of associated characters that may similarly change in response to selection. This paper is the second in a series which firstly, examined (i) the extent of variation for %P, %N and partitioning of N, P and dry matter to plant components, (ii) the effect of P supply on these characters, and (iii) the effect on these characters of selection for white clover plants able to tolerate grazing in low soil P conditions (Caradus, 1986), and secondly, in this paper, examines (iv) the heritability of %P, %N and partitioning of N and P to plant components, (v) the effect of P supply on heritability estimates and (vi) relationships between plant characters and the consequences of selection for high and low %P.…”

Nitrogen and phosphorus concentrations of white clover genotypes differing in response to added phosphorus

“…However, many of these correlations were only moderate (Table 4) so that it may be possible, if required, to select against these trends, such that high-yielding, high P-responsive genotypes could be obtained with either high or low % P since the correlation between leaf % P and P response coefficients was not significant (Table 4). Leaf size and proportion of leaf were not correlated (Table 4), as has been observed in other studies (Caradus 1986).…”

“…plant's N fixation or N status in addition to P. In fact, in lucerne, selections for high % P did not differ in response to added P from control populations (Miller et al 1987). Although large differences were found among white clover genotypes grown at two P levels for % P levels in leaf, stolon, and root, and partitioning of P within the plant, these did not result in differences in DM response to P (Caradus 1986). Similarly, Spencer et al (1980) found differences between eight lines of white clover for shoot %P but this was not translated into P response differences.…”

“…Selections for low shoot % P and high Nt P ratio may result in high-yielding but non-persistent plants. Previous study (Caradus 1986) has shown that for plants to be persistent in a grazed P-deficient sward they require a high proportion of P in stolon and roots. This means a low P harvest index…”