Haploid Inducing And Doubling Method And Genetic Segregation Of SSR And ISSR Markers In Maize

The five lines developed from maize parthenogenesis inducer CAUHO Inducer 1 and Fl of two lines 1145 and Y331 were used to study high efficient inducing, doubling method and genetic character of haploid.The results showed that the pollinating silk length and period were two important factors influencing haploid inducing rate and haploids per plant of the maize parthenogenesis inducer. Longer silk (>8cm) had very significantly higher inducing rate and more haploids per plant than those of shorter one(<5cm). The average haploid inducing rate of longer silk was 3.84%, 1.60% higher than that of shorter one. The average haploids per plant of longer silk were 7.84, 3.40 more than that of shorter one. Also later pollination ( 8.15-9.1) had very significantly higher inducing rate and more haploids per plant than those of earlier pollination(7.15-8.1). The average inducing rate of the later treatment was 4.72%, 2.36% higher than those of the earlier one. The average haploids per plant of the later treatment were 9.34, 4.66 more than those of the earlier one. No significant interaction was found between the pollinating silk length and period in haploid inducing rate and haploids per plant.Four chemical doubling methods (immersing shoot, immersing root, immersing seed and microinjecting growing point methods each with tree colchicine concentrations: 0.2%, 0.4%, 0.6%) were used to screen suitable doubling methods of haploid. The results showed that the survival rate of all treatments decreased as the colchicine concertration increased. Immersing shoot and microinjecting growing point had obvious lower survival rate, which were found less than 50% at every colchicine concentration. The doubling frequencies of immersing seed at 0.6% colchicine concentration and microinjecting growing point at 0.4% colchicine concentration had relatively higher doubling rates, 48.4% and 28.1% based on tassel fertile rate respectively. Their seeding plant rates were higher accordingly, 14.3% and 10.1% respectively. So the immersing seed method was best and the microinjecting growing point was better. Besides, 41 DH lines were developed from the doubled plant above.The genetic segregation of haploid was assessed with 22 SSR and 23 ISSR markers in a 90 haploid population. No distortion was found from the expected 1:1 ratio in all the markers used. So the segregation of gametes forming haploids is random basically and the segregation frequency of alleles is coincided with Mendel Law.The above results are useful to establish high efficiency haploid inducing and doubling system. Since the lines 1145 and Y331 used in the experiment were found to highly resistant or highly susceptible to maize stalk rot, which was found to be a dominant gene controlled resistence, no distoration would be useful to its molecular work based on DH population.