Evaluation of reciprocal hybrid crosses in guar
Gill, Stacy L.
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Guar, Cyamopsis tetragonoloba (L.) Taub, is grown in the United States on approximately 80,000 acres in northern Texas and Southwestern Oklahoma. The seed is processed and the endosperm is utilized in a wide array of food additives and other uses. Guar varieties with improved agronomic qualities are needed for it to be a viable alternative crop. Some traits are more heritable than others and respond more to plant breeding efforts. Improvements in plant types such as lodging reduction or yield increases can be obtained by selection and hybridization. The hand-pollination efforts of the past in guar have been successful, but progress has been slower than in some other legumes like soybeans. Guar flowers are very small, making hand-pollination a tedious process. Hand-pollination proves to be very expensive as many hours are invested in labor with low percentages of actual hybrid seed recovered. An approach to reduce costs and, at the same time to produce more F1 crosses has been undertaken, namely, to use insects as pollination vectors. This is done by enclosing plants to be crossed within a mesh covered structure called a cage. Two lines are grown to flowering inside a one meter square cage. The white mesh covering excludes pollen from other guar plants grown in the same field within crossing distance. In 2004, 108 cages, each containing an average of eight plants-one of each of the desired cross were used to test whether F1 hybrid seed production varied when parents were hand- or insect-pollinated. Plants were grown to maturity and total pod counts for each plant were taken. The numbers of putative crosses (pods containing putative F1 hybrid seed) were also recorded. Pods containing putative F1 hybrid seed are easily identified as they are only 1-2 seeded compared to the normally 8-10 seeded self-pollinated guar. Chi-square (XÂ²) analyses were used to identify individual guar lines that were more likely to be successful as parents in hybrid crosses as male or female parents. This information will be valuable in improving efficiency of guar breeding programs.