Population characteristics and tungro transmission by Nephotettix virescens (Hemiptera: Cicadellidae) on selected resistant rice cultivars

Abstract

Rice green leafhopper Nephotettix virescens (Distant) populations were collected in 1985 from fields planted with a leafhopper resistant rice, Onjza sativa cultivar IR64 in South Cotabato, Philippines. The populations were reared on IR64 for eight generations and tested on six cultivars, including susceptible TNI, moderately resistant IR26 and IR36, and resistant IR54, IR62, and IR64. Leafhoppers excreted larger amounts of basic honeydew, efficiently transmitted two tungro associated viruses, and showed greater population increase and lower nymphal mortality on all cultivars except IR62 than a greenhouse population reared on TNI. Nephotettix virescens were transferred and maintained on TNI, IR26, IR36, IR64, or a mixture of the four cultivars plus IR54 and IR56 in equal proportion. When the TNl-maintained colony was tested at the third generation, its feeding behaviour and tungro transmission rates on test cultivars were similar to those of the original population but amounts of basic honeydew excretion and the transmission rate on the resistant test cultivars were greatly reduced at the seventh or later generations. When the IR26-maintained colony was tested at the sixth, ninth, or 13th generation, it exhibited lower amounts of basic honeydew excretion on the resistant test cultivars but exhibited similar transmission efficiencies on other test cultivars. When the colonies maintained on IR36, IR64, or the cultivar mixture were tested similarly, their population characteristics and virus transmission efficiency were similar to the original population. These results indicate that N. virescens retain their 'virulence' to resistant cultivars when maintained on resistant cultivars, but quickly lose their 'virulence' when maintained on a susceptible cultivar. Colonies continuously reared on IR26, IR36 or IR64 showed 'cross-virulence' to many cultivars possessing a variety of genes for N. virescens resistance but often differed in feeding behaviour, virus transmission efficiency, and nymphal mortality on cultivars with the same genes for leafhopper resistance. Introductioncomposite disease caused by rice tungro bacilliform virus Tungro is the most important virus disease of rice, Oryza ( R T B V ) a n d r i c e t u n S r o spherical virus (RTSV) (Omura et al., sativa, in south and southeast Asia (Ling, 1972). It is a 1 9 8 3 )-R T B V a n d R T S V a r e transmitted in a semi-persistent manner by the leafhopper Nephotettix virescens (Distant)

Transgenic rice expressing Allium sativum leaf lectin with enhanced resistance against sap-sucking insect pests

“…One of the major constraints of increasing rice production in Asia as well as some parts of the world is the brown planthopper (Nilaparvata lugens; BPH) and green leafhopper (Nephotettix virescens; GLH), which cause huge amount of crop loss every year (Brookes and Barfoot 2003). These sap-sucking insect pests also cause ''hopperburn'' and physiological damage to rice plants through stylet probing while feeding, as well as they act as vectors for viral diseases (Dahal et al 1997;Foissac et al 2000).…”

The Use of Electrophoretic Isozymes to Detect Tungro Infected Rice

“…The use of electrophoretic approaches especially plant isozymes for taxonomic purposes have been widely conducted (Degani & El-batsri, 1990;Degani, Beiles, El-Batsri, Goren, & Gazit, 1995). However, the application of this approach in clarifying the Tungro diseases was used for the first time.…”

A novel approach for developing resistance in rice against phloem limited viruses by antagonizing the phloem feeding hemipteran vectors

“…The damage caused by BPH alone amount to 250 million US dollars per annum (Nagadhara et al 2003). BPH, as a serious rice pest, transmits viruses such as grassy stunt and ragged stunt viruses (Lee et al 1999), whereas GLH damages rice by direct feeding as well as transmitting viruses that cause rice dwarf, transitory yellowing, yellow dwarf and tungro diseases (Dahal et al 1997;Rao et al 1998). Of these diseases, tungro is the most serious caused by co-infection of two viruses, namely, Rice tungro bacilliform virus (RTBV) which is a double-stranded DNA virus and Rice tungro spherical virus (RTSV) which a positive-sense singlestranded RNA virus (Jones et al 1991).…”

“…Of these diseases, tungro is the most serious caused by co-infection of two viruses, namely, Rice tungro bacilliform virus (RTBV) which is a double-stranded DNA virus and Rice tungro spherical virus (RTSV) which a positive-sense singlestranded RNA virus (Jones et al 1991). Both the viruses are known to be transmitted in a semipersistent manner by the viruliferous GLH Dahal et al 1997). In South-east Asia alone, the rice tungro disease resulted in an annual yield loss of more than 340 million US dollars (Nagadhara et al 2003).…”

“…In South-east Asia alone, the rice tungro disease resulted in an annual yield loss of more than 340 million US dollars (Nagadhara et al 2003). Upon infection RTBV occurs in the xylem and phloem, where as RTSV is located only in the phloem tissue (Dahal et al 1997). Apart from spreading the viruses, both the insects are extremely harmful as they damage the plants by feeding on the phloem sap, disrupt the photosynthate flow to the root system and induce leaf senescence resulting into 'hopperburn' (Rao et al 1998;Nagadhara et al 2004).…”