Víctor A. González-Hernández

Fatty acids and physiological quality of tomatillo (Physalis philadelphica Lam.) seed during natural ageing

In Mexico, 44 thousand hectares are planted with tomatillo or husk tomato (Physalis philadelphica Lam.), which occupies fourth place among the countrys vegetable species. However, research on this species is scarce, especially that related to the process of seed deterioration. We studied the effects of deterioration in tomatillo seed, var. CHF1-Chapingo, stored from 2-mo up to 7 yr with no climate control, 18.2 ± 5 °C and 41 ± 10% relative humidity, on physiological and biochemical variables during germination. It was found that germination, vigor, and respiratory activity decrease significantly from the first year of storage; thus, after 7 yr, germination and vigor decreased 99%, and respiratory activity of seed after 48 h imbibition decreased 78%. Linoleic acid (unsaturated) content correlated positively with germination (R = 0.78**) and with speed of radicle emergence (R = 0.79**). Germination correlated with speed of radicle emergence (R = 0.99**) and with respiratory activity after 48 h of imbibition (R = 0.79**). Both respiratory activity and fatty acid content are involved in natural deterioration of tomatillo seed.

Synchronicity of pollination and inoculation with Claviceps africana and its effects on pollen–pistil compatibility and seed production in sorghum

Sorghum ergot (caused by Claviceps africana) is a disease that affects sorghum seed development and yield. The interaction between pollen tube growth and hyphal development determines whether ovaries will be fertilized or colonized. Thus their respective deposition times on the stigma are critical. The effect of the time interval between pollination and inoculation on stigma receptivity and seed production was measured under field conditions in the male-sterile line A9 at Montecillo, State of México (2240m altitude). Pollination and inoculation treatments, from simultaneous application to 2 and 4h difference, were imposed when all stigmas on the panicle had emerged. Control panicles were either only pollinated or only inoculated. Eighteen hours later, pollen grains that adhered to, and germinated within the stigma, pollen tubes in the style and ovary, and fertilized pistils were counted. Pistils showing some disease expression (germinated spores, mycelium growth, or tissue necrosis) at 18, 48, and 72h were recorded. The number of diseased florets was registered at the dough growth stage, while number of seeds, grain yield and 100-seeds weight was measured at the physiological maturity. The pathogen applied in a water suspension of macro and secondary conidia caused a decrease in stigma receptivity; the greatest decrease (40-60%) occurred when the pollen and the inoculum were deposited almost simultaneously, regardless of which was deposited first. The route of the pollen tube was also the route for fungal infection. On average, treatments first inoculated had 60% more diseased florets and 36% less grain yield, 30% fewer seeds and seed size decreased 8%, than those first pollinated.

Hardening of Pinus oaxacana Mirov seedlings under irrigation management in nursery

Introduccion: Las plantas deben someterse a un proceso de endurecimiento en el vivero para mejorar la supervivencia de las plantaciones forestales en areas degradadas. Objetivo: El efecto de tres niveles de riego se evaluo en la etapa de endurecimiento sobre algunas variables morfologicas y fisiologicas de Pinus oaxacana . Materiales y metodos: Los tratamientos evaluados fueron tres niveles de riego mas un testigo. El riego se realizo cuando los tubetes reducian su peso de saturacion 30 % (frecuente), 40 a 45 % (medio) y 45 a 50 % (escaso); en el testigo, el riego se aplico cada dos o tres dias. El experimento se establecio en un diseno de bloques completos al azar; cada tratamiento consto de 100 plantas. Resultados y discusion: Los indicadores morfologicos con diferencias significativas ( P ≤ 0.05) entre tratamientos fueron diametro del cuello de la raiz, peso seco de vastago y peso seco total. Los indicadores fisiologicos mediante la prueba de potencial de crecimiento de raiz no presentaron diferencias significativas. Las plantas con riego frecuente obtuvieron el mayor diametro, peso seco del vastago y peso seco total. Conclusiones: Una reduccion del riego entre 30 a 45 % en P. oaxacana permite la produccion de plantas endurecidas, con mayor posibilidad de exito al momento de su trasplante en campo.

Heterosis and combining ability of seed physiological quality traits of single cross vs. three-way sorghum hybrids

The aim of this research was to compare genetic parameters for traits related with seed germination and seedling vigour of single cross (SCH) vs . three-way (TWH) sorghum hybrids. The study was conducted in a sand bed under a greenhouse; 67 genotypes (four pairs of A- and B- lines, four R- lines, 13 SCH and 42 TWH) were allocated in a randomized complete blocks experimental design with three replications. Statistical analysis included ANOVA’s and Student “t” tests, while Tukey test (p £ 0.05) was applied for mean comparisons. The R-lines showed better physiological seed quality attributes than the A- and B- lines. The seed quality and heterosis values of SCH vs. that of TWH did not show significant differences (p > 0.05) for any variable; however, heterobeltiosis of SCH was higher than that of TWY for normal seedlings, dry weight of plumule and seedling emergence rate. The A2- line and R14 restorer line showed the highest GCA values in both types of hybrids. No differences (p ≤ 0.05) were found between maternal and paternal effects of the A- and B- lines involved in the male sterile cross (female parent) of the TWH, except for plumule length in Line 5.

Chemical treatments for recovering germination in onion seeds.

A factor limiting the availability of onion seed is its accelerated postharvest deterioration. The research aim was to evaluate the recovery of seed germination in aged onion after application of chemical solutions. The onion seeds were artificially aged for 48, 96 and 144 h. Next the seeds were placed in solutions: gibberellic acid (3.46 mg·L-1), (BAP (2.25 mg·L-1), calcium chloride (55.50 mg·L-1) and potassium nitrate (50.50 mg·L-1), 8 to 12 h according to cultivar. The imbibed seeds were placed in standard germination conditions. The CaCl2 treatment in aged seeds (48 h) increased the percentage of normal seedlings in the cultivar Contessa. All other seed treatments increased the time to reach T50 and negatively affected germination. The use of BAP caused the higher reduction in the percentage of normal seedlings, lower seedlings biomass and the consequent loss of vigor. Toro and Contessa were the cultivars with greatest vigor, and Crystal white wax and Cojumatlán presented intermediate vigor, while Red burgundy showed the lowest vigor. ADDITIONAL