9 2 5 , ▁commercial ▁C uc um is ▁m elo ▁( c antal oup ▁and ▁mus km el on ) ▁production ▁has ▁been ▁engaged ▁in ▁a ▁bi ological ▁" ar ms ▁race " ▁against ▁c uc ur bit ▁pow der y ▁mil de w ▁( CP M ) ▁caused ▁by ▁the ▁fung us ▁Pod os pha era ▁x anth ii , ▁with ▁new ▁cultiv ars ▁of ▁mel ons ▁being ▁developed ▁for ▁resistance ▁to ▁success ively ▁ar ising ▁races ▁of ▁the ▁fung us , ▁identified ▁simply ▁as ▁race ▁ 1 , ▁race ▁ 2 , ▁etc . ▁( se ven ▁in ▁total ▁by ▁ 2 0 0 4 ), ▁for ▁races ▁found ▁around ▁the ▁world , ▁and ▁race ▁N 1 ▁through ▁N 4 ▁for ▁some ▁diver gent ▁races ▁native ▁to ▁Japan . ▁ ▁Vari ous ▁sub ra ces ▁have ▁been ▁identified , ▁and ▁given ▁names ▁such ▁as ▁race ▁ 2 U . S ., ▁race ▁ 3 . 5 , ▁and ▁race ▁ 4 . 5 . ▁ ▁A ▁new ▁race ▁S ▁was ▁discovered ▁in ▁ 2 0 0 3 , ▁and ▁a ▁specific ▁mel on ▁cultiv ar ▁( C . ▁m elo ▁var . ▁acid ulus ▁' PI ▁ 3 1 3 9 7 0 ') ▁found ▁resist ant ▁to ▁it , ▁then ▁used ▁for ▁back cross ing ▁to ▁increase ▁resistance ▁in ▁other ▁cultiv ars . ▁Such ▁modern ▁select ive ▁bre eding ▁of ▁plants ▁for ▁ph y top ath ological ▁resistance ▁to ▁particular ▁fung al ▁races ▁involves ▁a ▁great ▁deal ▁of ▁gen