Effects Of Root Characteristics And Dry Matter Accumulation On Yield Formation In Perennial Rice

The perennial rice varieties which are bred via the asexual propagation characteristics of the rhizome of Oryza Longistaminata have been widely used in production.The"twice harvest one year"is one of the main application schemes of perennial rice,which refers to once sowing or transplanting,perennial rice can be harvested for two seasons.In the second season,new tillers would ratoon from the rhizome without tillage and seeds.However,the relationship of root characteristics and dry matter accumulation with yield formation of perennial rice under twice harvest one year scheme is unclear,which restricts the yield increase of perennial rice production.In order to clarify the relationship of the root characteristics and dry matter accumulation with yield of perennial rice,a single-factor randomized block test was conducted at the Manla Scientific Research Station of Yunnan University in Mengzhe Town,Menghai County,Xishuangbanna in 2019.Perennial rice 23（PR23）,Yunda 107（PR107）and annual rice variety RD23 were selected as materials.The root characteristics,dry matter accumulation,yield and yield composition of perennial rice were observed to analyze the effects of root system and dry matter accumulation on perennial rice yield formation.The results could provide theoretical basis and technical support for the breeding of perennial rice varieties and formulation of high-yield cultivation techniques.The results as following:1.Perennial rice has good yield potential.The annual yields of PR23 and PR107were 16.53 tha^-1 and 16.07 tha^-1,respectively.The early rice yields of PR23,PR107and RD23 were 10.1 tha^-1,11.5 tha^-1 and 7.7 tha^-1,respectively.PR23 and PR107 were higher than RD23.The high yield of PR23 mainly achieved through better seed setting rate and effective panicles combination,while PR107 mainly achieved through better grain type and thousand grain weight.Late rice yield of perennial rice was significantly lower than early rice,PR23 and PR107 were 6.43 tha^-1 and 4.64 tha^-1,respectively.Late rice yield of PR23 decreased mainly due to a significant decrease in thousand grain weight and effective panicles,while PR107 was mainly due to the significant decrease in seed setting rate and grain numbers per panicle.In production,the perennial rice yield can be improved by increasing the seed setting rate,grain weight and effective panicles through cultivation measures.2.The root morphology index values（root length,root diameter,root surface area,root branch number,root tip number）of perennial rice PR23 and PR107 during early rice season showed a gradual increase trend from tillering period to booting stage,while from booting stage to mature stage it decreased gradually.Compared with RD23,the root length,root diameter and root tips number of PR23 from full heading stage to mature stage significantly increased by 47.5%⁷6.4%,35%⁵5%,18.3%⁴1.4%,and35.4%¹24.8%,respectively（P<0.01）.The root volume of PR107 was significantly larger than that of RD23 from 15 days after heading to maturity（P<0.05）,which was16.5%and 36.6%higher than that of RD23,respectively,and other indicators of PR107 were not significantly different with RD23.The root morphology of perennial rice during late rice production gradually declined,root morphology index of PR23gradually decreased from tillering stage to maturity,and PR107 had the same trend with early rice.The root morphology of PR23 was significantly better than that of RD23 during late rice production,while the difference between PR107 and RD23 was not significant.The root morphology of perennial early rice is better than annual rice,which provides the foundation for high yield of early and late rice.3.The root weights of perennial rice PR23 and PR107 both increased from tillering to the full heading period,and gradually decreased after the full heading period,root weight of late rice was less than that of early rice.From 15 days after heading to maturity of early and late rice,the root weight decay rates of PR23 and PR107 were significantly lower than RD23,during early rice root weight decay rates of PR23 and PR107 were 2.1%and 17.0%,respectively,and that for late rice were 0.1%and 3.4%,respectively.From the full heading stage to maturity,root senescence mortality rate of perennial rice was lower than that of annual rice,and it can have a higher root population in the later growth period that could ensure the nutrients for the growth of above-ground biomass and yield.4.The leaf weight decay rate of early and late rice of perennial rice was significantly lower than that of annual rice.Leaf weight decay rate of PR23,PR107and RD23 of early rice from 15 days after heading to maturity were 43.16%,22.83%and 62.06%,respectively,and that for late rice were 13.83%,23.83%and 42.17%,respectively.It showed that the leaves of the perennial rice did not prematurely decay after filling,and still had a higher production capacity of photosynthetic products in the later period,that could ensure the demand for photosynthetic products in the grain and accumulate more photosynthetic products for late rice regrowth,takeng the early rice yield and late rice regrowth into account,which is one of the reasons why perennial rice has higher yield potential than annual rice.5.The stem weight and material conversion rate of perennial rice after full heading were significantly lower than annual rice.The stem weight of early rice of PR23 was significantly higher than that of RD23 from heading stage to maturity,and the stem output rate and conversion rate were 9.98%and 8.06%,which were 73.01%and 87.7%lower than RD23.The stem output rate and transport rate of PR107 were24.94%and 16.71%,respectively,which were 32.0%and 59.5%lower than RD23.The stem output rate and stem conversion rate of late rice PR23 were-80.96%and-143.09,respectively,while PR107 were-0.23%and-0.17%,both of them were significantly lower than RD23.Compared with RD23,stem weight of PR23 showed an increasing trend,while PR107 showed a downward trend.This showed that the perennial rice stem not only transported photosynthetic products to the grains after heading,it also stored in the stem,and that could store enough photosynthetic products for late rice regrowth.This is why the yield potential of perennial rice of early and late rice is higher than that of annual rice.6.The root morphology（root length,root surface area,root diameter,number of root tips,and number of root branches,etc.）of perennial rice from the booting stage to15 days after heading was significantly positively correlated with yield（r>0.642**）,indicating that establishing a good root morphology before booting and maintaining a better root configuration from the heading to 15 days after heading is conducive to high yield of perennial rice.The root configuration of perennial of early rice is better and the yield is higher;while the root of late rice was gradually declining and the yield was greatly reduced.7.Dry matter accumulation of perennial rice was closely related to its yield formation.The total amount of dry matter from booting stage to maturity of early rice was significantly or extremely significantly positively related to the seed setting rate（r=0.845*）and thousand-grain weight（r=0.960**）of perennial rice.The yield of late rice was significantly positively correlated with dry matter at heading stage（r=0.852**）and dry matter at maturity（r=0.795**）.Dry matter accumulation is the basis for yield formation,and late rice had a short growth period and insufficient dry matter accumulation were the main reasons for low late rice yield.To sum up,the root morphology of perennial rice during the whole growth period was better than that of annual rice,especially after full heading,the perennial rice has a larger root population,and the above-ground（sufficient"source"）had strong photosynthetic product production capacity.The output and transformation of stem materials better coordinated the photosynthetic products needs of early rice production and late rice regrowth.The aboveground dry matter accumulation had obvious advantages.Therefore,the yield potential of perennial rice of early and late rice was higher than that of annual rice.From the perspective of yield composition,to increase grain weight and seed setting rate of early rice and the number of spikes and seed setting rate of late rice through cultivation measures are effective ways to increase yield of perennial rice.From the perspective of root characteristics and dry matter accumulation characteristics,improving the root population and root vigor and increasing dry matter accumulation of late rice through fertilization and other cultivation techniques are important measures to increase the yield of perennial rice.