Genetic Control of Soybean Resistance to Soybean Pod Sucker (Riptortus Linearis L.)

Riptortus linearis represents the most common pod sucking pest on soybean. Genetic studies on inheritance of resistance to the pest are needed. The study used B4400 and B3802 genotypes as resistant parents, Tambora as susceptible parent. Crosses were made to form F2 population of Tambora x B4400, and Tambora x B3802. A total of 10-20 seeds each of resistant and susceptible parents, 220 F2 seeds of Tambora x B4400 crosses, and 232 F2 seeds of Tambora x B3802 crosses were grown in pots, one plant/pot. The plants were infested with adult R. linearis (riptortus), at the R2 stage. The results showed that the population of riptortus in each of the F2 soybean population at 7 and 15 days after infestation were >2 insects/25 plants, which enables the study of genetic resistance to soybean pod sucker. Heritability values indicated that resistance to pod sucker was controlled by genetic factors. The resistance to riptortus in B4400 and B3802 genotypes was controlled by two recessive genes located at different loci, and interacted with each other with epistatic dominant reaction. With an assumption that B and C genes were dominant, hence the resistance genes found in both soybean genotypes were bbcc

Pewarisan Sifat Resistensi terhadap Deltametrin pada Plutella Xylostella

A field population of Plutella xylostella (Lepidoptera: Plutellidae) in Central Java has been reported to become resistant to a pyretroid synthetic deltamethrin. The objective of this research was to study the genetics of resistance in that population. The resistant population wascontinously sprayed with deltamethrin in the laboratory to increase the resistant level. The resistant population used in this study was 51 more resistant to deltamethrin than was the susceptible population. Bioassays using F1 obtaining from the reciprocal mating between the susceptible and resistant parents showed that the resistance to deltamethrin in P. xylostella was inherited recessively and the maternal effects were observed. The degree of dominance (D) was -0.8 when resistant female was mated with the susceptible male and the D value was -0.3 when the susceptible female was mated with the resistant male. Using the monogenic model it was proved that the resistance was controlled by single gen. The implementation of these findings for the development of resistance management program will be discussed

Stability of Resistance to Imidacloprid in the Brown Planthopper (Nilaparvata Lugens Stål.) From Banyumas, Central Java

Imidacloprid is one of the insecticides that has been widely used to control the brown planthopper (Nilaparvata lugens Stål.). The excessive use of insecticides led to the development of insecticide resistance in N. lugens. This study was aimed to determine the stability of resistance to imidacloprid in N. lugens from Banyumas, Central Java Province. The five generations of selection increased the resistance ratio (RR) from 46.20-fold to 150.39-fold. To assess the stability of resistance to imidacloprid in N. lugens, the fifth generation was further reared for 10 generations without exposure to insecticides. The stability studies showed that resistance to imidacloprid was unstable with a decrease of resistance from 150.39-fold to 38.14-fold after 10 generations without selections. Continuous selections with imidacloprid for three generations could increase the resistance level from 150.39-fold to 216.13-fold. The unstable resistance could be managed by removing the selection pressure for a period of time or switching to insecticides with different mode of actions. Information regarding resistance stability would be useful to determine an effective resistance management strategies in N. lugens

Evaluasi Resistensi terhadap Metoksifenozida pada Spodoptera Exigua di Jawa

The objective of this research was to know the resistance level of beet armyworm Spodoptera exigua to methoxyfenozide. The lara were collected from the shallot production areas in the districts of Nganjuk (East Java), Bantul and Kulonprogo (Yogyakarta Specia Territory) and Brebes (Central JAva). The bioassay used first instars of S. exigua with artificial diets that had been dipped in a series of methoxyfenozide solutions. Larval mortality was recorded at 72 hours after the exposure. The LC50 value of methoxyfenozide for the population from Sanden (Bantul) was the lowest (0.53 ppm) among 16 tested population, therefore it was used as refenrence population to determine the resistance ratio (RR) values of other populations. The RR values of the tested populations varied from 1 to 240,8 times. Population collected from Wanasari (Brebes) was found to have the highest level of resistance of methoxyfenozide as a result of using methoxyfenozide intensively to S. exigua controlling. Penelitian ini bertujuan untuk mengetahui tingkat resistensi ulat bawang. Spodoptera exigua terhadap metoksifenozida. Larva dikumpulkan dari daerah sentra produksi bawang merah kabupaten Nganjuk (Jawa Timur), Bantul dan Kulonprogo (Daerah Istimewa Yogyakarta) dan Brebes (Jawa Tengah). Uji hayati menggunakan S.exigua instar satu dengan pakan buatan yang telah dicelup dalam seri larutan metoksifenozida. Mortalitas larva diamati 72 jam setelah perlakuan. Nilai LC50 metoksifenozida terhadap populasi Sanden (Bantul) adalah paling rendah (0,53 ppm) di antara 16 populasi yang di uji, oleh karena itu digunakan sebagai pembanding untuk menentukan nilai rasio resistensi (RR). Nilai RR populasi yang diuji bervariasi dari 1 hingga 240,8 kali. Populasi Wanasari (Brebes) mempunyai tingkat resistensi tertinggi terhadap metoksifenozida sebagai akibat penggunaan metoksifenozida secara intensif untuk pengendalian S. exigua