Novel approaches to implementation of pumpkin resistance in control of viral diseases
Authors: Bulajic Aleksandra , Vucurovic Ana , Stankovic Ivana , Ristic Danijela , Berenji Janos , Krstic Branka 
Published: January 2011

As there is a growing frequency of viral plant diseases in epidemic
proportions, the possibilities for successful control are constantly being
explored. Despite the fact that integral and simultaneous employment of
numerous control measures may contribute to the decreasing amount of yield
losses, especially concerning non-persistently aphid-transmitted viruses,
these measures are often not efficient enough. Research into the basis of
resistance to viral infection and principles of its inheritance, introduction
of sources of resistance in susceptible genotypes, by conventional or genetic
manipulations, are very intensive for cucurbit crops, especially pumpkins.
Pumpkin crops are being endangered by a great number of different viruses,
among which the Zucchini yellow mosaic virus, (ZYMV), Watermelon mosaic virus
(WMV) and Cucumber mosaic virus (CMV) are present every year in Serbia,
frequently causing epidemics. The majority of pumpkin cultivars are not
resistant or tolerant to viral infections, but sources of resistance have
been identified in various related species. So far, the identified sources of
resistance to the ZYMV are found in Cucurbita moschata and Citrullus lanatus
var. lanatus genotypes and consist of one or several major dominant genes of
resistance. It is a similar case with WMV, although the sources of dominant
major genes are identified in C. lanatus and C. colocynthis. The sources of
resistance to CMV in the form of one dominant gene have been identified in
the genotype C. moschata, although the introduction of this gene by
conventional means proved to be very difficult. Besides the aforementioned,
substantial efforts are being made in developing genotypes with multiple
resistance against several viruses and even other pathogens, as well as
genotypes with resistance to the most significant plant aphid species,
through mechanisms of antixenosis or antibiosis. The other way of obtaining
resistant genotypes includes genetic manipulation. Genetically modified
resistant pumpkins have been among the first successfully developed crops.
Genotypes with pathogen derived resistance can already be found in
commercially grown pumpkins in some parts of the world, and they have been
developed by introducing the coat protein gene of one, two or all three
viruses which are the most frequent, ZYMV, WMV and CMV. Yet, this approach to
the control of pumpkin viral diseases is related to possible negative
consequences, mostly through the already detected gene transfer to wild
plants and development of resistant transgenic weeds of unpredictable impact
on the environment. Improved host plant genetic resistance to viral
infections or biological vectors, developed by conventional or genetic
engineering methods, represents the most dynamic and prominent field of
research. It is economically and ecologically the most justified approach to
the control of pumpkin and other plant diseases caused by viruses
non-persistently transmitted by aphids.