Zucchini yellow mosaic virus (ZYMV), Genus, potyvirus, and family, potyviridae was discovered on squash plants in northern Italy [1]. It is transmitted by many species of aphids in a non-persistent manner, and the affected plants exhibit severe stunting, yellowing and mosaic symptoms, and deformation of fruits and leaves [2–4]. ZYMV is one of the most prevalent viruses on squash plants (more than 55%) [5] and muskmelon (90%) [6]. The ZYMV genome is monopartite positive-sense single-stranded RNA (+ ssRNA), encapsulated in flexuous filamentous particles (750 nm long and 12 nm in diameter) and has 9,600 nucleotides contained in elongated. The coat protein (CP) has a molecular weight of 36 kDa [7,8].
The isolates of the ZYMV differ in the symptoms they cause [3,9,10], also it differs in the insect which transmits it [11,12]. It was found that Malaysian isolate (ZYMV-MZ) was not transmitted by aphids, Myzus persicae, and Aphis gossypii [13], on the other hand, it was found that these insects could transmit isolates, ZYMV-TW, ZYMV-FL, ZYMV-CT, from Taiwan, Florida, and Connecticut, respectively, however, it could not transmit the French isolate (ZYMV-WK) [14].
A strain of ZYMV caused local lesion spots, as well as wilt symptoms of melon, which contained the semi-dominant gene (Fn gene) [15]. Subsequently, 22 isolates of ZYMV were isolated and then divided into three pathotypes according to their interaction with the melon plant (line 414723), which is resistant to some virus isolates [16–18]. More than 25 isolates were subsequently found from the virus (ZYMV); where different isolates of the virus were detected, such as California, Egypt, Florida, Italy, Singapore, and Taiwan [1,19–24].
There are biological and molecular similarities between many ZYMV isolates, whereas found similarities between nucleotide sequences of the cylindrical inclusions (CI) protein and nuclear inclusions (NIb) genes of other Egyptian ZYMV isolates and ZYMV TW-TN3 (100% homology) [25]. Also, in 12 Slovakia ZYMV isolate, there is a similarity between the nucleotide sequence of the whole DNA strand and the amino acid sequence by 90.4–98.8 and 78- 98.8%, respectively. On the other hand, the complete nucleotide sequence of coat protein gene for 50 ZYMV isolates collected from different regions was conducted. The isolates taken from central Europe were very close genetically [26]. By comparing nucleotide sequencing of Chile-ZYMV isolate with others took their information from National Center for Biotechnology Information (NCBI), it was found to similarity 95% with Florida and Taiwan isolates and 94% with isolates from Hungary and Japan [27]. This study aimed to identify biological and molecular differences between two zucchini yellow mosaic virus isolates affecting squash in Upper Egypt. This virus has great importance; there is a difference in the damage caused by the different isolates globally and the absence of previous studies on the isolates of Upper Egypt in this regard.