Preliminary Studies On Mango Resistant Mechanism To Rhytidodera Bowringii White

Two comparisions of the biological features on the stem borer, R . bowringii, and mango anatomical structures between resistant and susceptible varieties were made during 2000-2002 in SCUTA.The larvae of the longicorn were fed on 21 mango varieties in mango germplasm orchard in Haikou campus, where the screening experiment for evaluating the mango varietal resistance to the stem borer was carried out, and the watches for the biology of larvae and imagoes were made in lab. The results show that: 1. The weight and the eating capacity of the larvae are significantly different between the tested varieties and show logical relationship with the varietal resistantce data. i.e. on the resistant varieties,the less the larvae eat, the slower the larvae grow,and the longer the lifecycle of the longicorn was taken. On the susceptible varietyies, the case proves the contratary . 2. No obvious pernicious influences from all the tested resistant varieties upon the larva survival, adult life, somatotype, oviposition and egg hetchebility of R. bowringii were found in the experiment.The determination and measurement for the branch anatomical structure on 22 mango varieties were carried out by Germany biological microscope and micro-image analysis system(DC100 numerical camera shootigsystem and the experiment data were analysed by Qwin Stangdard image analysis software). The results indicate that: 1. The cuticle and epidermis thickness of the tender branches, the cell containing tanin of lignified branch medulla, the vessel number and size of lignified branch xylem are distinctly different between the tested varieties. 2. The cuticle thickness and epidermis thickness of the tender branches may be the first obstacle to infesting by the longicorn larvae due to the resistant varieties are with more thick cuticle and epidermis. 3. The contain of tanin cell of lignified branch medulla may be the one of the factors to restrain the larval growth. 4. Vassel area, numberand size of lignified branch xylem are notably possitivecorrelation to the larvae growth on the corresponding varieties. 5. The resin canal number of the phloem and medulla of tender branch shows no correlation with the variety resistantce data.The 13 resistant varieties of the tested varieties in this studies are preliminarily classified as three types for their resistant mechanisms accordding to the results showed above, i.e. there are 2 varieties (Xiangjiao M and Xiaofei M) with lowest attacking index by the stemborer but better larval growth and shorter lifecycle belonging to Antixenosis Type; 9 varieties (Zihua M, Fu3, 814 M ,Qiu M, Biantao M, Chuan M, Xiaoqingpi M, 135-2 M and Maqiesu M ) with low attacking index and poor larval growth and longer lifecycle belonging to Antibiosis Type; 2 varieties (AK. M and Ful M) with serious attacking index but very good growth belonging to Tolerance Type.