Study On The Acquisition,Reproduction And Preservation Of The Gynoecious In Cucumis Melo L.

Melon?Cucumis melo L.?as an important fruit vegetable is widely cultivated all over the world.China has the largest cultivation area and the highest total yield of melon in the world.At present,most of commercial melon are F₁ hybrid cultivars,and the production of most commercial melons requires laborious hand emasculation to produce hybrid seeds.The mechanical emasculation not only cost expensive labor,but also may lead the impurity of the hybrid seeds due to incomplete emasculation.In this study,using the hermaphrodite inbred lines?P_Y,P_B?and monoecious inbred lines?P_A?as parents,the F₂,F₃,BC₁F₂,F₂BC₁and BC₂ generations were obtained to study the genetic basis of the gynoecious plant of melon.In the meantime,the temporary preservation and the selfing preservation methods by inducing stamen of the gynoecious plant of melon were studied.The possibility of using SNP molecular marker to select homozygous MM plant was discussed.The study provided the theoretical basis of breeding and reproduction of gynoecious melon,and make the foundation for utilization of melon gynoecious line.The main results are as follows:1.7 sex types,i.e.,hermaphrodite,monoecious,gynoecious,gynomonoecious,androecious trimonoecious and andromonoecious were observed in P_Y×P_A F₂ population;3 sex types,hermaphrodite,gynoecious and gynomonoecious,were found in F₃ population of the P_Y×P_A F₂ gynomonoecious progeny,BC₁F₂ population of the?P_Y×P_A?×P_B gynomonoecious progeny?BC₁?,and BC₂ population of?P_Y×P_A?×P_Y BC₁ backcross with P_Y or P_B progeny.However,3 cases of the sex types segregation were found in F₂BC₁ population of F₂?P_Y×P_A?backcrossing with P_Y or P_B,i.e.,gynoecious,gynoecious/gynomonoecious,and gynoecious/hermaphrodite.2.The Chi Square test of sex segregation in different generations confirmed that the melon sex types were mainly controlled by the three genes:M/m,G/g and A/a.M_G<sub><sub>is monoecious,mmG_<sub><sub>is andromonoecious,mmgg_<sub>is hermaphrodite,gynoecious is M_ggaa,M_ggA_could be trimonoecious and gynomonoecious.The gynomonoecious plants were not stable,and could be converted to gynoecious plants or trimonoecious plants.The results seems show that there is a fourth gene?probably Gy/gy?to regulate the sex of melon.3.Using the hermaphrodite inbred lines?P_Y,P_B?and monoecious inbred lines?P_A?as parents,gynoecious plants could be found in the F₂ and F₃ population,BC₁ population of F₁backcrossing with hermaphrodite,BC₁F₂ population of BC₁ selfcrossing,BC₂ population of BC₁ backcrossing with hermaphrodite again,and F₂BC₁ population of F₂ backcrossing with hermaphrodite.However,the different ratio of gynoecious plants were investigated in different populations.Among them,all the F₂BC₁ plants of P_Y×P_A?F₂?backcrossing with P_B,were gynoecious,could be happened.4.The cutting propagation of branch tests showed that IAA,IBA and rooting powder could promote the adventitious roots of the lateral branches of the gynoecious plant.And the rooting rate treated with 1g/L IAA reached 40%.The stamen-inducing tests showed that both GA₃ and AgNO₃ could make the melon gynoecious plants produce bisexual flowers.Among them,the 500mg/L AgNO₃ treatment had the best effect;the bisexual flowers induced by GA₃ or AgNO₃ could be self-fertiled and produce viable seeds;no matter in spring-summer or autumn,bisexual flowers can be induced in the middle of growth satge of plants by using 500mg/L AgNO₃ treatment.The results showed that the gynoecious plant of melon could be preserved by cutting propagation with auxin or self-crossing propagation by stamen-inducing with GA₃ and AgNO₃.5.The SNP of the andromonoecoius gene was used to design primers to screening the homozygous gynoecious plants in the F₂BC₂ population.The results showed that the marker could distinguish the heterozygous and homozygous gynoecious plants.