Determining the occurrence and distribution of viruses causing diseases on cucurbit crops for developing effective management strategies.

Determining the occurrence and distribution of viruses causing diseases on cucurbit crops for developing effective management strategies.

Summary

Surveys were conducted during 2004-2006 in Illinois to determine occurrence and distribution of viruses in pumpkin, squash, and gourd fields.  CMV, PRSV, SqMV, TRSV, ToRSV, WMV, ZYMV, and unknown potyvirus(es) were detected as single and mixed infections. WMV was detected in more samples and SqMV was detected in samples from more counties than any other virus. ToRSV and TRSV were detected for the first time in Illinois in 2004 and 2005, respectively. Unknown potyvirus(es) are yet to be identified. General symptoms caused by viruses were mosaic and deformation of leaves and color-breaking and deformation of fruits.

Objectives/Performance Targets

The over-all goal of this two-year project was to identify viruses associated with cucurbit crops mainly pumpkin and squash in Illinois. The specific objectives were: 1) to determine the occurrence and distribution of viral diseases in pumpkin and squash in Illinois using serological detection methods; 2) to determine symptoms associated with each virus; 3) to test the “Koch’s Postulates” for all the viruses identified in pumpkin and squash; and 4) to use molecular diagnostic methods to confirm the identification of viruses detected for the first time in Illinois.

Accomplishments/Milestones

Viruses detected in the pumpkin, squash, and gourd fields surveyed in 2004, 2005, and 2006, were CMV, PRSV, SqMV, TRSV, ToRSV, WMV, ZYMV, and unknown potyvirus(es). ToRSV was detected only in one jack-o-lantern pumpkin sample in 2004 and TRSV was detected in jack-o-lantern pumpkin and processing pumpkin samples only in 2005. Processing pumpkin samples were generally free of viral infection and only single virus infections of PRSV, unknown potyvirus(es), and TRSV were detected in one sample each, collected in 2005. Most of the viruses detected during the surveys produced similar symptoms on pumpkin, squash, and gourd plants as the same virus produced a wide range of symptoms on different cultivars. Common symptoms observed on the infected plants were light and dark green mosaic, veinbanding and veinclearing, sometimes accompanied with puckering or deformation of pumpkin and squash leaves. Severe symptoms on the leaves were fernleaf and shoestring with reduction of fruit size, deformed fruit, and color breaking of fruit.

Impacts and Contributions/Outcomes

Illinois grows about 20,000 acres of pumpkin and 8,000 acres of other cucurbits (cucumbers, melons, and squashes). More than 90% of commercial processing pumpkins are produced and processed in Illinois. Also, more than 100,000 acres of cucurbits are produced in the North Central region annually. Viral diseases occur in cucurbit field in Illinois, as well as in the North Central Region, every year causing up to 100% crop losses. The identity and distribution of the viruses infecting in the North Central region was not precisely known. This research determined the occurrence and distribution of viruses in pumpkin, squash, and gourd fields in Illinois, which likely represent the North Central region. With the findings of this study, the researchers initiate the necessary program to develop effective methods for management for the threatening viral diseases in Illinois, the North Central region, and likely in the nation.