Variation in oat trichome presence. Miller S., Hizbai B.T., Wight C.P., Gardner K.,Yan W., Tinker N.A

Transcription

1 Variation in oat trichome presence Miller S., Hizbai B.T., Wight C.P., Gardner K.,Yan W., Tinker N.A

2 Groat trichomes: hair like growths on the grain Present a major health hazard to growers and processors for harvesting, handling and processing of the grain. During threshing and handling, cause skin itching, respiratory congestion and eye irritation for operators. Lock the seeds together and cause bridging in seeders and stoppages in the moving of seed in conveyance equipment. Trichomes also attract and trap fungal spores and dust, which can lead to infection on the seed.

3 Trichomes are clearly a disadvantage and growers and millers would like to have cultivars that lack them. However, little is known about the genetic control of this trait. The only study to investigate genetics of groat trichomes in oat Burrows et al Gene controlling reduced trichomes on oat groats Canadian Journal of Plant Science, 81(3): , /P recessive gene Gt-1 many genetic factors affect trichome expression Efforts are underway to identify the genetic factors controlling this trait.

4 Objective To establish a numerical rating system for groat trichome in oat varieties Evaluate hairiness of lines in the VAO 44 X Leggett breeding population. Identify QTLs associated with groat trichome in oat

5 Methods An F 5:6 oat population consisting of 136 recombinant inbred lines (RILs) developed from a cross between the cultivars VAO-44 (naked, bald) and Leggett (covered, hairy) was used. 2 seeds/line/pot were planted in a greenhouse 1 panicle per plant (2 panicles/line) were harvested Panicles from the two plants representing a line were scored separately as panicle A and Panicle B. 5 seeds from each panicle were analysed for hairiness - groats were photographed using dissecting microscope at same magnification

6 Hairiness index (Tricomidex) development Initial attempt - each kernel was rated for quantity (Q) and length (L) of trichomes in 3 areas: brush, crease (ventral) and pericarp (dorsal) - final score: INDEX = (Q b + L b ) + (Q v + L v ) + (Q d + L d ) 3 Quantity Length 0 = none very short = ½ ½ = ± short = 1 1 = + long = 2 2 = ++ 3 = +++ This became complicated and confusing

7 The initial approach was simplified - 4 categories ranging from 1 (least hairy) to 4 (most hairy) were established - visual scoring 5 seeds from each panicle each seed was scored individually Mean of the five scores was used as the hairiness level of the plant

8 Figure 1. Trichome Index developed from the VAO-44 X Leggett population

9 Results A summary of the hairiness levels for both plants are presented in Table 1. The results for both panicles were consistent as shown in the scatter plot in Fig 2. Therefore an average of the two plants will be used as a representative Table 1. Summary of hairiness level of the VAO-44 X Leggett population A B Average Min Max Mean

10 Trichome levels of panicle B Results r = Trichome levels of panicle A Figure 2. Scatterplots of the trichome index of plant A vs plant B

11 The trichome index showed a normal distribution with a progeny mean of 2.74 indicating that the trait is controlled by many genetic factors. This is consistent with Burrows et al (2001) findings. The frequency distribution (Fig. 3) shows there is transgressive segregation of the trait in both extremes indicating both parents carry alleles that increase and decrease the trichome levels.

12 Frequency VAO-44 Min 1.53 Max 3.85 Mean 2.74 Leggett More Hairiness level Fig 3. Frequency distribution for hairiness in 136 recombinant inbred lines of the VAO-44 x Leggett population.

13 Future work DNA for all the lines in the VAO-44 X Leggett population has been sent for G by S scoring waiting for results! The genotypic data will be used to construct a genetic map and for the identification of qtls that explain variation in the trait. This is a useful step in understanding the genetic architecture of groat trichomes in oat. Stay tuned!

14 Thank You!