Effects of ethephon , salicylic acid and cidef - 4 on the yield and quality of guinea

The effect of applying plant growth regulators on seed yield and quality of guinea grass (Panicum maximum) cv. Tanzania was studied in one crop on a sandy clay in Mexico. The treatments consisted of 3 growth regulators [ethephon, salicylic acid and a steroidal phytohormone (cidef-4)], 2 stages of application (before seed head emergence and at the beginning of anthesis) and 4 application concentrations [0, 600, 1200 and 1800 mg/kg active ingredient (a.i.) for ethephon; 0, 10–5, 10–4 and 10–3 M for salicylic acid; and 0, 2, 4 and 6 mg/kg a.i. for cidef-4]. The growth regulators were applied as a spray in water at 850 L/ha. Pure seed yield varied between the growth regulators evaluated (P<0.05), and the greatest yield (179 kg/ha) was obtained using cidef-4. Ethephon greatly reduced seed yields at the highest 2 rates when applied early, mainly through reducing number of heads emerging. Salicylic acid had a benefi cial effect on seed yield at the highest application rate, irrespective of when applied. Cidef-4 greatly increased seed yield, irrespective of when applied, with the effect tending to increase with application rate over the full range. It acted primarily through an increase in head density and to a lesser extent head size. Seed quality (1000-seed weight, seed purity and germination %) was not signifi cantly affected by any of the treatments applied. Introduction Seed production of tropical pasture grasses such as guinea grass (Panicum maximum) presents serious diffi culties associated with poor synchrony of fl owering and rapid abscission of ripe seeds, causing low yield and poor quality of seed (Boonman 1978; Oliveira and Humphreys 1986). These problems may be partially overcome by using different agronomic practices and genetic improvement, which may result in a reduction of forage yield (Hebblethwaite et al. 1980). The main management strategy to improve seed production in these species is to identify specifi c stages of plant development where yield can be maximised. Many studies on management of tropical grasses have revealed an increase in seed yield by imposing a fi nal closing cut at an appropriate time, applying nitrogen fertilisers and manipulating tillering density, or by combining these practices (Boonman 1978). In a previous study, where nitrogen fertilisation and harvesting time were evaluated in guinea grass cv. Tanzania, yield and seed quality increased with application of 100 and 150 kg/ha N (Joaquín et al. 2001a; 2001b). The highest seed yield was observed when guinea grass was harvested at 18–22 days after anthesis, when moisture content and percentage of spikelet abscission were 45–50% and 33–53%, respectively. However, seed yield in guinea grass might be further increased by the application of growth regulators, which have a profound effect on increasing synchrony of fl owering, homogeneity of seed ripening, seed yield and quality in several species of plants (Nickell 1979; Pérez and Reyes 1990). Information is needed regarding the effect of growth regulators on seed production of tropical pasture grasses. This study aimed to evaluate the effect of different rates of ethephon, salicylic acid and a commercial steroidal phytohormone (cidef-4), applied either before seed head emergence or at the beginning of anthesis, on seed yield and quality of guinea grass cv. Tanzania. Effects of ethephon, salicylic acid and cidef-4 on the yield and quality of guinea grass seed Correspondence: Dr Bertín Maurilio Joaquín Torres, Departa mento de Zootecnia, Universidad del Papaloapan, Loma Bonita, Oaxaca, C.P. 68400, México. E-mail: bjoaquin@ lomabonita.unpa.edu.mx 03_07_7_Joaquin.indd 55 9/3/07 8:36:09 AM 56 T.B.M. Joaquín et al. Materials and methods Site, experimental design and pasture