Watermelon Hybrid Generation Of Seed Purity And Biochemical Identification Methods

At present, F₁ hybrid seeds of watermelon have been extended broadly. However, bad isolation or late or incomplete castration often leads to seeds including maternal inbred system during artificial seed production, the loss often occur in watermelon production. Therefore, The purity of seeds must be checked before F₁ hybrid is packed. The main method of checking seeds purity is growing seeds in the field. Although this method is reliable, it costs lots of time and labor. So it is necessary to figure out a kind of accurate, rapid and economical method of checking seed purity.In this study, the electrophoresis of total proteins, peroxydase, esterase and polyphenol oxidase were done to detected the purity of dry seeds, just-germinated seeds and 5-day germinated seeds in watermelon cultivars"96-m×96-c","20-E×20-SG"and"Sumi NO 1×S84-2"by PAGE, SDS-PAGE and gradient PAGE. The results showed:1. In the method of PAGE, there were clear bands in total proteins of dry seeds, just-germinated seeds and 5-day germinated seeds in watermelon cultivars. The polyphenol oxidase bands could differentiate the purity of these three cultivars in just-germinated seeds. Peroxydase bands were different between the cultivars"96-m×96-c"and their parents as well as 5-day germinated seeds of"Sumi NO 1×S84-2 and"20-E×20-SG.". there are different esterase bands in 5-day germinated seeds of"Sumi NO 1×S84-2. the protein of 96-m×96-c and 20-E×20-SG could be distinguished from their female parent in the PAGE analysis.2. In the method of SDS-PAGE, many difference bands were found in total proteins between parents and F1 hybrids of dry seeds of 3 cultivars. Some bands were representing as character bands to differentiate the parents and F1 hybrids. And no obvious difference was found in 5-day germinated seeds.3. In the method of the gradient PAGE, the clarity and numbers of bands was better than PAGE because a series gradient was made in PAGE for better molecular sifting function. But the results were similar to PAGE's ones. One obvious specific band was found among peroxydase electrophoresis of 5-days germinated seeds in three watermelon cultivars. Therefore, this method can be used for checking the seed purity. The polyphenol oxidase bands could differentiate the purity of the 96-m×96-c cultivars in just-germinated seeds. the seeds protein of gradient PAGE could distinguished Sumi NO 1×S84-2 in just-germinated seeds as well as 20-E×20-SG and 96-m×96-c in 5-days germinated seeds from their female parent. This method may detect the seed purity of these cultivars accurately and rapidly.4. There was a specific bright band in peroxydase electrophoresis of Cultivar"20-E×20-SG"comparing with the other two cultivars. The further study showed it was a special protein whose function was unknown. The seeds purity of cultivar"20-E×20-SG"can be checked by this band and the result was similar with that of in field.5. The results showed that the method of polyphenol oxidase PAGE could distinguish the purity of the hybrid seeds from its parents of three watermelon cultivars in just germinated seeds. The method of SDS-PAGE could detect the purity of the three hybrid seeds. And the method of POD could differentiate the hybrid seeds form its female parent in 5-germinated seeds. It could be a character to detect the purity of these watermelons. However, the other isoenzymes could only detect the purity of hybrid seeds of watermelon at special stage or on certain variety and no obvious differences were found in other isoenzyme patterns. This suggested that it different to found a consistent method of isoenzymes in all hybrid seeds to identify the purity among its parents. At the same time, it showed there were a relative stability of isoenzymes at certain stage of watermelon, consequently, it might screen out some methods to detected the purity of hybrid seeds in following experiments to provide a kind of accurate, rapid and economical method of checking seeds purity in the future.