Cabbage Genotypes Research Articles

Behavior of neonate diamondback moth larvae [Plutella xylostella (L.)] on leaves and on extracted leaf waxes of resistant and susceptible cabbages

NeonatePlutella xylostella moved more rapidly, spent more time walking, and engaged in searching behaviors more often on leaves of NY 8329, a resistant cabbage with glossy leaves, than on Round-Up, a susceptible variety with normal wax bloom. The neonates also spent significantly more time palpating and more time biting and spinning silk on the susceptible cabbage (although the latter two differences were not significant). Very similar differences in neonate behavior occurred on leaf surface wax extracts (hexane and dichloromethane) of the two cabbage genotypes. Leaf surface waxes are thus strongly implicated in eliciting reduced acceptance of the glossy cabbage by neonateP. xylostella. The chemical compositions of the leaf wax extracts were markedly different. Several compounds, including the triterpenolsα- andβ-amyrin, were found only in the glossy waxes. The percentages of some major wax constituents differed between wax extracts of the two cabbage types. These differences in wax composition may condition the plant resistance in glossy types.

Optimal concentration of sucrose for head cabbage (Brassica oleracea L. convar. capitata (L.) Alef.) anther culture

Formation numbers of embryos and plants from anther culture were investigated for 6 genotypes of head cabbage (white cabbage, savoy cabbage, pointed-headed cabbage) with donor plants raised under cold (15°C/13°C) and warm (22°C/18°C) greenhouse conditions using media with 7%, 10%, 13%, 16%, 19%, and 22% sucrose. The average yields of embryos and plants obtained from donor plants in the two temperature regimes, were not significantly different. The main effect of the sucrose concentration could be described as a parabola from which the average optimal concentration of sucrose for pollen embryo formation for the six genotypes was calculated to 14.2 ± 0.1% sucrose and for plants to 14.0 ± 0.1% sucrose. The average optimal sucrose concentration resulted in a 1.7 times increase in formation of embryos and 1.5 times increase in plant formation compared with the 10% sucrose medium generally used. Considerable interactions of genotype x sucrose observed could be explained by different sucrose optima for each of the three forms of head cabbage.

Two Types of Resistance to the Diamondback Moth (Lepidoptera: Plutellidae) in Cabbage

Survival of larvae of the diamondback moth, Plutella xylostella (L.) was reduced on several genotypes of cabbage from the breeding program at Geneva, N.Y. Polar fractions of ethanol extracts of partially resistant lines 2535 and 2503, when incorporated into diet, reduced survival of P. xylostella larvae by 14.9 and 19.0%, respectively. Whether this effect was due to reduced feeding or postingestive toxicity was not determined. Although survival on glossy-leafed line 2518 was very low in the field and larvae on this line failed to form visible feeding mines during the first 72 h after egg hatch, extracts from 2518 had no activity. Survival of larvae confined on leaf disks of 2518 in the laboratory was much greater (80% of controls) than it was on whole plants in the field (0.36% of controls). In the field, neonate P. xylostella dispersed two to three times more rapidly on the leaves of 2518 than on other lines. Resistance to P. xylostella in the lines investigated was therefore due to at least two mechanisms, (1) antibiosis or nonpreference due to extractable compounds present in normal bloom resistant cabbage genotypes, 2503 and 2535, and (2) possible nonpreference for glossy-leafed 2518 by neonate larvae, as suggested by the greater dispersal rates of neonates on these plants. Survival is relatively high on 2518 in leaf disk bioassays in the laboratory, suggesting that nonpreference in combination with environmental stresses to larvae in the field may produce P. xylostella resistance in the glossy 2518.

Effect of Plant Age on Survival of Diamondback Moth on Two Cabbage Genotypes

Table 1. Percentage of larvae surviving on cabbage cultivar Round Up and diamondback moth-resistant glossy-leafed cabbage NY 2518, and relative resistance of NY 2518 (survival on NY 2518 expressed as a percentage of that on ‘Round Up’) at five plant ages and two inoculation schemes. Knowledge of age-dependent expression of resistance is critical for evaluation of breeding lines and for effective use of resistant cultivars in pest management. Resistance to the Lepidoptera pest complex in some Brassica has been shown to increase with plant’ age (Dickson and Eckenrode, 1980). Our studies of insect resistance now focus on the diamondback moth [Plutella xylostella (L.)], the most serious pest of cole crops worldwide (Talekar and Griggs, 1986). Resistance to this insect in glossy Brassica genotypes, descended from cauliflower P1234599, is due to reduced larval survival (Lin et al., 1983; Eigenbrode et al., 1990). The objective of this study was to measure survival of diamondback moth larvae throughout crop development in NY accession 2518, a glossy-leafed resistant inbred cabbage line, and the susceptible hybrid ‘Round Up’. Resistance was measured by inoculating the fourth expanded leaf of test plants with 100 to 200 diamondback moth eggs (depending on plant size) and determining percent of larvae surviving 8 to 10 days later (fourth instar (Eigenbrode et al., 1990). Two experimental designs produced plants for inoculation 14, 28, 42, 56, and 70 days after transplanting. In the first experiment (Single Cohort), 45 eight-week-old seedlings of each line were transplanted from Speedling-type flats into the field on 6 June 1988. Six to nine plants from each line were inoculated on 20 June, 5 and 18 July, and 1 and 15 Aug. In the second experiment (Single Inoculation), six to nine g-week-old seedlings from each line were transplanted on 6 and 20 June, 5 and 18 July, and 1 Aug. All plants in this design were inoculated on 15 Aug.

Chromosomal monogenic dominant male sterility in chinese cabbage (Brassica rapa supbs. pekinensis (Lour.) hanelt)

Strong indication was found for the existence of a chromosal monogenic dominant male sterility-gene in chenese cabbage. This source of male sterility can be of practical use for the production of hybrid varieties. A pronounced drawback is the required removal, in the breeding and seed production stage, of the approximately 50% male fertile plants from each offspring of male sterile plants. Fortunately this removal is facilitated by the penomenon of apical dominace in the flowering process in the whole Brassica rapa taxon. Moreover an advantage of dominant monogenic male sterility is its easy and rapid introduction into all available genotypes of chinese cabbage.

Germination of Brassica pollen and expression of incompatibility in vitro

Pollen derived from cabbage, broccoli, and collards (Brassica oleracea, var. capitata, Italica and acephala, respectively) will germinate in a synthetic medium consisting of sucrose, H3BO4, CaCl2 and purified polyethylene glycol 20,000. The optimum levels of constituents varied from genotype to genotype. With one genotype of cabbage, a germination percentage of 84% and tube lengths of at least 3.5 mm long were obtained. Whereas pollen from broccoli germinated in 1 to 2 hours, cabbage pollen required a 3 to 4 hour incubation period. Optimum germination occurred at pH 5.8 and at a pollen density of 0.5–2.0 mg/ml for cabbage. The effect of flower age on pollen germination varied from genotype to genotype. Of 7 cabbage genotypes tested, pollen germination either increased, decreased or remained the same as flower age increased. Pollen germination in vitro required polyethylene glycol purified by dialysis or passage through Sephadex G-25. Cabbage stigmas release a heat-labile substance capable of inhibiting germination of self-pollen, but stigma extracts from a cross plant have no effect.

Immunochemical Detection of Antigens in Self-incompatibility Genotypes of Cabbage

RECENT advances in immunochemistry permit the characterization of tissue specific antigens, and thus provide highly sensitive techniques for the study of gene action1. Of the new techniques available, immunodiffusion offers the following advantages over other serological tests: (a) multiple antigens from particular tissues can be resolved so that the antigens characteristic of different genotypes can be assessed; (b) only a small amount of plant tissue is needed to provide the test antigen; and (c) immunodiffusion tests are simple and easy to set up. This communication deals with the use of immunodiffusion to detect antigenic differentiation in plant tissues, specifically in relation to the control of self-incompatibility by multiple alleles of an “S” locus in plants2–6.