Rice hoja blanca: a complex plant-virus-vector pathosystem.

Abstract

Rice hoja blanca (RHB; white leaf) devastated rice (Oryza sativa) plantings in tropical America for half a century, before scientists could either identify its causal agent or understand the nature of its cyclical epidemics. The association of the planthopper Tagosodes orizicolus with RHB outbreaks, 20 years after its emergence in South America, suggested the existence of a viral pathogen. However, T. orizicolus could also cause severe direct feeding damage (hopperburn) to rice in the absence of hoja blanca, and breeders promptly realized that the genetic basis of resistance to these problems was different. Furthermore, it was observed that the causal agent of RHB could only be transmitted by a relatively low proportion of the individuals in any given population of T. orizicolus and that the pathogen was transovarially transmitted to the progeny of the planthopper vectors, affecting their normal biology. An international rice germplasm screening effort was initiated in the late 1950s to identify sources of resistance against RHB and the direct feeding damage caused by T. orizicolus, making better progress in the development of hopperburn-resistant than for hojablanca-resistant rice lines. In the 1980s, the identification of a novel virus as the causal agent of RHB, and genetic studies on the interaction of this virus with its planthopper vector, confirmed previous studies on the pathogenic nature of the virus to T. orizicolus and helped explain the cyclical nature of RHB epidemics. This disease is best controlled by hybridization of susceptible indica and resistant japonica rice genotypes and the adoption of integrated disease control practices.

Major QTLs Control Resistance to Rice Hoja Blanca Virus and Its VectorTagosodes orizicolus

“…Nevertheless, it is also important to regulate the insect populations to avoid epidemic bursts (Morales and Jennings 2010). For instance, large-scale cultivation of Fd50, which had strong antibiosis against T. orizicolus , helped in controlling RHB disease for many years in Colombia.…”

Complete Genome Sequence of Rice hoja blanca tenuivirus Isolated from a Susceptible Rice Cultivar in Colombia

“…Since then, HBD has been reported in countries of major rice production in Latin America, the Caribbean, and the southern United States. The vector of RHBV is Tagosodes orizicolus Müir (Hemiptera: Delphacidae), which can also be infected by the virus ( 4 ). Infected rice plants show symptoms that include chlorotic striping and mottling on the leaves, plant dwarfing, panicle sterility, premature wilting, and necrosis, causing serious yield losses (25 to 75%; [ 4 ]).…”

Conformationally Restricted Peptides from Rice Proteins Elicit Antibodies That Recognize the Corresponding Native Protein in ELISA Assays

“…Rice hoja blanca (RHB) disease has been reported in tropical and subtropical American countries that grow rice. Unlike the phytosanitary situation of rice in Asia, RHBV was the only viral disease in America until 1991 when the rice stripe necrosis virus emerged in South America [ 6 ]. RHBV is transmitted by the planthopper insect Tagosodes orizicolus, which grows up to an average size of 2.5 mm.…”

“…RHBV is transmitted by the planthopper insect Tagosodes orizicolus, which grows up to an average size of 2.5 mm. T. orizicolus requires high temperatures (about 27 °C) and humidity (>80% RH), and is also a direct rice pest [ 6 , 7 ]. Epidemics of RHB occur sporadically, but with catastrophic results in terms of rice crop yields [ 8 ].…”

“…Distribution of RHBV is determined by environmental conditions that favor the reproduction and survival of its vector. A potential planthopper vector requires up to 12 h to acquire the virus from an infected rice plant, and a minimum of a week to a month to complete the incubation inside the hopper insect T. orizicolus [ 6 ]. Also, the virus could be transmitted in a transovarial way; it means from the mother to the progeny.…”