Studies On Tomato 'LA2006' And 'Heinz 1706' At Low Temperature

Tomato is an important thermophilic vegetable crop in facility cultivation.It is susceptible to low temperature and cold damage in winter and spring,causing falling flowers and fruit,which seriously affects the yield and significantly reduces the economic benefits of tomato production.In order to investigate the cold tolerance mechanism of tomato,this paper selected cold resistant strain LA2006 and cold sensitive strain Heinz1706 as control.The differences of seed germination,seedling photosynthetic and growth,Pollen vigor and fruit setting of two strains under low temperature stress were studied,and the second generation sequencing technology was used to analyze the transcriptome of germinated seeds under normal temperature and cold stress,and to explore the mechanism of cold resistance line LA2006.The main findings are as follows:The germination of LA2006 and Heinz1706 seeds at 28? and 15? was investigated.The germination rate of the two lines was delayed 4 days after treatment at 15?,and the germination rate decreased significantly.However,the germination rate of LA2006 seeds was significantly higher than Heinz 1706 after 6 days of treatment,the seed germination rate of LA2006 reached 51.11%on the 8th day,which was 46.67%lower than that at 28?,while the germination rate of Heinz1706 was only 18.67%,which was 72.44%lower.The germination potential of LA2006 started 6 to 9 days at low temperature,extremely significantly higher than Heinz 1706.The above results indicated that the germination rate and germination potential of LA2006 seeds were significantly higher than those of Heinz1706 at low temperature,and had strong cold resistance potential.The physiological indexes and photosynthetic fluorescence rates of LA2006 and Heinz1706 plants were determined at 25/15? and 16/6? After low temperature treatment,the photosynthetic fluorescence rate parameters Fv/Fm(photochemical efficiency),Y(?)(actual quantum yield),ETR(electron transfer rate)of tomato seedlings decreased significantly,and NPQ(non-photochemical quenching coefficient)increased,the difference of Y(NO)is not significant.However,the difference between LA2006 and Heinz 1706 is not significant.The activity trends of POD,SOD and CAT of the two varieties under 25/15? treatment were basically the same,there was no significant difference.The activity of POD,SOD and CAT increased significantly under low temperature treatment than 25/15? treatment,and LA2006 was significantly higher than Heinzl706;There was no significant difference in H2O2 and MDA content and relative conductivity between the lower two varieties,while LA2006 was significantly lower than Heinz 1706 at low temperature,and the membrane lipid peroxidation of LA2006 was lower than that of Heinz1706.The above results indicated that the membrane lipid peroxidation of LA2006 seedlings was significantly lower than Heinz1706 at low temperature,and the antioxidant enzyme activity was significantly higher than Heinz 1706,and the ability to resist cold stress was stronger.The pollen vigor and germination of 28? and 10? were investigated.The pollen vigor of the two strains was significantly reduced under low temperature treatment at 10?.The pollen vigor of LA2006 was 82.3%,which was 15.08%lower than that of 28?,and the pollen vigor of Heinzl706 was only 52.64%,which was reduced by 46.48%.The pollen vigor of LA2006 was significantly higher than that of Heinzl706;the pollen germination began to be germinated at 10? for 1 h,and the pollen germination rate of LA2006 was significantly higher than that of Heinzl706;10? for 3 h,LA2006 pollen tube length was 72.58?m,while Heinzl706 was only 38.97?m,the pollen tube length of LA2006 is also significantly higher than Heinz 1706.The above results indicated that the pollen vigor and germination of LA2006 at low temperature were significantly higher than that of Heinzl7106,and it had strong cold resistance.The appearance changes of LA2006 and Heinzl706 plants at 25/15? and 16/6? were observed.After 1 week of cold treatment,there was no significant change in LA2006 plant height,and there was no delay in flowering,while Heinzl706 plants were short and low temperature.Under the stress,the rate of fruit set in LA2006 was significantly higher than that in Heinzl706.The above results showed that the growth and fruit setting rate of LA2006 seedlings were significantly higher than that of Heinz 1706,and the low temperature inhibited the growth of LA2006.By deep sequencing of germinated seeds of LA2006 and Heinz 1706 under low temperature conditions,KEGG analysis of transcriptome data indicated that these different expression genes were mainly involved in carbon metabolism,secondary metabolism biosynthesis,energy metabolism and signal transduction pathway and translation processes have been found to differ widely.Signal transduction pathway include plant hormone signaling,MAPK signaling pathways,and phosphatidylinositol signaling system,and we have primarily analyzed plant hormone signaling pathways.IAA,ETH,GA,and MYB and WRKY transcription factors are involved in the regulation of LA2006 seed germination at low temperatures in the plant hormone signaling pathway.