SCREENING OF KENAF (HIBISCUS-CANNABINUS L.) GENOTYPES FOR LOW-TEMPERATURE REQUIREMENTS DURING GERMINATION AND EVALUATION OF FEASIBILITY OF SEED PRODUCTION IN ITALY

Kenaf (Hibiscus cannabinus L.), an annual plant of the family Malvacea e, with potential use as a non-wood fiber source is a relatively new c rop in Italy where it can be used in the manufacture of paper and pulp products. Cultivars differ markedly in their response to daylength, b ut stem growth generally declines rapidly following the onset of flowe ring such that under Italian conditions sowing for fiber production ha s to be carried out early to allow maximum growth before floral initia tion. Sowing is generally delayed until soil temperature exceeds 12 de grees C (approximately the middle of May), and therefore it is importa nt to evaluate genetic diversity in response to low temperature during the germination stage to determine which kenaf cultivars are suited t o early sowing. These trials screened various lines to identify those able to germinate at low temperature and therefore suitable for early sowing. The lines were also grown to evaluate photoperiodic requiremen ts and seed yield in the trial environment (Experimental Centre of Rot taia, Pisa, central Italy, 43 degrees 40'N latitude;10 degrees 19'E lo ngitude). In addition, the germination characteristics of seed obtaine d here were tested at low constant temperature (8 degrees C) and at al ternating 20-30 degrees C temperature. Seed belonging to 15 lines - pr oduced in Australia and selected for tolerance to low temperature - sh owed high germination percentage at 8 degrees C in comparison with Tai nung 2, a cultivar sensitive to low temperature and produced in USA (7 5 and 12% as overall mean of lines and Tainung 2, respectively). Lines differed significantly in their response to temperature both in germi nation percentage and mean germination time. Lines showed a wide range of duration of vegetative period. Flowering took place from 31 July t o 23 August in most lines, and they are therefore considered early-mat uring-types. Lines differed in duration of the period from emergence t o seed maturity (from 134 to 187 days), in seed yield per plant (from 0.9 to 27.7 g plant(-1)), and harvest index (from 0.3 to 16.6%). In so me lines, flowering occurred in mid-August and seed filling was then n ot completed due to low air temperature and unfavourable moisture cond itions. Seed produced in central Italy had low quality due to more rap id deterioration and susceptibility to fungal pathogens. Sensitivity t o low temperature during germination was greater in most lines and ger mination percentages were considerably lower than for seed produced in northeastern Australia. Environmental conditions in central Italy app ear inadequate for seed production. (C) 1998 Elsevier Science B.V. All rights reserved.