Nikkei drops as China worries linger; retail investors sell small caps

* Nikkei off 1.0 pct, Topix down 0.9 pct * Mothers index nosedives on retail investors' selling * China cash crunch worries still weigh - analysts * Market to resume upward trend after July poll - Goldman Sachs By Ayai Tomisawa TOKYO, April 26 (Reuters) - Japan's Nikkei share average dropped below the 13,000-mark on Wednesday in volatile trade as worries about a cash crunch in China remained, while the mood was soured by retail investors' heavy selling in small cap stocks.