Emergence of Heterodera cajani Juveniles from Cysts and Egg Sacs uri icon

abstract

  • The effects of temperature, host root exudates, host age, cyst maturity, and cyst wall fragments on emergence of Heterodera cajani juveniles from egg sacs and cysts were investigated in laboratory and greenhouse experiments. Emergence from egg sacs was greater and more rapid (P = 0.05) than from white (young) or brown (mature) cysts. From white cysts, 50?80% of the juveniles emerged within 1 month at 25?30°C. Emergence of the remainingjuveniles was not entirely temperature dependent and was slow and gradual. Fifty-three percent of the juveniles from brown cysts emerged at 25°C, 52% at 20°C, and 5% at 15°C. About 48% of the juveniles did not emerge even after incubation for 525 days at 25° C. These dormant juveniles were either free or within eggs in cysts. Juvenile emergence was greater from cysts produced on 30-day-old pigeonpea (cv. ICPL 87) plants than from cysts produced on 60-, 90-, 120-, and 150-day old plants. Root exudates from 15-day-old pigeonpea cv. ICPL 87 stimulated emergence of 15?25% dormant juveniles in mature cysts. Emergence from free eggs was about 14-times greater than from encysted eggs. Cyst wall fragments and other cyst contents repressed emergence of juveniles from eggs. The pattern of second-stage juvenile emergence in H.cajani is complex and temperature is a major, but not the only important factor. Apart of the encystedjuvenile population undergoes diapause

publication date

  • 1996