Germination of guar (Cyamopsis tetragonoloba (L.) Taub.) genotypes with reduced temperature requirements

Abstract

Guar (Cyamopsis tetragonoloba (L.) Taub.) is an annual legume with a long crop cycle and high temperature threshold for seed germination (20-21°C). In semi-arid Mediterranean areas, inadequate soil warmth delays guar planting to May/early June and harvest to October-November, when high rainfall hinders seed maturation and lowers gum quality. Nine world guar genotypes (from India, Pakistan, USA, South Africa) were tested for germination capability and speed in response to temperature. All source seeds were field grown in Sicily for use in germination assays. The following temperature regimes were imposed adopting a completely randomized design: A) seven constant temperatures from 5°C to 35°C (5°C increments), and B) two alternating temperatures of 15/10°C and 20/15°C (6h/18h thermoperiod), each consisting of four replicates of 25 seeds. Optimal germination temperatures were always 30 and 35°C, but Indian genotypes also demonstrated substantial germination percentages (33-43%) at constant temperatures as low as 15°C. Mean germination time (MGT) of genotypes India2, Kinman, Lewis, and Monument were 1.1 to 1.7 days at 30 and 35°C. At lower temperatures (15°C), the germination percentage and MGT improved significantly when the seeds were exposed at 20°C for 6 hours a day. In particular, Kinman, India2 and Monument gave good results, achieving 80%, 76% and 66% germination, respectively, with MGTs of 5 days. This alternating temperature regime is typical in soil during the Mediterranean spring. Results may be useful both for farmers to identify optimum timing for guar sowing, and for breeders to cross genotypes that tolerate low germination temperatures with high yielding genotypes.

Seed Dormancy Breaking and Germination in Bituminaria basaltica and B. bituminosa (Fabaceae)

“…Knowledge on seed germination requirements is crucial to assess the real potential of wild genetic resources to be exploited within agricultural systems [ 46 , 47 ]. This is particularly important for legumes, where the role of seed coat in imposing PY has been widely recognized [ 6 , 7 , 48 ].…”

Potential Areas for Growing <i>Cyamopsis tetragonoloba</i> (L.) under Rainfed Conditions in Mexico

“…The Climate. Temperature is one of the main environmental factors that affect seed germination [30]. It has to be considered at planting time keeping in mind the crop cycle which can be longer than 160 days in large cycle genotypes [30].…”

“…Temperature is one of the main environmental factors that affect seed germination [30]. It has to be considered at planting time keeping in mind the crop cycle which can be longer than 160 days in large cycle genotypes [30]. The climates considered as optimal for Mexico were both: the sub-humid zones cataloged as Aw, Bs, Cf and the temperate regions Cs and Cw (Table 1) while the optimum temperature was in the range of 25˚C to 30˚C.…”

Variability of the photoperiod response in guar (Cyamopsis tetragonoloba (L.) Taub.) genotypes of different geographic origin

“…Although the ecological optimum of guar perfectly matches to the conditions of the semi-arid climatic zone of the northwest of India (~27° N), several attempts have been made to introduce this crop into higher latitudes: in the southern states of the USA -Texas (~29° N), Arizona (~34° N), Oklahoma (~35° N) (Lubbers, 1987), in southern Italy (~39° N) (Gresta et al, 2018). The main complication for successful guar cultivation in the countries of the higher latitudes is the prolonged vegetation period of plants causing harvesting delay before the onset of autumn rains, which negatively affects the yield.…”

“…Under these conditions, the guar plants completed their vegetation from mid-October to early November. Therefore, it was concluded that early maturity is a key breeding trait for this crop when cultivated in the Mediterranean region (Gresta et al, 2018).…”