Effects Of The Cotyledons And True Leaves Of Eight Cruciferous Plants On The Growth,Development And Physiological Metabolism Of Plutella Xylostella (L.)

The diamondback moth(DBM),Plutella xylostella L.,is one of the most destructive pest insects of cruciferous plants,which is widely distributed all over the world and causes huge economic losses to vegetable production all over the world every year.The cotyledon is the most important organ in growth stage of plant seedlings,which plays an important role in seedling survival,growth and plant yield formation.At present,most of studies on plantinsect interactions have focused on the true leaves of plants as insect feeding sources,but paid little attention to plant cotyledons.We studied the effects of cotyledons and true leaves of eight cruciferous plants on feeding selectivity,growth and development,pupal weight and physiological metabolism of P.xylostella larvae,and the chemical constituents of cotyledons and true leaves of eight plants and their correlation with growth and physiological metabolism of P.xylostella were detected and analyzed.The main results obtained were as follows:1.P.xylostella larvae preferred to feed on true leaves of host plants,but also completed growth and development when feeding only on cotyledons of host plants.The development duration of P.xylostella was significantly prolonged when feeding on cotyledons,and the pre-adult developmental period ranged from 14.3 d(Brassica oleracea L.‘Lvqiu 66’)to 18.6d(Brassica napus L.‘Shanyou 0913’).However,the pre-adult developmental period of P.xylostella feeding on true leaves was significantly shortened,ranging from 12.3 d(Brassica alboglabra L.‘Zhonghuajianyegailan’)to 16.3 d(B.napus L.‘Shanyou 0913’).The weight of pupa of P.xylostella when feeding on true leaf was significantly higher than that feeding on cotyledons.2.The SOD activity of P.xylostella larvae fed on cotyledons of Brassica pekinensis L.(‘Gailiangqinza 3’),Raphanus sativus L.(‘Gailiangloutouqin’),B.napus L.(‘Shanyou0913’),Brassica campestris L.(‘Siyueman’)and B.oleracea L.(‘Lvqiu 66’)was significantly higher than that fed on true leaves.The POD activity of P.xylostella larvae fed on B.campestris L.(‘Siyueman’)and B.alboglabra L.(‘Zhonghuajianyegailan’)cotyledons was significantly higher than that fed on true leaves.The CAT activity of P.xylostella larvae fed on B.alboglabra L.(‘Zhonghuajianyegailan’)cotyledons was significantly higher than that fed on true leaves,but the CAT activity of P.xylostella larvae fed on B.pekinensis L.(‘Gailiangqinza 3’)and B.campestris L.(‘Siyueman’)cotyledons was significantly lower than that fed on true leaves.The GST activity in P.xylostella fed on cotyledons of eight host plants was significantly higher than that fed on true leaves.The Car E activity of P.xylostella larvae fed on cotyledons of B.napus L.(‘Shanyou 0913’),B.campestris L.(‘Siyueman’)and B.oleracea L.(‘Lvqiu 66’)was significantly higher than that fed on true leaves.The Car E activity of P.xylostella larvae fed on cotyledons of R.sativus L.(‘Gailiangloutouqin’),Brassica campestris L.(‘Chaojihuojiqin’)and B.alboglabra L.(‘Zhonghuajianyegailan’)was significantly lower than that fed on true leaves.The Ach E activity of P.xylostella larvae fed on cotyledons of B.pekinensis L.(‘Gailiangqinza 3’),R.sativus L.(‘Gailiangloutouqin’),B.napus L.(‘Shanyou 0913’),B.campestris L.(‘Siyueman’)and B.alboglabra L.(‘Zhonghuajianyegailan’)was significantly higher than that fed on true leaves.3.The contents of soluble sugar,total amino acids,tannin,flavonoid and total phenolic in true leaves were significantly higher than those in cotyledons.The developmental duration of P.xylostella was negatively correlated with the soluble sugar content of host plants,while the pupal weight was positively correlated.There was no significant correlation between the amino acids content and the developmental duration or physiological metabolism of P.xylostella.The activities of protective enzymes and detoxifying enzymes of P.xylostella were negatively correlated with the content of secondary metabolites in plant leaves.In conclusion,P.xylostella preferred to feed on true leaves,and true leaves and cotyledons of different host plants had significant effects on the development and physiological metabolism of P.xylostella.The nutrients and secondary metabolites in leaves were the key factors affecting the growth and physiological metabolism of P.xylostella.However,P.xylostella could improve host adaptability and complete growth and development by regulating physiological metabolism.The results of this study not only contribute to the in-depth understanding of the interaction between P.xylostella and host plants in the long-term evolutionary process,but also contribute to the development of integrated control technology for P.xylostella.