Combination of Piper guineense Essential Oil with Cowpea Varietal Resistance in Control of Cowpea Seed Beetle, Callosobruchus maculatus Fabricius (Coleoptera： Chrysomelidae： Bruchinae)

To reduce the risks associated with over-dependence on synthetic insecticides and ensure leguminous food security, an experiment was conducted to evaluate the potentials of integrating Piper guineense essential oil （PgEO） with cowpea varietal resistance in the control of cowpea seed beetle, Callosobruehus maculatus Fabricius. Four cowpea varieties （Sokoto, Drum, Oloyin and Gwallam） were studied. Data collected included oviposition, progeny emergence, Reproductive Efficiency （RE） and Percentage Seed Damage （PSD）. At first filial generation, numbers of eggs laid on Oloyin variety treated with 25 μL PgEO per 25 g cowpea seeds （2.15） were significantly （p〈0.05） lower than the values obtained in untreated cowpea （3.61） and hexane-treated seeds （3.07）. C. maculatus RE on Oloyin （33.73） was significantly （p〈0.05） lower than values obtained on other varieties （47.34-54.67） for seeds without PgEO; and were significantly greater than 0.00 observed on Oloyin seeds treated with 50 pL PgEO. PSD on Oloyin （6.63%） was significantly （p〈0.05） lower than the values obtained on Sokoto （10.04%） and Drum （9.79%） for seeds without PgEO, while there was no damage in Oloyin treated with 50 pL PgEO. Significantly （p〈0.05） lower F2 progeny emergence occurred on Oloyin （4.02） and Sokoto （4.71） compared with Drum （9.03） and Gwallam （6.07） from the untreated cowpea seeds. The results implied that application of PgEO to Oloyin gave better protection from infestation of C. maculatus than other varieties. Hence, combination of varietal resistance with PgEO for management ofbruchid could be an effective mean of improving cowpea food security.

Phenotypic Expression of Whitebacked Planthopper Resistance in the Newly Established japonica/indica Doubled Haploid Rice Population

A new doubled haploid (DH) rice population was established from a cross between WBPH-resistant japonica Chunjiang 06 (CJ-06) and susceptible indica TN1. Sucking inhibitory and ovicidal resistance of the DH rice lines were evaluated on the basis of non-preference response of WBPH immigrants and honeydew excretion by WBPH females, and appearance of watery lesions in the necrotic discoloration of leaf sheaths ovipositied by WBPH,respectively. Both the major gene resistance to WBPH, sucking inhibitory and ovicidal resistance, showed 1 (resistant): 1 (susceptible) segregation ratio in the DH population. Relative density of WBPH populations and damage scores in the DH population indicated combined functions of both the major resistance genes as well as QTLs affecting the host plant response to WBPH infestations. Thus, the newly developed CJ-06/TN1 DH population could be a useful material to analyze major genes and QTLs for WBPH resistance in japonica rice.

Differential Expression of Whitebacked Planthopper Resistance in the japonica/indica Doubled Haploid Rice Population under Field Evaluation and Seedbox Screening Test

Whitebacked planthopper (WBPH) -resistance in a japonica / indica doubled haploid (DH) rice population established from a cross between WBPH-resistant japonica Chun]iang 06 and susceptible indica TN1, was comparatively evaluated through a field experiment based on the WBPH immigrant density and standardized seedbox screening test (SSST). All the susceptible DH lines in the field experiment behaved accordingly in SSST. However, 35 of resistant 66 lines (53%) in the field, were categorized to susceptible groups in SSST. Likewise, there were no significant differences in WBPH immigrant densities among 70 DH lines that were highly resistant to susceptible in SSST. The results revealed that SSST could not evaluate properly WBPH resistance in the DH lines. Four QTLs for WBPH-resistance phenotyped by the immigrant density were detected on chromosomes 2, 3, 4, and 11. Of them, the QTL on chromosome 4 was the most effective (LOD 21.8, variance 78%). Five QTLs associated with seedling mortality were mapped on chromosomes 2, 3, 4, 5 and 6. In addition to the QTL (LOD 10.5, variance 68%) on chromosome 4, there was another major QTL (LOD 12.7, variance 71%) located on chromosome 5, which was SSST-specific but might be irrespective of the WBPH resistance traits.

Resistance Performance to Whitebacked Planthopper in Different Phenotypes of Japonica/Indica Doubled Haploid Rice Lines

Field performance of whitebacked planthopper （WBPH）-resistance of four phenotypes was evaluated in Chunjiang 06 （C J-06） / TN1 DH rice lines, which were expressed by different combinations of sucking inhibitory and ovicidal traits inherited independently from C J-06. WBPH established the highest populations in susceptible DH lines that had neither sucking inhibitorynor ovicidal resistance. Both immigration and subsequent population levels were kept below the damage-causing density in the sucking inhibitory DH lines even under a WBPH outbreak. WBPH could not build up populations in the DH lines having both the sucking inhibitory and ovicidal resistance. Although WBPH immigrated preferentially to non-sucking inhibitory DH lines with ovicidal resistance, subsequent population buildup was significantly suppressed. It was concluded that the differential performance to WBPH-resistance in CJ-06 / TN1 DH lines was primarily due to the sucking inhibitory trait, and complementarity to the ovicidal trait.

Tomato Hybrid and Local Varieties Screened for Resistance to Bacterial Wilt Caused by <i>Ralstonia solanacearum</i>under Screen House and Field Conditions

Bacterial wilt is the most damaging disease of tomato in Benin. To select resistant varieties of tomato against bacterial wilt, 21 tomato varieties were evaluated twice under screen house and field conditions in a randomized complete block design with four replicates and 21 treatments which are the tested varieties. Three weeks old tomato seedlings were inoculated by crown flooding with 40 ml of a bacterial suspension of R. solanacearum strain CR-1103-2, phylotype I sequvar 14. At 28 days after inoculation, the control resistant varieties Hawaii 7997 and PADMA maintained their resistance and the known susceptible variety Tohounvi showed to be susceptible to the bacterial wilt. Among the hybrid tomato varieties, only Cobra 26 was moderately resistant. No resistant line was found among the tested local varieties. The hybrid varieties Buffalo, Petomech, Tropimech, Sumo, Prado, Ninja, Jaguar, Anaya, Topaze, Cobra 34, Heinz, Kiara, Euclid and local Kêkêfo, Akikonkouin, Agbotrui and Adjaa were all susceptible. In conclusion, Cobra 26 emerges as a new variety of tomato moderately resistant to bacterial wilt. This is a new finding since it adds. All the tested varieties, regardless of their resistance, were colonized by R. solanacearum. This is a challenge for tomato farmers who must practice sanitation in their fields when producing tomato susceptible or resistant varieties. The variety Cobra 26 must be scaled up to farmers.

Damage Caused by Psyllids and Influence of Climatic Factors in Brazilian Accesses of Guava Trees Cultivated in Organic System

The psyllid (Triozoida sp.) is the primary pest of guava tree in the Central Northern region of S?o Paulo State, Brazil. The variation of climatic factors may influence directly or indirectly the behavior of agricultural pests. The present work had objectives to evaluate the damages caused by psyllid in accesses of guava trees in order to identify materials with potential resistance to pest and the possible correlations of the damage with the meteorological factors, in an orchard of guava conducted in an organic system. Eighty-five guava accesses were evaluated. Each one was analyzed at random 10 leaves containing the symptom of the psyllid attack, through visual range of notes. The averages of the notes were compared by Scott-Knott test at 5% probability. The 25 accesses with the highest average damage of psyllid had the data submitted to correlation (Pearson), with the minimum and maximum temperature (°C), precipitation (mm) and relative humidity (%). Guava accesses used commercially were the most susceptible to the attack of psyllid, compared to the selections, with an emphasis to access “L4P14”, “L7P28” and “L8P32B”, which were the least attacked. The study of correlation between psyllid damages and meteorological factors, must be used the medium temperature, relative humidity and rainfall accumulated in the period of 14 days before the evaluations. There is a positive correlation between minimum temperasture, precipitation and relative humidity with the damage of psyllids in leaves of guava.