Anther Culture And Endogenous Hormone Concentrations In Bitter Melon (momordica Charantia L.)

Bitter melon (Momordica charantia L.) is not only a valuable vegetable crop but also an important medicinal plant in China and East Asia. Anther culture is one of the most effective ways of obtaining haploid and homozygotic plants, and it has special significance for the genetic improvement of plants. In this study, four cultivars of bitter melon were used for anther culture, and it was first time to differentiate buds in anther culture of bitter melon. Because explants of bitter melon were apt to form callus rather than adventitious buds, the present investigation measured and correlated endogenous hormone status on explants and calluses with their competence. The main results were as follows.(1) The relationship between microspore developmental stages and length of flower buds, color of anthers was established. When the microspores developed at the late-uninucleate stage, the flower buds were 2.597-4.213 mm in longitudinal diameter, 1.933-2.050 mm in diameter and the anthers were green-white or light green.(2) After 4℃cold pretreatment, callus induction rate of 3 genotypes increased while Changbai decreased. Cold pretreatment to anthers for 1-2 days resulted in the highest callus formation rate. While anthers pretreated more than 4 days, callus could hardly be induced.(3) The callus formation rate of bitter melon reached the highest when medium added with 2,4-D 0.5mg/L and BA 2.0 mg/L, and Bixiu reached 79.42%. Low concentration of 2, 4-D (0.1 mg/L) in combination with each level of 6-BA was unable to induce callus. However, with the concentration of 2,4-D up to 1.0 mg/L, the callus was prone to brown.(4) The induction rate decreased when the concentration of sucrose increased. Higher concentration of sucrose could inhibited callus derived from anther wall.5% sucrose in medium caused a relatively higher induction rate.(5) Anthers cultured under illumination condition resulted in lower induction rate than those cultured in darkness, however callus under light were denser and more vigorous. The anthers cultured at 25℃in the dark for 7 days and then cultured under light resulted in the most high induction rate.(6) Callus could be morphologically divided into two types:one type was slight yellow, loosened callus. The other type was viridescence, granular, smooth callus.(7) On MS medium supplemented with TDZ 0.5 mg/L,2,4-D 0.1 mg/L and triacontanol 2.0 mg/L, adventitious buds differentiated from callus of Bixiu. On MS medium supplemented with glutamine 0.1 mg/L, TDZ 0.5 mg/L and 2,4-D 0.1 mg/L, protuberant structures were produced on the surface of callus. Callus of Changbai differentiated roots when medium supplemented with 6-BA 0.5 mg/L and NAA 1.0 mg/L.(8) Anthers of Changbai differentiated 33 roots, and chromosomal examination of root tip cells showed that 4 roots were haploids.(9) The endogenous hormone concentrations of the initial explants and calluses were determined by means of high pressure liquid chromatography (HPLC). The endogenous IAA was higher in the explants that were easier to induce callus, and higher concentrations of ZT was positive to buds differentiation, while GA3 was negative to the buds formation.