PROMOTING STENOSPERMIC GRAPE SEED TRACE DEVELOPMENT AND GERMINATION WITH PLANT-GROWTH REGULATORS

Plant growth regulators (PGRs) [antigibberellins (mepiquat chloride, u niconazole, ancymidol, daminozide, chlormequat, ethephon, methazole), cytokinins (BAP, kinetin, BTP, 2iP), and ABA] were evaluated at variou s concentrations and timings for promotion of seed trace development a nd germination of four stenospermic grape cultivars (Vitis spp.): 'Ven us', 'Mars', 'Reliance', and 'Saturn'. Data include seed trace number per berry, percent of seed traces with endosperm (sinkers), sinker fre sh weight, and percent seed trace germination. Several PGRs effectivel y increased seed number and percent sinkers over control treatments. P GRs had little effect on seed fresh weight and percent germination. PG Rs promoted greater increases in percent sinkers than seed number on a ll cultivars. The number of viable seeds per sample (seed number x per cent sinkers) was increased over controls by up to 802% on 'Reliance', 239% on 'Saturn', 154% on 'Mars', and 153% on 'Venus'. A moderate per centage of viable seeds from treatments and controls of 'Mars', 'Venus ', and 'Saturn' germinated and established normal seedlings. The very small seed traces of 'Reliance' did not germinate from either controls or treatments. The results indicate that PGRs can stimulate seed trac e formation in some stenospermic cultivars and therefore may be useful tools in grape breeding programs. Chemical names used: abscisic add ( +/-)cis-trans isomer (ABA); lopropyl-a-(4-methoxy-phenyl)-5-pyrimidine methanol (ancymidol); 6-benzylaminopurine (BAP); 6-benzylamino-9-(2 te tra-hydropropanyl)-9H-purine (BTP); (2-chloroethyl) trimethyl-ammonium chloride (chlormequat); succinic acid 2,2 dimethyl-hydrazide (daminoz ide); (2-chloroethyl) phosphonic acid (ethephon); 6-(dimethyl-allylami no) purine (2iP); 6-furfurylaminopurine (kinetin); N,N-dimethyl-piperi dinium chloride (mepiquatchloride); rophenyl)-4-methyl-1,2,4-oxadiazol idine-3,5-dione] (methazole); 4,4-di-methyl-2-(1,2,4-triazol-1-yl)-1-p entan-3-ol (uniconazole).