Morphophysiological determinants of yield in rapeseed (Brassica campestris and Brassica napus). I. Growth and morphological characters

Abstract

Variation in sowing date was found to have a marked effect on the seed yield and different morphological and growth characteristics of spring cultivars of the oilseed rape species Brassica campestris and Brassica napus. The two species differed appreciably, however, in their responses to successive delays in sowing date. In B. napus, there was a significant and continuous decline in seed yield with later sowings. This decline in seed yield was associated primarily with a reduction in the total dry weight of the plant at the final harvest which, in turn, was most closely correlated with the duration of the vegetative phase of growth. The total dry weight of the plant and the seed yield were greatest in the first sowing where flowering was substantially later than in either of the later sowings. Since earlier-flowering cultivars of B. napus would be better adapted to Western Australian conditions, where there is a rapid decline in soil moisture reserves during the spring, significant improvements in seed yield could depend largely on increasing the rate of pre-anthesis growth. In this experiment, however, no significant variation in the relative rate of growth prior to flowering was observed because of the marked negative association between net assimilation rate and leaf area ratio. Further studies of the variation in growth amongst a far wider range of genotypes will, nevertheless, be necessary to properly assess the feasibility of increasing relative growth rates by selection. The seed yield of B. campestris was substantially greater in the second sowing than in either the first or third sowings. Although seed yield was significantly correlated with both total dry weight of the plant at final harvest and the harvest index, the latter appeared to be the most important determinant of seed yield in this species. By contrast with B. napus, most of the dry weight of the plant at the final harvest was accumulated during the post-anthesis phase of growth. Accordingly, the character leaf area duration between anthesis and final harvest was found to be the most significant determinant of the total dry weight of the plant in B. campestris. The leaf weight ratio of the plant at anthesis also contributed significantly to total dry weight at the final harvest; this indicates that the pattern of dry matter distribution in the plant during the vegetative phase could prove a useful criterion for selecting potentially high-yielding strains of this species.

Growth Analysis of Brassica Napus Cv. Tower

“…A similar relationship has been reported in com (Williams et al 1965) and in alfalfa (Wilfong et al 1967). ln Brassica oleracea, Watson (1958) Major (197j), and greater than that reported by Thurling (1974 (Allen andMorgan 1972, 1975) and in soybean (Buttery 1969;Wallace andMunger'1965 Koller et al 1970). In the present instance, the observed upswing in NAR occurred after the cessation of flowering, and after maximal pod area would have occurred (Tayo and Morgan 1975 Thorne and Koller (1974) Williams et al (1965), CGR is also representative of the most common agronomic measurement; i.e., yield of DM per unit land area.…”

“…Maximum CGR occurred earlier in the high seeding rates than in the low seedins rates. The (Thurling 1974). In the present study there was no suggestion of an optimum LAI.…”

“…were influenced by both seeding rares and irrigation. There Tayo and Morgan 1975) and Australia (Thurling 1974 (Clarke and Simpson 1978 (Fig. 3).…”

Canola response to high and moderately high temperature stresses during seed maturation

“…The yield reduction in Surpass400 was 52% for the main stem, but partial compensation by pods on the later-formed stems reduced the seed yield loss to 40%. Thurling (1974) reported experiments with various grain crops, including canola, having an indeterminate habit is likely to have plasticity in yield components, thus resulting in yield compensation.…”

Comparative growth analysis of Brassica napus and Brassica juncea under Swedish conditions

“…Inanaga and Kumura (1974), Thurling (1974), Allen and Morgan (1975), Tayo and Morgan (1975), Major (1977), Clarke and Simpson (1978), Kasa and Kondra (1986), Augustinussen (1987), Mendham et al (1990) and Morrison et al (1990).…”