TOWARDS THE RELIABLE PREDICTION OF TIME TO FLOWERING IN 6 ANNUAL CROPS .4. CULTIVATED AND WILD MUNG BEAN

Eight genotypes of cultivated mung bean, black gram and rice bean (Vig na mungo, Vigna radiata ssp. radiata and Vigna umbellata, respectively ) were sown at six sites in Australia on various dates in order to pro vide a range of photothermal environments. In addition, four accession s of the related wild species Vigna radiata ssp. sublobata were sown o n five occasions. Times from sowing to first flowering (f) varied betw een environments from 34 to 317 d; pre-flowering temperature and photo period means ranged from 12.7-degrees to 29.1-degrees-C and from 11.8 to 15.5 h d-1. No effect of photoperiod was detected on rate of progre ss towards first flowering (1/f) in, four genotypes, but in each case a significant positive relation was detected between 1/f and mean temp erature. These simple thermal time relations did not differ significan tly among these four genotypes; the common base temperature was 7.9-de grees-C. In two genotypes observations were well described by a therma l response plane when the mean photoperiod was less than 13 h d-1 (p < 0.01) but photoperiods greater than 14 h d-1 delayed flowering. In ea ch of the remaining genotypes the observations were best described by photothermal planes, that is, 1/f was modulated by temperature and pho toperiod. Predictions from the models based on our data were in good a greement with the times to first flowering observed in three genotypes in an earlier controlled environment study.